Postoperative radiotherapy improves survival of patients with ypN2 non-small cell lung cancer after neoadjuvant chemotherapy followed by surgery - A propensity score matching study of the Surveillance, Epidemiology, and End Results database.

Background: For patients with ypN2 non-small cell lung cancer (NSCLC) after neoadjuvant chemotherapy followed by surgery (NCS), the role of postoperative radiotherapy (PORT) is unclear. The aim of our study was to evaluate the effect of PORT on survival of ypN2 NSCLC patients after NCS.

Methods: Between 2004 and 2015, patients with ypN2 NSCLC after NCS were filtrated from the Surveillance, Epidemiology, and End Results (SEER) database. Propensity score matching (PSM) was used to balance the baseline characteristics of the PORT and non-PORT groups. Kaplan-Meier method and Cox proportional hazards models were adopted to estimate overall survival (OS) and cancer-specific survival (CSS).

Results: A total of 257 patients who met the criteria were included in the study. After PSM, 115 patients remained in each group. The survival of patients in the PORT group was significantly better than those in the non-PORT group. Median OS was 36 months vs. 26 months, and 5-year OS rate was 40.5% vs. 21.0% (p = 0.002). The median CSS was 38 months vs. 27 months, and the 5-year CSS rate was 43.7% vs. 22.1% (p < 0.001). Multivariable analysis showed that PORT was an independent prognostic factor for OS (HR = 0.59, 95% CI: 0.43-0.82, p = 0.001) and CSS (HR = 0.56, 95% CI: 0.41-0.78, p = 0.001). Subgroup analysis showed that patients in the following subgroups could benefit from PORT: age ≤ 70, diagnosed in the later period (2010-2015), white race, squamous cell carcinoma, grade III-IV, lobectomy, stage T3-4, or with positive regional nodes ≤3 or > 3.

Conclusions: For patients with ypN2 NSCLC after NCS, PORT significantly improves OS and CSS. These results need to be confirmed by further randomized studies.