Objective: We aimed to examine whether use of hormone replacement therapy (HRT) and oral contraceptives (OC) affect the risk of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) in women.
Methods: Using data from 29,875 women enrolled in the prospective "Diet, Cancer, and Health" study between 1993 and 1997, women with available information on HRT and OC use at baseline were identified. Statistical analyses were based on the Cox's proportional hazards model.
Results: The mean age at enrollment in the study was 56.7 years, whereas the mean age at the end of follow-up was 67.5 years. 1,175 cases of BCC and 76 cases of SCC were identified in the cohort during follow-up through 2007. The BCC incidence rate ratio was 1.15 (95% CI: 1.07-1.37) for ever users of HRT at baseline compared to never users, whereas risk of BCC was unaffected by duration of HRT use. Ever use of HRT was not associated with SCC risk but a significantly increased risk of 1.35 (95% CI: 1.05-1.72) associated with every 5 years of HRT use was observed. No convincing associations between OC use and BCC or SCC risk were observed.
Conclusion: The findings indicated that HRT but not OC may increase the risk of NMSC. However, further studies are warranted as risk estimates for SCC had relatively low precision due to a limited number of SCC cases.