Only 10 to 15 percent of patients with metastatic kidney cancer respond to standard immunotherapy, and there are no standard effective therapies for patients who fail or can't tolerate standard immunotherapy. In this study, however, 42 percent (21 of 50) of patients had their tumors shrink at least 25 percent within the first 12 weeks. Six of those patients had a reduction of 50 percent or more.
Another 26 percent (13 patients) had their tumors stabilize within 25 percent of pre-treatment size. The remaining 32 percent left the study because of progressive disease or adverse effects, such as a painful rash or diarrhea.
"This is the most exciting thing in oncology since Gleevec," said the study's lead investigator, Mark Ratain, M.D., professor of medicine and chief of clinical pharmacology at the University of Chicago. "All but one of the kidney cancer patients in this study had advanced disease that did not respond to at least one previous systemic treatment, yet almost half of them had a rapid and very encouraging response to this drug."
The study also served to validate a new approach to phase II trial design. Most phase II trials test the effects of a new drug on patients with a specific disease, such as colon cancer, and limit the goal to determining the percentage of patients who have at least a 50% reduction in tumor size. This study, a "randomized discontinuation trial," enrolled patients with many different tumor types for 12 weeks, then randomized patients with stable disease to placebo vs. continued treatment.