Clinically unpredictable prognostic factors in the outcome of medullary thyroid cancer.

Total thyroidectomy and central neck dissection are the procedures of choice in patients affected with medullary thyroid cancer. It is known that a medullary thyroid cancer with node metastases can be rarely cured, and therefore the utility of a modified radical neck dissection in the absence of suspicious node metastases still needs further evidence. The study aims to verify whether other epidemiological and pathological parameters could affect the prognosis of medullary thyroid cancer patients. We prospectively studied 70 medullary thyroid cancer patients consecutively operated on (from 2000 to 2004) at the same institution and analysed by the same pathologists. All patients underwent total thyroidectomy and central lymphadenectomy. In 27 cases, the ipsilateral (n=19) or bilateral (n=8) modified radical neck dissection was performed in the presence of suspicious lateral neck node metastases. After surgical treatment, basal and stimulated serum calcitonins (Cts) were measured in all patients. Follow-up ranged between 1 and 4 years. Patients were considered 'cured' when stimulated Ct was undetectable. Age, sex, tumour size, tumour capsule, multicentricity, nodes in the central neck and mean number of positive nodes were analysed in 'cured' and 'not-cured' patients. The presence of node metastases in the central compartment was significantly correlated with the outcome of the patients, being present in 9 and 72% of cured and not-cured patients respectively (P<0.000001). Tumour size was also significantly correlated with the outcome of the disease (P<0.00006). The presence of the tumour capsule correlated with better prognosis (P=0.0005) and absence of node metastases (P=0.0080). By multivariate analysis, the presence of node metastasis remained the most significant variable affecting the outcome of the disease (P=0.000014). Our results show that the outcome of encapsulated cancer is significantly better regardless of tumour size and node metastases. Although the early diagnosis and the extensive surgical treatment may favour the good outcome of medullary thyroid cancer, they do not always guarantee the definitive cure of the disease, being the capsular infiltration an independent bad prognostic factor.