This paper reviews the evidence for a relationship between oral contraceptive use and certain neoplasms: cancers of the kidney, colon and gallbladder (including the extrahepatic bile ducts) and tumours (benign or malignant) of the pituitary. Special reference is made to controlled epidemiological studies, both case-control and cohort. There is no convincing evidence that oral contraceptive use is causally related, either negatively or positively, to any of the tumours studied.
PIP: Case-controlled and cohort analyses of the possible effect of oral contraceptive (OC) use on skin cancers are reviewed. The possibility that OCs may increase risk of skin neoplasms is suggested by the doubling in prevalence of skin malignancies in among whites every 10-15 years, the occurrence of hyperpigmentation in pregnancy, and the reports that pregnancy may accelerate the course of existing melanoma. The lesions of concern are benign melanocytic nevi, or moles, and malignant melanoma. Nevi are risk factors for melanoma. Pregnancy increases synthesis of melanin, but does not cause numbers of melanocytes to increase. Pregnancy is known to induce mild atypia in nevi, but not to increase their numbers significantly. Nor does OC use increase numbers of nevi. Case reports on whether pregnancy enhances development of malignant melanoma, and whether such lesions have estrogen receptors are contradictory. There is no evidence from cancer registries in the US, Canada, Scandinavia or Europe that the incidence or mortality from melanoma in women relative to men has risen with the introduction of OCs. In 9 case-control studies, relative risks for OC users was 1 in 4 studies, equal to 1 in 2, and 1 in 3. The studies as a group suffer from lack of definition of phenotype (susceptibility to moles) or sun exposure, as well as different definitions of types of skin cancers. 2 large cohort studies each found 20 cases, again with unknown confounding variables of phenotype and sun exposure. Thus while even a small increase in melanoma, a cancer fatal in 30% of cases with rising incidence, would be important for public health, there is no coherent evidence that pill use enhances risk of skin cancer.