There may be a glimmer of hope in the fight against glioblastoma, the aggressive brain cancer that claimed the life of Sen. John McCain last year.

A small trial reported by the University of California at Los Angeles found that patients with recurrent glioblastoma who were given the checkpoint inhibitor Keytruda^® prior to surgery lived, on average, 417 days. That’s longer than the average survival rate of 228 days.

The treatment is a form of immunotherapy, and the study marks the first time an immune-system treatment has shown any benefit to glioblastoma patients. Authors of the study were quick to add that glioblastoma was not cured in the trial participants and that the early-phase study involved fewer than three dozen patients.

While the study is small and can make it difficult to draw broad conclusions on its impact to most patients, it does have merit said  Dr. Michael Vogelbaum, Moffitt Cancer Center’s chief of Neurosurgery and program leader of Neuro-Oncology.

“The study is remarkable in two ways,” he said. “First, it is one of the few studies that carefully evaluated the effects of treatment on brain tumor tissues. Secondly, it used the surgical procedure itself to help prime the immune system to attack any residual tumor left after surgery.”

Glioblastoma suppresses the immune system, not only at the site of the cancer but throughout the body. That makes it difficult to find effective treatments, especially since tumors like this differ in their characteristics and behavior. Keytruda blocks a protein known as PD-1, which prevents T cells from seeing and attacking the cancer. By disabling that protein, the immune system can better attack a tumor.

“This study helps support the idea that reversal of glioma-induced immunosuppression can lead to more effective treatment of this deadly disease,” Vogelbaum said. “It should be viewed as evidence supporting the development of a larger trial that is designed to provide more certainty about the survival benefit associated with the use of immune checkpoint inhibitors prior to a planned brain tumor surgery.”

More research is needed, but there appears to be a path forward.