A meta-analysis of CD274 (PD-L1) assessment and prognosis in colorectal cancer and its role in predicting response to anti-PD-1 therapy

[Display omitted] •CD274 expression in immune cells is associated with good prognosis.•Survival data for CD274 expression in tumour tissue is heterogenous.•Data is sparse for CD274 as a biomarker of colorectal cancer immunotherapy response.•CD274 assessment should be standardised as per upper GI cancer.•Once standardised, thresholds can be assessed for response to immunotherapy. PD-1 checkpoint inhibitors are novel therapeutic agents in colorectal cancer (CRC). Immunohistochemical staining for CD274 assessment is standardised in upper GI cancer, but not in CRC. Methodologies of relevant studies were scrutinized and meta-analysis of survival and CD274/PDCD1 performed. Furthermore, anti-PD-1 therapy clinical trial results in CRC were assessed with particular emphasis on CD274 assessment. 24 studies were included. CD274 on immune cells was associated with good prognosis. CD274 on tumour cells has heterogenous outcomes and does not meet requirements of a prognostic marker. As a marker of response to anti-PD-1 therapy, CD274 assessment is not standardised in CRC. CD274 does not appear useful as a prognostic marker. As a marker of response to anti-PD-1 therapy, assessment methodology requires standardisation. As the Combined Positive Score (CPS) is used in upper GI cancer, this seems a logical method to adopt. Thresholds for CRC remain to be determined.