Objective: The clinical course of patients with medullary thyroid carcinoma (MTC) is variable, even in the subgroup of patients after surgery with curative intent and postoperatively persistent elevated calcitonin levels. This study aimed to evaluate the long-term prognosis of survival in patients with MTC.
Patients: Long-term survival was analysed in 32 patients with MTC being treated in an endocrine centre over a 40-year period. Patients were classified as having sporadic MTC, familial MTC (FMTC), multiple endocrine neoplasia (MEN) IIA or MEN IIB.
Results: Seventeen patients had sporadic MTC (53.1%), eight had MEN IIA (25%) and three had MEN IIB (9.4%); the remaining four patients (12.5%) had not undergone genetic analysis until now. The overall average age at diagnosis was 42.0 years, and the median follow-up time was 9.5 years (range 0.5-39 years). Mortality due to progressive MTC was 15.6%. The 5-year survival rate was 96% (95% CI 89-100), the 10-year survival rate 91% (95% CI 79-100), and the 15-year survival rate 85% (95% CI 78-100). The estimated mean survival time after initial diagnosis was 31 years (95% CI 26.7-37.0). There is a significant difference in survival time between patients achieving complete remission compared with patients with biochemical persistent disease (P = 0.038) or metastasis (P = 0.0003). In five patients, advanced imaging with positron emission tomography/computed tomography (PET/CT) identified additional sites of tumour load. Eight more lymph node metastases were found in four patients and one local tumour recurrence in one patient by PET/CT.
Conclusion: The overall prognosis of MTC is favourable, even if the rate of biochemical cure is lower in MTC than in differentiated types of thyroid cancer. This is also true for patients with biochemically persistent disease. Whether the identification of further tumour sites by advanced imaging procedures such as PET/CT translates into a better prognosis in patients with persistently elevated calcitonin levels remains to be investigated.