Survival Benefit of Breast Surgery for Low-Grade Ductal Carcinoma In Situ: A Population-Based Cohort Study.

IMPORTANCE While the prevalence of ductal carcinoma in situ (DCIS) of the breast has increased substantially following the introduction of breast-screening methods, the clinical significance of early detection and treatment for DCIS remains unclear. OBJECTIVE To investigate the survival benefit of breast surgery for low-grade DCIS. DESIGN, SETTING, AND PARTICIPANTS A retrospective longitudinal cohort study using the Surveillance, Epidemiology, and End Results (SEER) database from October 9, 2014, to January 15, 2015, at the Dana-Farber/Brigham Women's Cancer Center. Between 1988 and 2011, 57,222 eligible cases of DCIS with known nuclear grade and surgery status were identified. EXPOSURES Patients were divided into surgery and nonsurgery groups. MAIN OUTCOMES AND MEASURES Propensity score weighting was used to balance patient backgrounds between groups. A log-rank test and multivariable Cox proportional hazards model was used to assess factors related to overall and breast cancer-specific survival. RESULTS Of 57,222 cases of DCIS identified in this study, 1169 cases (2.0%) were managed without surgery and 56,053 cases (98.0%) were managed with surgery. With a median follow-up of 72 months from diagnosis, there were 576 breast cancer-specific deaths (1.0%). The weighted 10-year breast cancer-specific survival was 93.4% for the nonsurgery group and 98.5% for the surgery group (log-rank test, P < .001). The degree of survival benefit among those managed surgically differed according to nuclear grade (P = .003). For low-grade DCIS, the weighted 10-year breast cancer-specific survival of the nonsurgery group was 98.8% and that of the surgery group was 98.6% (P = .95). Multivariable analysis showed there was no significant difference in the weighted hazard ratios of breast cancer-specific survival between the surgery and nonsurgery groups for low-grade DCIS. The weighted hazard ratios of intermediate- and high-grade DCIS were significantly different (low grade: hazard ratio, 0.85; 95% CI, 0.21-3.52; intermediate grade: hazard ratio, 0.23; 95% CI, 0.14-0.42; and high grade: hazard ratio, 0.15; 95% CI, 0.11-0.23) and similar results were seen for overall survival. CONCLUSIONS AND RELEVANCE The survival benefit of performing breast surgery for low-grade DCIS was lower than that for intermediate- or high-grade DCIS. A prospective clinical trial is warranted to investigate the feasibility of active surveillance for the management of low-grade DCIS.