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.