Personal history of psoriasis and risk of nonmelanoma skin cancer (NMSC) among women in the United States: A population-based cohort study

Background: To our knowledge, no prospective studies have examined the association between personal history of psoriasis and risk of nonmelanoma skin cancer. Objective: We sought to examine this association based on 2 prospective cohorts, the Nurses' Health Study and Nurses' Health Study II. Methods: Diagnoses of nonmelanoma skin cancer, including basal cell carcinoma and squamous cell carcinoma (SCC), were obtained by self-reported questionnaires. Information on clinician-diagnosed psoriasis and diagnosis year was collected and validated with a supplementary questionnaire. Results: After 2,487,941 and 2,478,148 person-years of follow-up, we documented 1725 SCC cases and 16,075 basal cell carcinoma cases, respectively. For the combined cohorts, personal history of psoriasis was associated with an elevated risk of SCC, with a multivariate-adjusted relative risk (RR) of 1.51 (95% confidence interval [CI] 1.11-2.05). The associations appeared stronger with increasing psoriasis severity, with RR of 1.42 (95% CI 0.94-2.15) in the mild psoriasis group and RR of 1.99 (95% CI 0.74-5.32) in the moderate to severe psoriasis group (P trend = .03). There was no association between psoriasis and the risk of basal cell carcinoma (RR 0.95; 95% CI 0.75-1.18). Limitations: Lack of treatment data may bias the result. Conclusion: Personal history of psoriasis may be associated with an increased risk of SCC. Further investigations are warranted to understand the underlying mechanisms.