Postoperative Radiotherapy in the Management of Advanced or Recurrent Differentiated Thyroid Cancer

Abstract

To evaluate outcome and prognostic factors of postoperative radiotherapy for differentiated thyroid cancer (DTC).In this retrospective study, 80 patients who received postoperative radiotherapy for DTC from January 2000 to December 2019 were analyzed. The median follow-up duration was 7.5 years (range, 0.6-18.7 years).Thirty-three (41.3%) patients had recurrent tumor and 21 (26.3%) patients still had gross disease even after radical surgery. Cervical node metastasis was present in 54 (67.5%) patients, while 7 (8.75%) patients were presented with distant metastasis. The median total dose and fraction size were 63.0 Gy and 2.0 Gy, respectively. The 5-year locoregional recurrence free survival (LRFS) was 80.7% and the five-year overall survival (OS) was 89.1%. Multivariate analysis showed age ≥ 55 (HR 6.11; 95% CI 1.51-25.25), male (HR 3.22; 95% CI 1.02-11.11), gross residual disease after surgery (HR 2.80; 95% CI 1.01-7.77) and esophageal invasion (HR 5.50; 95% CI 1.38-21.93) were significantly associated with worse LRFS. However, only the age ≥ 55 (HR, 1.10; 95% CI, 1.03-1.18) and the presence of gross residual disease (HR, 4.56; 95% CI, 1.02-20.31) were significant prognostic factors for OS. No severe toxicity was reported.Postoperative radiotherapy can be one of the feasible and safe modalities for advanced or recurrent DTC, since the locoregional control was comparable to other studies despite unfavorable clinicopathologic elements of the study population. The age ≥55 and gross residual disease significantly affect both locoregional control and overall survival. However, due to the lack of a control in this study, there is a limitation to definitely confirm the efficacy of adjuvant RT and therefore a further study is necessary to find those who can benefit from it.