Neoadjuvant Atezolizumab in Combination with Dual HER2 Blockade Plus Epirubicin in Women with Early HER2-positive Breast Cancer: the Randomized Phase 2 ABCSG-52/ATHENE Trial

The role of anthracyclines in the treatment of early breast cancer (EBC) is increasingly being challenged, especially in de-escalation strategies. However, owing to their immunogenic effects, anthracyclines are promising combination partners with immunotherapies. In the randomized phase 2 trial ABCSG-52 (EudraCT no. 2019-002364-27), we investigated epirubicin plus immunotherapy in women with human epidermal growth factor receptor 2 (HER2)-positive EBC. A total of 58 patients were randomized 1:1 to two cycles of a chemotherapy-free induction phase (part 1) of dual HER2 blockade with trastuzumab and pertuzumab (TP) plus the anti-programmed death ligand 1 antibody atezolizumab (TP-A) or TP alone. Thereafter, all patients received four cycles of TP-A in combination with epirubicin (part 2). The primary endpoint, pathological complete response (pCR), was met in 35 patients (60.3%; 95% confidence interval (CI) 47.5% to 71.9%), 19 patients (65.5%) in the TP-A group and 16 patients (55.2%) in the TP group. The residual cancer burden 0/I rate and objective response rate (secondary endpoints) in all patients with evaluable data were 80.0% (n = 44/55; 95% CI 67.6% to 88.4%) and 89.3% (n = 50/56; 95% CI 78.5% to 95.0%), respectively. Grade ≥3 adverse events were reported in 17 patients (29.3%). Based on our findings, we conclude that a neoadjuvant chemotherapy de-escalation immunotherapy regimen with trastuzumab, pertuzumab, atezolizumab and epirubicin is effective and safe in patients with HER2-positive EBC.