PREDIX II HER2: Improving pre-operative systemic therapy for human epidermal growth factor receptor 2 (HER2) amplified breast cancer (BC).

Abstract

TPS605 Background: Neo-adjuvant systemic therapy (NAT) is the standard of care for most patients with early HER2-amplified and triple negative breast cancer (BC). Increasing the rate of pathological complete response (pCR) is highly meaningful for those patients, as pCR is strongly predictive for improved long-term disease-related outcomes. Clinical and preclinical evidence support the hypothesis that pCR-rates may be augmented by the addition of checkpoint inhibitors, such as monoclonal antibodies targeting the Programmed Death Ligand receptor 1 (PD-L1), to standard systemic NAT. Studies in different BC patient cohorts (e.g., IMPassion130, PANACEA, KATE2) have indicated that PD-L1 protein expression on tumor-infiltrating lymphocytes (TIL’s) is a predictive marker for checkpoint inhibitor efficacy. Methods: We have initiated a phase II open-label, 2:1 randomized clinical trial where women with early HER2-amplified, PD-L1+ BC (cT2-3 and/or cN+) are treated with standard NAT (composed of anti-HER2 antibodies with a chemotherapy backbone of sequentially taxanes + carboplatin and epirubicin + cyclophosphamide [EC]) +/- atezolizumab during EC. N = 190 patients will be accrued in nine centers in Sweden to be able to demonstrate a 20% increase in pCR-rate, with a power of 80% and a two-sided alpha of 10%. Firstly, a prescreening is performed to select patients with a PD-L1 expression of > 1% on TIL’s. Important exclusion criteria are significant organ dysfunction and (with some exceptions) active auto-immune diseases. Extensive translational side-studies are performed to explore predictive markers for treatment efficacy, including clinicopathologic studies, molecular imaging and microbiome analyses, as well as monitoring of acute and chronic treatment-related toxicity, objective cognitive function and quality of life. As of February 11th, 4 patients have been prescreened and 1 enrolled in the trial. The clinical trial registry number is NCT03894007. Clinical trial information: NCT03894007 .