ABREAST: a prospective, real-world study on the effect of nab-paclitaxel treatment on clinical outcomes and quality of life of patients with metastatic breast cancer.

The efficacy of nab-paclitaxel in patients with metastatic breast cancer (MBC) has been demonstrated in randomized clinical trials. However, real-world evidence on effectiveness remains limited. The primary objective of this multicenter prospective study was to assess the overall response rate (ORR) of patients with MBC treated with nab-paclitaxel. Secondary objectives included progression-free survival (PFS), overall survival (OS) and quality of life, assessed with the Functional Assessment of Cancer Therapy-Breast (FACT-B) instrument. Eligible patients (N = 150; 36% with de novo MBC presentation) with a median age of 64.5 years were enrolled (86% were ER+, 33.3% (50/150) were ≥ 70 years of age and 53% were treated in the third or later line of treatment). A median of 6 cycles were administered but 26% of patients required dose reduction due to toxicity. The ORR was 26.7% [95% confidence interval (CI) 19.6-33.7], the median PFS was 6.2 months (95% CI 5.2-7.3), and the median OS 21.1 months (95% CI 17.2-not estimable). There was no statistical significant difference in the median PFS of patients < and ≥ 70 years of age. The patients' baseline FACT-B total score remained unchanged. The serious and non-serious adverse event incidence rates were 13% and 48%, respectively. This prospective study provides further evidence on quality of life, efficacy, and safety of nab-paclitaxel in patients with MBC and sheds more light in special subpopulations such as the elderly and those treated beyond the second line.