Excellent long-term control in locoregionally recurrent radioactive iodine-refractory papillary thyroid cancer with the addition of external beam radiation therapy to maximal surgical resection.

Abstract

e16035 Background: Locoregionally recurrent radioactive iodine (RAI) refractory papillary thyroid cancer represents a small percentage of papillary thyroid cancers but is an aggressive disease with significantly lower survival rates. This retrospective review is our experience with these cancers treated with maximal surgical resection followed by external beam radiotherapy. Methods: 26 patients treated from 2001-2011 were eligible for review. After obtaining IRB approval, medical records were reviewed for clinical outcome. All patients had histologically proven recurrences that were negative on I-131 scans. All patients were maximally resected. All patients received external radiotherapy to the thyroid bed, bilateral cervical lymph node levels II-IV, level VI, and superior mediastinal nodes. 15/26 patients received intensity modulated, 9/26 patients received 3-D conformal, and 2/26 patients received Tomotherapy radiation treatment. The mean dose was 5790 cGy (range 5280-6800 cGy). Results: All histologies were papillary thyroid cancer with 4/26 exhibiting tall cell features and 1/26 diffuse sclerosing features. All patients had locoregional relapse in the cervical nodes (16/26) or in the mediastinum (5/26) or both areas (5/26). The mean pre-treatment thyroglobulin was 5.2 (range <0.1 to 599.1). The mean post-treatment thyroglobulin was 1.0 (range <0.1-5.2). Median follow-up was 55 months (range 7-123 months). 0/26 patients failed locoregionally. 2/26 patients failed distantly (lungs). 20/26 patients (77%) of patients had undetectable thyroglobulin at last follow-up. 4/26 patients had detectable thyroglobulin (2.5-16.9), but had not recurred on imaging. 2/26 required PEG placement during treatment, but 0/26 patients were PEG-dependent on long-term follow-up. 1/26 patients experienced grade III osteoradionecrosis of the mandible. Conclusions: External beam radiotherapy provides excellent locoregional control for locoregionally recurrent radioactive iodine-refractory papillary thyroid cancers. Long-term grade III and IV toxicities are uncommon.