The two approaches were compared in more than 600 patients with treatment-naive mesothelioma in the phase 3 CheckMate 743 trial, which was supported by the manufacturer of both immunotherapies, Bristol-Myers Squibb.
The trial “met its primary endpoint of statistically improving overall survival for the experimental arm vs chemotherapy in a prespecified interim analysis,” reported Paul Baas, MD, PhD, Netherlands Cancer Institute, Amsterdam, The Netherlands,
The combined nivo+ipi immunotherapy regimen was associated with a 26% improvement in overall survival. At 2 years, 41% of patients in the immunotherapy arm were still alive, vs 27% in the chemotherapy group.
“This is the first positive randomized trial of dual immunotherapy in the first-line treatment of patients with mesothelioma,” he said. He suggested that it should therefore “be considered as a new standard of care.”
The data were presented on August 8 in the presidential symposium of the World Congress on Lung Cancer 2020, which was held online because of the COVID-19 pandemic.
A key analysis for the study was by histologic subgroup. It is known that standard-of-care chemotherapy performs better in patients with epithelioid as opposed to nonepithelioid tumor subtypes.
Bass highlighted that the performance of nivo+ipi was “almost the same” in patients with epithelioid and nonepithelioid tumors, at a median overall survival of 18.7 months and 18.1 months, respectively.
In contrast, overall survival in the chemotherapy arm was markedly lower in patients with nonepithelioid tumors, at 8.8 months vs 16.5 months among those with epithelioid tumors.
This was reflected in the hazard ratios for overall survival vs nivo+ipi, at 0.46 and 0.86, respectively, the latter nonsignificantly different from combination immunotherapy.
For study discussant Dean A. Fennell, MD, PhD, professor and consultant in thoracic medical oncology, University of Leicester, United Kingdom, the epithet of a “new standard of care” for nivo+ipi should be reserved for nonepithelioid disease.
In this setting, he described the overall survival improvement as “transformative,” considering the “marked chemo resistance” of nonepithelioid tumors, which is “almost certainly” associated with epithelial-to-mesenchymal transition (EMT).
In the future, he suggested, combinations of chemotherapy and immunotherapy involving all histologies or selective targeting of nonepithelioid mesothelioma “could further extend the benefit for patients.”
Improving survival in mesothelioma
“We have been trying to improve the overall survival of patients with mesothelioma now for many decades,” Bass commented. Platinum-based chemotherapy plus pemetrexed is a standard of care, although the 5-year survival rate «is still below 10%,” he noted.
Randomized trials of single-agent immune checkpoint inhibitor therapy in the second-line treatment of patients with mesothelioma have not shown any significant benefits.
However, nivolumab and ipilimumab have a “complementary mechanism of action,” and two previous reports have indicated that together, they have clinical activity in the second-line setting.
The team conducted CheckMate 743 to determine the efficacy of the combination in the first-line setting.
The study involved 605 patients with pleural mesothelioma who had received no prior systemic therapy and had good performance status.
“Patients could have a subsequent therapy,” Bass noted; 44.0% of patients in the experimental arm received subsequent therapy, vs 44.1% of those in the chemotherapy arm.
Of the latter, 20% received an immune checkpoint inhibitor as subsequent therapy.
The minimum follow-up for overall survival was 22.1 months; the median follow-up was 29.7 months.
Nivo+ipi was associated with a significant improvement in overall survival vs standard-of-care chemotherapy, at a median overall survival of 18.1 months vs 14.1 months, with a hazard ratio of 0.74 (P = .0020).
The results indicated that overall survival was similar across key subgroups, which suggests that “no subgroup was harmed” by nivo+ipi, Bass said.