The results of the IMpassion131 trial that were presented at the 2020 Congress of the European Society for Medical Oncology1 started important discussions in the oncology community about the role of atezolizumab, a programmed death–ligand 1 (PD-L1) inhibitor, in treating metastatic triple-negative breast cancer (mTNBC), especially surrounding the discrepancy in the overall survival (OS) results of the IMpassion131 trial compared with those of previously published IMpassion130.2 These trials tested the benefit of adding atezolizumab to taxane in first-line treatment of mTNBC. IMpassion130 demonstrated a progression-free survival (PFS) benefit with the addition of atezolizumab to nab-paclitaxel in the intention-to-treat (ITT) analysis and PD-L1–positive subgroup and seemingly an OS benefit only in the PD-L1–positive subgroup, whereas in IMpassion131, atezolizumab plus paclitaxel did not improve PFS nor OS in the ITT or PD-L1–positive group vs paclitaxel alone. Several explanations have been proposed for these discrepant results.3,4 We believe these discussions miss a simpler and parsimonious explanation, that atezolizumab does not improve OS in mTNBC. In this Viewpoint, we offer some reasons why this may be the best explanation for the observed differences between IMpassion130 and IMpassion131.
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Van Wambeke S, Gyawali B. Atezolizumab in Metastatic Triple-Negative Breast Cancer—No Contradiction in the Eyes of a Dispassionate Observer. JAMA Oncol. 2021;7(9):1285–1286. doi:10.1001/jamaoncol.2021.1966
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