Purpose: Triple negative breast cancer is more aggressive than other breast cancer subtypes and accounts for up to 20% of all breast cancers. Despite the poorer prognosis, there are no approved targeted treatments available and chemotherapy remains the only choice. We examined treatment patterns and outcomes among elderly metastatic triple-negative breast cancer (mTNBC) patients in routine clinical practice. Methods: Patients were identified from the linked SEER-Medicare database between

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... 1 and 12/31/2013 and included de novo Stage IV (n = 776) and patients with distant metastasis followed an initial diagnosis of Stage I -III disease (n = 1851). Kaplan-Meier analyses and time-varying Cox proportional hazards regression were used to assess overall survival (OS). Results: The mean age at metastatic diagnosis was 77.6 years and 1259 (48%) patients received chemotherapy. Compared to <70 year olds, ≥70 year olds had worse performance status, higher comorbidity burden, and were less likely to receive chemotherapy (45% vs. 66%). Patients treated with chemotherapy had increased OS compared to untreated patients, and the survival advantage was more pronounced in the <70 year olds with a 6-month longer unadjusted OS compared to the ≥70 cohort (log rank p < 0.0001). This finding was supported in the adjusted multivariate model which showed a 46% increased risk of death for untreated patients in the <70 year olds and a 17% increased risk of death for untreated patients in the ≥70 year olds (vs. treated). Conclusions: In this real-world analysis, 48% of elderly mTNBC patients did not receive chemotherapy and a greater proportion were