Anti-programmed death-ligand 1 (PD-L1) treatments can improve colorectal carcinoma (CRC) survival; however, there is still controversy regarding the relationship between PD-L1 expression and the outcome of immunotherapeutic treatment and survival. The discrepancies are partly caused by the lack of a unified scoring system. This retrospective, cross-sectional study evaluated PD-L1 by immunohistochemistry in 127 CRC cases and compared the 3 scoring systems used to assess PD-L1: Tumor Percentage Score (TPS), Combined Positive Score (CPS), and immune cell (IC) score. Correlations were calculated using the χ 2 test. Kaplan-Meier curves with the Log-rank test were used to measure the contribution of PD-L1 expression to survival. PD-L1-positive rate were 29.9%, 57.5%, and 55.9% based on TPS, CPS, and IC score, respectively. TPS showed a better correlation with the clinicopathologic features being significantly higher with young age, T4, and adenocarcinomas (compared with mucinous/signet ring). TPS also showed an increasing trend with higher grade, lymph node stage, and male sex, although these variables were not significantly associated with PD-L1 expression. There was no correlation between PD-L1 expression and mismatch repair protein status in the 3 scoring methods. The probability of survival was higher for PD-L1-negative cases in the first 60 months after surgery if scored by the TPS method ( P =0.058). Future efforts correlating PD-L1 status with response to treatment are needed to decide on the best scoring method to be used for making therapy decisions.
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