Does Endocrine Therapy for DCIS Patients Treated with Breast-Conserving Surgery Followed by Postoperative Radiation Therapy is Needed? A Brazilian Retrospective Cohort Study

Abstract

International previous clinical trials have demonstrated increased local control. Adjuvant endocrine therapy (ET) is a component of hormone receptor-positive breast ductal carcinoma in situ (DCIS) treatment. Previous trials have shown local control benefits. However, there are still questions regarding the reproducibility of those results in real-life scenarios and for different populations, especially in patients who received breast-conserving surgery followed by postoperative radiation therapy. Therefore, we retrospectively evaluated the impact of adjuvant ET for CDIS from a large State database in Brazil. We retrospectively evaluated the Fundação Oncocentro de São Paulo (FOSP) database, which collects information on hospitals and oncology departments in the State of São Paulo, Brazil. The endpoints were local control (LC), disease-specific survival (DSS), and overall survival (OS). Moreover, we investigated the influence of medical practice (public health care system, insurance, private) and educational level (illiterate and incomplete middle school were grouped as low; complete middle school, high school, and undergraduate were grouped as medium/high). Data from 2,192 patients who underwent breast-conserving surgery and postoperative radiotherapy and were treated between 2000 and 2020 were analyzed. The median follow-up time was 48.99 months (IQR 29.93 - 88.67). In the cohort, 53.33% (n = 1169) of patients received adjuvant ET, and 46.67% did not (n = 1023). Overall, patients not receiving adjuvant ET tend to be older (p = 0.021) and have a lower educational level (p < 0.001). Median OS and DSS were not reached. The 10-year OS and DSS for patients receiving adjuvant ET versus those not receiving it was 89.36% vs. 91.47% and 97.54% vs. 98.48%, respectively. The HR for OS for adjuvant ET vs. no ET was 0.96 (95% CI 0.63 - 1.4; p = 0.83). The HR for DSS for adjuvant ET vs. no ET was 0.79 (95% CI 0.29 - 2.12; p = 0.63). The only variable associated with survival was educational level. The 10-year OS was significantly higher for patients with medium/high educational levels (93.25% vs. 87.31%). The HR for death for medium/high versus low educational level was 0.51 (95% CI 0.32 - 0.83; p = 0.007). Recurrence rates were low in the cohort. Only 1.5% of patients had local recurrence, and 0.2% had a regional recurrence. There was no significant difference between recurrence rates for adjuvant ET (p = 0.19 and p = 0.78, respectively). The benefits of adjuvant ET in DCIS patients found in international clinical trials could not be demonstrated in a Brazilian cohort. Educational level significantly impacted survival and ET usage, reflecting the influence of socioeconomic factors. Identifying these more vulnerable populations can allow for more precise interventions.