External Beam Radiotherapy for Medullary Thyroid Cancer Following Total or Near-Total Thyroidectomy

Objectives: Medullary thyroid carcinoma (MTC) often presents with advanced disease and takes an aggressive course as compared with more well-differentiated thyroid cancers. The role of adjuvant therapy, specifically external beam radiotherapy (EBRT), remains disputed. This study investigated the impact of EBRT on survival in MTC. Study Design: Cross-sectional analysis of a national database. Setting: Patients with MTC were identified from the SEER program (Surveillance, Epidemiology, and End Results). Methods: Collected variables included age, sex, race, T and N stages, lymph node yield, and use of EBRT. Propensity score matching was performed to determine the association of EBRT with overall and disease-specific survival. Results: A total of 2046 patients with locoregional MTC were identified. Of these, 152 received EBRT. Patients receiving EBRT were older and had more advanced disease. EBRT was not associated with differences in overall survival (hazard ratio, 1.12; 95% CI, 0.76-1.65) or disease-specific survival (1.66; 0.93-2.95), as well as in subset analysis of age and disease extent. Long-term overall survival was similar, with 77.3% (95% CI, 70.1%-85.3%) and 58.3% (48.2%-70.5%) of patients without EBRT alive at 5 and 10 years, respectively (vs 70.7% [63.2%-79.1%] and 52.3% [43.3%-63.2%] of patients with EBRT). There were no differences in 5- and 10-year disease-specific survival. Conclusion: EBRT was not associated with improved overall or disease-specific survival in patients with MTC. Decisions regarding EBRT must be made with consideration of morbidity relative to benefit for individual patients.