Experimental Drugs Do Battle Against Advanced Prostate Cancer

TUESDAY Jan. 31, 2012 -- Two new drugs, taken alone or potentially together, may boost survival for men with advanced prostate cancer, studies suggest.

The results were so promising that both trials were stopped early to make sure all participants could benefit from the drugs.

Men enrolled in both studies had what's known as "metastatic castration-resistant prostate cancers" -- tumors that had continued to grow and spread despite standard treatment aimed at lowering testosterone levels. (The male hormone testosterone is thought to feed prostate cancer).

The data were presented in San Francisco on Tuesday as part of the Genitourinary Cancers Symposium, sponsored in part by the American Society of Clinical Oncology (ASCO).

According to ASCO, more than 241,000 men in the United States will be diagnosed with prostate cancer in 2012, and 28,000 men will die from the disease.

Prostate cancer often spreads to the bone, but one of the new drugs, called radium-223 chloride (Ra-223), improved survival and delayed cancer-related bone problems in men with advanced, spreading tumors, the researchers said. The first in a new class of prostate cancer medications, Ra-223 delivers bursts of radiation to the bone, targeting the tumor.

The study included 922 men with advanced prostate cancer that had spread to the bone. The men were randomly selected to receive either Ra-223 plus best supportive care or a placebo along with similar care. Supportive care was aimed at alleviating the symptoms of the cancer, including pain.

The new drug seemed to help, boosting survival to an average of 14 months compared with just over 11 months for those on the placebo. Additionally, the average time to the first bone-break, fracture or need for radiation or surgery was significantly delayed among men treated with the new drug compared to their counterparts who received placebo -- from 8.4 months without Ra-223 to 13.6 months with it. The treatment also appeared safe, the research team concluded.

"The U.S. Food and Drug Administration said it will fast track [this drug], and I don't think additional data will be required," study lead author Dr. Oliver Sartor, professor of cancer research at the Tulane University School of Medicine in New Orleans, said at a meeting press briefing. He said the hope is that this drug will be available to patients in 2012. Ra-223 is being developed by Algeta ASA and Bayer Healthcare. The study was funded by Algeta ASA.

In a second trial, another experimental medicine, called MDV3100, appeared to boost survival by close to five months among men with advanced prostate cancer. This drug works by preventing male sex hormones (such as testosterone) from binding to receptors on cancer cells (the tumor needs these hormones to survive and thrive).

In the study, close to 1,200 men received either MDV3100 or an inactive placebo. Median overall survival was 18.4 months for men treated with the experimental drug compared with 13.6 months for those receiving placebo.

The new drug also reduced the risk of death by 37 percent compared to placebo, the researchers said.

Side effects included fatigue, diarrhea and hot flushes, and were generally considered mild, lead author Dr. Howard Scher, chief of the genitourinary oncology service and chair of Urologic Oncology at Memorial Sloan-Kettering Cancer Center in New York City, said at the press briefing. This drug is being developed by Medivation and Astellas Pharma. The study was funded by Medivation.

"This is very impressive and unprecedented," added Dr. Nicholas Vogelzang, chair and medical director of the developmental therapeutics committee of U.S. Oncology, a research network specializing in cancer clinical trials. He moderated the press conference announcing the new study results. "This is going to change the way we take care of patients who we see in the office," he said.

The real gold may be in combining the two therapies, the experts theorized. "These drugs are going to be used in sequence and we would expect the survival to be fairly dramatically pushed forward," according to Scher. "There will be a major bump up in the overall survival of this group of patients in the next two to three years."

Vogelzang agreed: "The synergistic benefit will have to be demonstrated, but it is very plausible that combining and sequencing these agents may add even more value than what we see here." He was a co-investigator on the Ra-223 study.

Findings presented at medical meetings are typically considered preliminary until they have been published in a peer-reviewed journal.

More information

There's much more on prostate cancer at the American Cancer Society.

Posted: January 2012


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