Oral contraceptive use and risk of cutaneous malignant melanoma.

The relation between cutaneous malignant melanoma (MM) and the use of oral contraceptives (OC) was investigated in a case-control study carried out from 1979 to 1991 among patients in hospitals and clinics in the Philadelphia (PA) and New York City (NY) metropolitan areas (United States). Cases were 615 women under age 70 who recently had been diagnosed with invasive melanoma; controls were 2,107 women of the same ages who had been treated for other conditions unrelated either to OC use or to skin diseases. The cases were categorized as severe or nonsevere based on the depth of invasion of the tumor or the presence or absence of metastases. Among the severe cases, OC use was not associated with MM: the relative risk (RR) estimate for ever-use was 1.1 (95 percent confidence interval [CI] = 0.8-1.5) and the estimate for 10 or more years of use was 1.1 (CI = 0.6-2.1). Nor was risk associated with recent use, long latency, or young age at first use. Among the nonsevere cases, ever-use of oral contraceptives was associated positively with MM (RR = 1.5, CI = 1.1-2.4) but there was no trend with increased duration of use. The findings provide evidence against the hypothesis that OC use increases the risk of malignant melanoma. The elevated estimates among the nonsevere cases most likely reflect selection bias rather than a causal relation.