After a dry spell, metastatic prostate cancer sees dramatic improvement with new therapies

Prostate cancer has seen its share of progress over the past few years, including several new drugs that have been approved for patients with metastatic disease. On Tuesday, results of two clinical studies were announced that foreshadow additional therapies that will help further extend survival and improve quality of life. While prostate cancer is one of the most common cancers, it has a 99 percent five-year survival rate, with most patients diagnosed at an early stage. But for more than 28,000 men this year, prostate cancer will be fatal. For many of these patients, those with metastatic prostate cancer to the bones or men whose cancer doesn't respond to standard hormonal treatment, Alpharadin and MDV3100 could be very useful. Alpharadin (radium-223) is an intravenous drug that uses alpha particles (a type of ionizing radiation) to kill cancer cells. MDV3100, a new form of hormone therapy, is a pill that works by preventing the tumor cells from using testosterone that can spur cancer growth. The two drugs work very differently and both improve survival, which led some researchers to suggest that combining these agents with other therapies could produce a synergistic response. In the Alpharadin trial (called ALSYMPCA), 922 prostate cancer patients with bone metastases were randomized two to one to Alpharadin or placebo, with all patients receiving best supportive care. Because the most common site of prostate cancer metastasis is typically bone tissue, targeting a drug to delay or attack cancer at the bone seems like a smart idea. That's what Alpharadin does--it targets the cancer cells that have invaded the bone tissue. It's not a cure, but it did prolong survival by 30 percent (14 months versus 11.2 months) and delayed the time to a patient's first skeletal-related event, such as a spinal cord compression or bone fracture by a median of 5.2 months (13.6 months versus 8.4 months). The side effects of the drug are surprisingly minimal--a slight increase in neutropenia and diarrhea. The AFFIRM trial, which involved MDV3100, also randomized patients two to one with the experimental treatment versus placebo. The trial included 1,199 patients with metastatic prostate cancer that had progressed after treatment with docetaxel and other hormonal therapies. The drug increased survival by a median of 4.8 months over placebo (18.4 months versus 13.6 months). Howard Scher, MD, chief of genitourinary oncology at Memorial Sloan-Kettering Cancer Center in New York and co-lead investigator of the AFFIRM study, also noted that more patients treated with the drug experienced tumor shrinkage and more than a 50 percent decline in PSA levels. The drug also delayed cancer growth by five months. Side effects, which included diarrhea, fatigue and hot flashes, were well-tolerated and had similar rates of toxicity to the placebo arm. Nicholas Vogelzang, MD, chair and medical director of the Developmental Therapeutics Committee of US Oncology, who moderated the press briefing on Tuesday, called the results unprecedented. "This will definitely change the way we take care of patients every day in the office." He may not have to wait long. MDV3100 has been submitted to the Food and Drug Administration. And both MDV3100 and Alpharadin have been granted fast-track status, which means they will likely have a quicker-than-usual review by the agency.