Validation of the IASLC Residual Tumor Classification in Patients with Stage III-N2 Non-Small Cell Lung Cancer Undergoing Neoadjuvant Chemoradiotherapy Followed by Surgery

Objective: The aim of this study was to validate the International Association for the Study of Lung Cancer (IASLC) residual tumor classification in patients with stage III-N2 non-small cell lung cancer (NSCLC) undergoing neoadjuvant concurrent chemoradiotherapy (nCCRT) followed by surgery. Background: As adequate nodal assessment is crucial for determining prognosis in patients with clinical N2 NSCLC undergoing nCCRT followed by surgery, the new classification may have better prognostic implications. Methods: Using a registry for thoracic cancer surgery at a tertiary hospital in Seoul, Korea, between 2003 and 2019, we analyzed 910 patients with stage III-N2 NSCLC who underwent nCCRT followed by surgery. We classified resections using IASLC criteria: complete (R0), uncertain (R[un]), and incomplete resection (R1/R2). Recurrence and mortality were compared using adjusted subdistribution hazard model and Cox-proportional hazards model, respectively. Results: Of the 96.3% (n = 876) patients who were R0 by Union for International Cancer Control (UICC) criteria, 34.5% (n = 3O2) remained R0 by IASLC criteria and 37.6% (n = 329) and 28% (n = 245) migrated to R(un) and R1, respectively. Most of the migration from UICC-R0 to lASLC-R(un) and IASLC-R1/R2 occurred due to inadequate nodal assessment (85.5%) and extracapsular nodal extension (77.6%), respectively. Compared to R0, the adjusted hazard ratios in R(un) and R1/R2 were 1.20 (95% confidence interval, 0.94-1.52), 1.50 (1.17-1.52) (P fortrend =.001) for recurrence and 1.18 (0.93-1.51) and 1.51 (1.17-1.96) for death (P for trend =.002). Conclusions: The IASLC R classification has prognostic relevance in patients with stage III-N2 NSCLC undergoing nCCRT followed by surgery. The IASLC classification will improve the thoroughness of intraoperative nodal assessment and the completeness of resection.