Details of the CONFIRM results
Relapsed mesothelioma is an “unmet need,” and, until now, “there have been no phase 3 trials which have demonstrated improved overall survival,” Dr. Fennell said in his presentation.
However, three phase 2 trials have shown that immune checkpoint targeting via PD-1 has shown useful clinical activity as a monotherapy in the relapsed setting, and one of these trials has led to approval of nivolumab in Japan for this indication.
CONFIRM was an investigator-initiated phase 3 trial in patients with relapsed mesothelioma who had received more than one prior line of therapy and had a good performance status.
Recruitment began in April 2017, and the “target sample size was 336 patients,” Dr. Fennell said, but the trial was “halted at 332 patients (in March 2020) due to the peaking of the COVID-19 pandemic in the U.K.”
“However, at the time, it was felt there were sufficient events” to justify the current analysis of the coprimary endpoints of PFS and OS, despite the latter being 59 events short of the target of 291.
Dr. Fennell said that baseline characteristics were “generally well balanced” between the nivolumab (n = 221) and placebo (n = 111) arms.
However, there were more patients with a PD-L1 tumor proportion score (TPS) of at least 1% among the patients given nivolumab, at 37% versus 29% in the placebo arm.
After a median follow-up of 17.1 months in the nivolumab arm and 14.2 months in the placebo group, overall survival was significantly longer with the active treatment, at 9.2 months versus 6.6 months with placebo (hazard ratio, 0.72; P = .018).
The proportion of patients alive at 12 months was 39.5% in the nivolumab group and 26.9% in patients given placebo. Investigator-assessed PFS was also significantly longer with nivolumab, at 3.0 months versus 1.8 months with placebo (HR, 0.61; P < .001).
The proportion of patients disease free at 12 months was 14.5% with active treatment versus 4.9% months with the placebo.
“The role for PD-L1 as a potential biomarker was assessed,” Dr. Fennell said, using the Dako 22C3 antibody, with 150 nivolumab and 84 placebo patients divided into those with a TPS <1% or ≥1%.
He noted that PD-L1 expression in the tumor “did not predict survival for patients in the CONFIRM trial,” with neither PD-L1 positive nor PD-L1 negative patients demonstrating a significant improvement in overall survival with nivolumab vs placebo.
“For histology, epithelioid mesothelioma patients benefited from nivolumab,” Dr. Fennell continued, with a hazard ratio for death of 0.71 versus placebo (P = .021). “However, for the nonepithelioid subgroup, in this immature survival analysis ... the P value was not significant,” but this was a small subgroup of patients (12% in both nivolumab and placebo groups).
The safety analysis revealed that the proportion of patients with any serious adverse events, of any grade or grade 3 or higher, was almost identical between the active and placebo arms, Dr. Fennel reported. There were five deaths (3.6%) related to a serious adverse event in the nivolumab arm and four (5.3%) in the placebo group.
This research was funded by the Stand Up to Cancer campaign for Cancer Research UK, supported by Cancer Research UK core funding at the Southampton Clinical Trials Unit, and investigator-initiated support from Bristol-Myers Squibb for free drug labeling and distribution and funding for RECIST reporting. Dr. Fennell reported relationships with Astex Therapeutics, AstraZeneca, Atara Biotherapeutics, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Clovis Oncology, Eli Lilly, Inventiva, Lab 21, Merck, and Roche. Dr. Hui reported relationships with AstraZeneca, Bristol-Myers Squibb, Eli Lilly, Merck, Novartis, Pfizer, Roche, and Seagen.
A version of this article first appeared on Medscape.com.