OPRM1 and cancer: Multivariate Cox regression models identified positive MOR mRNA expression as a significant prognostic factor in all cancer types (HR 1.347, 95% CI 1.200-1.512, P<0.001 for OS; HR 1.359, 95% CI 1.220-1.513, P<0.001 for PFS; HR 1.269, 95% CI 1.016-1.585, P<0.001 for DFS; HR 1.474, 95% CI 1.284-1.693, P<0.001 for DSS) (Figure S8).