ABSTRACT

OBJECTIVES – To evaluate the long term risks of invasive breast cancer and death related to breast cancer after nonscreen detected ductal carcinoma in situ. Risks for women in the general population and for women diagnosed with ductal carcinoma in situ via the screening programme were compared. DESIGN – Population based cohort study. SETTING – Data from the National Disease Registration Service. PARTICIPANTS – All 27 543 women in England who were diagnosed with ductal carcinoma in situ, outside the NHS breast screening programme, during 1990 to 2018. MAIN OUTCOME MEASURES – Incident invasive breast cancer and death caused by breast cancer. RESULTS – By 31 December 2018, 3651 women with non-screen detected ductal carcinoma in situ had developed invasive breast cancer, more than four times higher than expected from national cancer incidence rates (ratio of observed to expected rate was 4.21 (95% conference interval 4.07 to 4.35)). The ratio of observed to expected rate of developing invasive breast cancer remained increased throughout follow-up among women aged <45-70 years. The 25 year cumulative risks