SEQUENTIAL TREATMENT PATTERNS IN METASTATIC TRIPLE-NEGATIVE BREAST CANCER (MTNBC) USING JAPANESE CLAIMS DATA

OBJECTIVES: To analyze sequential treatment patterns in patients with TNBC and visualize transitions across treatment lines using a large Japanese claims database.
METHODS: A retrospective observational study was conducted using the JMDC claims database in Japan. TNBC patients were identified using a proxy definition based on the use of TNBC-related anticancer agents and the absence of hormone receptor-targeted and HER2-targeted therapies. Metastatic patients were identified using ICD-10 codes (C77-C80). Drugs administered within the same month were treated as combination regimens, and first-, second-, and third-line therapies were constructed at the patient level. Treatment frequencies and transitions between treatment lines were summarized descriptively and visualized using Sankey diagrams.
RESULTS: In first-line treatment, epirubicin/cyclophosphamide (19.7%) and doxorubicin/cyclophosphamide (16.4%) were the most frequently observed regimens. In second-line treatment, paclitaxel (29.9%) and docetaxel (23.4%) were the most common regimens. In third-line treatment, gemcitabine (18.9%) and capecitabine (18.2%) were the major regimens observed. Transition analyses demonstrated that the most frequently observed sequential treatment patterns from first- to third-line therapy consisted of anthracycline plus cyclophosphamide regimens followed by taxane-based therapies and subsequently capecitabine- or gemcitabine-based regimens. Among these, the most common treatment sequences were doxorubicin/cyclophosphamide → paclitaxel → capecitabine and epirubicin/cyclophosphamide → paclitaxel → capecitabine. Sankey diagram analyses showed substantial heterogeneity in treatment sequences among patients with mTNBC.
CONCLUSIONS: This study visualized real-world treatment sequences among Japanese patients with mTNBC. While anthracycline plus cyclophosphamide regimens were frequently followed by taxane-based therapies, diverse regimens including gemcitabine, capecitabine, and eribulin were commonly observed in later treatment lines. The treatment sequences identified in this study may serve as a foundation for future cost-effectiveness analyses and optimization of sequential treatment strategies.