Adjuvant external beam radiation for medullary thyroid carcinoma

BACKGROUND: Adjuvant radiation is rarely used to treat medullary thyroid carcinoma (MTC). We hypothesized that external beam radiation therapy (EBRT) would improve overall survival (OS) in MTC patients. METHODS: The Surveillance, Epidemiology, and End Results (SEER) database identified patients who underwent total thyroidectomy and lymph nodes excision for MTC between 1988 and 2004. The Kaplan-Meier method was used for univariate comparisons of OS. Multivariate Cox proportional hazards models controlled for gender, age, lymph node status, tumor size, extent of disease, and EBRT. RESULTS: After 12 years, EBRT did not significantly improve OS (log rank, P < 0.14). In node-positive patients, univariate analysis demonstrated an OS benefit with EBRT (log rank, P < 0.05). In a multivariate model of node-positive patients, only increasing age (P < 0.001) and tumor size (P < 0.001) significantly influenced OS. CONCLUSIONS: The OS benefit attributed to EBRT in node-positive patients by univariate analysis could not be duplicated when controlling for known prognostic factors.