Comparison of sequential planar 177Lu-DOTA-TATE dosimetry scans with 68Ga-DOTA-TATE PET/CT images in patients with metastasized neuroendocrine tumours undergoing peptide receptor radionuclide therapy
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The aim of the study was to compare sequential 177Lu-DOTA-TATE planar scans (177Lu-DOTA-TATE) in patients with metastasized neuroendocrine tumours (NET) acquired during peptide receptor radionuclide therapy (PRRT) for dosimetry purposes with the pre-therapeutic 68Ga-DOTA-TATE positron emission tomography (PET)/CT (68Ga-DOTA-TATE) maximum intensity projection (MIP) images obtained in the same patients concerning the sensitivity of the different methods.
A total of 44 patients (59 ± 11 years old) with biopsy-proven NET underwent 68Ga-DOTA-TATE and 177Lu-DOTA-TATE imaging within 7.9 ± 7.5 days between the two examinations. 177Lu-DOTA-TATE planar images were acquired at 0.5, 2, 24, 48 and 72 h post-injection; lesions were given a score from 0 to 4 depending on the uptake of the radiopharmaceutical (0 being lowest and 4 highest). The number of tumour lesions which were identified on 177Lu-DOTA-TATE scans (in relation to the acquisition time after injection of the therapeutic dose as well as with regard to the body region) was compared to those detected on 68Ga-DOTA-TATE studies obtained before PRRT.
A total of 318 lesions were detected; 280 (88%) lesions were concordant. Among the discordant lesions, 29 were 68Ga-DOTA-TATE positive and 177Lu-DOTA-TATE negative, whereas 9 were 68Ga-DOTA-TATE negative and 177Lu-DOTA-TATE positive. The sensitivity, positive predictive value and accuracy for 177Lu-DOTA-TATE as compared to 68Ga-DOTA-TATE were 91, 97 and 88%, respectively. Significantly more lesions were seen on the delayed (72 h) 177Lu-DOTA-TATE images (91%) as compared to the immediate (30 min) images (68%). The highest concordance was observed for bone metastases (97%) and the lowest for head/neck lesions (75%). Concordant lesions (n = 77; mean size 3.8 cm) were significantly larger than discordant lesions (n = 38; mean size 1.6 cm) (p < 0.05). No such significance was found for differences in maximum standardized uptake value (SUVmax). However, concordant liver lesions with a score from 1 to 3 in the 72-h 177Lu-DOTA-TATE scan had a lower SUVmax (n = 23; mean 10.9) than those metastases with a score of 4 (n = 97; mean SUVmax 18) (p < 0.05).
Although 177Lu-DOTA-TATE planar dosimetry scans exhibited a very good sensitivity for the detection of metastases, they failed to pick up 9% of lesions seen on the 68Ga-DOTA-TATE PET/CT. Three-dimensional dosimetry using single photon emission computed tomography/CT could be applied to investigate this issue further. Delayed (72 h) images are most suitable for drawing regions of interest for dosimetric calculations.
Keywords177Lu-DOTA-TATE Dosimetry scan 68Ga-DOTA-TATE Neuroendocrine tumour
The authors would like to thank the nursing and technician staff in the Bad Berka Zentralklinik for their technical assistance. We would also like to thank all supporting personnel of the radiopharmacy department for their expert help and effort. We are grateful for the support from the coworkers of the Department of Nuclear Medicine/PET Centre, Bad Berka, Germany. All of the patients included in this study were enrolled in the Department of Nuclear Medicine/PET Centre, Bad Berka, Germany. Image acquisition, patients’ therapeutic management and follow-up were also performed in the Department of Nuclear Medicine/PET Centre, Bad Berka, Germany. Aurora Sainz-Esteban performed this study during a European programme of internship abroad between the Zentralklinik Bad Berka (Bad Berka, Germany) and the Hospital Universitario Marqués de Valdecilla (Santander, Spain).
Each author has contributed significantly to the submitted work. Aurora Sainz-Esteban contributed to the conception and design of the study, acquired, analysed and interpreted the data and wrote the manuscript. Vikas Prasad contributed to the conception and design of the study, performed the PET/CT and the dosimetry studies, analysed the data and critically revised and approved the final manuscript. Christiane Schuchardt and Carolin Zachert performed the dosimetry studies and critically read the manuscript. José Manuel Carril critically revised and approved the final manuscript. Richard Paul Baum conceived the study, performed the PET/CT and dosimetry studies and critically revised and approved the final manuscript.
Conflicts of interest
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