Prognostic Variables Affecting Primary Treatment Outcome for Medullary Thyroid Cancer

Abstract

Identifying prognostic risk factors and determining the efficacy of common surgical treatments is critical to determine optimal treatment strategies for patients with medullary thyroid carcinoma (MTC). The objective of this study was to review a contemporary institutional experience with MTC primary treatment with 2 goals: to identify prognostic factors that impact survival and to study the effect of neck dissection on those outcomes. This study was a retrospective case series of patients with MTC who underwent at least a total thyroidectomy with curative intent. Clinical parameters including tumor and nodal staging with corresponding pathology findings were identified. Survival endpoints included overall survival, disease-free survival, and biochemical cure. Sixty-seven patients were included. The majority presented with early T-stage disease. Fifty (76%) patients were N0 at presentation. Seventeen (24%) had some evidence of neck disease on clinical examination or imaging. Forty (71%) achieved biochemical cure, and the 5-year biochemical recurrence-free survival for those cases was 86.5%. Among patients who had successful resection of all gross disease, 92% had no evidence of structural disease at 5 years. Overall survival was 91% at 5 years. Increased pre-operative calcitonin (Ct) level, primary tumor size, extrathyroidal extension, and neck metastases decrease the rate of biochemical cure. Larger tumor size increases the risk of structural disease recurrence and biochemical relapse after initial cure. The presence and number of neck metastases correlate with biochemical relapse. The presence of lateral neck nodes (pN1b) does not have different survival implications than centrally confined disease (pN1a). This study shows increasing tumor size, increased Ct level, and cervical metastases are poor prognostic factors. Patients with large tumors, high Ct level, or unfavorable pathologic findings may warrant more aggressive initial treatment, although limitations of the study prevent any conclusion regarding the effect of neck dissection. ATA = American Thyroid Association BRFS = biochemical recurrence-free survival CND = central neck dissection Ct = calcitonin DFS = disease-free survival MTC = medullary thyroid carcinoma OR = odds ratio OS = overall survival pCND = prophylactic CND.