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.