Patterns of failure and outcomes in triple-negative compared to estrogen receptor–positive breast cancer.

e12760 Background: Advances in molecular classification have led to subtype-specific treatments for breast cancer, improving outcomes while revealing distinct recurrence patterns. This study compares outcomes and failure patterns between triple-negative breast cancer (TNBC) and estrogen receptor–positive (ER-positive) disease. Methods: We conducted a retrospective analysis using whole dataset of the Oncology Research Information Exchange Network (ORIEN), including women with non-metastatic breast cancer. Patients were categorized as TNBC or ER-positive. Outcomes included overall survival (OS), disease-free survival (DFS), locoregional control, and patterns of failure. Results: A total of 1,277 patients with stage I–III breast cancer were included, comprising 276 patients with TNBC and 1,001 with ER-positive disease. The median age was 52 years (interquartile range [IQR], 44–62). Most patients were White (83.3%) and non-Hispanic (84.5%). HER2 was positive in 13.4% of ER-positive disease. Compared with TNBC, ER-positive patients more frequently presented with clinical stage I (37.8% vs. 31.9%) and stage II disease (43.0% vs. 39.9%). In contrast, clinical stage III disease was more common among patients with TNBC than those with ER-positive disease (15.2% vs. 8.0%). Neoadjuvant systemic therapy was administered to 154 patients, including 62 (22.5%) with TNBC and 92 (9.2%) with ER-positive disease. Pathological complete response after neoadjuvant systemic therapy was observed in 14 (9.1%) patients (6 TNBC and 8 ER-positive). Adjuvant systemic therapy was delivered to 641 patients, including 108 (39.1%) with TNBC and 533 (53.2%) with ER-positive disease. Among the ER-positive patients who received adjuvant systemic therapy (n = 533), 498 (93.4%) received adjuvant endocrine therapy. Radiation therapy was delivered to approximately two-thirds of patients in both groups. Among those treated with radiation, 83.7% received whole-breast or chest wall irradiation with nodal coverage. Lymph node irradiation was administered in 36.8% of patients, not administered in 33.7%, and was unknown in 29.5%. With a median follow-up of 75.2 months (range, 0–393.7 months), TNBC was associated with significantly worse overall survival (hazard ratio [HR] 2.85, 95% confidence interval [CI] 2.04–3.96), disease-free survival (HR 2.10, 95% CI 1.56–2.83), and distant metastasis–free survival (HR 2.28, 95% CI 1.25–4.16) compared with ER-positive disease. No significant differences were observed in local control (HR 1.17, 95% CI 0.51–2.70) or regional control (HR 2.28, 95% CI 0.85–6.11) between the two groups. Conclusions: TNBC was associated with significantly worse survival outcomes and higher rates of distant failure compared with ER-positive disease. These results highlight distant metastasis as the dominant pattern of failure in TNBC and support the need for more effective systemic therapies.