Cardiovascular events and mortality in a population-based cohort initially diagnosed with ductal carcinoma in situ

Background: Ductal carcinoma in situ (DCIS) patients are usually diagnosed through cancer screening programs, suggesting a healthy user effect. In this population-based cohort, we assessed the risk of cardiovascular events and mortality in DCIS patients. Methods: Using the Korean National Health Insurance Service database, 13,740 women, who were initially diagnosed with DCIS between 2007 and 2013, were analyzed. A control group was matched according to age and the year of diagnosis at a 3:1 ratio (n = 41,220). Follow-up was performed until 2016. Subgroup analysis was performed according to the subsequent diagnosis of invasive breast cancer within 1 year: pure DCIS and DCIS+Invasive group. Results: DCIS patients were more likely to have underlying diseases, higher incomes, and to live in urban districts compared to the control group. Women diagnosed of DCIS had lower myocardial infarct risk (hazard ratio [HR] 0.64; 95% confidence interval [CI] 0.46–0.90) and lower stroke risk (HR 0.77; 95% CI 0.60–0.98) compared to the control group. This trend of lower risk was sustained after adjusting for age, income, residence and comorbidities. The mortality rate was similar between the control group and pure DCIS patients but was higher in the DCIS+Invasive group (HR 1.63; 95% CI 1.34–1.98). However, after adjusting for age, income, residence and comorbidities, mortality did not differ between the control group and DCIS+Invasive group (HR 0.99; 95% CI 0.78–1.24). Conclusions: DCIS patients were at lower risk for MI and stroke compared to a control group despite a higher rate of comorbidities, which may reflect changes in health behaviour. The importance of managing pre-existing comorbidities along with DCIS treatment should be emphasized.