Formal discussant of this trial William Y. Kim, MD, of the University of North Carolina’s Lineberger Comprehensive Cancer Center, Chapel Hill, commented on the fact that the IMvigor study had a substantial number of patients compared with other phase II trials in bladder cancer. “This trial was not enriched for PD-L1 expression, and importantly, negative PD-L1 staining did not preclude response to atezolizumab.”

Although the phenomenon of pseudoprogression has been observed in other trials of checkpoint inhibitors in melanoma, only two patients in this trial of urothelial cancer had any appearance of pseudoprogression.

Dr. Kim pointed out that immune-related response criteria were developed primarily based on melanoma patients treated with CTLA-4 (cytotoxic T-lymphocyte–associated antigen) inhibition. “I do believe these criteria are important, but their utility in tumors other than melanoma is not known,” he added.

“The IMvigor 210 trial suggests that atezolizumab has the potential to change the treatment landscape of platinum-resistant urothelial cancer. We eagerly await results of cohort 1 and need further follow-up to assess the durability of response,” Dr. Kim said.

Two randomized controlled phase III trials of atezolizumab are currently ongoing in advanced bladder and urothelial cancers, and an expanded-access trial is open for post-platinum patients. ■

Disclosure: Dr. Kim reported no potential conflicts of interest.