Atezolizumab combination improves advanced TNBC survival
medwireNews: First-line treatment with the programmed cell death ligand 1 (PD-L1) inhibitor atezolizumab plus nab-paclitaxel has achieved a significant progression-free survival (PFS) advantage over taxane chemotherapy alone in patients with metastatic triple-negative breast cancer (TNBC), research suggests.
The primary endpoint of the intention-to-treat analysis showed a benefit with atezolizumab 840 mg on days 1 and 15 of a 28-day cycle plus nab-paclitaxel 100 mg/m2 on days 1, 8 and 15 compared with placebo plus nab-paclitaxel on the same dosing schedule, with a median PFS of 7.2 versus 5.5 months and a significant hazard ratio (HR) for progression or death of 0.80.
However, presenting author Peter Schmid, from Barts Cancer Institute in London, UK, explained to delegates that the improvement in the whole population of 902 patients was driven by the subgroup of patients with PD-L1-positive disease.
The 185 patients with PD-L1 expression of 1% or more on tumour-infiltrating cells in the atezolizumab arm had a median PFS of 7.5 months versus 5.0 months for the 184 PD-L1-positive controls, with a significant HR of 0.62.
After a median follow-up of 12.9 months, median overall survival (OS) in the intention-to-treat analysis was “numerically better” in the atezolizumab than placebo group, at 21.3 versus 17.6 months and a HR of 0.84, but the difference was not statistically significant.
The hierarchical trial design prevented formal OS analysis of the PD-L1-positive patient subgroup, but the atezolizumab plus nab-paclitaxel patients in this subgroup achieved a median OS of 25.0 months versus 15.5 months for controls, giving a HR of 0.62.
The objective response rate was also higher among the PD-L1 patients given the atezolizumab regimen, at 58.9% versus 42.6% for those using placebo plus nab-paclitaxel; this included a higher rate of complete response, at 10.3% and 1.1%, respectively.
The toxicity profile was “consistent” with earlier separate studies of atezolizumab and nab-paclitaxel, with grade 3 or 4 side effects reported by 48.7% of patients in the combination arm and 42.2% of controls. Peripheral neuropathy at this severity was more common with atezolizumab plus nab-paclitaxel, affecting 5.5% of patients versus 2.7% with placebo and nab-paclitaxel.
“A benefit with atezolizumab–nab-paclitaxel in patients with PD-L1-positive tumors that was shown in our trial provides evidence of the efficacy of immunotherapy in at least a subset of patients”, the IMpassion130 investigators conclude.
“It is important for patients’ PD-L1 expression status on tumor-infiltrating immune cells to be taken into consideration to inform treatment choices for patients with metastatic triple-negative breast cancer.”
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