Conisation as a marker of persistent human papilloma virus infection and risk of breast cancer

Background: Human papillomavirus (HPV) infection may increase breast cancer (BC) risk. Methods: To examine this, we used nationwide medical registries to identify all Danish women who underwent conisation to remove HPV-associated cervical precancerous lesions (n = 87 782) from 1978 to 2013. We computed the absolute risk of BC and standardised incidence ratios (SIRs) and 95% confidence intervals (95% CIs) for breast cancer, based on national breast cancer incidence rates. Results: Conisation was associated with slightly increased BC incidence (SIR = 1.1, 95% CI = 1.0-1.1), and an absolute BC risk of 7.7% (95% CI = 7.3-8.1%) in 35.9 years of follow-up. BC risk was elevated throughout follow-up, especially in the first 5 years (<1 year: SIR = 1.2, 95% CI = 0.92-1.5; 1-5 years: SIR = 1.2, 95% CI = 1.1-1.3; >= 5 years: SIR = 1.1, 95% CI = 1.0-1.1). Women who underwent conisation and had autoimmune disease had elevated BC risk after 5 years of follow-up (SIR = 1.4, 95% CI = 1.0-1.8). Conclusions: BC risk is slightly elevated in women with persistent HPV infection, possibly due to detection bias.