External beam radiotherapy for differentiated thyroid cancer.

PURPOSE: To evaluate the efficacy of external beam radiation therapy (EBRT) for differentiated thyroid carcinomas.

METHODS: Forty-two patients with a locally advanced or recurrent differentiated thyroid carcinoma received high-dose EBRT. Thirty-three patients had local-regional disease and 9 patients also had asymptomatic disease metastases. Twenty patients (48%) had macroscopic local-regional disease before EBRT.

RESULTS: The 5-year outcomes for the overall population and for the subset of those without distant metastases before EBRT were local-regional control (88% and 89%, respectively), cause-specific survival (80% and 86%, respectively), and overall survival (54% and 60%, respectively). Local-regional control was improved for patients with microscopic residual disease compared with macroscopic disease, those with previously untreated tumors, and for those who received more than 64 Gy.

CONCLUSION: EBRT increases the likelihood of local-regional control for patients with locally advanced differentiated thyroid carcinoma.