Population-based study and meta-analysis of the association of oral contraceptive use and risk of liver cancer

In 1999, the International Agency for Research on Cancer concluded that there was sufficient evidence for an association between oral contraceptive use and risk of liver cancer. This conclusion was based on case-control studies with few liver cancer cases. Updated analysis reevaluated the association. Both in the Million Women Study (1.3 million participants, median follow-up 21.4 years) and the UK Biobank (253,408 participants, median follow-up 12.6 years) no evidence was seen for an association of oral contraceptive use and risk of liver cancer or hepatocellular carcinoma or intrahepatic cholangiocarcinoma. Meta-analysis of 23 observational studies also found no evidence of an association. In meta-analysis of duration of oral contraceptive use, there was a slightly increase risk of liver cancer per 5 years of use of oral contraceptives, but residual confounding could not be ruled out.