Drug shows promise in prostate cancer spread to bone

The investigational agent cabozantinib (XL184) shows promise for treating metastatic prostate cancer, according to a multicenter study presented at the American Society of Clinical Oncology annual meeting in Chicago.

"Not only did three-quarters of bone scans have partial or complete resolution, but this was accompanied by improvement in bone pain and decreased need for narcotic use," said lead author Maha Hussain, MD, of the University of Michigan Comprehensive Cancer Center, Ann Arbor.

The trial enrolled 171 men with metastatic prostate cancer. In more than three-fourths of the men enrolled, cancer had spread to the bone.

Researchers found that 76% of patients saw some or all of their tumor shrink on bone scans following treatment with cabozantinib. In addition, among patients who were on narcotics due to bone pain, 67% reported less pain and 56% either stopped taking narcotics or reduced the dosage. In addition, more than two-thirds of patients had some tumor regressions in areas of spread outside the bone. The treatment effects lasted on average 29 weeks.

Cabozantinib produced moderate side effects, including fatigue, gastrointestinal symptoms, and hypertension.

"What’s interesting about this drug is it brings to the table something we haven’t seen before. Dramatic improvements in bone scans are unprecedented in this disease. Despite measurable progress, current treatment options for prostate cancer tend to be modest in effect, so adding to and improving these options is a high priority," Dr. Hussain said.

Funding for the study was provided by Exelixis, the manufacturer of cabozantinib.