Postoperative Radiation Therapy for Resected Stage IIIA-N2 Non-Small-Cell Lung Cancer: A Population Study from 1988 to 2014 Using the Surveillance, Epidemiology, and End Results Database

Abstract

The use of postoperative radiotherapy(PORT) after resection of stage IIIA-N2 non-small-cell lung cancer(NSCLC) remains controversial. Large real-world data studies are absent regarding the value of PORT across different time periods as all treatment methods develop. We explored the effects of PORT on the survival of patients with resected stage IIIA-N2 NSCLC and assessed the temporal changes spanning 27 years. Within the Surveillance, Epidemiology, and End Results Database, we selected stage IIIA-N2 NSCLC patients who underwent a lobectomy or pneumectomy and coded as receiving PORT or never receiving radiation therapy over three time periods: 1988 to 1996, 1997 to 2005, 2006 to 2014. For each period, survival rates were assessed with Kaplan-Meier method, log-rank test and multivariable hazard ratios were estimated from Cox proportional hazards models. A total of 5568 patients (718, 2020, 2830 in period 1, 2, 3 respectively) were included, 45.4% of which received PORT. The yearly PORT use varied largely with the highest 74.4% in 1994 and the lowest 27.8% in 2005. Overall survival(OS) was significantly improved over the periods ( p<0.001) in the whole cohort, PORT group and non-PORT group, respectively. Median survivals in the three periods were 20 vs 14, 26 vs 24, 39 vs 33 months for PORT vs non-PORT group. The use of PORT had significant impact on survival in period 1(p<0.001) and 3(p=0.001) but not in period 2(p=0.256). However, in subgroup analysis, the OS benefit of PORT was significantly in each period in patients with 50% or more lymph node ratio(LNR, defined as number of positive nodes/ number of resected nodes): Period 1: hazard ratio(HR), 0.646; 95% confidence interval(CI): 0.482-0.865, p=0.003. Period 2: HR, 0.846; 95% CI: 0.717-0.998, p=0.047. Period 3: HR, 0.773; 95% CI: 0.634-0.942, p=0.011). This population-based study demonstrates significant improvements in OS of these selected resected stage IIIA-N2 NSCLC patients from 1988-2014. The benefits of PORT are not significantly in each time period but are lasting and stable throughout the years in patients with LNR of 50% or more, although other integrated factors such as the progress of surgery and medication may contribute to a better survival. Further investigations in other cohorts and prospective studies are warranted.