Metastatic Lymph Node Station Number Predicts Survival in Small Cell Lung Cancer

PurposeAs for pathologic N category, various regrouping strategies have been raised in non-small cell lung cancer (NSCLC) but little was done in small cell lung cancer(SCLC). On the basis of the suggestions discussed in NSCLC, we proposed a novel, metastatic lymph node station number (MNSN) - based pathologic N parameter and compared its efficacy in predicting survival with pN in SCLC. MethodsWe retrospectively analyzed the patients operated and pathologically diagnosed as SCLC in our hospital between 2009 and 2019. Kaplan-Meier method and Cox regression analysis were used to compare survival between groups defined by pN and MNSN. ResultsFrom 2009 to 2019, 566 patients received surgery for SCLC and 530 of them were eligible for subsequent analysis, with a median follow-up time of 21 months. The 5-year overall survival (OS) rates were 58.8%, 38.6%, 27.9% for pN0, pN1, pN2 stages and were 58.8%, 36.8%, 22.1%, 0% for MNSN0, 1-2, 3-5, 6-7 groups, respectively. Analyses of overall and recurrence-free survival (RFS) revealed that pN1 could not be distinguished from pN2 (OS, p = 0.099; RFS, p = 0.254), but the groups in MNSN were well separated from each other (OS, p< 0.001, p = 0.001, p = 0.063; RFS, p< 0.001, p = 0.026, p = 0.01, compared with the former group). When adjusted for sex, age, smoking, tumor purity and T stage, MNSN groups were independent hazard factors for OS and RFS. ConclusionsBased on our cohort study, the MNSN-based N parameter might be a better indicator to predict survival than pN in SCLC and worth considering in the definition of N category in the future.