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

Background: 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).

Materials And Methods: 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).

Results: 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.

Conclusions: 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.

Implications For Practice: 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.