Prospective comparison of (68)Ga-DOTATATE and (18)F-FDOPA PET/CT in patients with various pheochromocytomas and paragangliomas with emphasis on sporadic cases.

PURPOSE: Pheochromocytomas/paragangliomas (PHEOs/PGLs) overexpress somatostatin receptors and recent studies have already shown excellent results in the localization of these tumors using (68)Ga-labeled somatostatin analogs ((68)Ga-DOTA-SSA), especially in patients with germline succinate dehydrogenase subunit B gene (SDHB) mutations and head and neck PGLs (HNPGLs). The value of (68)Ga-DOTA-SSA has to be established in sporadic cases, including PHEOs. Thus, the aim of this study was to compare (68)Ga-DOTATATE PET/CT, (18)F-FDOPA PET/CT, and conventional imaging in patients with various PHEOs/PGLs with a special emphasis on sporadic cases, including those located in the adrenal gland. DESIGN: (68)Ga-DOTATATE, (18)F-FDOPA PET/CT, and conventional imaging (contrast-enhanced CT and MRI with MR angiography sequences) were prospectively performed in 30 patients (8 with SDHD mutations, 1 with a MAX mutation and 21 sporadic cases) with PHEO/PGL at initial diagnosis or relapse. RESULTS: The patient-based sensitivities were 93 % (28/30), 97 % (29/30), and 93 % (28/30) for (68)Ga-DOTATATE PET/CT, (18)F-FDOPA PET/CT, and conventional imaging, respectively. The lesion-based sensitivities were 93 % (43/46), 89 % (41/46), and 76 % (35/46) for (68)Ga-DOTATATE PET/CT, (18)F-FDOPA PET/CT, and conventional imaging respectively (p = 0.042). (68)Ga-DOTATATE PET/CT detected a higher number of HNPGLs (30/30) than (18)F-FDOPA PET/CT (26/30; p = 0.112) and conventional imaging (24/30; p = 0.024). (68)Ga-DOTATATE PET/CT missed two PHEOs of a few millimeters in size and a large recurrent PHEO. One lesion was considered false-positive on (68)Ga-DOTATATE PET/CT and corresponded to a typical focal lesion of fibrous dysplasia on MRI. Among the 11 lesions missed by conventional imaging, 7 were detected by conventional imaging with knowledge of the PET results (4 HNPGLs, 2 LNs, and 1 recurrent PHEO). CONCLUSION: (68)Ga-DOTATATE PET/CT is the most sensitive tool in the detection of HNPGLs, especially SDHD-related tumors, which may be very small and fail to concentrate sufficient (18)F-FDOPA. The present study further expands the use of (68)Ga-DOTATATE for all patients with HNPGLs, regardless of their genotype. (68)Ga-DOTATATE PET/CT may be inferior to (18)F-FDOPA PET/CT in the detection PHEOs.

(18)F-DOPA PET/CT in the diagnosis and localization of persistent medullary thyroid carcinoma.

PURPOSE: To evaluate the performance of (18)F-L-dihydroxyphenylalanine ((18)F-DOPA) PET/CT in the detection of locoregional and distant medullary thyroid carcinoma (MTC) metastases and to compare imaging findings with histological data. METHODS: We retrospectively evaluated 86 MTC patients with persistently high serum calcitonin levels after initial surgery who had undergone (18)F-DOPA PET/CT between January 2007 and December 2014 in two referral centres. They were followed up for at least 6 months after the PET/CT assessment. The results were compared with histological data or with the findings obtained during follow-up using a complementary imaging modality. RESULTS: (18)F-DOPA PET/CT was positive in 65 of the 86 patients, corresponding to a patient-based sensitivity of 75.6 %. Distant metastatic disease (M1) was seen in 29 patients including 11 with previously unknown metastases revealed only by PET/CT. Among the 36 patients without distant metastatic spread, 25 had nodal involvement limited to the neck, and 10 of these 25 patients underwent reoperation. The lymph node compartment-based sensitivity of (18)F-DOPA PET/CT was 100 % in the two institutions but lesion-based sensitivity was only 24 %. Preoperative and postoperative median calcitonin levels were 405 pg/mL (range 128 - 1,960 pg/mL) and 259 pg/mL (range 33 - 1,516 pg/mL), respectively. None of the patients achieved normalization of serum calcitonin after reoperation. CONCLUSION: (18)F-DOPA PET/CT enables early diagnosis of a significant number of patients with distant metastasis. It has a limited sensitivity in the detection of residual disease but provides high performance for regional analysis. A surgical compartment-oriented approach could be the approach of choice whatever the number of nodes revealed by (18)F-DOPA PET/CT.