The role of postoperative external-beam radiotherapy in the management of patients with papillary thyroid cancer invading the trachea

Purpose: To determine the role of adjuvant external-beam radiotherapy (EBRT) in the management of patients with well-differentiated thyroid cancer invading the trachea. Methods and Materials: Of 1,098 thyroid cancer patients, 68 (6%) were found to have tracheal invasion, and they all received "shave" excision of the tracheal cartilage. Among them, 12 patients had no postoperative residuum, 43 patients had microscopic residuum, and 13 patients had macroscopic residuum. All patients were divided into two groups according to treatment modality with or without EBRT; (1) the control group (n = 43) and (2) the EBRT group (n = 25). Results: The locoregional recurrence rate for EBRT patients was much lower than that of control patients (51% for the control group vs. 8% for the EBRT group) (p < 0.01). The 10-year local progression-free survival rate for the EBRT group was significantly better than that of the control group (89% in the EBRT group vs. 38% in the control group) (log-rank, p < 0.01). The use of adjuvant EBRT after conservative surgery was an independent prognostic factor in univariate and multivariate analyses. Conclusions: External-beam radiotherapy was found to be effective, particularly in patients with thyroid cancer invading the trachea with microscopic or gross residuum after conservative surgery.