New data, new insights
“We already know the KEYNOTE-045 trial is positive,” commented the invited discussant, Dr. Jones. “This longer follow-up data is important because we need to better describe the magnitude of benefit.”
The updated survival findings are exciting because they resemble those seen with ipilimumab in melanoma, with about a fifth of patients still alive several years out, he said. Longer follow-up is needed, but “the data we see today are in keeping with the possibility that we might be seeing a similar long-term tail – the so-called immuno-oncology tail – of survival for patients with urothelial cancer as well.”
Although not statistically significant, the difference in progression-free survival is clinically important, according to Dr. Jones. This benefit is driven by both higher response rate and longer duration of response with pembrolizumab.
Long-term toxicity, especially immune-related toxicity, is also a consideration. “There is a small increment in the number of some of these toxicities, but essentially it hasn’t changed. So it would appear that there is certainly not an unexpected peak of latent immunotoxicity with this treatment,” he noted.
“Our confidence in the data for second-line pembrolizumab, if it needed to be further increased, is increased. This does help our patients make an informed decision about whether or not to accept this treatment,” he summarized.
Turning to the IMvigor 211 biomarker study, Dr. Jones said, “I would argue that the choice of second-line therapy in advanced urothelial cancer is not a clinically important decision. The reason for saying that is the case for second-line chemotherapy is poor. We’ve all used it, but we’ve never had high level evidence of benefit. … But it’s important because when we consider moving into the first-line setting, where there are active alternatives, or maybe even more into the perioperative setting, it actually could be vitally important.”
Studies of immunotherapies and targeted therapies in other cancers suggest that a clinically useful predictive biomarker will identify patients who will derive at least a doubling of favorable outcome or a halving of unfavorable outcome when given the drug as compared with a control. “So it appears that the bar has been set quite high,” Dr. Jones said.
“These IMvigor 211 data are exploratory, and they would need further independent validation, in my view,” he said. Nevertheless, “this may provide us the opportunity to use combinations of biomarkers where now we are seeing a hazard ratio of 0.50 [for risk of death] combining PD-L1 with high tumor mutational burden (TMB). That hazard ratio is bringing it into the area where it may be of a magnitude big enough to use in clinical practice, if this could be validated.”
“I would say that none of these data support a role for second-line cytotoxics after failure of platinum, at least not in preference to a checkpoint inhibitor,” Dr. Jones concluded. “There is still no biomarker to inform a choice in second-line treatment. However, TMB, either alone or in combination with other markers, shows promise, which we need to validate in future randomized trials.”
SOURCE: Bellmunt J et al. GUC 2018 Abstract 410; Powles T et al. GUC 2018, Abstract 409.