SAN FRANCISCO – First-line dual immune checkpoint inhibitor therapy for microsatellite instability–high/DNA mismatch repair–deficient (MSI-H/dMMR) metastatic colorectal cancer has impressive durability, an update of the multicohort CheckMate 142 trial shows.
“We all know that MSI-H colorectal cancer patients have a poor prognosis,” said lead investigator, codirector of the Colorectal Center and section head of the GI oncology program at the University of Southern California Norris Comprehensive Cancer Center, Los Angeles. First-line chemotherapy in this population yields median overall survival on the order of 20-22 months.
The cohort of 45 patients treated on the phase 2 trial received the programmed death–1 inhibitor nivolumab (Opdivo) every 2 weeks, plus a low dose of the CTLA4 inhibitor ipilimumab (Yervoy) every 6 weeks as first-line therapy for MSI-H metastatic colorectal cancer. (Nivolumab, with or without ipilimumab, has received Food and Drug Administration accelerated approval as second-line therapy based on data from other cohorts in the trial.)
Previously reported initial results, at a median follow-up of 13.8 months, showed that the investigator-assessed objective response rate was 60% (). As of the update, now at a median follow-up of 19.9 months, that rate was 64%, according to data reported at the 2020 GI Cancers Symposium.
“Nivolumab and ipilimumab demonstrates clinically meaningful durable benefits and may present an option for first-line treatment for MSI-H metastatic colorectal cancer patients,” Dr. Lenz summarized.
“The incredible complete response rates and overall response rates seen are never seen with chemotherapy, and it’s very well tolerated, so if I have a choice, I would start with nivolumab-ipilimumab in first-line MSI-H,” he added. “The [National Comprehensive Cancer Network] guidelines recommend that you can start in first line with this combination if patients are not candidates for chemotherapy. So they leave this door open, that you have an opportunity to use immunotherapy in this patient population.”
Choosing single or dual immunotherapy
Given the so-called financial toxicity of dual nivolumab and ipilimumab therapy and lack of a randomized comparison against single-agent nivolumab, a session attendee said, can clinicians simply use the latter?
“Very importantly, in this clinical trial, ipilimumab was given every 6 weeks. As you know, the 2-week regimens are significantly more toxic,” Dr. Lenz noted. The combination using this low dose has safety similar to that seen with nivolumab alone. And in cross-trial comparisons, at least, “the combination seems to be a little bit more active, so I always choose both,” he said, adding that the financial aspects are beyond his purview.
However, session cochair, the Mok Hing Yiu Professor of Medicine in the department of medicine and therapeutics at the Chinese University of Hong Kong, had a different view.
“I think there is still room for a randomized study to prove the combination’s superiority against single immunotherapy,” he said in an interview. “If I’m treating an MSI patient, I would stick to single immunotherapy until I see more evidence that this combination has a substantial improvement in the outcome that is worth the money.”