Cancer
Oral contraceptive use and risk of melanoma: results from a prospective cohort study among 59,407 nurses Linske de Bruijn* Henriette M. van Duijne van Duijne Linske de Bruijn Henriette M. van Duijne Nina E. Berentzen Roel C.H. Vermeulen Jelle J. Vlaanderen Hans Kromhout Katarzyna Jóźwiak Flora E. van Leeuwen
Background: The incidence of melanoma increases worldwide, which cannot be entirely explained by exposure to UV and other risk factors. Oral contraceptive (OC) use may also influence melanoma risk, although studies which evaluated this association reported conflicting results. We therefore assessed the association of OC use with melanoma risk in a large cohort of female nurses.
Methods: The Nightingale Study comprises 59,947 Dutch female nurses, aged 18-65 years in 2011 (mean age: 46.9 years). Participants provided data on OC use in the baseline questionnaire (2011) and were followed for cancer occurrence up to August 2021. Missing exposure and covariate data (e.g. lifestyle factors including UV exposure) were imputed using multiple imputation by chained equations. Associations of OC use with risk of melanoma were assessed using proportional hazard models with attained age as timescale while adjusting for age at baseline. Women who never used OC or used OC before 2011 for ≤five years were used as reference group.
Results: During follow-up, 302 women were diagnosed with melanoma. In comparison to the reference group, melanoma risk was significantly increased for participants who ever used OC (Hazard ratio (HR)=1.36, 95%Confidence Interval (CI)=1.00-1.85) or currently used OC (HR=2.14, 95%CI=1.43-3.18). Risk was not significantly increased among former users who had used OC for >5 years (HR=1.23, 95%CI=0.90-1.69), even when last OC use was <2 years before baseline (HR=1.14, 95%CI=0.57-2.27). Among current OC users, risk did not increase with longer duration of use (HRper one year increase=0.97, 95%CI=0.93-1.00).
Conclusion: Current OC use, but not duration or recency of OC use, was associated with increased melanoma risk among nurses. Future studies should focus on the type and dose of OC in relation to melanoma risk to further clarify potential mechanisms behind the increased risk of melanoma associated with current OC use.