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, tumour and treatment characteristics collected prospectively were analysed. 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 yrs (TN or non-TN disease respectively). OS 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 MBC patients (N = 920) diagnosed between February 1999 to January 2021 were included. OS ≥ 10yrs 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 < 0.001). 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. Conclusion Effective clinical trial outcomes can be achieved in a real-world setting. OS ≥ 10-years and durable responses, with potential cure is possible. Real-world data provides valuable long-term outcome information and optimism for MBC patients.