Regarding OS, subgroup analyses by cancer type showed that loss of Smad4 staining predicted an unfavorable prognosis in cervical carcinoma (HR = 3.43, 95% CI: 1.65–7.12; Pheterogeneity = 0.436), gastric cancer (HR = 2.02, 95% CI: 1.44–2.83; Pheterogeneity = 0.197), colorectal cancer (HR = 3.76, 95% CI: 1.53–9.25; Pheterogeneity<0.001) and pancreatic cancer (HR = 1.39, 95% CI: 1.19–1.61; Pheterogeneity = 0.185). Here, SMAD4 is linked to cancer.