A possible association between oral contraception and the development of cutaneous melanoma has been raised largely because of the hyperpigmentation of pregnancy and the effect pregnancy may have on the outcome of established disease. Present evidence suggests there is no causal link between oral contraceptive (OC) use and melanoma (or with benign melanocytic nevi), nor has a specific subgroup of women or subtype of melanoma been consistently implicated as being at increased risk of this disease due to use of OCs.
PIP: Evidence from case-control and cohort studies and animal research is reviewed to examine whether oral contraceptive (OC) use is related to cancer of the kidney, colon, rectum, gall bladder, extrahepatic bile ducts, benign or malignant pituitary tumors or prolactinemia. While animal research suggests possible hormone sensitivity, there are only 2 cohort studies available on renal adeno-carcinoma; result are contradictory. Colon and rectal cancer are sometimes studied separately and sometimes together despite different etiologic factors. Colon cancer is less common in women of higher parity, and associated with other female sex hormone related cancers. 3 case-control studies have produced no consistent results except for a possible higher risk of right colon cancer in OC users. Cohort studies on colorectal cancer resulted in very few cases and no significant increase in risk for these very common malignancies among OC users. Gallbladder cancer is associated with gallstones, a condition known to be enhanced by estrogens, yet 1 case-control study found no change in risk. In contract, cancer of the extrahepatic bile duct, usually more common in men, was found to be elevated in OC users in 1 small study. The question of pituitary tumors is complicated by difficulties in diagnosis, differentiating between hyperplasia, microadenomas, galactorrhea, prolactinemia and cycle irregularity. Basic research indicates that estrogens stimulate prolactin secretion and development of pituitary tumors. Yet of 6 case-control studies only 2 reported relative risks significantly above 1. Only 6 cases have been found in 3 large cohort studies. Therefore it is probable that any association of pituitary tumors with pills is largely due to their prescription for women with menstrual irregularity, some of whom had pre-existing pituitary adenomas.