PVR and digestive system cancer: Furthermore, subgroup analysis demonstrated that the level of CD155 expression was significantly associated with OS in patients with digestive system cancer (pooled HR = 1.570, 95% CI = 1.120–2.201, P = 0.009), hepatobiliary pancreatic cancer (pooled HR = 1.677, 95% CI = 1.037–2.712, P = 0.035), digestive tract cancer (pooled HR = 1.512, 95% CI = 1.016–2.250, P = 0.042), breast cancer (pooled HR = 2.137, 95% CI = 1.448–3.154, P < 0.001), lung cancer (pooled HR = 1.706, 95% CI = 1.193–2.440, P = 0.003), head and neck cancer (pooled HR = 1.470, 95% CI = 1.160–1.862, P = 0.001).