A Validation Study of the Recommended Change in Residual Tumor Descriptors Proposed by the International Association for the Study of Lung Cancer for Patients With pN2 NSCLC

IntroductionThis study aimed to validate the residual tumor (R) descriptors proposed by the International Association for the Study of Lung Cancer (IASLC) for patients with pathologic N2 (pN2) NSCLC.MethodsWe retrospectively reviewed the data of patients with pN2 NSCLC who underwent anatomical resection during the period 2004 to 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 IASLC R descriptors.ResultsAmong 1039 patients, 91.1%, 8.1%, and 0.8% of the patients respectively received complete resection (R0), R1, and R2 defined using the UICC criteria, whereas 41.6%, 20.4%, and 38% respectively received R0, uncertain resection (R[un]), and R1/2 resection defined using the IASLC criteria. Furthermore, 206 patients (21.8%) were reclassified from having UICC R0 to having IASLC R(un) mainly owing to the highest mediastinal lymph node involvement (89.8%). Owing to extracapsular extension, 309 patients (32.6%) with UICC R0 were reclassified as having IASLC R1/2. Patients with IASLC R(un) 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(un) was similar after adjustment for subdivided N2 descriptors including pN2a1, pN2a2, and pN2b.ConclusionsAlong with subdivided N descriptors, detailed R descriptors proposed on the basis of the IASLC criteria can ensure optimal staging, enabling the most appropriate decision-making on adjuvant therapy for patients with pN2 NSCLC.