PTGS2 and colorectal cancer: BC: Breast cancer; CRC: Colorectal cancer; HCC: Hepatocellular carcinoma; HR: Hazard ratio; PCa: Prostate cancer; PIK3CA: Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha; PTGS2: Prostaglandin-endoperoxide synthase 2; RCT: Randomized controlled trials; RR: Relative risk