Postoperative Radiotherapy for Resected Stage IIIA-N2 Non-small-cell Lung Cancer: A Population-Based Time-Trend Study.

Introduction: The value of postoperative radiotherapy (PORT) for resected stage IIIA-N2 non-small-cell lung cancer (NSCLC) is controversial with few studies focusing on whether PORT always plays a part in clinical practice and generates benefits to patients across different time periods. We investigated this issue using the Surveillance, Epidemiology, and End Results Database (SEER) and assessed the temporal trends spanning 27 years.

Methods: Within SEER, we selected stage IIIA-N2 NSCLC patients who underwent a lobectomy or pneumonectomy and coded as receiving PORT or never receiving radiotherapy over three time periods: 1988 to 1996, 1997 to 2005, 2006 to 2014. For each period, survival analyses were performed and propensity score matching (PSM) was used in the potentially beneficial subgroup.

Results: 45.4% of 5568 eligible patients received PORT. The yearly PORT use rates varied largely from 27.8% to 74.4%. Overall survival (OS) was distinctly improved over the period. The application of PORT had a significant impact on survival only in period 1 and 3. In subgroup analysis, the OS benefit of PORT was significant in each period in patients with 50% or more lymph node ratio (LNR) both before (hazard ratios, and P values of 0.647, P = .002; 0.804, P = .008; 0.721, P < .001 for period 1, 2, 3, respectively) and after PSM (0.642, P = .006; 0.785, P = .004; 0.748, P = .003 for period 1, 2, 3, respectively).

Conclusions: The benefits of PORT are lasting and stable throughout the years in patients with LNR of 50% or more. This might provide a clue on proper patient selection for PORT application.