Neoadjuvant Phase II Trial in Patients With T1c Operable, HER2-positive Breast Cancer According to TOP2A Status

In this phase II study, we propose a treatment strategy that not only takes advantage of the complementary action of trastuzumab and pertuzumab but also the relevance of an anthracycline-based regimen. Indeed, besides the cardiac toxicity that can be induced by these three agents, anthracycline chemotherapy may not confer benefit to all patients. The underlying scientific hypothesis is based on data from the NEOSPHERE neoadjuvant trial showing that addition of pertuzumab to trastuzumab plus docetaxel improved the pCR rate (46% versus 29% without pertuzumab) in T2-T3 tumors. Therefore, we hypothesize that for smaller tumors (T1c), the pCR rate should be higher, on the order of 60% in patients with the coamplification (with anthracycline therapy) and 55% for the group without coamplification (without anthracycline therapy). The sample size of 90 patients (45 per group) planned for the phase II study will allow 15% precision with the expected pCR rates of 60% (95%CI: 45%-75%) for patients with coamplification and 55% (95%CI: 40%-70%) for those without coamplification. In addition, exploratory analyses will aim to identify predictive markers of pCR in order to target biologically defined subpopulations in which pCR rates might even be higher.