Reappraisal of the role of postoperative radiation therapy in patients with pIIIa-N2 non-small cell lung cancer: A propensity score matching analysis

BACKGROUND: Reappraisal of the role of postoperative radiotherapy in pN2 non-small cell lung cancer (NSCLC) patients according to N1 lymph node involvement. METHODS: A total of 218 pIIIa-N2 NSCLC patients who underwent complete surgical resection with systematic nodal dissections were enrolled. Propensity scores were used for matching N1 involvement. Overall survival (OS) and disease-free survival (DFS) were analyzed retrospectively. RESULTS: After matching, pN2b patients without N1 involvement (pN0N2b) exhibited better prognoses than those with N1 involvement (pN1N2b) (5-year OS: 37.5% vs. 7.1%, P = 0.008; 5-year DFS: 31.8% vs. 4.6%, P = 0.004). Similar results were not detected in pN2a disease (5-year OS: 37.8% vs. 31.0%, P = 0.517; 5-year DFS: 27.1% vs. 20.2%, P = 0.788). The five-year OS of patients who received no adjuvant therapy (22 pN2a cases, 7 pN0N2b, 5 pN1N2b), adjuvant chemotherapy alone (74 pN2a cases, 11 pN0N2b, 17 pN1N2b) or chemoradiotherapy (25 pN2a cases, 7 pN0N2b, 6 pN1N2b) were compared (pN2a: 31.3%, 37.0%, and 32.0%, P = 0.808; pN0N2b: 0.0%, 18.2%, and 71.4%, P = 0.108; pN1N2b: 0.0%, 0.0%, and 33.3%, P < 0.0001). The five-year DFS was also analyzed (pN2a: 31.6%, 24.0%, and 18.3%, P = 0.410; pN0N2b: 0.0%, 11.1%, and 57.1%, P = 0.192; pN1N2b: 0.0%, 0.0%, and 16.7%, P < 0.0001). Multivariate analysis revealed that the novel classification based on N1 involvement and pN2a/pN2b staging was an independent prognostic factor of OS and DFS. CONCLUSION: N1 involvement significantly impacted the prognosis of pN2b NSCLC patients. The benefit of adjuvant therapy in pN2a and pN0N2b patients requires confirmation by further study.