Expression of PD-L1 and PD-L2 in colorectal cancer (CRC): A post-hoc integrated analysis of SCRUM-Japan GI-SCREEN CRC.

Abstract

120 Background: PD-1, PD-L1/L2 axis is responsible for cancer immune escape which facilitate disease progression. However, expression of these proteins in CRC and its significance in clinical prognosis are yet to be fully clarified. Methods: This was a post-hoc analysis using FFPE tumor samples from the Nationwide Cancer Genome Screening Project, SCRUM-Japan GI-SCREEN for metastatic CRC. Patients (Pts) with MSI-H or BRAF V600E mutant tumors were prioritized to be included. PD-L1 (22C3) and PD-L2 expressions were centrally assessed using immunohistochemical assays at QualTek and NeoGenomics, respectively. Tumor infiltrating lymphocytes (TILs) were morphologically evaluated by H&E staining. Clinical information including biomarker status and overall survival (OS) were extracted from SCRUM-Japan GI-SCREEN database. Results: In total, 200 pts were included in this study with a median age of 65 (range, 29–88) years; male/female (116/84); MSI status MSI-H/non-MSI-H/unknown (8/189/3); RAS wild-type/mutant (113/87); and BRAF V600E wild-type/mutant (173/27). Positivity rate of PD-L1 in tumor cells (TC), immune cells (IC), PD-L2 on TC and IC were 10.8%, 46.9%, 0% and 20.3%, respectively. Expression of PD-L1 on TC or IC and PD-L2 on IC were associated with TIL (p = 0.023, p = 0.009, respectively). PD-L1 on TC was highly seen in BRAF V600E-mutated tumors (p = 0.043), but not related to other factors including RAS and MSI status. The pts with PD-L1+ tumors on TC or IC had longer OS than those with PD-L1- (Median, 31.9 vs 23.5 months; HR = 0.67, 95% CI, 0.46–0.99; p = 0.040), while OS in pts with PD-L2+ tumors was similar to that with PD-L2- (Median, 21.4 vs 27.3 months; HR = 0.87, 95% CI, 0.53–1.44; p = 0.60). The PD-L1 expression was also associated with the longer OS in pts with BRAF wild-type or non-MSI-H tumors. Conclusions: Our study suggested different prognostic impact of PD-L1 and PD-L2 expression in CRC pts, which require further evaluations as potential therapeutic targets for CRC. Clinical trial information: UMIN000016343.