The role of tumour biomarkers in choosing the appropriate positron emission tomography imaging in follow‐up of medullary thyroid cancer

We aimed to demonstrate the importance of serum calcitonin (Ct) and carcinoembryonic‐antigen (CEA) levels in the selection of appropriate positron emission tomography/computed tomography (PET/CT) modality in the follow‐up of operated patients with medullary thyroid cancer. Methods Fourteen operated patients (8 Female, 6 Male) with MTC underwent PET/CT imaging with somatostatin ( 68 Ga‐DOTATATE) and glucose ( 18 FDG) analogs due to elevated Ct or CEA at follow‐up. Ct and CEA levels and both PET/CT findings were compared based on both patients and lesions. Results Positive findings were found in 10 patients with 68 Ga‐DOTATATE‐PET/CT and in 8 patients with 18 FDG‐PET/CT, and sensitivity was found as 71.4% and 57.1% for both imaging methods, respectively ( P  > 0.05). Lesion could be detected with 68 Ga‐DOTATATE‐PET/CT in 3 patients in whom lesion could not be detected with 18 FDG‐PET/CT. In one patient, whereas no pathological lesion was with 68 Ga‐DOTATATE‐PET/CT, lesion could be detected with 18 FDG‐PET/CT in this patient. Of the total 67 lesions, 62 could be shown with 68 Ga‐DOTATATE‐PET/CT, while 48 lesions could be detected with 18 FDG‐PET/CT ( P  < 0.05). A statistically significant positive correlation was found between Ct level and the number of lesions detected on the 68 Ga‐DOTATATE‐PET/CT, and similarly between CEA level and the number of lesions detected on the 18 FDG‐PET/CT. Conclusions It was found that 68 Ga‐DOTATATE‐PET/CT is superior over 18 FDG‐PET/CT method in detection of recurrent disease in the follow‐up of MTC, and serum Ct and CEA levels are important biomarkers in the selection of appropriate PET/CT modality.