Role of Postoperative Radiotherapy in the Treatment of Adenoid Cystic Carcinoma of the Trachea and Bronchus with Positive Surgical Margin: Rethinking about the Resection Range

Abstract

Adenoid Cystic carcinoma (ACC) of the tracheobronchial tree is quite uncommon. The experience regarding their treatment and long-term outcome is limited. The aim of this study was to evaluate the role of postoperative radiotherapy in the treatment of ACC of the trachea and bronchus with positive surgical margin. Operated patients were enrolled in this study with pathologically confirmed trachea or bronchus ACC in Shanghai Chest Hospital. Clinical, pathologic and radiotherapeutic data were retrospectively reviewed. Survival analysis was performed using the Kaplan-Meier and log-rank tests. Multivariate analysis was performed using the Cox regression model. Meanwhile, the chi-square test was applied to analyze the failure pattern among different groups (R0/0: negative margin resection without postoperative radiotherapy; R1/0: positive margin resection without postoperative radiotherapy and R1/1: positive margin resection with postoperative radiotherapy). From January 2001 to December 2014, 77 patients were eligible for the study. The median follow-up time was 67 months (range, 16-203). The 5-year and 10- year OS rates in R0/0, R1/1, R1/0 patients were 100.0%, 98.9%, 90.0% and 85.7%, 89.9%, 59.1%, respectively(P = 0.086). Pairwise comparisons showed OS of group R1/1 was similar to group R0/0 (P = 0.438), although much better than group R1/0 (P = 0.032). The 5-year and 10- year local PFS rates in R0/0, R1/1, R1/0 patients were 85.9%, 98.0%, 78.8% and 43.0%, 98.0%, 33.8%, respectively (P = 0.003). Pairwise comparisons showed a difference between group R1/1 and R0/0 (P = 0.023) and between group R1/1 and R1/0 (P = 0.001). Cox multivariate analysis of patients with positive surgical margin identified the radiologic appearance (P = 0.012) and postoperative radiotherapy (P = 0.006) as significantly favorable prognostic factors for local PFS, and only postoperative radiotherapy as the corresponding variable for OS. Thirty-two patients had experienced recurrence by the end of follow-up, including local recurrence (n = 3), local recurrence with metastases (n = 5), pure pulmonary metastases (n = 16), pure bone metastases (n = 1) and multiple metastases (n = 7). Chi-square test suggested patients without postoperative radiotherapy were more prone to local recurrence than those received postoperative radiotherapy (P = 0.001). Similar outcome was not demonstrated for distant metastases (P = 1.000). For patients with positive surgical margin, postoperative radiotherapy can significantly prolong local PFS and OS, thus achieving similar survival to those with complete resection. Patients without postoperative radiotherapy are more likely to relapse instead of metastasize. These results suggest that postoperative radiotherapy provide an effective complement to operation with positive surgical margin. Appropriate resection range of ACC of trachea and bronchus should be rethinking.