Background and Objective Immune checkpoint inhibition has shed light on a new era in cancer therapy, and randomized clinical trials have demonstrated that a meaningful portion of the overall population of metastatic gastric cancer (GC) patients may derive clinical benefit from immunotherapy, which raises the relevance in identifying predictive biomarkers. Programmed cell death-ligand 1 (PD-L1) expression has demonstrated a significant association between level of expression and the magnitude of benefit derived from immune checkpoint inhibition in GC. Nevertheless, this biomarker shows several pitfalls that must be considered in the therapeutic decision to incorporate immune checkpoint inhibition as the standard of care of GC, such as spatial and temporal heterogeneity, interobserver variability, immunohistochemistry (IHC) assay, and influence by chemotherapy or radiation therapy. Methods In the present comprehensive review, we revised the main studies regarding PD-L1 evaluation in GC. Key Content and Findings Here we describe the molecular characteristics of the tumor microenvironment in GC, the obstacles in the interpretation of PD-L1 expression and present the data of the clinical trials that have evaluated the efficacy and safety of immune checkpoint inhibition and the association with the biomarker expression, both in first-line and later lines of therapy. Conclusions From the emerging predictive biomarkers for immune checkpoint inhibition, PD-L1 has demonstrated a meaningful association between level of expression in tumor microenvironment and the magnitude of benefit derived from immune checkpoint inhibition in GC.

O câncer gástrico (CG) é a terceira principal causa de morte por câncer em ambos os sexos e a quinta neoplasia maligna mais comum em todo o mundo. Possui distribuição global heterogênea, sendo mais incidente no leste asiático, no leste europeu e na América do Sul.

O câncer colorretal (CCR) é a terceira neoplasia maligna mais comumente diagnosticada e a quarta maior causa de morte por câncer no mundo, com cerca de 1,4 milhão de casos novos e quase 700 mil mortes anuais, segundo dados levantados em 2012. Para esse tumor, são estimados 1,1 milhão de mortes anuais até 2030.

O câncer de esôfago (CE) é uma neoplasia altamente incidente, principalmente entre os homens. Segundo informações publicadas pelo Globocan, o CE respondeu pela sétima posição em incidência entre todos os tipos de tumor no ano de 2018, tendo sido responsável por 572.034 novos casos.