Metastatic breast cancer outcome in a real-world setting: analysis for long-term survival and curability in a prospective dataset

BACKGROUND: Treatment advances in metastatic breast cancer (MBC) have led to prolongation in overall survival (OS), nevertheless MBC is considered an incurable disease. Real-world data provides an opportunity to assess outcomes in an unselected patient population receiving standard-of-care therapy and assess for potential curability. METHOD: Patient, tumor and treatment characteristics collected prospectively were analyzed. Univariate and multivariate analyses were performed for characteristics associated with OS ≥10-years. Time-to-next treatment (TTNT) and OS were compared to published clinical trials with significant survival benefits. Patients were deemed long-term survivors (LTS) if OS ≥5 or 10 years (TN or non-TN disease, respectively). Overall survival surpassing results in the recent ESME cohort analysis were deemed long-term responders (LTR). A stringent definition was used to define potentially cured patients. RESULTS: Metastatic breast cancer patients (n = 920) diagnosed between February 1999 and January 2021 were included. Overall survival ≥10 years was significantly more likely in those with de novo MBC, one anatomical metastatic site throughout the illness, HER2-positive disease, ≤3 metastatic sites at diagnosis, pathological concordance between primary/metastatic tissue and clinical trial participation (all P < .001). Efficacy of first-line chemotherapy (n = 452) or endocrine therapy (n = 272) demonstrated similar or longer TTNT and/or OS compared to published results for most regimens evaluated. LTS or LTR were seen in 16% of patients, with 8.7% potentially cured. CONCLUSIONS: Effective clinical trial outcomes can be achieved in a real-world setting. Overall survival ≥10-years and durable responses, with potential cure is possible. Real-world data provides valuable long-term outcome information and optimism for MBC patients.