Risk factors for ductal carcinoma in situ of the breast in the UK Biobank cohort study

Ductal carcinoma in situ of the breast (DCIS) is considered to be a non-obligate precursor of invasive breast cancer (IBC). This suggests that risk factors for DCIS should be a subset of those for IBC. To this end, we investigated whether demographic, lifestyle, and reproductive factors that have been linked to IBC risk are also associated with DCIS risk. This study was conducted in 263,788 women aged 40–69 years at enrolment into the UK Biobank population-based cohort. Information on demographic, reproductive and health factors was collected at baseline using computerized questionnaires, while incident DCIS was ascertained through linkage to UK cancer registries. Age-adjusted and multivariable hazard ratios were estimated using Cox proportional hazards models in the total sample and by menopausal status. During an average of 7 years of follow-up, 1,016 women developed DCIS. Multivariable analysis indicated that age, physical activity, height, family history of breast cancer, menopausal status, parity, and years between menarche and first live birth had associations with DCIS risk. Among post-menopausal women not using hormone replacement therapy, body mass index ≥30 kg/m² was associated with increased DCIS risk. This study, the largest to date including both pre-menopausal and post-menopausal women, confirms previous findings indicating correspondence between risk factors for DCIS and IBC and highlights the potential contribution to DCIS risk of anthropometric measures not previously reported to be associated with the disease, such as height and BMI amongst post-menopausal women.