Journal of Cancer Research and Clinical Oncology

, Volume 138, Issue 11, pp 1799–1811

Impact of radiotherapy on microsurgical reconstruction of the head and neck

Authors

  • Bettina Hohlweg-Majert
    • Clinic for Oral, Maxillofacial and Plastical SurgeryMedicine & Aesthetics
    • Clinic for Oral, Maxillofacial and Plastical SurgeryMedicine & Aesthetics
  • Katharina Gust
    • Clinic for Oral, Maxillofacial and Plastical SurgeryMedicine & Aesthetics
  • Victoria Kehl
    • Institute for Medical Statistics and EpidemiologyTechnische Universität München
  • Klaus-Dietrich Wolff
    • Department of Oral and Maxillofacial SurgeryTechnische Universität München
  • Steffi Pigorsch
    • Department of Radiation OncologyTechnische Universität München
Original Paper

DOI: 10.1007/s00432-012-1263-6

Cite this article as:
Hohlweg-Majert, B., Ristow, O., Gust, K. et al. J Cancer Res Clin Oncol (2012) 138: 1799. doi:10.1007/s00432-012-1263-6

Abstract

Purpose

To examine tissue oxygenation and perfusion of free microvascular grafts after primary reconstruction, regarding outcome for patients received adjuvant radiotherapy and different types of grafts.

Patients and methods

Free microvascular grafts (n = 48) after primary reconstruction of the head and neck were examined for tissue oxygenation and perfusion over a period of 6 months. 28 patients received adjuvant radiotherapy. Using a laser doppler flowmetry combined with tissue spectroscopy of the Oxygen-to-see®—equipment (LEA Medizintechnik, Giessen), we were able to determine oxygen saturation, hemoglobin concentration, blood flow and blood flow velocity in the graft in each of two tissue depths (2, 8 mm). Different types of graft were compared.

Result

Comparison of irradiated and non-irradiated grafts showed significant differences in tissue perfusion and oxygenation. Results for all radiated radial and fibula flaps showed no significant (p > 0.05) differences for all reviewed parameters. However, it showed no dose-volume effect with impaired functionality was found for irradiated grafts.

Conclusion

Mircovascular free tissue grafts show an increased perfusion and oxygenation after radiation compared to non-irradiated grafts.

Keywords

Microvascular reconstructionRadiotherapyHead and neck oncologyFree flap

Introduction

Defect coverage of the head and neck heavily relies on microsurgical reconstruction using the free flap technique (Holzle et al. 2008). These techniques have demonstrated good performance with a more than 90 % rate of success and have gained acceptance as standard practice (Hidalgo et al. 1998; Hirigoyen et al. 1995; Chalian et al. 2001; Disa et al. 2001; Smith et al. 2007). Because of a rise not only in tumor incidence, but also in patients’ expectations regarding their quality of life after surgery, the need for functionally and esthetically high-quality reconstruction is now greater than ever. Limitations of that technique, however, have to be considered causing a postoperative loss of the microvascular flap. The most frequent complications are thrombosis of the vein or artery of the pedicle. The principal risk factors for flap loss in microvascular reconstruction are (1) prior operations on the neck, (2) atherosclerosis, and (3) previous radiation treatment.

However, therapy of advanced head and neck cancers frequently mandates the use of definitive or adjuvant external beam radiation (XRT). Radiation therapy can damage small vessels and has the potential to adversely affect micro vascular anastomoses. Specific vascular damage after XRT includes (1) diminished smooth muscle density, (2) endothelial cell dehiscence, and (3) vessel wall fibrosis (De Wilde and Donders 1986; Guelinckx et al. 1984; Choi et al. 2004). To provide a positive outcome of a successful revision, possible complications have to be detected early. Clinical diagnostic is the gold standard for the postoperative evaluation of transplanted flaps. There is a sustained need for objective and noninvasive examination techniques that would potentially optimize postoperative treatment. Although many methods of free flap monitoring are available, to the best of our knowledge, there is still no single reliable noninvasive technique for early recognition of flap failure and for differentiation between arterial occlusion and venous congestion.

With the oxygen analysis system (Oxygen-to-see®, LEA Medizintechnik, Giessen), a non-invasive examination technique for monitoring maxillofacial reconstruction is available. Using this technique, microcirculatory parameters of (1) oxygen saturation, (2) hemoglobin concentration, (3) blood flow and (4) blood flow velocity can be assed, by laser Doppler flowmetry and tissue spectrophotometry.

Therefore, the goals of this study were to examine tissue oxygenation and perfusion for free microvascular grafts after primary reconstruction using the Oxygen-to-see®—equipment (O2C®); specifically regarding oxygen saturation, hemoglobin concentration, blood flow and blood flow velocity in the graft in each of two tissue depths (2, 8 mm). Also we wanted to find out whether there is a difference of outcome for patients received adjuvant radiotherapy and for the different types of grafts that were used.

Materials and methods

Patients

This Health Insurance Portability and Accountability Act-compliant (HIPAA) study had institutional review board approval, and informed consent was obtained from all patients. Over a period from September 2008 to December 2009, 44 consecutive patients were recruited and prospectively included in our study. Twelve female (27.3 %) and 32 male (72.2 %) patients were enrolled (mean age 58 year, age range, 23–74 years). To ensure a better comparability of the groups all included patients were reconstructed after new malignant growth. 39 underwent primary-, 5 underwent secondary-reconstruction.

Inclusion criteria were microsurgical defect coverage in the head neck region using the free flap technique. Radiation therapy was conducted to 28 patients after surgery. 16 patients have not been treated with radiation and served as reference group.

Exclusion criteria were (1) radiation alio loco, (2) preoperative radiation alio loco, (3) further treatment in the patients’ local area, (4) revision of the microvascular flap, (5) poor general health and (4) bad compliance or.

Technical equipment

For monitoring the Oxygen-to-see® (O2C®, LEA Medizintechnik, Giessen) diagnosis device was used. Providing the possibility to monitor tissue perfusion by relying on a combination of laser Doppler flowmetry and tissue spectrophotometry. The O2C® type LW 1212 is equipped with an Intel Pentium 3 processor, 1 GHz and a Windows-NT user interface. The computer is provided with a 20.5 GB hard drive disk and 256 MB memory.

The functionality of the O2C® diagnosis device is based on an integrated laser, category 3b, protection class I. Its light sources consist of a semiconductor diode and a halogen lamp. Light is sent with a wavelength of 820 nm and maximum output of less than 30 mW at continuous wave. Using a glass fiber probe, which is attached to the device, laser light is sent into tissue. The probe records blood flow, blood flow velocity, oxygen saturation of hemoglobin and relative concentration of hemoglobin. The glass fiber probe can be used for different applications: (1) at the skin, (2) oral mucosa, (3) internal organs and (4) intestinal tract.

In this study we used a flat probe, which can be fixed in a stable way parallel to the tissue surface. The probe consists of glass fibers that send laser light into tissue and that receive the signal from tissue to send it back to the main device. The fibers’ diameter amounts to 400 μm each and the fibers are arranged in the probe with 2 mm spaces. By increasing the distance between the single glass fibers it is possible to measure tissue in different depths. In the following study the four parameters oxygen saturation of hemoglobin, relative concentration of hemoglobin, blood flow, and blood flow velocity were monitored in 2 and 8 mm tissue depth.

Measurement principles

The measurement methodology of the O2C® device is based on a combination of laser Doppler spectroscopy to observe the blood flow and white light spectroscopy to determine the oxygen saturation and the amount of hemoglobin.

Laser Doppler spectroscopy

The name of the laser Doppler spectroscopy was derived from the Doppler phenomenon, which was described by the Austrian physicist and mathematician Christian Doppler in 1842. The Doppler effect is defined as the change in frequency and length of a wave, which results from an observer moving relative to the source of the wave. A common example is the perceived tone pitch of a siren approaching, passing, and receding from an observer. The received frequency is higher during the approach and lower during the recession.

The corresponding effect can be observed in laser light. After entering tissue light changes its color when hitting a moving molecule, e.g. erythrocytes. The sensor of the O2C® device detects the reflected laser light, records the change, and converts this information into the parameter of blood velocity. Based on this laser technique blood velocity and blood flow are measurable. Blood velocity is defined as the average pace of moving erythrocytes. Blood flow is determined by a combination of the amount of existing erythrocytes and their blood velocity in the examined measure volume.

Tissue spectroscopy

As a second measurement principle the O2C® device applies the tissue spectroscopy. This technique measures the relative hemoglobin concentration and the oxygen saturation of the hemoglobin. As hemoglobin is the strongest light absorber in tissue, the hemoglobin value is determined by the amount of light, absorbed by tissue. The greater the amount of blood contained in the measure volume, the more light, which is emitted by the laser, will be absorbed by the hemoglobin. Therefore, correspondingly the sensor will detect less light. The O2C® device calculates the relative hemoglobin amount based on the absorbed light rate of the illuminated tissue volume.

The oxygen saturation is determined by the color of blood. Blood changes its color with the degree of hemoglobin’s oxygen saturation. Arterial blood is light red whereas venous blood shows a light blue colour. White light gets reflected, scattered, and a part of the light spectrum is absorbed when the white light interacts with the erythrocytes. The light assumes the color of hemoglobin and is recorded by the measurement probes on the tissue surface. This color reflects the oxygen saturation of the erythrocytes.

The O2C® device measures the parameters hemoglobin concentration, blood flow and blood velocity in arbitrary units (“AU”). The developer of the device chooses these units arbitrarily. The reason for the introduction of “Arbitrary Units” is based on the origin of the values. The measured signals for blood flow are electrical values of frequencies and amplitudes, so that the unit would be a combination of electrical units. Therefore usually a new unit for blood flow is introduced. To calculate the blood flow in ml/min, it would be necessary to compare the electrical signals with a method that measures the blood flow in ml/min (e.g. plethysmography, microspheres) for each organ (or organs with similar optical properties). Then the arbitrary units can be converted in ml/min. This “calibration” has to be done at the measured organ, as there is no artificial model at the moment, which simulates tissue in a realistic way. The same applies for the unit of haemoglobin rHb [A.U.].

Data collection

Sequence of measurements

For this study, patients were measured at four different times. (1) First measurement (M1) was performed directly postoperative 1–2 days after the placement of the implant; radiotherapy has not yet started at this point in time. (2) Second measurement (M2) was 4 weeks after the operation, when radiotherapy was already partly applied. (3) Third measurement (M3) was performed 3 month after the operation. (4) Last measurement (M4) was conducted 6 month after the operation. At this point in time, all patients had finished their radiotherapy and the tissue experienced some time of regeneration.

Preparation of measurements

Clinical examination was performed on every transplant before measurement. Special attention was paid to dehiscence and flap color: using a wooden spatula Nikolski`s sign was performed and time of capillary filling recorded.

Due to the big surface area of the probe, extra oral measurements of the flap turned out to be unproblematic. However, intra oral measurements have been compounded by the position of the implant, postoperative swellings and movement artifacts when swallowing and modified anatomic structures. Moist oral environment with salivation, wound secretion and blood can also aggravate the measurement and distort the determination of the hemoglobin value.

Radiotherapy

During the radiation the graft was part of the target volume and therefore within the main area of irradiation. The treatment planning CT contoured the grafts in all CT layers (3 mm layer formation). The graft volume was determined using the radiation treatment planning software Eclipse (Varian Medical Systems, Palo Alto, Californa, USA) and Oncentra Masterplan® (Nucletron, Columbia, USA). Based on the treatment plan (main plan and boost plan) minimal (Dmin), medium (Dmean) and maximal (Dmax) total dose was determined using a dose-volume-histogram.

Correlation between a higher medium radiation dose of the graft and higher values of the tissue parameters measured with the O2C® device was investigated.

Statistical analysis

All of the statistical computations were processed using JMP 5.1 (SAS Institute Inc., Cary, NC) and SPSS 11.5 software (SPSS Inc., Chicago, IL). As in the analysis several means were to be compared, the significance test was performed using the t test for independent samples, with a significance threshold of p ≤ 0.05. In error charts the means of the four parameters determined at four different measurements were displayed using a 95 % confidence level. The error charts were used directly comparing irradiated and non-irradiated lobe implants at the four different measurement times after operation process. In addition, a dose-volume histogram was used to perform further explorative analysis. Using Pearson’s correlation coefficient, we analyzed the degree of a possible linear relation between radiation dose and measurement values of the O2C® device.

Results

Tumor

The patient group showed 8 different tumor types. 35 patients (79.5 %) were diagnosed with squamous cell carcinoma. 3 patients (6.8 %) suffered from adenocystic carcinoma. The remaining 6 patients each had one of the following tumor types: embryonic rhabdomyosarcoma, myoepthelioma, ameloblastoma, mukoepidermoid carcinoma, pleomorphic adenoma carcinoma, and leiomyosarcoma (each 2.3 %). 42 tumors were found to be malignant. The myoepthelioma was classified as benign salivary gland tumor and the ameloblastoma as semi malignant tumor.

Localisation

Focusing on the patients with squamous cell carcinoma (n = 35) we observed that in 30 cases the carcinoma was localized in the lower jaw, in 4 cases overlapping different areas in upper and lower jaw, and once in the upper jaw. In 18 cases out of the group of 35 the carcinoma was found in the right half of the face: in 17 cases in the lower jaw of the right half of the face, in one case in different overlapping areas of upper and lower jaw. The carcinoma was localized in the left half of the face in 13 cases: 9 times in the lower jaw, 3 times in an area overlapping upper and lower jaw, and once in the upper jaw. For 4 patients a squamous cell carcinoma crossing the midline of the lower jaw was documented.

Stages

Out of 42 patients with malignant tumors, 10 patients showed tumors of the category T1 (23.8 %), 14 of the category T2 (33.3 %), 3 of the category T3 (7.1 %), and 14 of the category T4 (33.3). One patient was diagnosed a carcinoma in situ (Cis). Furthermore, there existed two benign tumors. Taking only the 35 squamous cell carcinoma patients in scope, the tumors show a similar distribution to the different categories: 8 patients with T1 tumors, 12 with T2, 3 with T3, 11 with T4, and one with carcinoma in situ.

Involvement of lymph nodes

N0 situation was observed for 27 out of 44 tumor patients. 6 patients showed metastases in one solitary ipsilateral lymph node with a maximum diameter of 3 cm (N1). For one patient the lymph node metastases measured 3–6 cm (N2a). 5 patients had multiple metastases ipsilateral (N2b). Bilateral and contralateral affected lymph nodes (N2) were observed in the case of 2 patients. No N3 situation was documented.

Minimum safety distance, status of resection and level of differentiation

Based upon the reports of the histopathology examination, the most frequently observed minimum safety distance amounts to 0.5 cm (n = 11), followed by 0.2 cm (n = 8) and 0.4 cm (n = 6). In 3 cases the resection status could not be assessed (Rx); for one patient a microscopically determined residual tumor (R1) was recorded. The resection status of all other 40 patients was R0.

Histopathology examination resulted in the following differentiation: (1) highly differentiated tissue (G1) in 5 cases, (2) moderately differentiated tissue (G2) in 22 cases, and (3) lowly differentiated tissue (G3) in 13 cases.

Radiation therapy

An adjuvant radiation therapy was indicated for tumor stages pT2 (n = 11), pT3 (n = 3), and pT4 (n = 14). Three of the pT4 patients refused the radiation therapy. Furthermore, two patients with rpT1 tumors and who developed an early recurrence of an adenocystic carcinoma and a squamous cell carcinoma received radiation. 11 patients with T2 tumors received radiation post operatively; one patient diagnosed with carcinoma in situ was irradiated. For the whole present patient group the radiation was performed in pure curative intention rather than in the sense of palliative treatment. The clear indication of chemotherapy was given in case of extra capsular affected lymph nodes, in case of close margins for resections of lower than 0.5 cm as well as for R1 resections.

Out of 28 patients receiving radiation therapy, 9 were treated with combined radio chemotherapy. Patients with impaired liver and renal function (n = 2) were not administered cystostatics.

Referencing total radiation dose and minimum safety distance after histopathology examination, a clear correlation can be observed: the smaller the safety margin between tumor issue and benign tissue the higher the total radiation dose. 14 out of 28 patients received a total radiation dose of 64 Gray (Gy). A dose of 58 Gy was applied to one patient who cancelled the therapy. Another patient was treated with 40 Gy radiation dose for organ maintaining (Nervous opticus) reasons. 7 patients received 60 Gy, 2 patients 66 Gy (Bernier et al. 2004; Cooper et al. 2004) and 3 patients (one with Rx situation) received 70 Gy.

Applying a single dose of 2 Gy in 5 fractions per week, patients were treated in a norm fractionation with up to 62 Gy average total radiation dose. The exposure time averaged to 41.7 days (7–68 days). On average, it started 50.4 days (minimum 23 days, maximum 98 days) after the operation. Preoperative treatment of 40 Gy total doses was given to 5 patients, 60 Gy was given twice, 64 Gy once and 65 Gy norm fractionated with 2 Gy single doses once. For 17.9 % of the patients receiving radiation therapy the targeted area included exclusively the primary tumor region with minimum safety distance, for 3.6 % the primary tumor region with ipsilateral cervical lymph drainage region, and for 78.6 % in addition to the primary tumor the lymph drainage pathway was irradiated from both sides. At the time of the surgical tumor therapy no distant metastases were observed for any of the examined patients.

Clinical picture

At the beginning of the first measurement session directly after the operation 5 microsurgical grafts showed postoperative wound dehiscence. During the following checkup this was not observed anymore. At this point in time, two patients had already started their radiation therapy. During the radiotherapy one graft showed dehiscence after 3 month. The next checkup (3 month later) did not show any signs of impaired wound healing. Six month after insertion 44 grafts have healed irritation free. 11 grafts showed metaplasia. The grafts have healed irritation free from both a functional and an aesthetical point of view into the receiving area.

Concomitant diseases

30 patients, dividing into 75 % male and 25 % female, smoked cigarettes on a regular basis. For 20 patients’ nicotine and alcohol abuse was observed at the same time. 13 patients stated neither cigarette nor alcohol consumption. 10 patients suffered from arterial hypertension that was medically stabilized. 5 patients stated a coronary heart disease and 5 patients had a non insulin dependent diabetes mellitus of type II. 27 out of 44 patients showed at least one additional concomitant disease. The most frequent concomitant disease was hypo- or hyper-thyroidism, liver disease as e.g. cirrhosis or hepatitis, asthma bronchiale, osteoporosis, renal insufficiency, lung disease as e.g. emphysema or recovered tuberculosis, depression or Meniere’s disease. Besides the liver cirrhosis patients, the patients did not take medication. Especially, no patient received medication compromising the blood flow.

Defect coverage

The graft was chosen preoperatively based on clinical radiological examination. In general, a CT scanning was used for radiological assessment. In case of soft tissue MRT imaging was applied. The graft selection was based on assessment of three-dimensional extension, infiltration of neighboring structures, and tumor localization. For the selection of the donor side the following was taken into account: preoperative individual blood circulation (e.g. blood vessel imaging using CT angiography for fibula graft and perforator) and handedness of patients. Out of 22 patients with radial forearm flap, 18 patients preferred the left side, 4 patients the right side. 13 patients received an osteocutanous fibula flap, 7 patients an anterior lateral thigh flap and 2 a perforator flap.

Evaluation of O2C® measurements

Table 1 shows number of patients radiated or not radiated at the four different measurements (M1-M4).
Table 1

Number of patients radiated or non-radiated for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4)

 

Measurement 1

Measurement 2

Measurement 3

Measurement 4

Radiated

5 (10.4 %)

10 (20.8 %)

26 (54.2 %)

28 (58.3 %)

Non-radiated

43 (89.6 %)

38 (79.2 %)

22 (45.8 %)

20 (41.7 %)

The following figures show the mean values of the 8 parameters measured by the O2C® device (Figs. 1, 2, 3, 4, 5, 6, 7 and 8). The values of the irradiated grafts to non-irradiated grafts were compared at four different measurements. Significant differences (p ≤ 0.05) between irradiated and non irradiated grafts were recognized 3 and 6 month post operative, respectively regarding oxygen saturation in 2 mm tissue depth, as well as regarding blood flow and blood velocity in 2 and 8 mm tissue depth.
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Fig. 1

Oxygen saturation (%) in 2 mm depth comparing radiated (black-error bars) and non-radiated (grey-error bars) grafts for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4). Note, significant differences between measurement 3 and 4; this can lead to the conclusion that oxygen saturation is influenced by radiation therapy

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Fig. 2

Hemoglobin concentration [arbitrary units (AU)] in 2 mm tissue depth comparing radiated (black-error bars) and non-radiated (grey-error bars) grafts for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4). Results are not significant

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Fig. 3

Results for blood flow (AU) measurements in 2 mm depth comparing radiated (black-error bars) and non-radiated (grey-error bars) grafts for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4)

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Fig. 4

Blood flow velocity (AU) in 2 mm tissue depth comparing radiated (black-error bars) and non-radiated (grey-error bars) grafts, for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4). Significant differences can be noted between three (M3) and 6 month (M4) after operation

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Fig. 5

Oxygen saturation (%) in 8 mm tissue depth comparing radiated (black-error bars) and non-radiated (grey-error bars) grafts, for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4)

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Fig. 6

Hemoglobin concentration (AU), comparing radiated (black-error bars) with non-radiated (grey-error bars) grafts in 8 mm tissue depth for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4)

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Fig. 7

Blood flow (AU) measurement in 8 mm tissue depth comparing radiated (black-error bars) and non-radiated (grey-error bars) grafts for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4). Significantly higher blood flow was found for radiated grafts at the third (p = 0.005) and fourth (p = 0.005) measurement to the non-irradiated grafts

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Fig. 8

Blood flow velocity (AU) in 8 mm tissue depth comparing radiated (black-error bars) and non-radiated (grey-error bars) grafts for all four measurements: directly after operation (M1), 4 weeks after operation (M2), 3 months after operation (M3) and 6 months after operation (M4)

Measurements in 2 mm tissue depth

Average values of recorded superficial oxygen saturation in 2 mm depth are relatively widely spread for the five patients that were radiated directly postoperative. In the second measurement the values of the irradiated patients diverge compared to the third and fourth measurement. In the group of non-irradiated test persons the fourth measurement showed more variation than at the beginning of the measurement session (first and second measurement). Comparing mean values of irradiated with non-radiated patients, all values of the irradiated patients lay above 60 % and below 60 % for non-radiated patients. Significant differences between irradiated and non-irradiated grafts were observed in measurement 3 (26 irradiated patients; p = 0.005) and 4 (28 irradiated patients; p = 0.006) (Fig. 1). This can lead to the conclusion that oxygen saturation is influenced by radiation therapy.

Higher results for the radiated than the non-irradiated grafts were found for the hemoglobin concentration in 2 mm tissue depth for all measurements; results are not significant (Fig. 2).

Results for blood flow measurements in 2 mm depth are shown in Fig. 3. There is a great dispersion for all measurements and all grafts. However, mean values for all measurements of non-radiated grafts are constant between 47 and 66 AU (M1: 47.07 AU; M2: 57.09 AU; M3: 51.45 AU; M4: 66.14 AU). Comparing results of non-radiated and radiated grafts, there are almost no differences in blood flow for the first measurement, directly after operation. For measurement 2, 4 weeks after transplant, blood flow is higher for the irradiated grafts. However, there is a significant difference, showing a better blood flow for the irradiated grafts, regarding measurement 3 (p = 0.006) 3 month after operation, and 4 (p = 0.002), 6 month after operation.

For blood flow velocity in 2 mm tissue depth, comparing irradiated and non-irradiated grafts, significant differences three (M3) and 6 month (M4) after operation can be evaluated (Fig. 4). Higher values were found for the irradiated (M3: 22.2 AU; M4: 22.47 AU) than for the non-irradiated tissues (M3: 15.10; M4: 16.26). Regarding the complete measuring period (M1 to M4) there is almost no change in blood flow velocity for the non-irradiated grafts (M1: 15.7 AU; M2: 15.18 AU; M3: 15.10 AU; M4: 16.26 AU).

Measurements in 8 mm tissue depth

Reviewing oxygen saturation in 8 mm tissue depth revealed that saturation is lower for the non-irradiated tissues for all measurements. However, no significant difference between irradiated and non-irradiated tissue could be found. Note that results of measurement 2 are noticeably lower for both irradiated and non-irradiated grafts (Fig. 5). This might be due to decreased oxygen saturation directly after operation.

Measuring results for hemoglobin concentration, comparing non-irradiated with radiated grafts in 8 mm tissue depth, are inconstant and showed no significances (Fig. 6).

Assessing the data of blood flow measurement in 8 mm tissue depth, significantly higher blood flow was found for irradiated grafts at the third (p = 0.005) and fourth (p = 0.005) measurement (M3: 196.11 AU; M4: 234.46 AU) compared to the non-irradiated grafts (M3: 139.54 AU; M4: 148.88 AU), indicating the influence of radiation on the blood flow (Fig. 7). However, results showed an almost similar initial value for the first and second measurement, comparing the non-irradiated and irradiated grafts. For the third measurement a clear divergence can be denoted. There is clear increase in blood flow for the irradiated grafts from measurement 2 (164.29 AU) to measurement 3 (196.11 AU) and again to measurement 4 (234.46 AU). For the non-irradiated grafts, measurements were almost similar, with only minimal changes in blood flow during the 6 months (M1: 136.52 AU to M4: 148.88 AU). Note the mean variation of the last measurement of non-irradiated grafts, showing lower values for the third and Fourth measurement; this might be caused by the long regeneration time after operation.

Significant difference was found for blood flow velocity in 8 mm tissue depth (Fig. 8). Higher amounts were found for irradiated compared to non-irradiated grafts. While there is a steady rise for values of irradiated grafts, blood flow velocity for non-irradiated grafts levels for weeks after operation. This might be due to regeneration processes after transplantation.

Transplant specific variations

Analyzing the results of different irradiated and non-irradiated grafts, data concentrates on the two most used flaps; radial forearm flap (n = 22), osteocutaneous fibula flap (n = 13).

Results for all radiated radial and fibula flaps showed no significant (p > 0.05) differences for all reviewed parameters. However, there is a noticeable higher blood flow for the radiated radial forearm flap in 2 mm tissue depth.

Results of the fourth measurement of all evaluated radial flaps comparing radiated and non-radiated tissue is shown in Table 2. In 2 mm tissue depth, a significant difference in blood flow can be found with a higher blood flow for the irradiated (177.82 ± 80.12) than the non-irradiated grafts (86.70 ± 77.18). Trends were shown with mildly higher oxygen saturation and blood flow velocity in 2 mm tissue depth and blood flow and blood flow velocity in 8 mm tissue depth for all radiated radial flaps; however, no significance was found (p > 0.05). Table 3 shows results of all evaluated fibula flaps, comparing irradiated and non-irradiated grafts. Significant differences was found for, oxygen saturation, blood flow and blood flow velocity in 2 mm tissue depth; furthermore for the blood flow an blood flow velocity in 8 mm tissue depth with higher results for the irradiated grafts.
Table 2

Comparison of radiated and non-radiated radial flaps for all four measurements for all parameters evaluated

 

Radiation

N

Mean values

Standard deviation

P

Oxygen saturation 2 mm (%)

Yes

9

75.30

14.73

0.057

No

12

57.79

22.52

 

Hemoglobin concentration 2 mm (AU)

Yes

9

70.98

14.05

0.276

No

12

64.34

12.96

 

Blood flow 2 mm (AU)

Yes

9

177.82

80.12

0.016

No

12

86.70

77.18

 

Blood flow velocity 2 mm (AU)

Yes

9

24.23

6.81

0.088

No

12

18.29

7.93

 

Oxygen saturation 8 mm (AU)

Yes

9

74.28

11.68

 

No

12

63.70

28.78

0.266

Hemoglobin concentration 8 mm (AU)

Yes

9

59.25

19.68

0.361

No

12

69.93

29.58

 

Blood flow 8 mm (AU)

Yes

9

246.94

66.03

0.069

No

12

178.81

89.18

 

Blood flow velocity 8 mm (AU)

Yes

9

46.68

15.60

0.080

No

12

33.64

16.30

 
Table 3

Comparison of radiated and non-radiated radial flaps at all four measurements for all parameters evaluated

 

Radiation

N

Mean values

Standard deviation

P

Oxygen saturation 2 mm (%)

Yes

12

73.32

14.03

0.006

No

9

39.95

22.04

 

Hemoglobin concentration 2 mm (AU)

Yes

12

70.18

16.01

0.135

No

9

55.61

15.46

 

Blood flow 2 mm (AU)

Yes

12

135.15

63.43

0.008

No

9

33.03

36.85

 

Blood flow velocity 2 mm (AU)

Yes

12

21.70

5.54

0.005

No

9

12.31

2.85

 

Oxygen saturation 8 mm (AU)

Yes

12

67.68

21.58

0.797

No

9

65.03

6.24

 

Hemoglobin concentration 8 mm (AU)

Yes

12

66.59

22.48

0.200

No

9

50.46

17.40

 

Blood flow 8 mm (AU)

Yes

12

249.23

75.76

0.001

No

9

75.49

33.50

 

Blood flow velocity 8 mm (AU)

Yes

12

44.28

12.81

0.001

No

12

17.79

5.96

 

Correlation of dose volume effect and measuring values

For evaluated parameters using the O2C® unit, no correlation between rising parameters after radiation and total radiation volume could be found.

Discussion

The results of our study show that radiation has an influence on the transplanted tissues blood circulation; causing higher blood diffusion, thus giving a higher blood supply.

Significant differences (p < 0.05) between irradiated and non irradiated grafts were recognized 3 and 6 month post operative with higher values for the irradiated grafts, respectively regarding oxygen saturation in 2 mm tissue depth as well as blood flow and blood flow velocity in 2 and 8 mm tissue depth. Interestingly, radiation had no influence on the hemoglobin concentration. Comparing different transplants used, no graft-specific differences for the saturation or perfusion status was found after radiation. For evaluated parameters using the O2C® unit, no correlation between rising parameters after radiation and total radiation volume could be found. Furthermore during our study, there were no clinical signs for tissue changes of irradiated tissues.

Micro vascular flap transfer is the ‘working horse’ for defect coverage in head and neck surgery (Holzle et al. 2008). Despite of success rates to 96–98 % of free microvascular grafts, there is a risk for transplant loss caused by perfusion dysfunction (Hidalgo et al. 1998; Hirigoyen et al. 1995). These complications have to be detected early in order to prevent flap loss and increase the chance of a successful revision (Holzle et al. 2005). A objective, reliable, simple, reproductive and non-invasive monitoring process would be a helpful addition to the standard used clinical examination, complexion and recapilarisation (Hirigoyen et al. 1995).

Previous work has introduced other techniques trying to evaluated transplanted grafts reliably. However, temperature measurement, pH measurement systems or Doppler sonography found their limits due to invasiveness and missing sensitivity (Furnas and Rosen 1991; Machens et al. 1994). Another method tested is the tissue partial pressure measurement. Unfortunatly this technique does not for fill hygiene standards anymore (Kamolz et al. 2002). Furthermore, infrared spectrophotometry (Thorniley et al. 1998) as well as tissue spectrophotometry (Wolff et al. 1996) are common used techniques. However, tissue perfusion can only be measured using duplexsonographie (Numata et al. 2002), PET-CT, SPECT or doppler flowmetrie technique (Yuen and Feng 2000). But to the best of our knowledge no study has been performed, comparing all possible measuring techniques noninvasively using one performing unit.

With the O2C® analysis system (Oxygen-to-see®), a non-invasive examination tequnique for monitoring transplanted graft is available. Providing the examiner simultaneously with the data of tissue perfusion and tissue oxygenation microcirculatory parameters: (1) oxygen saturation, (2) hemoglobin concentration, (3) blood flow and (4) blood flow velocity.

Hölzle et al. did not find a comparable tool, evaluating laser Doppler flowmetry and tissue spectrophotometry in one unit. Further advantage is the noninvasiveness and the potential of continues monitoring. Technique and handling are easy to learn and administrate. All measured data is recorded at the same time. Also, new special probes for the laser Doppler, allow to record microcirculation in two different tissue depths up to 12 mm (Holzle et al. 2005). Until now, this advanced feature was not integrated to laser Doppler units, recording tissue depth up to 1–2 mm, (Sloan and Sasaki 1985). Furthermore, so far available O2C®-probes only provided reliable results for cutaneous grafts; muscular or osseous grafts were limited (Holzle et al. 2005).

Patients’ data was reviewed with respect to the reproducibility of references. Due to the small number reviewed (n = 48), significance for a gender or age specific allocation could not be found. However, compared to data of major studies for maxilla facial surgery (Kessler et al. 2007; Dietl et al. 2005; Holzle et al. 2005), partition of 32 male (72.2 %) and 12 women (27.2 %) with a mean age of 58.4 years is representative. Furthermore, in our study the tumor identity is confirmed to literature (Leemans et al. 1997; Vokes and Weichselbaum 1993).

The results of our study show that there is an increase of blood flow and blood flow velocity as well as a distinct rise of hemoglobin oxygenation at the surface of the graft after radiation compared to non-irradiated tissues. By the means of our results there have to be parameters that influence the tissue to gain an oxygenation values to 70.69 after radiation compared to 52.3 % of non radiated flaps. Radiation might cause a loss of flexibility for vascular system by indurating vessels walls (Quarmby et al. 1999). This stable enlargement of the vessels, not able to constrict anymore, end up in a rise of hemoglobin’s oxygenation. Thes late effects, caused by changes of vessels endothel are called hyallinisation (Herrmann et al. 2006). For results of hemoglobins oxygenation in 8 mm tissue depth no significant differences between radiated and non-irradiated tissues was found. Still higher values were found for radiated (64.7 %) than irradiated (69.14 %) tissues. This might mainly be due to an increase pressure on the vascular system caused by ongoing tissue fibrosis (Yarnold and Brotons 2010). This scarring of connective tissue and vessels might influence and reduce blood flow as well as hemoglobin oxygenation.

The results of the perfusion parameters, blood flow and blood flow velocity, show a significant difference between the radiated compared to the non-irradiated grafts for measurements three and 6 months after operation for both tissue depths.

Physiology of the vascular system clarifies the connection between tissues blood flow and oxygenation. Oxygen supply directly affects state of vessel contraction. The endothelia cells recognize a lack of oxygen, as in our study caused by radicals due to the radiation. Using a paracrine signal, endothelial growth factor is activated causing a dilatation of the vascular system. Based on this dilatation of the vessels, an increased blood flow is stimulated while transporting more oxygen (Silverthorn 2009). If the supply of oxygen is sufficient, local regularities are decreased, vascular resistance increases and blood flow declines. There is a direct line drawn between increase of oxygenation and increase of tissues blood flow.

Apart from the endocrine system also the nervous system is involved in those cycles (Silverthorn 2009). A neural impact on the vasomotricity of the transplanted issue is unlikely in our study, as tissue in the transplanted area is not or not sufficiently innervated.

Semergidis et al. investigated the radiotherapy reaction of mouth and face regarding blood circulation using Laser-Doppler and ultrasound (n = 44). They showed that therapeutic radio therapy with medium total radiation dose of 50 Gy does not significantly effect blood flow parameters and hence blood circulation in the cranio maxillofacial area until up to 8 month postoperative (Semergidis et al. 1996). Benediktosson et al. studied conservative breast reconstructions (n = 24) and stated that postoperative radiotherapy after conservative breast reconstructions; did not lead to long time changes of basal skin circulation in the breast (Benediktsson et al. 1997). They performed their measurements one year after radiotherapy with 50 Gy total dose using Laser-Doppler-Flowmetry as well as fluorescence flowmetry.

In contrast to our study, both above-mentioned publications did not focus on transplanted tissue. Furthermore, the medium total radiation dose of 50 Gy is not in line with the radiation dose of the present, which was between 60 Gy and 64 Gy. Despite of different measurement methods the present study is compared to both above-mentioned studies. Both, Semergidis et al. and Benediktsson et al. investigated perfusion in human tissue after radio therapy. Both studies showed that in contrast to the present study, ionizing radiation does not affect perfusion.

A study of mouse skin grafts treated with a small radiation dose of 5 Gy in vivo was performed by Thanik et al. Based on Laser-Doppler perfusion analysis they showed that localized low-dose radiation affected angiogenetic chemokines, mobilized progenitor cells in the systemic blood circulation which hence lead to creation of new blood vessels out of endothelium’s progenitor cells. This resulted in an increased blood flow of the irradiated graft tissue (Thanik et al. 2010). Regarding the increase of blood flow parameters in irradiated transplants, similar results could be stated in the present study. Thanik et al. explained their results were due to the application of low-dose radiation. However, small animal and human organism are not directly comparable; both, tissue and implied radiation dose have different characteristics.

But to the best of our knowledge at this point in time no comparable literature could be found on studies of irradiated microvascular grafts in human crani-maxillofacial area monitored with O2C® method.

The present study investigates the impact of radiation dose level, which is applied to micro vascular tissue graft on four tissue perfusion and oxygenation parameters measured with the O2C® device. Analysis of Pearson’s correlation coefficient and of a two-sided test of significance could not confirm a direct relationship between the tissue parameters. Meaning, an assumed linear relation between radiation dose level and increase of perfusion and oxygenation parameters could not be shown. However, given only limited evidence due to the small amount of patients (n = 20) a relation between the two observed factors cannot be excluded.

In general, radiation dose in head and neck area amounts to 50 Gy in the main plan including lymphatic drainage area, which is irradiated electively. Boost radiation on primary tumor and affected lymph nodes happens at maximal 64–70 Gy. Therefore, the individual values of the examined group of patients of the four parameters measured in 2 and 8 mm tissue depth at four different measurements vary only in a very small range. No corresponding literature reference could be found. Also, no study could be found that analyzed irradiated non-transplanted tissue at different radiation dose levels with regard to measured perfusion and oxygenation status. Therefore, a comparison of the results of this study is not possible.

In the following discussion it will be considered that graft vitality can possibly be affected by radiation therapy. Within a time period of 6 month four different measurements with the O2C® device were performed to clinically assess the grafts. At no point in time the grafts showed no clinical distinctive features with regard to color, form and blood circulation compared to non-irradiated grafts. Three month postoperative the graft has healed without irritation. Due to the micro vascular graft original form and function was almost fully restored. After 6 month at the fourth measurement, 11 of 44 grafts showed metaplasia. As the number of patients is only small and the visual assessment is subjective no statistical analysis regarding significant differences between irradiated and non-irradiated grafts was performed. The wound healing process of irradiated grafts did not differ from non-irradiated grafts. Based on this, the prognosis regarding the graft healing under radiation can be said to be very good. No study could be found that analyzed clinical findings of postoperatively irradiated grafts in the maxillofacial area.

Lee et al. studied the healing of micro vascular free grafts in preoperatively irradiated tissue in a data set of 81 cases. They compared pre-irradiated tissue of facial skin with non irradiated oral mucosa and non irradiated facial skin and stated a 4 times higher risk of wound healing complications in case of pre-irradiated tissue (Lee and Thiele 2010). In a study conducted by Jose et al. in 1991 the impact of radiation therapy on free micro vascular tissue transfer (n = 41) in the maxillofacial area under pre and postoperative radiation was clinically investigated. Jose et al. also documented complications due to prior radiation therapy (Jose et al. 1991). Furthermore, Deutsch et al. confirm those results based on a group of 140 patients (Deutsch et al. 1999). All studies documented their results with clinical findings.

However, Choi et al. (n = 100) showed in 2004 that percutaneous radiation therapy after micro vascular tissue transfer in the maxillofacial area does not at all impact the rate of complications. Application of radiation therapy, timing, total dose and target volume did not show any relation to a possible graft loss (Choi et al. 2004). In his study, clinical diagnosis were collected and documented until on average 11 month after the transplantation. The present study can confirm the results of the Choi et al. study. Indication of a loss of graft vitality after radiation was also not found. In contrast, the tissue graft was showed increased blood circulation and oxygen supply.

Suh et al. studied micro vascular free tissue grafts after tumor recurrence in pre-irradiated situs. Those were used for secondary defect coverage and postoperative second radiation with medium radiation dose of 63 Gy (Suh et al. 2008). Acute and late complications occurred post radiatio, however, no graft was lost. For 50 % of the free micro vascular grafts it was possible to cover the defect with functional plastic reconstructions at pre-irradiated tissue with subsequent radiation. The result confirms the statement of the present study, that micro vascular grafts show no contra indication with regard to subsequent radiation within the direct postoperative interval. Finally, we can state that most complications can occur in pre-irradiated situs postoperative.

Due to modern radiation therapy with precise calculation of radiation dose during the planning side effects in irradiated tissue can be reduced. The biggest advantage resides in the optimization of the radiation plan adapted to the organs at risk.

Regarding surgical activity, primary plastic reconstructions has a success rate of up to 98 %. As a result radiation therapy can be applied at an early stage. Micro vascular tissue transfer broadens the therapeutic bounds of combined surgical radiation therapeutic oncological treatment.

A limitation of our study is that blood flow measurements are very sensitive. Particularly, regarding the pressure used when applying the probe to tissue as well as any movements at the time of measurement. In order to gain reliable and reproducible measurement results the probe should be applied to the skin without any significant pressure and fixed in a stable and locked position. During the measurement, any movements of the patient should be avoided as they are recorded by the device and may lead to distorted results. Intra oral measurements increase the difficulty as already minor movements of the tongue can distort the measurement result. Oxygen saturation and hemoglobin measurements are independent of movements. These measurements are, however, influenced by light. If surgery light, sunlight, or the like shines on the probe, the device might show incorrect measured values. Furthermore, colored disinfect, blood marks or make up can influence the measurement.

Conclusion

Mircovascular free tissue grafts show an increased perfusion and oxygenation after radiation compared to non-irradiated grafts. However, as far as our study shows, this change of parameters has no clinical advantage or disadvantage for patients’ treatment. A graft-specific difference for perfusion or oxygenation after radiation could not be found. A correlation between radiation dose and parameter changes measured with the O2C® device was not affirmed. In our study, loss of graft vitality, after radiation did not occur.

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© Springer-Verlag 2012