Atezolizumab monotherapy window preceding combined neoadjuvant chemo- and immune therapy in triple negative breast cancer (TNBC) - the neoMono trial.

INTRODUCTION Exploratory data suggest a benefit of an immune-checkpoint inhibitor (ICI) monotherapy window in early TNBC. The neoMono trial prospectively analyzed whether the addition of an atezolizumab monotherapy window prior to neoadjuvant atezolizumab and chemotherapy improves pCR rates in early TNBC. METHODS NeoMono is a phase 2 randomized multicenter trial that recruited patients with primary TNBC larger than 10 mm. Neoadjuvant treatment consisted of neoadjuvant atezolizumab and chemotherapy, in arm A preceded by atezolizumab monotherapy two weeks before combination therapy. This study used a Bayesian trial design. RESULTS A total of 359 patients were included. Overall, pCR rates in study arms A and B were similar (ITT population: 65.7% and 69.0%, respectively). In an exploratory analysis pCR rates in PD-L1-positive tumors were 91.5% in arm A and 82.2% in arm B. The corresponding pCR rates in the PD-L1-negative group were 56.1% in arm A and 64.5% in arm B. In patients with low-risk TNBC (cT1c AND cN0) pCR rates in the PD-L1-positive group were 100.0% in arm A and 90.0% in arm B, the corresponding pCR rates in the PD-L1 (IC)-negative group were 65.9% and 76.3 %, respectively. CONCLUSION The neoMono trial demonstrated the highest pCR rates reported in a phase II/III trial in TNBC, particularly in the case of PD-L1 positivity. While no significant impact of an ICI monotherapy window on the pCR rate in the unselected ITT population could be demonstrated, our data reinforce the use of combinations of neoadjuvant chemotherapy and ICI in this indication.CCR-25-2186R1.