Comparative Effectiveness of Palliative Chemotherapy in Metastatic Breast Cancer: A Real-World Evidence Analysis

In the absence of randomized controlled trials, real-world evidence may aid practitioners in optimizing the selection of therapy for patients with cancer. The study's aim was to determine real-word use, as well as compare effectiveness, of single-agent and combination chemotherapy as palliative treatment for female patients with metastatic breast cancer (mBC).

Using administrative claims data from the Symphony Health's Integrated Oncology Dataverse, female patients with mBC treated with at least one chemotherapy-only treatment (COT) between January 1, 2013, and December 31, 2017 were selected. The frequency of use of single-agent versus combination chemotherapy overall and by line of therapy (LOT) was calculated whereas effectiveness was measured using time to next treatment (TNT).

A total of 12,381 patients with mBC were identified, and 3,777 (31%) received at least one line of COT. Of the 5,586 observed LOTs among the 3,777 patients, 66.5% were single-agent and 33.5% combination chemotherapy. Combination chemotherapy was most frequently used in first-line (45%) and least frequently in fifth-line (16%). Across all LOTs, median TNT was significantly longer for single-agent versus combination chemotherapy (5.3 months vs. 4.1 months, p < .0001). Comparison of median TNT by LOT showed significance in third-line and greater but not in first-line or second-line. Among single agents, the median TNT for patients receiving capecitabine was longest in comparison to all other single agents.

The frequency of combination COT use, particularly in first-line, warrants further research given published guideline recommendations. The observed TNT difference favoring single-agent treatment in later lines supports guideline recommendations. Variance between single-agent preference and observed TNT was noteworthy.

Although published data from evidence- and consensus-based guidelines recommend single-agent over combination chemotherapy, the extensive list of agents available for use and a gap in the comparative effectiveness research of these agents have resulted in significant variances in patterns of care. The aim of this study was to assess real-world treatment patterns and their effectiveness during palliative therapy of metastatic breast cancer. The objective was to understand when and how chemotherapy-only treatment is used in metastatic breast cancer and whether comparative effectiveness analysis supports the observed patterns of care.