Survival outcomes after omission of surgery for ductal carcinoma in situ: A National Cancer Database (NCDB) analysis.

e12574 Background: Clinical trials of active surveillance (AS) for Ductal Carcinoma in Situ (DCIS) are underway. We sought to understand the historical management of biologically favorable DCIS and to determine the long-term outcomes of patients who did not have surgery at time of diagnosis. We hypothesized that women who had biologically favorable DCIS and underwent AS would have excellent long-term outcomes. Methods: The NCDB was queried from 2004 to 2017 for women diagnosed with DCIS. This cohort was further refined to identify those with biologically favorable DCIS defined as grade 1 or 2 and hormone receptor (HR) positive. Women under age 40 were excluded. AS was defined as either no surgery or surgery >12 months from diagnosis. A Cochran-Armitage test was used to assess the trend of surgery omission over year of diagnosis. Multivariable logistic regression was used to assess association between baseline factors and AS. Kaplan-Meier curves were estimated to show overall survival (OS) in this biologically favorable DCIS group that underwent AS, stratified by age (<50, 50-65, >65). Univariate and multivariable Cox proportional hazard models were used to determine the effects of prognostic factors on survival distributions. Results: There were 74,868 women with grade 1 or 2, HR positive DCIS, of whom 2,384 (3.2%) were treated with AS. The proportion of patients with biologically favorable DCIS who underwent AS increased over time, peaking in 2017 with 4.2% of DCIS cases diagnosed that year treated with observation (p<0.001). Only 17% of the patients in the AS group received hormonal therapy. On multivariable analysis, increasing age (OR 1.02, p<0.001), black race (OR 1.7, p<0.001), and being uninsured (OR 2.2, p<0.001) were all associated with increased likelihood of AS. In an unadjusted analysis, receipt of surgery was associated with improved OS in the entire cohort. However, the OS benefit from surgery differed when stratified by age. In women <50 years of age, OS outcomes were similar, with 10-year OS of 97.4% in the immediate surgery cohort vs 99.1% in AS cohort (p=0.43). In contrast, in women >50 years of age, 10-year OS was higher for women undergoing surgery (85.3% vs 70.0% in AS group, p <0.001). This association with OS in this older cohort persisted even after adjusting for age, race and comorbidity as well as facility demographics. Conclusions: The proportion of patients with low or intermediate grade, hormone receptor positive DCIS not treated with surgery has remained small but is increasing over time. AS of biologically favorable DCIS in younger, healthier women is not associated with adverse survival. In older women, the finding of benefit of surgery over AS is very likely confounded by underlying health factors that are not fully captured with co-morbidity scores.