Background: In the phase III IMpassion130 trial, combining atezolizumab with first-line nanoparticle albumin-bound-paclitaxel for advanced triple-negative breast cancer (aTNBC) showed a statistically significant progression-free survival (PFS) benefit in the intention-to-treat (ITT) and programmed death-ligand 1 (PD-L1)-positive populations, and a clinically meaningful overall survival (OS) effect in PD-L1-positive aTNBC. The phase III KEYNOTE-355 trial adding pembrolizumab to chemotherapy for aTNBC showed similar PFS effects. IMpassion131 evaluated first-line atezolizumab–paclitaxel in aTNBC. Patients and methods: Eligible patients [no prior systemic therapy or ≥12 months since (neo)adjuvant chemotherapy] were randomised 2:1 to atezolizumab 840 mg or placebo (days 1, 15), both with paclitaxel 90 mg/m2 (days 1, 8, 15), every 28 days until disease progression or unacceptable toxicity. Stratification factors were tumour PD-L1 status, prior taxane, liver metastases and geographical region. The primary endpoint was investigator-assessed PFS, tested hierarchically first in the PD-L1-positive [immune cell expression ≥1%, VENTANA PD-L1 (SP142) assay] population, and then in the ITT population. OS was a secondary endpoint. Results: Of 651 randomised patients, 45% had PD-L1-positive aTNBC. At the primary PFS analysis, adding atezolizumab to paclitaxel did not improve investigator-assessed PFS in the PD-L1-positive population [hazard ratio (HR) 0.82, 95% confidence interval (CI) 0.60-1.12; P = 0.20; median PFS 6.0 months with atezolizumab–paclitaxel versus 5.7 months with placebo–paclitaxel]. In the PD-L1-positive population, atezolizumab–paclitaxel was associated with more favourable unconfirmed best overall response rate (63% versus 55% with placebo–paclitaxel) and median duration of response (7.2 versus 5.5 months, respectively). Final OS results showed no difference between arms (HR 1.11, 95% CI 0.76-1.64; median 22.1 months with atezolizumab–paclitaxel versus 28.3 months with placebo–paclitaxel in the PD-L1-positive population). Results in the ITT population were consistent with the PD-L1-positive population. The safety profile was consistent with known effects of each study drug. Conclusion: Combining atezolizumab with paclitaxel did not improve PFS or OS versus paclitaxel alone. ClinicalTrials.gov: NCT03125902.

Original languageEnglish
Pages (from-to)994-1004
Number of pages11
JournalAnnals of Oncology
Issue number8
StatePublished - Aug 2021


FundersFunder number
Heron Therapeutics
Janssen-Cilag and Regeneron
Lilly Oncology
Lilly and Daiichi-Sankyo
Roche/Genentech and Novartis
Varifarma and Takeda
Zodiac Pharma
Bristol-Myers Squibb
F. Hoffmann-La Roche
Genomic Health
Boehringer Ingelheim
Takeda Pharmaceutical Company
Merck Sharp and Dohme
Les Laboratories Pierre Fabre
Ipsen Biopharmaceuticals
Clovis Oncology
Jounce Therapeutics
Astellas Pharma


    • PD-L1
    • advanced breast cancer
    • atezolizumab
    • immune checkpoint inhibitor
    • paclitaxel
    • triple-negative breast cancer


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