Real-world treatment patterns and clinical outcomes with tucatinib-based therapy in patients with HER2-positive metastatic breast cancer: analyses of two nationwide administrative health claims databases.

Purpose: To describe real-world characteristics and clinical outcomes among patients with HER2+ MBC receiving tucatinib-based treatments.

Methods: This retrospective study included patients diagnosed with HER2+ MBC between January 2017 and December 2022 from two administrative health claims databases, MerativeMarketScan and the Komodo Healthcare Map. Patient characteristics were captured at baseline (≤ 6 months prior to tucatinib initiation). Outcomes were assessed starting from tucatinib-based treatment initiation and included real-world time to discontinuation (rwTTD) and treatment persistence.

Results: There were 150 patients in MarketScan who received tucatinib-based therapy: median (IQR) prior lines of therapy (LOT) was 2 (2-4) and 110 patients (73.3%) had brain metastases. 436 patients in Komodo received tucatinib-based therapy: median (IQR) prior LOTs were 2 (1-3), and 307 (70.4%) had brain metastases. Median (95% CI) rwTTD was 7.4 (5.0-13.1) months in MarketScan (median follow-up 9.7 months) and 9.0 (7.4-9.8) months in Komodo (median follow-up 10.3 months). In patients who received tucatinib in combination with trastuzumab and capecitabine immediately following trastuzumab deruxtecan (T-DXd) and after ≥ 2 prior HER2-directed therapies (MarketScan: n = 26, median prior LOT 4; Komodo: n = 34, median prior LOT 3), median (95% CI) rwTTD was 5.5 (3.4-not reached [NR]) months in MarketScan and 4.8 (3.2-NR) months in Komodo.

Conclusion: These results reinforce the real-world effectiveness of tucatinib in patients with HER2+ MBC, including patients with prior T-DXd treatment. Further research is needed to determine the optimal treatment sequencing for patients with HER2+ MBC.