Real-World Evidence on the Use of Endocrine Therapy for Ductal Carcinoma In Situ in Patients Treated With Breast-Conser ving Surger y Followed by Postoperative Radiation Therapy: A Brazilian Retrospective Cohort Study

There is a lack of data regarding the real-world reproducibility of findings from randomized controlled trials. This retrospective cohort study evaluated 2,192 patients from the Fundacao Oncocentro de Sao Paulo (FOSP) database and the benefits of adjuvant hormone therapy were not reproduced. Education significantly impacted survival and hormone therapy usage, reflecting the influence of socioeconomic factors. Introduction/Background: This study aims to evaluate the reproducibility of findings from randomized controlled trials regarding adjuvant hormone therapy (HT) for breast ductal carcinoma in situ (DCIS) in a real-life scenario. Materi-als/Methods: This retrospective cohort study used Fundacao Oncocentro de Sao Paulo database. It included DCIS patients DCIS who received breast-conserving surgery and postoperative radiation therapy. The endpoints were local control (LC), breast cancer-specific survival (BCSS), and overall survival (OS). Results: We analyzed 2192 patients treated between 2000 and 2020. The median FU was 48.99 months. Most patients (53.33%; n = 1169) received adjuvant HT. Patients not receiving adjuvant HT tend to be older ( P = .021) and have a lower educational level ( P < .001). At the end of FU, 1.5% of patients had local recurrence, and there was no significant difference between groups ( P = .19). The 10-year OS and BCSS were 89.4% and 97.5% for adjuvant HT versus 91.5% and 98.5% for no adjuvant HT, respectively, and there were no significant differences between groups. The 10-year OS was 93.25% for medium/high education level versus 87.31% for low (HR for death 0.51; 95% CI, 0.32-0.83; P = .007). Conclusions: The benefits of adjuvant HT for DCIS were not reproduced in a Brazilian cohort. Education significantly impacted survival and HT usage, reflecting the influence of socioeconomic factors. These findings can allow for more precise interventions.