Abstract: Objective To evaluate the clinical results and adverse of external beam radiation therapy (EBRT) on relapse/metastases thyroid carcinoma. Methods A prospective cohort of 64 patients was treated between January 2008 and January 2018 with EBRT. All patients were diagnosis with surgery, 45 females and 19 males, median age was 61 years old. Pathology characters included:34 papillary thyroid carcinoma, 13 follicular thyroid carcinoma, 7 medullary carcinoma and 6 undif-ferentiated thyroid cancer. EBRT use 6MV-X, three-dimensional conformal or intensity modulated radiotherapy, relapse lesions were treated with the total dose and per-friction dose with 50.4Gy-60Gy, 1.8-2Gy/f, metastases lesions were treated according to clinical decision(bone lesions 24-50Gy/6-25f, 2-4Gy/f, brain, lung or liver lesions 48-64Gy/7-8f, 6-8Gy/f(under image-guided radiotherapy). The RECIST 1.1 standard was used to assess the EBRT on 40 evaluable lesions efficiency, the NRS（numerical rating scale） was used to assess pain, response rates to radiotherapy were calculated following the criteria of NRS, accounting for the use of concomitant analgesics. Meanwhile the TG change rate and clinical adverse were also reported. Results 1)40 evaluable lesions of relapse or metastases showed disease control at 1 month(DCR 90.62%), 2)the mean NRS score before treatment was 7.65±0.67, and pain score were reduced to 4.36±1.09 after one month and 2.15±1.28 after three months. NRS-based response categories ranged from 75% to 91.67% respectively, p<0.05. 3)The medium downgrade level of TG-Ab for differential thyroid cancer patients was 56%(0%-99%), all patients showed no serious adverse judging by CTC-3. Conclusion EBRT is a valid option for relapse/metastases thyroid patients with endurable side effects, could be an effective treatment option for clinical trail.

Key words: Thyroid carcinoma, relapse cancer, metastases cancer, EBRT, clinical effect.