Solar ultraviolet radiation (UVR) exposure is clearly associated with increased mortality from nonmelanoma skin cancer--usually squamous cell carcinoma. However, the association with cutaneous melanoma is unclear from the evidence in ecologic studies and the few analytic studies show that high levels of intermittent UV exposure prior to diagnosis are somehow associated with improved survival from melanoma. Understanding this conundrum is critical to present coherent public health messages and to improve the mortality rates from melanoma.

Solar UV radiation (UVR) exposure is clearly associated with increased mortality from nonmelanoma skin cancer-usually squamous cell carcinoma. However, the association with cutaneous melanoma is unclear from the evidence in ecologic studies and several analytic studies have conflicting results regarding the effect of high levels of intermittent UV exposure prior to diagnosis on mortality. Understanding this conundrum is critical to present coherent public health messages and to improve the mortality rates from melanoma.

Background:Combined oral contraceptive (COC) use reduces epithelial ovarian cancer (EOC) risk. However, little is known about risk with COC use before the first full-term pregnancy (FFTP).Methods:This Canadian population-based case–control study (2001–2012) included 854 invasive cases/2139 controls aged ⩾40 years who were parous and had information on COC use. We estimated odds ratios (aORs) and 95% confidence intervals (CI) adjusted for study site, age, parity, breastfeeding, age at FFTP, familial breast/ovarian cancer, tubal ligation, and body mass.Results:Among parous women, per year of COC use exclusively before the FFTP was associated with a 9% risk reduction (95% CI=0.86–0.96). Results were similar for high-grade serous and endometrioid/clear cell EOC. In contrast, per year of use exclusively after the FFTP was not associated with risk (aOR=0.98, 95% CI=0.95–1.02).Conclusions:Combined oral contraceptive use before the FFTP may provide a risk reduction that remains for many years, informing possible prevention strategies.