Immunotherapy for Breast Cancer Has Arrived

The impact of immunotherapy as a component of standard treatment has been felt much more slowly in breast cancer than in other malignancies. Small trials have suggested the potential of checkpoint inhibitors, particularly in triple-negative breast cancer (TNBC), but randomized trials have been lacking.

Now, investigators report the results of an industry-sponsored, randomized, phase III trial (IMpassion130) in which 902 untreated TNBC patients received nab-paclitaxel with or without atezolizumab, a monoclonal antibody that targets PD-L1 and prevents interaction with PD-1 and B7-1, a costimulatory cell surface protein. Through this mechanism, T-cell suppression is reversed, leading to an antitumor effect. Also, taxanes are not only active in TNBC, they also may potentiate the antitumor effect of checkpoint inhibitors such as atezolizumab.

At a median follow-up of 12.9 months, median progression-free survival (PFS; the primary endpoint) was prolonged for patients receiving nab-paclitaxel plus atezolizumab versus nab-paclitaxel plus placebo (7.2 vs. 5.5 months; hazard ratio, 0.80; P=0.002). In the subset of patients with PD-L1–positive tumors, median PFS was also prolonged with atezolizumab (7.5 vs. 5.0 months; HR, 0.62; P<0.001). Overall survival (OS) was nonsignificantly longer with atezolizumab versus placebo for all patients (21.3 and 17.6 months, respectively). Adverse events were similar between treatment arms, although nausea, cough, neutropenia, fever, and hypothyroidism were more common among those receiving atezolizumab.