Heinz-Josef Lenz, MD, on MSI-H/dMMR Metastatic Colorectal Cancer: Expanded Analyses From CheckMate 8HW

I presented this year the expanded analysis on CheckMate 8HW. Till today we knew that first-line Nivo Ipi improved unprecedentedly the PFS in first line versus chemo with a hazard ratio of 0.21, and PFS2 improved by a hazard ratio of 0.28. We have also seen at ASCO GI that first-line Nivo Ipi improved statistically significant and clinically meaningful the PFS with a hazard ratio of 0.62. What we have not seen is the PFS2 of Nivo Ipi versus Nivo, and we will show today the expanded analysis with a significantly longer follow-up. The median follow-up is now 47 months with this analysis. The comparison of Nivo Ipi versus chemo showed a median PFS of 54.1 months for Nivo Ipi and 5.9 months for chemotherapy. This translated again into a statistically significant and clinically meaningful hazard ratio of 0.21. So it has shown continued benefit of Nivo Ipi over chemotherapy, suggesting that we have a new standard of care for patients with microsatellite instability/mismatch repair–deficient metastatic colon cancer. Now it's important to know that CheckMate was a randomized phase 3 study with 839 patients randomized to Nivo alone, Nivo Ipi, or chemotherapy. There were two dual endpoints: one, progression-free survival of Nivo Ipi versus chemo, and the second dual endpoint was PFS of Nivo Ipi versus Nivo. All patients had centrally confirmed microsatellite instability or mismatch repair deficiency. We presented for the first time the PFS2 of Nivo Ipi versus Nivo, which also showed a statistically significant improvement of the PFS2 with a hazard ratio of 0.57. Why is PFS2 so important? Because PFS2 is defined as the progression of the subsequent treatment or the start of the second subsequent treatment or death, indicating that the sequence—how we give immunotherapy followed by chemotherapy—is significantly better than when you would do chemo followed by immunotherapy. And despite the crossover of 71%, the hazard ratio of Nivo Ipi versus chemo remained at 0.21. In this analysis, we also looked at very interesting other side factors in this patient population. For example, patients who developed grade 3/4 toxicity—do they do better or do they do worse? And we showed they do at least as good, maybe numerically actually better, because the progression-free survival was even better than in the cohort and the overall response rate was 77% compared to 71% in the overall cohort. Interestingly, the complete remission increased to 38%. So certainly these patients who had toxicity did not do worse—statistically the same—but they looked actually a little bit better. We also looked at the emergence of treatment-related side effects and the majority of these happened in the first six months. Comparing Nivo and Nivo Ipi, the frequency of these side effects were very similar with two exceptions: the skin toxicity and the endocrine toxicity are more frequent in the Nivo Ipi arm. So we have learned a lot about mismatch repair–deficient metastatic colon cancer. And all these data suggest since the side effect profile is very manageable for Nivo Ipi, that Nivo Ipi is the new standard of care for patients with diagnosed metastatic colon cancer which are microsatellite instability–high or have mismatch repair deficiency.