AbstractBackground and ObjectivesT cells are central in antitumor immunity in gastric cancer (GC). The inducible costimulatory molecule (ICOS) is a T cell receptor that primarily transmits positive signals for T cell activation and is associated with poor prognosis in GC. In contrast, the costimulatory molecule programmed death 1 (PD‐1) is an inhibitory receptor related to tumor immune escape. This study aimed to analyze soluble sites and sPD‐1 levels in GC.MethodsThis study enrolled 83 GC patients and 20 healthy controls.ResultsThe median survival time was 23.22 months in the GC patients. Low levels of sPD‐1 and sICOS in GC patients compared to the control group (p = 0.003; p < 0.0001, respectively). High sPD‐1 levels in stage IV patients compared to I/II and III stages groups (p = 0.008 and p = 0.0004, respectively). GC patients with stages I and II had higher levels of sICOS compared to III and IV stages (p = 0.0005 and p = 0.02, respectively). There were no significant differences in sPD‐1 and sICOS levels between Lauren subtypes.ConclusionThese results suggest a predominance of inhibitory costimulatory signals in advanced stages of GC, facilitating tumor immune escape, as the opposite occurs in early stages, resulting in an effective antitumor T‐cell‐mediated immune response.