Clinical value of 68Ga-DOTATATE PET/CT in the evaluation of recurrent medullary thyroid cancer patients.

Objectives Medullary thyroid cancer (MTC) represents an imaging challenge for nuclear medicine with many PET and SPECT radiopharmaceuticals evaluated with varying success. It is known that these tumors express somatostatin receptors (SSTR). Thus, the objective of this study was to assess the clinical value of 68Ga-DOTATATE PET/CT in the identification of recurrent disease. As a secondary objective we proposed to study the technique's value for detecting multi organ disease in patients with MEN syndromes (multiple endocrine neoplasia).

Methods We retrospectively studied 17 patients with MTC (13 women; age: 47.3±15.9 yr), who had been previously treated with neck surgery, with high levels of serum calcitonin (median: 720 pg/mL, ranging from 12.3 to 12900 pg/mL). Scans were performed after the injection of 66-178 MBq of 68Ga-DOTATATE with a PET/CT equipped with a CT component of 64 rows. Images were reconstructed by an iterative algorithm (OSEM) with time of flight correction (TOF). Two blinded and independent readers assessed all images. Findings were confirmed by histopathology (n=8) and/or conventional imaging and clinical follow up (median interval: 38.5 months; range: 8 to 65 months).

Results 68Ga-DOTATATE PET/CT was positive in 15 patients (88%). Of these patients, 12 showed locoregional and/or distant disease (80%). Compared to previous conventional images, additional lesions were found in 4 of these patients. In the remaining 3 patients (20%), the study only showed tumor involvement of a second associated endocrine organ. These cases corresponded to adrenal disease related to pheochromocytoma (MEN II syndrome). Besides, the two negative patients presented during follow up persistently high calcitonin levels despite negative clinical and conventional imaging findings. Considering the total patient sample, 68Ga-DOTATATE PET/CT led to a management change in 10 cases (59%).

Conclusions Our results suggest that 68Ga-DOTATATE PET/CT is a clinically relevant technique for therapeutic planning of patients with recurrent MTC either in sporadic cases or in those with multi organ neoplasia.