Surgical Resection of SCLC: Prognostic Factors and the Tumor Microenvironment.

INTRODUCTION: Surgery in SCLC is limited to very early stages, but several reports suggest a potential broader role. Little is known of the influence of microenvironment on the biology of SCLC.

METHODS: We assessed the clinical prognostic factors in a large series of resected SCLC patients. The prognostic value of programmed cell death ligand 1 (PD-L1) expression in tumor cells and tumor infiltrating lymphocytes (TILs) and the percentage of CD3-, CD20-, CD45- and CD68-positive cells, were also investigated.

RESULTS: Two hundred five SCLC cases were resected between 2005 and 2015 and the median follow-up was 29 months (range: 2 to 135 months). Median survival of all patients was 69 months, and 5-year survival rates were 63.8%, 65.5%, 34.9%, and 0% for pathologic stages I, II, III, and IV, respectively. By multivariate analysis complete resection, cigarette index, lymph node metastatic rate, percentage of CD3-positive cells, PD-L1 expression in tumor cells, and TILs were independent prognostic factors. High PD-L1 expression was present in 3.2% and 33.5% of all tumor samples in tumor cells and TILs, respectively. High PD-L1 expression in tumor cells or TILs correlated with shorter survival, whereas high expression of CD3, CD20, and CD45 correlated with better survival.

CONCLUSIONS: Resected stage II SCLC patients have similar survival as stage I, suggesting that surgery could be extended to patients with hilar lymph node involvement. Survival was better in tumors with a higher percentage of T cells and B cells, whereas PD-L1 expression in tumor cells and TILs correlated with worse survival, which suggests a potential role of immunotherapy in resected SCLC.