The current status of an FDG-PET cancer screening program in Japan, based on a 4-year (2006–2009) nationwide survey
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The aim of this study was to survey the 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) cancer screening program conducted in Japan.
The “FDG-PET cancer screening program” included both FDG-PET and positron emission tomography with computed tomography (PET/CT) with or without other combined screening tests that were performed for cancer screening in asymptomatic subjects. A total of 155,456 subjects who underwent the FDG-PET cancer screening program during 2006–2009 were analyzed.
Of the 155,456 subjects, positive findings suggesting possible cancer were noted in 16,955 (10.9 %). The number of cases with detected cancer was 1,912 (1.23 % of the total screened cases, annual range 1.14–1.30 %). Of the 1,912 cases of detected cancer, positive findings on FDG-PET were present in 1,491 cases (0.96 % of the total number of screened cases). According to the results of further examinations, the true positive rate for subjects with suggested possible cancer (positive predictive value) was 32.3 % with FDG-PET. Cancers of the colon/rectum, thyroid, lung, and breast were most frequently found (396, 353, 319, and 163 cases, respectively) with high PET sensitivity (85.9, 90.7, 86.8, 84.0 %, respectively). Prostate cancer and gastric cancer (165 and 124 cases, respectively) had low PET sensitivity (37.0 and 37.9 %, respectively). The Union for International Cancer Control (UICC) clinical stage of cancer found with the FDG-PET cancer screening program was mainly Stage I.
The FDG-PET screening program in Japan has detected a variety of cancers at an early stage. However, several cancers were found in repeated FDG-PET cancer screening program, indicating the limitation of a one-time FDG-PET cancer screening program. The value of the FDG-PET cancer screening program is left to the judgment of individuals with regard to its potentials and limitations.
KeywordsFDG PET PET/CT Cancer screening
Screening is the investigation of a group of asymptomatic individuals in order to detect a disease that has a high probability of development. The National Cancer Institute (NCI) estimates that appropriate cancer screening can prevent 3–35 % of premature deaths caused by cancer. The NCI suggests that cancer screening might decrease cancer morbidity because treatment for earlier-stage cancers is often less aggressive than that for more advanced cancers. Only a few screening methods have evidence supporting their use in reducing cancer-related mortality .
Fluorine-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) and positron emission tomography/computed tomography (PET/CT) have had a considerable impact in the field of oncology in terms of differentiating between benign and malignant tumors, staging cancers, evaluating the effectiveness of treatment, and predicting prognosis. PET and PET/CT can provide whole-body imaging, and have the potential to reveal malignancies anywhere in the body. The performance of FDG-PET for cancer screening was first published by the HIMEDIC Imaging Center at Lake Yamanaka. They established a cancer screening program which consisted of an FDG-PET examination combined with screening tests such as ultrasonography and computed tomography to compensate for the limitations of FDG-PET . Since then, cancer screening using FDG-PET based on Yamanaka’s method has become widespread in Japan, and is performed in more than 130 facilities. The performance profile of FDG-PET cancer screening in 2005 was reported. A total of 43,996 healthy subjects underwent FDG-PET (including PET/CT) scanning with or without other tests for cancer screening in 38 PET centers in Japan . The yearly survey was continued until 2009 in Japan. PET cancer screening is more widespread than before, and PET/CT scanners were more widely used than ever. The potential of the FDG-PET cancer screening program is investigated in the present report through the results of 155,456 cases that underwent FDG-PET cancer screening from 2006 to 2009. This report aims at clarifying the performance of FDG-PET cancer screening, but does not attempt to confirm nor deny the effectiveness of the PET cancer screening program as a cancer screening method.
Materials and methods
Cooperated PET centers for the survey
Asahikawa-Kosei General Hospital
University of Fukui Hospital
Keiyukai Sapporo Hospital
Sugita Genpaku Memorial Obama Municipal Hospital
Institute of Biomedical Research and Innovation
Sapporo Minamisanjo Hospital
Fukui Red Cross Hospital
Himeji Central Hospital’s Clinic
Central CI Clinic
Fukui-ken Saiseikai Hospital
Agape Kabutoyama Hospital
LSI Sapporo Clinic
Iida Municipal Hospital
Sumoto Itsuki Hospital
Tomakomai City Hospital
Kouseikai Takai Hospital
Aomori PET Diagnostic Imaging Center
Ichinose Neurosurgical Hospital
Akita Research Institute of Brain and Blood Vessels
Kizawame Memorial Hospital
Wakayama-minami Radiology Clinic
Sendai Kousei Hospital
Juntendo University Shizuoka Hospital
Tottori University Hospital
Kousei Sendai Clinic
Seirei Hamamatsu General Hospital
Tottori Municipal Hospital
Southern Tohoku General Hospital, Miyagi
Hamamatsu Medical Imaging Center
Kawasaki Medical School Hospital
Southern Tohoku General Hospital, Fukushima
Nagoya Central Hospital
Kurashiki Central Hospital
Shirakawa Kosei General Hospital
Daiyukai Daiichi Hospital
Tsuyama Central Hospital
Dokkyo Medical University Hospital
KARIYA TOYOTA General Hospital
Okayama Diagnostic Imaging Center
Utsunomiya Central Clinic
Nagoya PET Imaging Center
Okayama Kyokuto Hospital
East Nagoya Imaging Diagnosis Center
Okamura Isshindow Hospital
Saitama Medical University
Tokorozawa PET Diagnostic Imaging Clinic
Handa Medical Association Health Care Center
Hiroshima Heiwa Clinic
Asahi General Hospital
Mie University Hospital
St. Hill Hospital
Sannou Medical Center
Iga City Medical Checkup Center
Tokushima University Hospital
Yotsukaido Tokushukai Hospital
Saiseikai Matsusaka General Hospital
Kagawa University Hospital
Nippon Medical School Clinical Imaging Center for Healthcare
Mie Advanced Medical PET Center
Takinomiya General Hospital
National Center for Global Health and Medicine
Kusatsu General Hospital
Shikoku Cancer Center
Oumikusatsu Tokusyukai Hospital
Ehime Prefectural Central Hospital
Japanese Foundation for Cancer Research Cancer Screening Center
Kochi University Hospital
Mitsubishi Kyoto Hospital
Kyushu University Hospital
Yotsuya Medical Cube
Takeda Oncologic Positron Imaging Center
Kurume University School of Medicine
Kinki University Institute of Advanced Clinical Medicine
Kouhoukai Takagi Hospital
Iwai Medical Foundation Medicheck Imaging Center
Saiseikai Nakatsu Hospital, Osaka
Koga Hospital 21
Panasonic Health Care Center
Fukuoka Wajiro PET Diagnostic Imaging Clinic
Hanwa Intelligent Medical Center
Kitakyushu PET Center
General Sagami Kosei Hospital
Nishi Isahaya Hospital
Toyama PET Imaging Center
Saiseikai Kumamoto Hospital
Public Central Hospital of Matto Ishikawa
HIMEDIC Clinic West
Oita Diagnostic Imaging Center
Asanogawa General Hospital
Kagoshima-kyousaikai Nanpuh Hospital
Tousenkai Healthcare System Keiju PET-CT, Linac Center
Atsuchi Memorial Clinic
Kanazawa Cardiovascular Hospital
Contents of the investigation
The questionnaire regarding the FDG-PET cancer screening consists of an “Investigation of facilities” section that describes the situation of each facility, and an “Investigation of suspected cancer cases” section that describes the inspection of suspected cancer cases. The “Investigation of facilities” section surveyed the following areas: (1) the type and methods of FDG-PET (FDG-PET machines, injected radioactive of FDG, presence and method of attenuation correction, time to obtain PET or PET/CT, screening range, performance of delayed scanning and start time); (2) characteristics of the CT scanner integrated in the PET/CT system (mAs, CT image reconstruction interval); (3) fixed or optional other cancer screening tests combined with FDG-PET; (4) total number, gender, and age of subjects who underwent FDG-PET cancer screening; (5) number of repeated annual FDG-PET cancer screening (at least 2 consecutive years); (6) number, gender, age of subjects with positive findings by FDG-PET and/or combined screening test suggesting possible cancer; (7) number of positive/negative findings by FDG-PET and/or combined screening tests in the case of suggested possible cancer; (8) number of excluded cancer cases with combined screening tests after cancer was suspected by FDG-PET.
Detailed information was required only for possible cancer cases in the “Investigation of suspected cancer cases” section. Five types of investigation sheets were provided: “lung cancer,” “colon/rectum cancer,” “thyroid cancer,” and “breast cancer” (which are all frequently detected by FDG-PET), and “other cancers”. The “Investigation of suspected cancer cases” section asked about the following: (1) gender; (2) age; (3) past history of cancer; (4) with or without of repeated annual FDG-PET cancer screening and other suspected cancers by previous FDG-PET screening if any; (5) findings of FDG-PET and delayed imaging if present; (6) results of the combined cancer screening tests; and (7) final results of further detailed examinations. The “Investigation of suspected cancer cases” section consisted of three categories, namely, “proved cancer,” “excluded cancer,” and “strict follow-up because of disproved cancer.”
Definition of terms
In this article, the term “FDG-PET” is defined as an examination performed with a PET scanner or PET/CT scanner. “FDG-PET cancer screening program” is defined as a cancer screening program using FDG-PET that is aimed at the detection of cancer at an early stage. Any PET or PET/CT detector, FDG-PET method, combined screening test, and method of further examination were included in the present report. Any method of selecting subjects and of handling the associated expense burden was allowed. Cases with a past history of cancer, or screening for recurrence requested by the attending physician or patient were excluded from the present report. However, when the cancer was considered to have been cured and FDG-PET was performed to screen for other sites of cancer, the FDG-PET test was included. “Combined screening tests,” defined by each PET center, were those undergone by more than half of the subjects who underwent FDG-PET cancer screening at each PET center. If a screening test was performed at another facility within a short interval and the results were provided to the PET center, it was included in category of “combined screening tests.” If further examination was judged necessary on the basis of the obtained PET information, any additional test other than the pre-fixed screening program was not considered to be a “combined screening test.” If a cancer screening test was performed using a PET/CT scanner, regardless of the method used or manner of interpretation, the information obtained from the CT integrated in the PET/CT scanner was not regarded as a combined screening test, but as PET/CT itself. This was because the CT findings could not be ignored when using PET/CT. Hence “PET positive” is defined as positive findings on PET or PET/CT. Accordingly, the cases with PET/negative and CT/positive findings on screening tests performed by PET/CT were defined as “PET/positive”.
“Required further examination” is defined as cases for which a thorough examination was recommended on the basis of the comprehensive results of FDG-PET and/or any combined screening tests. Cases for which reexamination was recommended are not included in “required further examination.” “Obtained result of further examination” is defined as being clearly categorized as “proved cancer,” “excluded cancer,” or “strict follow-up because of disproved cancer” through the results of additional examinations and treatment.
The Chi-square test for independence was performed to compare the detection rate, sensitivity, and positive predictive value between PET and PET-CT. A P value of less than 0.05 was considered to be statistically significant.
Characteristics of subjects who underwent FDG-PET cancer screening
Number of subjects who underwent FDG-PET cancer screening program
A PET/CT scanner was used in 95,046 cases (61.1 %), and a dedicated PET scanner in 60,410 (38.9 %). In 2006, the number of different scanners used in the FDG-PET screening program was almost the same (dedicated PET scanner: 21,524 cases, PET/CT scanner: 21,527 cases). After 2007, the use of PET/CT scanners was higher than PET (in 2007: dedicated PET scanner: 15,217 cases, PET/CT scanner: 24,650 cases; in 2008: dedicated PET scanner: 12,037 cases, PET/CT scanner: 26,892 cases, and in 2009: dedicated PET scanner: 11,629 cases, PET/CT scanner: 21,970 cases).
The FDG-PET scanning method was analyzed in 109 facilities with 171 scanners consisting of 44 PET scanners and 127 PET/CT scanners. Injected radioactivity of FDG was consistent in 38 facilities (range 111–370 MBq; average 188.2 MBq), and variable in 71 facilities. The facilities with variable injected radioactivities of FDG used 3.61 MBq per kilogram body weight on average (range 2.6–5.0 MBq/kg), with total radioactivity of 216.9 MBq on average (range 156–300 MBq) if used in subjects 165 cm tall and weighing 60 kg. Maximum injected radioactivity of FDG ranged widely from 210 to 518 MBq (average 338.4 MBq). Attenuation correction was performed in 108 facilities. All the attenuation correction with PET scanners was performed by conventional transmission scanning, and all the attenuation correction of PET/CT cameras was performed by CT scanning.
The start time of the emission scan was most frequently 60 min after injection of FDG (average 60.1 min). Total required scanning time (including the scanning time of CT and transmission scan) was 25.5 min on average. The scanned range was most frequently “parietal to knee” regardless of whether a PET scanner or PET/CT scanner was used. Delayed scanning was performed regularly at 28 facilities, if necessary at 67, and never at 22 facilities (8 facilities had multiple answers, and the decision depended on the scanner type used). The start time of delayed scanning was frequently 120 min after injection of FDG (average 117.9 min).
Characteristics of CT scanners integrated in the PET/CT systems
The majority of PET centers used variable “mAs” values rather than a consistent mAs value (the product of X-ray tube current and exposure time) fixed to CT scanners integrated in the PET/CT system. Although the displayed CT scanning parameters on the machines and their definitions differ according to the manufacturer, the average displayed tube current (mAs), pitch, and computed tomography dose index-volume (CTDIvol) (mGy) of the scanner in facilities that applied a consistent mAs value to CT scanning were 95.2 mAs, 1.27, and 6.2 mGy, respectively, whereas in facilities applying variable mAs values, they were 114.2 mAs (maximum mAs value), 1.47 and 6.3 mGy, respectively. Tube voltage (kV) was most frequently 120 or 140 kV.
The CT image reconstruction interval was most frequently 3.75 or 5 mm. The location of the hands at the time of PET/CT scanning was elevated and pulled down at equal frequencies, and CT images were most frequently obtained during resting breathing.
Combined screening tests
Combined screening tests and rate (%) of PET centers performing each test
Head and neck CT
Head and neck MRI
Inspection and palpation of breast
Prostate specific antigen (PSA)
Carcinoembryonic antigen (CEA)
Cancer antigen 19-9 (CA19-9)
Cancer antigen 125 (CA125)
Squamous cell carcinoma antigen (SCC)
Helicobacter pylori infection test
Cytokeratin-19 fragment (CYFRA)
Pro-gastrin releasing peptide (Pro-GRP)
Cancer antigen 15-3 (CA15-3)
Neuron specific enolase (NSE)
Fecal occult blood test (FOBT)
Characteristics of subjects with positive findings suggesting possible cancer
Number of subjects who were positive by screening FDG-PET and/or one or more of the combined screening tests if any
The rate of suspected cancer was 9.8 % (range 9.3–10.8 %) for dedicated PET combined with other screening examinations, lower than the rate of 11.6 % (range 10.7–12.0 %), which was found for PET/CT combined with other screening examinations (P < 0.01).
Analysis of suspected cancer according to the interpretation by FDG-PET and/or combined screening examination
Analysis of detected cancers
Number and rate of found cancers which was positive by screening FDG-PET and/or one or more of the combined screening tests if any
Number of cancers detected by the screening program
Bile duct cancer
Small intense tumor
Primary unknown cancer
Gastrointestinal stromal tumor (GIST)
Metastatic bone tumor
Head and neck cancer
Bone marrow disease
According to the results of further examinations, the true positive rate for subjects with suggested possible cancer (positive predictive value) was 32.3 % (1,491/4,609) with PET, with no statistically significant difference noted between PET/CT at 32.6 % (1,000/3,069) and PET at 31.9 % (491/1,540). Of the 7,197 cases in which a final result was obtained, repeated annual FDG-PET cancer screening tests were performed in 1,240 cases, with cancer found in 22.9 % of them, lower than that in the unrepeated cases (27.5 %).
The cancers found in the FDG-PET cancer screening program were of a wide variety, as listed in Table 6. The most frequently detected cancers with high PET-positive rates were colon/rectum cancer (396 cases, 85.9 %), thyroid cancer (353 cases, 90.7 %), lung cancer (319 cases, 86.8 %), and breast cancer (163 cases, 84.0 %). Low PET-positive rates, but high positive rates in combined screening tests were found with prostate cancer (165 cases, 37.0 %) and gastric cancer (124 cases, 37.9 %). Renal cancer, malignant lymphoma, pancreas cancer, esophagus cancer, uterine cancer, and bladder cancer were also frequently found. Cancers were most frequently found in the age groups of 50–59 years and 60–69 years, accounting for 66.9 % of the total found cancers. Cancers were most frequently found in the age group of 60–69 years in men and 50–59 years in women.
Clinical stage for six representative kinds of cancers
PET-positive rate and number of found cancer according to UICC Stage
Kind of cancer
FDG-PET screening program
Repeated FDG-PET cancer program
Analysis of detected non-cancerous lesions
Number of benign lesions detected by the screening program
Colonic adenoma (polyp)
Benign prostate hypertrophy
Benign parotid tumor
Old inflammatory change of lung
Inflammatory change of lung
There have been many arguments regarding the application of FDG-PET for cancer screening [1, 4, 5, 6]. PET examination has the potential to detect many types of malignant neoplasms; therefore, cancer screening with PET is expected to detect malignant neoplasms throughout the body. However, it is well known that PET has limited detectability for several types of malignant neoplasms due to their small size, low glucose metabolism, and high physiological background FDG uptake. As a result, researchers involved in cancer screening using FDG-PET share a common understanding that cancer screening using PET or PET/CT must be established as a program in combination with several other modalities to compensate for what is not apparent with PET and PET/CT [2, 3, 5, 6]. The Japanese Society of Nuclear Medicine published guidelines for “FDG-PET cancer screening”, which include details about common examinations adopted in Japan that have the potential to contribute to an increased cancer detection rate. These guidelines facilitate uniform and accurate PET cancer screening at many PET centers, but do not advocate any particular screening methods to be combined with PET examination. Therefore, PET centers modify their cancer screening programs depending on their circumstances (even though they share some common ground, as shown in the present report). The suspected cancer detection rate with combined screening tests is much higher than that of FDG-PET; thus, adoption of a common combined screening test and improvement in accuracy will contribute to increasing the specificity of the FDG-PET cancer screening program. The rate of suspected cancer was higher in PET/CT combined with other screening examinations than dedicated PET combined with other screening examinations. From the result of suspected cancer according to the interpretation of FDG-PET and/or combined screening examinations, the estimated rate of suspected cancer was higher with PET/CT than PET. As a result, PET/CT increased the rate of suspected cancer, but this was not associated with any specific type of cancer.
The age-specific incidence of cancer shows a sudden rise after 60 years of age in Japan based on the report from the Foundation for Promotion of Cancer Research (FPCR) . The number of FDG-PET cancer screening programs is highest for subjects aged 50–59 years (33.2 % of all subjects), and the incidence of cancer increases with age. Subjects receiving FDG-PET cancer screening are younger than the reported age groups with the most frequent incidence of cancer. The number of malignant neoplasms found by the FDG-PET cancer screening program is higher than the age-matched annual incidence of cancer in Japan. The distinctive feature of FDG-PET cancer screening is that it can detect various kinds of cancers, including cancers with unestablished organized screening methodologies. Moreover, the majority of found cancers were of Stage I, with expected good prognoses with existing treatment methods. The incidence of cancer in this survey is similar to those in several reports from single or multicenter facilities [3, 5, 8, 9, 10, 11, 12, 13], indicating that PET cancer screening is conducted with a considerable level of consistency throughout Japan. Detection rates with FDG-PET cancer screening are higher than the total detection rates of other cancer screening modalities performed in Japan (such as chest radiography and sputum cytology, mammography with inspection and palpation of breast, upper gastrointestinal fluoroscopy, FOBT, and uterine cervical cytology), which have already proven cancer screening efficacy . Terauchi et al.  reported strict limitations of FDG-PET for cancer screening based on data from the Research Center for Cancer Prevention and Screening (RCCPS) and National Cancer Center in Japan, which were particularly notable in screening for colon cancer, lung cancer and gastric cancer. All found lung cancers were categorized as Stage I, and most found colon cancers were localized in the intramucosal layer. The results of the present report indicate that cancer screening by PET examination alone was limited to small and/or early cancers; therefore, combined examinations to detect cancers missed by FDG-PET is mandatory. On the other hand, combined examinations are associated with an increased number of false positives, and can lead to an increase in unnecessary further examinations and follow-up. Combined screening tests must be specific for a particular cancer. FDG-PET cancer screening is not a completely established method for cancer screening. FDG-PET cancer screening should be used with a sufficient explanation and adequate understanding of its advantages, disadvantages and limitations.
One problem is the appropriate time interval for conducting FDG-PET cancer screening. The present results show that cancer was found in 22.9 % of suspected cancer cases in which repeated annual FDG-PET cancer screening tests were performed. Although most cancers found in the repeated annual FDG-PET cancer screening tests were Stage I, the cancer detection rate was not low. Estimated from the data of the HIMEDIC Imaging Center at Lake Yamanaka, cancer was found in 1.58 % of cases at the first screening, and in 1.18 % of cases at the second screening, but only in 0.69 % of cases in the third screening. The detection rate was estimated to decrease in PET examinations, but was stable in the combined screening test at a rate of approximately 0.2 % . The present results showed that cancer at Stage I was frequently found by FDG-PET cancer screening, with a high sensitivity of FDG-PET for both the first and repeated examinations. These results highlight the limitation of a one-time FDG-PET cancer screening program, and that two consecutive screenings followed by a combined screening test may be able to detect more malignancies. Among subjects who underwent a repeated FDG-PET cancer screening program, Stage III and IV cancers comprised 11.4 % of the found cancers. Found cancers in a repeated FDG-PET screening program may be interpreted as negative on the first time examination or show a rapid onset within 1 year. It is absolutely clear that the FDG-PET cancer screening program cannot detect all malignancies.
The main issue for FDG-PET cancer screening will be how it can detect various cancers and reduce their mortality rate. FDG-PET cancer screening detected many prostate cancers and thyroid cancers, which are associated with relatively long survival times. In contrast, FDG-PET cancer screening programs detected pancreas cancer at an early clinical stage , but the high mortality rate of even early-stage pancreas cancer means that the FDG-PET cancer screening program may be non-contributory for this tumor. Although a randomized control study is a maximally efficient method for showing the benefit of FDG-PET cancer screening, it requires a long observation time and a large population. The United States Preventive Services Task Force (USPSTF) advocated an “analytic framework” consisting of chain logic of evidence supporting a connection between the preventive service and improved health outcomes . As a result, the value of FDG-PET cancer screening might be indirectly estimated by detailed analysis of found cancers compared to the known epidemiological trend of cancer. Moreover, decision modeling analysis may also have the potential to clarify the clinical benefit of a PET cancer screening program , even though direct evidence such as reduction of mortality is essential.
Radiation exposure is a major problem in FDG-PET cancer screening. According to the International Commission on Radiation Protection (ICRP), the estimated cancer incidence induced by radiation exposure was 0.0048 % per mSv . Murano et al. reported that the average effective dose of radiation exposure in a PET center is estimated to be 4.4 mSv with a dedicated PET study and 14.2 mSv with a PET/CT study. The average radiation exposure associated with FDG-PET cancer screening will increase because of the increasing availability of PET/CT scanners. Risk–benefit analysis has shown that FDG-PET cancer screening is beneficial for examinees above the break-even ages based on a Japanese nationwide survey. However, that survey mentioned that the risks and benefits of radiation exposure must be explained to examinees because of the larger radiation dose used in cancer FDG-PET screening compared with other radiological tests .
The high cost of an FDG-PET cancer screening program is another huge problem. Effective combined screening tests, at the minimum, for compensating for FDG-PET should be selected as a screening program, which can lead to a lower cost and burden on the recipients of such screening. Although the cost of FDG-PET in Japan is lower than that in the United States ($1,000 vs. $2,000, respectively) [1, 19], it is still far higher than that of a screening examination covered by health insurance plans. Therefore, cost effectiveness is not expected in an FDG-PET cancer screening program. If maximum cost effectiveness is required for an FDG-PET cancer screening program, the program should target a group at high risk for a cancer that is commonly detected by PET and PET/CT. Otherwise, the value of a FDG-PET cancer screening program is left to the judgment of the individual provided that the advantages, disadvantages and limitations of FDG-PET for cancer screening are fully disclosed.
Beside malignancies, many benign lesions were found with the FDG-PET cancer screening program. They are regarded as false positive cases. However, colonic adenoma has the potential for malignant transformation [20, 21], and screening and removal of adenomatous polyps are significant aspects of prevention and improvement of prognosis. The clinical importance of screening for adenomas is to detect advanced adenomas (defined as larger adenomas with a diameter of 10 mm or more). The sensitivity of FDG-PET for detecting adenomas depends on their size and histologic grade [22, 23]. Thus, FDG-PET has a high potential of detecting adenomas that should be removed and suggesting the need for further examinations such as colonoscopy. Moreover, some non-malignant diseases (such as tuberculosis, inflammatory changes of the lung, and sarcoidosis) are also clinically important, and in some instances, early detection may enhance the quality of life and longevity. Therefore, FDG-PET screening may provide an opportunity to favorably alter the prognosis in various cases.
A limitation of this survey is inadequate investigation of subjects who were judged to be negative in the FDG-PET cancer screening program. Also, the present survey received inadequate answers from subjects who were judged as having possible malignancy by the FDG-PET cancer screening program, even though proven malignancies appeared to be obtained more frequently.
The FDG-PET screening program in Japan has detected a variety of cancers at an early stage. However, several cancers were found in repeated FDG-PET cancer screening program, indicating an important limitation of a one-time FDG-PET cancer screening program. The value of the FDG-PET cancer screening program is left to the judgment of individuals with regard to its potentials and limitations.
This work was supported by the National Cancer Center Research and Development Fund 23-A-25, Japanese Council of PET Imaging: working group on epidemiology study for PET cancer screening, the PET cancer screening research group of "Yokohama City University". The authors would like to express our sincere appreciation and gratitude for Sachiko Yanagida from Japan Radioisotope Association for management of this survey and data, and Yoshihide Nakamura from Japan Radioisotope Association for management of this survey.
Conflict of interest
The authors declare no conflict of interest.
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