Rates of pathologic complete response (pCR) after datopotamab deruxtecan (Dato) plus durvalumab (Durva) in the neoadjuvant setting: Results from the I-SPY2.2 trial.
Authors: Rebecca Arielle Shatsky, Meghna S. Trivedi, Coral Oghenerukevwe Omene, Kevin Kalinsky, Evanthia T. Roussos Torres, Brittani Thomas, Amy Sanford, Kathy S. Albain, Amy Sanders Clark, Carla Isadora Falkson, Claudine Isaacs, Alexandra Thomas, Jennifer Tseng, Laura van 't Veer, Hope S. Rugo, Nola Hylton, Douglas Yee, Christina Yau, Laura Esserman
Journal: Journal of Clinical Oncology (2024)

LBA501 Background: I-SPY2.2 is a multicenter phase 2 platform sequential multiple assignment randomized trial (SMART) in the neoadjuvant breast cancer setting that evaluates novel experimental regimens as first in a sequence (Block A) followed by standard chemo/targeted therapies (Blocks B/C) if indicated. The goal is to achieve a pCR after novel targeted agents alone or in sequence with standard therapies, with the optimal therapy assigned based on the tumor response predictive subtype (RPS). RPS incorporates expression-based immune, DNA repair deficiency (DRD), and luminal signatures with hormone receptor (HR) and HER2 status to subset patients into 6 subtypes: S1: HR+HER2-Immune-DRD-; S2: HR-HER2-Immune-DRD-; S3: HER2-Immune+; S4: HER2-Immune-DRD+; S5: HER2+/non-Luminal; S6: HER2+/Luminal. Methods: RPS S1, S2, S3, and S4 were eligible for assignment to Dato+Durva in Block A. Patients were followed by MRI during treatment (at 3, 6, and 12 weeks after start of Blocks A and B). Predicted responders by MRI and biopsy at the end of Block A or B have the option of going to surgery early; otherwise, they proceed to next treatment Block (B +/- C). Randomization to Block B includes a taxane-based regimen specific to the RPS, and options include S1: paclitaxel; S2 and S3: paclitaxel + carboplatin + pembrolizumab; S4: paclitaxel + carboplatin vs. paclitaxel + carboplatin + pembrolizumab. Patients who did not go to surgery after Block B proceeded to Block C (AC or AC + Pembrolizumab if HR-HER2-). The primary endpoint is pCR. Efficacy is evaluated within each RPS and HR+HER2- and HR-HER2- signatures. To estimate the arm's efficacy as a stand-alone therapy, we use a Bayesian covariate-adjusted model to estimate the pCR rate and compare the posterior distribution to a subtype-specific fixed threshold. This model uses pCR data when available and MRI data when pCR is not. To estimate pCR rate in the context of a multi-decision treatment regimen, we use a Bayesian model based on if and when a pCR occurred in the trial. The posterior is compared to a subtype-specific dynamic control generated from historical I-SPY data. Results: 106 patients were randomly assigned to the Dato+Durva arm between September 2022 and August 2023. The results for Dato+Durva as a stand-alone therapy are summarized in Table. After completion of Block A, 36 patients proceeded to surgery without completing Blocks B/C. Conclusions: Dato+Durva meets threshold for graduation within the RPS S3 subtype based on estimated pCR rate of 72% and warrants further investigation in a larger randomized controlled trial. Clinical trial information: NCT01042379 . [Table: see text]