An experimental drug is showing promise for the treatment of men with an aggressive form of advanced prostate cancer. A new multicenter study found that the hormone treatment called MDV3100 is safe and effective for patients with castration-resistant prostate cancer (CRPC). This form of cancer, where the testicles have been removed surgically, is known for its poor prognosis and limited treatment options. The research appears in The Lancet.
According to the findings of the Phase 1-2 study, MDV3100 not only shrank patients' tumors, but also reduced blood levels of the tumor marker prostate-specific antigen (PSA). In addition, it stabilized the disease that had spread to soft tissues and the bone, and it reduced the number of circulating tumor cells in the blood.
"We were encouraged to see antitumor activity in men whose disease had spread to other parts of the body after either becoming resistant to previous hormone treatments or progressing following chemotherapy," the study's lead author Howard Scher, M.D., Chief of the Genitourinary Oncology Service at Memorial Sloan-Kettering, said in a statement. "These findings strengthen the drug's potential to change the outlook for a group of patients who currently have limited effective treatment options from which to choose."
According to the research, MDV3100 slows tumor growth and induces tumor cells to die in men with CRPC, which depends on male hormones to grow, but is unresponsive or becomes resistant to standard therapies used to lower or block those hormones.
In the current study, 140 patients were treated with doses of MDV3100 ranging from 30 to 600 mg daily. PET imaging, bones scans, and blood tests were used to assess the antitumor effects of the drug at all dosages. Investigators reported declines in PSA of at least 50 percent in more than half of the patients and tumor regressions in 22 percent of the patients. Overall, two-thirds of patients had partial remissions or stable disease in tumors that had spread to soft tissue or bone.
The findings also showed that the number of circulating tumor cells fell in 49 percent of patients. This is important because previous research shows that changes in circulating tumor cell counts after treatment were more predictive of survival than were changes in PSA.
Based on the positive results of the current study, a multinational, randomized Phase 3 clinical trial has begun to examine MDV3100 versus a placebo for the treatment of men with advanced prostate cancer who were previously treated with chemotherapy.
