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CHICAGO -- Patients with advanced non-small-cell lung cancer (NSCLC) treated with pembrolizumab (Keytruda) had a greater median survival than patients treated with standard chemotherapy, even if the former had low levels of PD-L1, researchers reported here.

Depending on the percentage of PD-L1 expression in the tumor, survival was between 4 and 8 months longer for patients treated with immunotherapy alone versus those treated with chemotherapy, according to Gilberto Lopes, MD, MBA, of the Sylvester Comprehensive Cancer Center at the University of Miami, and colleagues.

The benefit in overall survival (OS) was accomplished without an increase in adverse events (62.7% with pembrolizumab vs 89.9% with chemo), Lopes said at a press conference at American Society of Clinical Oncology (ASCO) annual meeting.

Serious adverse events were seen in 17.8% of the patients on pembrolizumab and in 41% of patients on chemotherapy, he added.

"Given the overall efficacy and safety profile, pembrolizumab monotherapy is a standard-of-care first-line therapy for PD-L1 expressing, locally advanced or metastatic, squamous or nonsquamous non-small-cell lung cancer," Lopes said.

Pembrolizumab currently has FDA approval for NSCLC patients with a PD-L1 level of ≥50% based on results of the phase III trial. Lopes suggested the current study's findings would expand the population of patients with NSCLC who could be treated with immunotherapy, rather than chemotherapy, in the first-line setting.

The patient population for the KEYNOTE-042 trial consisted of those with previously untreated advanced/metastatic NSCLC, without sensitizing EGFR or ALK alterations, and a PD-L1 tumor proportion score (TPS) ≥1%.

ASCO expert John Heymach, MD, of the MD Anderson Cancer Center in Houston, said the study results are part of "a new era in treatment" and that immunotherapy is pushing the use of chemotherapy to the back burner for many cancer patients. He said about 75% of NSCLC patients with advanced disease would be eligible to receive pembrolizumab, or other target agents, in lieu of chemotherapy as a first-line treatment.

"Immunotherapy with pembrolizumab alone benefits a much larger number of patients than we had previously thought," Heymach said. "This is yet another promising result with immunotherapy in lung cancer that brings new momentum to the treatment of this notoriously difficult disease."

Eligible patients were randomized 1:1 to ≤35 cycles of pembrolizumab 200 mg Q3W, or investigator's choice of ≤6 cycles of paclitaxel plus carboplatin or pemetrexed plus carboplatin with optional pemetrexed maintenance in nonsquamous disease only.

Randomization was stratified by region (east Asia vs non-east Asia), ECOG performance status (0 vs 1), histology (squamous vs nonsquamous), and TPS (≥50% vs 1-49%).

Lopes said that 299 patients with PD-L1 expression of ≥50% who were assigned pembrolizumab achieved a median OS of 20.0 months versus median OS of 12.2 months for 300 patients who received chemotherapy (hazard ratio 0.69, P=0.003).

Of the 413 patients who had a PD-L1 expression of ≥20% treated with pembrolizumab, the median OS was 17.7 months versus median OS 13 months for the 405 patients assigned to chemotherapy (P=0.002).

The 637 patients who had a PD-L1 level of ≥1% who were assigned to receive pembrolizumab achieved a median OS of 16.7 months compared with a median OS 12.1 months for 637 patients assigned to receive placebo (P=0.0018).

"These data confirm and potentially extend the role of [pembrolizumab] monotherapy as a standard first-line treatment for PD-L1–expressing advanced/metastatic NSCLC," the authors concluded, adding that the external data monitoring committee recommended continuing the trial to evaluate progression-free survival.

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