Primary results from IMpassion131, a double-blind placebo-controlled randomised phase III trial of first- line paclitaxel (PAC) +/- atezolizumab (atezo) for unresectable locally advanced/metastatic triple-negative breast cancer (mTNBC)
AuthorsMiles, D. W.
Barrios, C. H.
Wardley, Andrew M
AffiliationMedical Oncology, Mount Vernon Cancer Centre, Northwood, UK
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AbstractBackground: In the phase 3 IMpassion130 trial, combining atezo with first-line nabpaclitaxel for mTNBC showed significantly improved progression-free survival (PFS) and clinically meaningful overall survival (OS) benefit in patients with PD-L1+ mTNBC [Schmid NEJM 2018]. IMpassion131 (NCT03125902) evaluated atezo + PAC as firstline treatment for mTNBC. Methods: Eligible patients (no prior systemic therapy or ≥12 months since [neo] adjuvant chemotherapy) were randomised 2:1 to atezo 840 mg or placebo (d 1 & 15 q28d), both with PAC 90 mg/m2 (d 1, 8 & 15 q28d) until disease progression or unacceptable toxicity. Stratification factors were tumour PD-L1 status (immune cell [IC] expression <1% vs 1% by VENTANA SP142 assay), prior taxane, liver metastases and geographic region. The primary endpoint was investigator-assessed PFS, tested hierarchically first in the PD-L1+ (IC 1%) population, then in the intent-to-treat (ITT) population. OS and overall response rate (ORR) were secondary endpoints. Results: Of 651 randomised patients, 45% had PD-L1+ mTNBC, 48% were taxane pretreated, 31% had de novo mTNBC and 27% liver metastases. Adding atezo to PAC did not improve PFS or OS in either the PD-L1+ or ITT populations (Table). PFS results in subgroups were consistent with primary results. PAC exposure was not compromised by the addition of atezo. Grade 5 (2% placebo vs 2% atezo) and grade 3/4 AEs (43% vs 49%) were balanced between arms and the safety profile was consistent with known risks of each study drug. Conclusions: Atezo + PAC did not improve PFS or OS vs placebo + PAC. No new safety signals were seen. Potential reasons for the contrast with the benefit seen in IMpassion130 (atezo + nab-paclitaxel) need further exploration.
CitationMiles DW, Gligorov J, André F, Cameron D, Schneeweiss A, Barrios CH, et al. LBA15 Primary results from IMpassion131, a double-blind placebo-controlled randomised phase III trial of first-line paclitaxel (PAC) ± atezolizumab (atezo) for unresectable locally advanced/metastatic triple-negative breast cancer (mTNBC). Annals of Oncology. 2020;31:S1147-S8.
JournalAnnals of Oncology