It's early but it sure looks promising.
In very early testing, 19 of 20 patients showed an improvement in the scans used to determine whether cancer has spread to the bone. In some cases, the bone scans could no longer detect any cancer, and the men were able to stop taking the narcotics they were using to control bone pain. To be sure, the results are from very few patients and there was no control group. It is still not known if XL184 prolongs life or how long the improvement in bone scans will last.
“There’s really no precedent for another drug that does this,” said Dr. Matthew R. Smith, a prostate cancer specialist at theMassachusetts General Hospital.
Also, bone scans actually measure bone formation, not the presence of cancer itself. So it cannot be completely ruled out that XL184 somehow stopped bone growth without killing the cancer. However, Dr. Smith said he doubted that was the case because there were signs the drug also controlled tumors outside the bones.
Drugs now used to treat advanced prostate cancer, like Taxotere, do not have much affect on bone scans, Dr. Smith said. Bone drugs like Zometa from Novartis and denosumab from Amgen can protect cancerous bones from fractures, but have not been shown to fight the cancer itself.
Another investigator in the trial, Dr. David C. Smith of the University of Michigan, said he could not believe it when the bone scan of one patient, who previously had widespread cancer in his bones, came back completely clean.
“I thought they had scanned the wrong person,” said Dr. Smith, who is not related to the doctor in Massachusetts. “I’ve never seen anything like this.”