Serum total bilirubin and risk of cancer: a Swedish cohort study and meta-analysis

Bilirubin has strong antioxidant properties that have been hypothesized to be preventive against the development of cancer. Thus, we aimed to investigate the association between serum total bil-irubin (STB) and risk of overall and site-specific cancers in the large Swedish Apolipoprotein Mortality Risk (AMORIS) cohort. We also performed a systematic review and meta-analysis for specific cancer types (colorectal, breast and lung). We found no association between high levels of STB and risk of overall cancer. Regarding site-specific cancer, there was an inverse association between increased STB and lung cancer (Hazard Ratio (HR) for the 4th quartile (Q4) vs. Q1: 0.50; 95%CI: 0.44-0.59) and gynecological cancer (HR for Q4 vs. Q1: 0.86; 95%CI: 0.76-0.99). A positive association was found with melanoma (HR for Q4 vs. Q1: 1.25; 95%CI: 1.06-1.47) and breast cancer (HR for Q4 vs. Q1: 1.13; 95%CI: 1.01-1.25) risk. The meta-analysis showed an inverse as-sociation between high levels of STB and risk of lung cancer (Relative risk (RR): 0.69; 95%CI: 0.55-0.86). No associations were seen for colorectal and breast cancer risk. Further studies are required to establish if bilirubin can be used as a biomarker for risk assessment and/or as a novel therapeutic target.