Prior DCIS and overall mortality in women with stage I breast cancer.

Abstract

e12593 Background: Whether a prior diagnosis of ductal carcinoma in situ (DCIS) impacts women later diagnosed with invasive breast cancer is unclear. If localized breast cancer following DCIS is more aggressive than localized breast cancer alone, this could inform therapy decisions. To our knowledge, no study has examined the impact of prior DCIS on overall mortality in women with stage I invasive breast cancer. The study objective was to determine if overall mortality for women with stage I breast cancer with prior DCIS is different from those with stage I disease without prior DCIS. Our hypothesis was that women with prior DCIS would have higher mortality compared to those without prior DCIS. Methods: 302,484 patients with stage I cancer diagnosed from 1998 to 2016 were ascertained from SEER. Of these, 5,011 (1.7%) had prior DCIS. Patients with DCIS were matched 1:2 to women with no prior DCIS based on age, year of diagnosis, race/ethnicity, marital status, and invasive breast cancer characteristics including histology, tumor grade, tumor size, T stage, N stage, ER/PR status, surgery type, radiation, and chemotherapy status. The primary study outcome was overall mortality. Cox proportional hazards models were used to compute hazard ratios (HR) and 95% confidence intervals (CI). Results: Cases and controls had similar demographics. Compared to women with stage I breast cancer without prior DCIS, overall mortality was statistically significantly lower in women with stage I breast cancer with prior DCIS (hazard ratio [HR] 0.89 95% confidence interval [CI]0.80-0.98). Other factors associated with overall mortality were bilateral mastectomy (adjusted HR: 0.62; 95% CI: 0.49-0.78), radiation therapy (adjusted HR: 0.64; 95% CI: 0.56-0.75) and chemotherapy (adjusted HR: 0.85; 95% CI: 0.72-0.99). Factors associated with higher overall mortality included age (trend p < 0.001), tumor grade (trend p = 0.003), and negative PR receptor status (adjusted HR: 1.29; 95% CI: 1.13-1.45). Breast cancer specific mortality, however, was statistically significantly higher in women with prior DCIS to their breast cancer diagnosis compared to women without prior DCIS to their breast cancer diagnosis (HR 1.24 95% CI 1.01-1.52). Conclusions: Contrary to our hypothesis, women with prior DCIS and subsequent stage I breast cancer have lower overall mortality compared to matched controls with stage I breast cancer without prior DCIS. In contrast, those with prior DCIS have higher breast cancer specific mortality than those without prior DCIS. Reasons for this discrepancy are unknown, but since DCIS is most commonly diagnosed on mammogram, differences may be related to sociodemographic characteristics that are associated with both higher screening adherence and higher overall survival, such as higher income, higher education achievement , and higher access to health care.