Abstract Recent trials have shown the efficacy of trastuzumab deruxtecan (T-DXd) in HER2-negative patients, but there is not yet a way to identify which patients will best respond, especially with the inability of current HER2 IHC and FISH assays to accurately determine HER2 expression in the unamplified setting.Here, we present a heavily pre-treated patient with triple-negative breast cancer (HER2 IHC 0 who had a complete response to T-DXd.In this case, we used a CLIA-certified reverse-phase protein array-based proteomic assay (RPPA) to determine that the Strong Time-Consistent Solution for Cooperative Differential Games with Network Structure patient had moderate HER2 protein expression (HER2Total 2+, 42%) and activation (HER2Y1248 1+, 23%).Using these results, we determined that the patient may benefit from T-Dxd despite being Analytically Computing the Moments of a Conic Combination of Independent Noncentral Chi-Square Random Variables and Its Application for the Extended Cox–Ingersoll–Ross Process with Time-Varying Dimension traditionally qualified as HER2 IHC 0.
These findings highlight the potential for proteomics-based assays that may more accurately quantitate HER2 and (its activation) in the HER2 unamplified/IHC 0 setting to better select patients whose tumors are classically molecularly defined as HER2 IHC 0, but still could respond to HER2-directed therapy, and give patients access to therapies which for which they otherwise would not be eligible.