PD-L1 as a prognostic factor in early-stage colon carcinoma within the immunohistochemical molecular subtype classification

Colorectal cancer (CRC) is a very heterogeneous disease. Efforts to characterize and search for biomarkers for these patients are currently ongoing in the hope of establishing a more targeted therapeutic approach. The role of PD-1 ligand (PD-L1) expression as a biomarker has not yet been fully elucidated. The Consensus Molecular Subtype classification has been delineated, but although already acknowledged in the most recent international guidelines, it has yet to be implemented in clinical practice. We investigate PD-L1 expression as a biomarker of prognosis in the early-stage setting and integrate it with the Consensus Molecular Subtype (CMS), in an effort to differentiate those patients with a worse prognosis who could potentially benefit from an early, more aggressive treatment. Our results suggest PD-L1 as an independent prognostic factor in early stage setting when assessed by immunohistochemistry. Additionally, PD-L1 expression appears to be a viable biomarker to differentiate patients in the CMS (CMS2/CMS3) who lack a clear prognosis.