Post-Hoc Analysis of the Phase II DESTINY-PanTumor02 Study: Local and Central HER2 IHC Concordance and Trastuzumab Deruxtecan Efficacy by HER2 IHC Status in HER2-Expressing Solid Tumors.

Makker, Vicky; Lee, Jung-Yun; Oh, Do-Youn; Oaknin, Ana; Puvvada, Soham; Jung, Lindsey; McEwen, Robert; Michelini, Flavia et al. · Clin Cancer Res · 2026

prospective_cohort · Level II

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Abstract

Accurate HER2 status assessment is crucial to identify patients with HER2-expressing tumors. In this post-hoc analysis of DESTINY-PanTumor02 (NCT04482309), we report concordance between local and central HER2 immunohistochemistry (IHC) results. This open-label, Phase 2 study evaluated trastuzumab deruxtecan (T-DXd; 5.4 mg/kg once every 3 weeks) for HER2-expressing (IHC 3+/2+ by local or central testing) locally advanced, unresectable or metastatic solid tumors after ≥1 systemic treatment or without alternative treatments. In total, 267 patients received T-DXd; 75.7% were enrolled based on local test result. Concordance between local and central HER2 test results was 58.6% for IHC 3+, 54.5% for IHC 2+, and 73.4% for IHC 3+ and IHC 2+ tumors combined. The moderate concordance observed between local and central IHC testing in DESTINY-PanTumor02 highlights the need for a validated diagnostic test and standardized algorithm for HER2 status assessment in solid tumors to ensure appropriate patient identification for HER2-directed therapies.