Prognostic Value of Uncertain Resection for Overall Survival in Non-small Cell Lung Cancer

Background In this study, we aimed to evaluate the R(un) category proposed by the International Association for the Study of Lung Cancer (IASLC) for non-small cell lung cancer (NSCLC). Methods We retrospectively reviewed the medical records of patients with NSCLC who underwent segmentectomy or lobectomy between 2014 and 2015 at our institution. Residual tumor (R) status was reclassified from the Union for International Cancer Control designation to the IASLC-proposed R classification [R0 and R(un)]. The underlying reasons for the R(un) reclassification were analyzed according to pathological stage, lymph node status, and resected lobe. A Cox proportional hazard model was used to evaluate the impacts of R(un) categorization on overall survival. Results Of 355 cases, 44.5% were reclassified as R(un). The most common reason for the reclassification was insufficient number of harvested lymph nodes or no station 7 lymph nodes. When stratified by tumor location, the absence of station 7 lymph nodes was especially prominent in both the right and left upper lung resections. In the multivariate Cox regression model, IASLC R classification was associated with poor overall survival in node-positive cases (hazard ratio: 2.657; P =.016). Conclusions Various factors resulted in reclassification to R(un) because the R(un) group was highly heterogeneous. Careful consideration is required to determine whether R(un) classification can be used as an indicator of lymph node dissection quality. For advanced cases, the R(un) definition may be useful in predicting poor prognosis.