Oral contraceptives and cancer: an update.

Most up-to-date information on oral contraceptives (OCs) and breast cancer risk comes from a collaborative re-analysis of individual data on 53297 cases and 100239 controls. It is now established that there is a moderately increased breast cancer risk among current OC users, which tends to level off in the few years after stopping use. With regard to cervical cancer, OC use has been found to be associated with increased risk in human papilloma virus-positive women. With reference to the well known protective effects of OCs against endometrial carcinogenesis, additional information has suggested a consistent protection across types of OCs used. Further data on ovarian cancer confirm that the protection of OCs is long lasting, and may well be observed 15 to 20 years after stopping use. Several studies have suggested an inverse relationship between use of OCs and risk of colorectal cancer, and in a meta-analysis of published data the pooled relative risk of colorectal cancer for DC ever-use was 0.82 (95% confidence interval 0.74 to 0.97). There was no association with duration of use. The increased risk for hepatocellular carcinoma in the absence of hepatitis B viruses is the only established evidence of a direct association between OC use and cancer risk, which led an International Agency for Research on Cancer Working Group to classify OCs as carcinogenic to humans in 1998.