Postoperative Radiation Therapy Has No Effect in Improving the Survival of Patients Aged ≤55 Years with Completely Resected Pathological Stage IIIA-N2 Non-Small-Cell Lung Cancer

Abstract

For patients with completely resected pathological stage IIIA–N2 non-small cell lung cancer (NSCLC), studies has shown that postoperative radiotherapy (PORT) does not improve survivals of elderly patients (＞65 years). However, the role of PORT for younger patients is not well defined. This study is to evaluate the effect of PORT on survivals as well as tumor control in patients ≤65 years. Between Jan. 2003 and Dec. 2015, patients, ≤65 years, with pIIIA–N2 NSCLC after complete resection in our single institution were retrospectively analyzed. The effect of PORT on overall survival (OS), disease free survival (DFS), loco-regional recurrence free survival (LRFS), and distant metastasis free survival (DMFS) was evaluated with Kaplan-Meier method and log-rank test. Multivariable Cox regression analysis was used to identify independent risk factors for death. Pearson chi-square test was used to compare the constituent ratios between groups. Propensity score-matched (PSM) analysis was conducted to generate comparable study arms. Statistically significant difference was set as p<0.05. Overall, 940 consecutive patients ≤65 years were enrolled. The median follow-up was 31.1 months. The median age was 55 years (range, 25–65 years). The characteristics were comparable between the PORT group and non-PORT group, except that more patients with ≥4 positive lymph nodes and receiving chemotherapy in the PORT group. The 3- and 5-year OS rates were 75.3% and 63.1%, respectively, in the PORT group, which were statistically significantly higher than 68.2% and 53.3% in the non-PORT group (p=0.023). The differences between the two groups were also significant in the DFS and LRFS rates (p=0.006 and 0.000, respectively), but not in the DMFS rate (p=0.062). After adjustment by PSM, PORT still resulted in significantly better survivals of OS, DFS, LRFS and DMFS than non-PORT group (p=0.009, 0.000, 0.000 and 0.000, respectively). Then patients were divided into younger group (≤50 years, n=269), middle-age group (51-55 years, n=218) and older group (56-65 years, n=453). PORT significantly improved the OS in the older group, The 3- and 5-year OS rates were 75.8% and 59.1% in the PORT group vs. 61.5% and 45.7% in the non-PORT group, respectively (p=0.019). The OS was not improved by PORT in the younger or middle-age groups (p=0.859 and 0.524, respectively). When the patients in the younger and middle-age groups was merged together (≤55 years), the OS was not improved by PORT neither (p=0.626). In multivariable analysis, PORT was not significantly associated with better prognosis of patients ≤55 years old (p=0.902). For patients with completely resected pIIIA–N2 NSCLC, PORT can significantly improve the OS of patients aged 56-65 years, but not in patients aged ≤55 years. The result needs to be validated in the future study.