Prognostic value of SOX2 and CD8+TIL in limited stage small cell lung cancer.

Abstract

e21108 Background: SOX2 is a transcriptional factor that drives embryonic stem cell to neuroendocrine cells in lung development and is highly expressed in SCLC. The serum SOX2 antibody in SCLC has been known to mediate neurologic paraneoplastic syndrome. In this study, we evaluated the expression of SOX2 and CD8+ tumor infiltrating lymphocyte (TIL) in LS-SCLC from clinical tumor tissue and their impact on PFS and OS. Methods: Among the total 245 patients with SCLC treated between 2010 and 2018, 75 patients with LS-SCLC with available tumor tissue were enrolled. SOX2 and CD8+ TIL were evaluated by immunohistochemistry. High SOX2 expression was defined as above 100 of H score that was derived from multiplying intensity by the proportion of stained tumor cells. The number of CD8+TILs was counted under high magnification (x400) with four fields in intratumoral area. The cut value for high CD8+TIL was the above the median of total case. Results: 64 patients (85.4%) received etoposide/platinum and definite local therapy (radiation therapy or surgery) and 18 patients (24.0%) received surgical resection. High expression of CD8+ TIL was related to significantly longer PFS (13.9 vs. 8.0 months, P = 0.014) and tended to related to longer OS (32.1 vs. 17.4 months, P = 0.056) than low expression. High expression of SOX2 was tended to related with longer OS and PFS compared to low expression of SOX2 (median, 21.7 vs. 17.1 months, P = 0.118; 12.7 vs. 9.0 months, P = 0.110, respectively) without statistical significance. 29 patients with high CD8+TIL among 52 patients with high SOX2 had significantly longer PFS and OS compared to the other groups (median PFS 19.3 vs. 8.4 months, P = 0.002 and median OS 35.7 vs. 17.4 months, P = 0.004, respectively). Multivariate Cox regression analysis showed that combined high expression SOX2 and CD8+ TIL was an independent good prognostic factor for OS (HR = 0.449, P = 0.018) and PFS of SCLC (HR = 0.481, P = 0.021). Conclusions: In our study, high expression level of combined SOX2 and CD8+ TIL were related to longer OS and PFS, and it could be used as a prognostic biomarker for LS-SCLC. [Table: see text]