Could 2 Prostate Cancer Drugs Fight Disease in Earlier Stages?

Two drugs that interfere with cancer's ability to use testosterone for fuel, apalutamide (Erleada) and enzalutamide (Xtandi), are already approved for use against more advanced prostate tumors that don't respond to regular therapy.

But these trials show that the drugs also can improve survival and slow progression in prostate cancers that do respond to regular therapy, which typically involves medication that halts production of testosterone.

Both clinical trials involved patients with prostate cancer that had spread to other parts of their body but who still responded to androgen-deprivation therapy.

"We're slowly starting to see a migration of drugs traditionally saved for advanced stages of disease, where we're incorporating them into earlier stages of disease," said Dr. Bobby Liaw, medical director of the Blavatnik Family Chelsea Medical Center at Mount Sinai, in New York City. He was not involved in the trials.

Apalutamide combined with androgen-deprivation therapy caused a 33% reduction in overall risk of death, compared against patients who received a placebo alongside their androgen-deprivation therapy, said the lead researcher of that clinical trial, Dr. Kim Chi.

Apalutamide also delayed progression of the cancer by 52%, and the length of time before patients required chemotherapy by 61%, said Chi, medical director of the Clinical Trials Unit at the BC Cancer Agency-Vancouver Prostate Center in Canada.

Adding the hormone blocker significantly improved patients' outcomes with few side effects, Chi said.

"It's well-tolerated, both from a side-effect profile and from a quality-of-life perspective," Chi said, noting that side effects differ little from a placebo.

The second trial involved adding enzalutamide to androgen-deprivation therapy, and again positive results were found.

About 80% of men treated with enzalutamide were alive after three years, compared with 72% of men who received standard treatment, the researchers said.

Study co-chair Ian Davis is a professor at Monash University in Australia. "The actual result in patients starting hormonal therapy -- noting patients had a 60% improvement in the time it takes to detect the cancer growing again along with a 33% increase chance of survival -- was far higher than we expected," he said in a news release.

In that trial, 1,125 men were randomly assigned to receive either enzalutamide or placebo, the study authors said.

The next step for researchers will be head-to-head comparisons that will help doctors decide which drugs would work best for specific patients, Liaw said.

"We don't yet have any data to compare these drugs side-to-side. That's where we're going to start to see a bit of debate over which one is arguably the best drug to start with first," Liaw said. "We've never had a lot of satisfying data to help us figure out what is the proper sequence, is there an optimal sequence, should we be combining certain drugs to get a better effect?"

Cost will also be an issue in using these new drugs to fight prostate cancer. "These are really expensive drugs," Liaw said. "These are drugs that cost thousands for a month's supply."

Regardless, it is good for doctors to have more drugs on hand to help patients battle prostate cancer, he concluded.

"We're certainly hoping to have their disease controlled, not just now but for the long haul, and that's what these drugs are showing they have the capability of doing," Liaw said.

Both trials were to be presented at the American Society for Clinical Oncology's annual meeting, in Chicago, this weekend, and they will also be published in the New England Journal of Medicine.

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