Postoperative radiotherapy for advanced medullary thyroid cancer - local disease control in the modern era

Background. The purpose of this study is to catalog modern-era postoperative radiotherapy (external beam radiotherapy [EBRT]) outcomes for advanced medullary thyroid cancer. Methods. Thirty-four consecutive patients with stage IVa-c disease were evaluated. Ten patients had recurrent disease, 16 had mediastinal involvement, and 10 had distant metastasis. Positive surgical margins were present in 12 cases. Median pre-EBRT serum calcitonin was 556. All patients received conformal EBRT or intensity-modulated radiotherapy. Median EBRT dose was 60 Gy and median follow-up was 46.5 months. Results. Kaplan-Meier estimates of locoregional relapse-free survival, disease-specific survival, and overall survival at 5 years were 87%, 62%, and 56%, respectively. Disease in 3 patients with gross residual disease was controlled locoregionally. Distant disease at the time of EBRT did not predict survival. Two (9%) patients reported symptomatic chronic morbidity. Conclusion. Surgery followed by EBRT provided durable locoregional disease control with limited morbidity. Postoperative EBRT merits consideration in cases of advanced disease at high risk for locoregional recurrence.