Oral contraceptives and cancer. A review of the evidence.

The following review considers epidemiological data published from 1990 onwards on oral contraceptives (OCs) and the risk of cancers of the breast, cervix uteri, endometrium, ovary, liver and skin. In several studies, breast cancer risk was seen to be elevated among women who were current users of an OC, or had recently stopped using an OC, whereas there was no residual risk 5 or more years after stopping OC use. No interaction was observed between type of OC, or with any recognised risk factor for breast cancer, or time-factor, except for some potential excess risk for women who started OC use at a young age. Most studies have confirmed that OCs moderately increase the risk of cervical cancer, particularly in human papilloma virus (HPV)-positive women, thus suggesting that OCs may act as a promoter for HPV-induced carcinogenesis. Recent epidemiological studies have confirmed that combined OCs provide substantial protection against endometrial and ovarian cancers, and results suggest that such protection is long-lasting, and may persist for 15 years or more after stopping OC use. Most case-control studies have shown a relationship between OC use and hepatocellular carcinoma. However, data from cohort studies or analysis of vital statistics indicate that the public health impact of such an association is modest, if not negligible. No association was observed between combined OC use and the incidence of skin melanoma, or any other common skin neoplasm. In terms of clinical and public health implications, the most relevant points regarding OC use are: (i) recent data confirm that OCs confer presistent protection against ovarian cancer; and (ii) any increased risk of breast cancer in OC users is moderate and is restricted to current/recent users. This is reassuring for younger women, whose baseline risk of this disease is extremely low.