METHODS: We used data from the Sister Study, a large (n = 50,884) prospective cohort of women who had a sister diagnosed with breast cancer, but who were free of breast cancer themselves at baseline. Participants completed a structured questionnaire that included demographics, lifestyle factors, and medical history, including any diagnosis of severe acne. Adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association of severe acne and breast cancer (invasive disease or ductal carcinoma in situ).
RESULTS: During an average of 8.4 years of follow-up, 3049 breast cancer cases were diagnosed. Ever being diagnosed with severe acne was associated with a higher risk of breast cancer (HR 1.23; 95% CI 0.98, 1.54), particularly in women who were diagnosed prior to age 18 years (HR 1.40; 95% CI 1.04, 1.90). Results were similar when limited to invasive cancers.
CONCLUSIONS: Our study supports a non-significant positive association between severe acne-a potential marker of hormonal imbalance-and breast cancer risk. These findings suggest that severe acne, when considered along with other risk factors, could help to identify women who may be at a higher risk of breast cancer.