Atezolizumab Misses Event-Free Survival Endpoint in Early Triple-Negative Breast Cancer

Adding atezolizumab to neoadjuvant chemotherapy did not significantly improve event-free survival (EFS) in patients with stage II or III triple-negative breast cancer in the phase 3 NSABP B-59/GeparDouze trial published in Nature Medicine.

The multinational, double-blind, placebo-controlled trial randomly assigned 1550 patients to atezolizumab or placebo with sequential taxane-carboplatin-anthracycline–based neoadjuvant chemotherapy. Adjuvant atezolizumab or placebo was administered after surgery to complete 1 year of study therapy.

At a median follow-up of 46.9 months, the 4-year EFS rate was 85.2% with atezolizumab and 81.9% with placebo (hazard ratio, 0.80; 95% CI, 0.621-1.030; P=0.083). The difference did not meet the prespecified threshold for statistical significance. Overall survival data remained immature; 4-year overall survival was 90.2% with atezolizumab and 89.5% with placebo. Pathologic complete response, a secondary end point, occurred in 63.3% and 57.0%, respectively, an absolute difference of 6.3 percentage points (P=0.009).

Grade 3 or higher treatment-emergent adverse events were reported in 75.3% of patients receiving atezolizumab and 73.4% receiving placebo. Immune-related adverse events were reported in 27.6% and 11.4%, respectively. During the neoadjuvant phase, 25.5% of patients discontinued atezolizumab and 18.8% discontinued placebo.

Prespecified subgroup analyses suggested possible heterogeneity according to nodal status and tumor-infiltrating lymphocyte levels, while exploratory post hoc molecular analyses suggested a possible effect in tumors with the basal-like immune-activated subtype. Because the primary EFS end point was negative and subgroup analyses were not adjusted for multiple comparisons, these findings should be considered hypothesis-generating rather than confirmatory evidence of benefit in a selected population.

Source: Loibl S, Tang G, Nekljudova V, et al. Atezolizumab in early triple-negative breast cancer: the randomized phase 3 NSABP B-59/GeparDouze trial. Nat Med. Published online September 1, 2026. doi:10.1038/s41591-026-04565-6