"Pembrolizumab monotherapy remains a standard of care first-line treatment for this group of patients," said lead researcher Dr. Michael Boyer of the University of Sydney, Australia, in reporting the results at the International Association for the Study of Lung Cancer (IASLC) virtual World Conference on Lung Cancer. The results were published simultaneously in the Journal of Clinical Oncology.
The KEYNOTE-598 phase-3 trial enrolled 568 patients with stage-IV NSCLC, a PD-L1 tumor proportion score of 50% or greater and no EGFR or ALK aberrations.
Half were randomly allocated to ipilimumab at 1 mg/kg every six weeks and half to saline placebo for up to 18 cycles. Patients in both groups received 200 mg of pembrolizumab every three weeks for up to 35 cycles.
Median overall survival was 21.4 months for patients taking pembrolizumab plus ipilimumab and 21.9 months for those on pembrolizumab alone (P=0.74). The restricted mean survival-time differences were -0.56 at the maximum observation time and -0.52 at two years, which met criteria for futility, Dr. Boyer reported.
Median progression-free survival (PFS) was 8.2 months in the combination group and 8.4 months in the monotherapy group (P=0.72).
Based on the results, the study was stopped due to futility on the recommendation of the independent data-monitoring committee, which determined the benefit/risk profile of combination therapy did not support continuing the trial.
Treatment-related adverse events occurred in 76.2% of patients treated with combination therapy versus 68.3% of those treated with monotherapy. Grade-3 to -5 adverse events occurred in 35.1% of patients on the ipilimumab/pembrolizumab combination versus 19.6% of those on pembrolizumab alone.
Serious adverse events occurred in 27.7% of patients on combination therapy, leading to death in seven and 13.9% on pembrolizumab monotherapy (no deaths).
KEYNOTE-598 was sponsored by Merck, which markets pembrolizumab as Keytruda.
"KEYNOTE-598 is the first head-to-head study designed to answer the question of whether combining Keytruda with ipilimumab provided additional clinical benefits beyond treatment with pembrolizumab alone in metastatic non-small cell lung cancer, Dr. Roy Baynes, chief medical officer, Merck Research Laboratories, said in a news release.
"The results are clear - the combination did not add clinical benefit but did add toxicity," said Dr. Baynes.
SOURCE: https://bit.ly/3oCNxSb Journal of Clinical Oncology, online January 29, 2021.
By Megan Brooks
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