A Validation Study on the Recommended Change in Residual Tumor Descriptors Proposed by the International Association for the Study of Lung Cancer for Patients with pN2 Non-small Cell Lung Cancer.

Abstract1 Introduction This study aimed to validate the residual tumor (R) descriptors proposed by the International Association for the Study of Lung Cancer (IASLC) for patients with pathological N2 (pN2) non-small cell lung cancer (NSCLC). Methods We retrospectively reviewed the data of patients with pN2 NSCLC who underwent anatomical resection during 2004–2018. The R status classified using the Union for International Cancer Control (UICC) criteria was compared with that reassigned using the IASLC criteria. Survival analysis was performed using Cox proportional hazards models to assess the prognostic significance of IASLCR descriptors. Results Among 1039 patients, 91.1%, 8.1%, and 0.8% of the patients received R0, R1, and R2 resection, defined using the UICC criteria, whereas 41.6%, 20.4%, and 38% received R0, R-uncertain, and R1/2 resection, defined using the IASLC criteria, respectively. Furthermore, 206 (21.8%) patients were reclassified from having UICC R0 to having IASLC R-uncertain mainly due to the highest mediastinal lymph node involvement (89.8%). Owing to extracapsular extension, 309 (32.6%) patients with UICC R0 were reclassified as having IASLC R1/2. Patients with IASLC R-uncertain had significantly worse and better prognosis than those with IASLC R0 and IASLC R1/2, respectively. In multivariable analysis, the prognostic difference between IASLC R0 and R-uncertain was similar after adjustment for subdivided N2 descriptors including pN2a1, pN2a2, and pN2b. Conclusions Along with subdivided N descriptors, detailed R descriptors proposed based on the IASLC criteria can ensure optimal staging, enabling the most appropriate decision-making on adjuvant therapy for pN2 NSCLC patients.