Early in the trial, preliminary analysis of 17 men receiving low doses of itraconazole showed that only two of them (11.8 percent) had stable or declining PSA. Because of the limited response, no further men were given low doses of the drug.
However, 11 of 24 (48.4 percent) men taking high doses of itraconazole had stable or declining PSA levels lasting at least 24 weeks. In addition, nearly a third of men taking the high dose had PSA reductions of 30 percent or more. Metastatic prostate cancer patients receiving no treatment typically would worsen in eight to 12 weeks, according to Antonarakis.
The investigators also found that 12 of 14 men taking high doses of itraconazole had lower levels of circulating tumor cells present in their blood after therapy, compared with their baseline levels.
Seven patients experienced side effects, including low potassium, hypertension and fluid retention, but the problems were resolved with potassium replacement pills, anti-hypertension drugs, and diuretics.
"We also tested whether itraconazole acted as hormone therapy by tracking levels of testosterone and DHEA (a testosterone derivative) in the blood, and we found no reductions of either testosterone or DHEA," says Antonarakis. "This finding shows that itraconazole is not just another hormone therapy, and has a unique mechanism of action."
Antonarakis and colleagues next plan to examine blood and skin samples taken from study participants specifically to look for levels of proteins linked to tumor blood vessel formation and the Hedgehog pathway.
"With these results, we believe that high-dose itraconazole is worth studying in a larger group of men with advanced prostate cancer," adds Antonarakis.
|Contact: Vanessa Wasta|
Johns Hopkins Medical Institutions