Prostate cancer. Source: NHGRI

New research presented at the American Society of Clinical Oncology’s annual symposium last week indicates that two novel prostate cancer drugs could extend the lives of men with drug-resistant prostate cancer. The work was presented by two individual teams at the Genitourinary Cancers Symposium in San Francisco last Thursday, reports The New York Times.

Because of the nature of the disease, many cancer patients that have been successfully treated and ‘cured’ continue to live with the worry that their cancer will relapse and return. This status can be even worse for some patients with prostate cancer, which can develop into a cancer form that appears to be ‘frozen’, whereby it doesn’t spread or respond to any treatments. For these patients (thought to be between 2 to 8%), there are no longer any viable therapeutic options available and, in some cases, this can lead to the death of the patient.

The research presented last week may present a new avenue of treatment for these patients, offering them an extended lifespan. The two teams, each working on their own drug therapy, tested their compounds in patients who appeared to be on the verge of seeing a cancer ‘eruption’, as predicted by their levels of a prostate-specific antigen. All of the patients involved had previously received standard cancer treatments that had since ended, and were still receiving treatment that repressed their testosterone levels, inhibiting prostate cancer growth. In total, the two trials involved working with roughly 2,600 prostate cancer patients internationally.

Both drugs were found to extend survival significantly more than a placebo. Patients who were given enzalutamide lived for a median time of 36 months without their cancer becoming metastatic, in comparison to 14 months for patients receiving a placebo. Even more significant, patients given apalutamide survived for a median time of 40 months before either their cancer metastasised or they died, an average survival time that is 2 years greater than patients on the placebo. The results of this trial were published in the New England Journal of Medicine (the data from the enzalutamide trial are currently undergoing peer-review). These results lead both teams to conclude that their drug reduced the risk of cancer metastasis by roughly 70%.

Some of the patients that were taking either drug did report mild side effects, including fainting and hypertension, but they typically considered their quality of life to be as high as it was prior to starting the treatment.

The drugs work by inhibiting receptors that enable prostate cells to respond to testosterone, preventing the hormone from stimulating cancer growth. Similar drug trials have been in progress for several years, but these two are thought to be the largest Phase III trials seen so far. Both therapies will need to win regulatory approval to reach the market; apalutamide has already been submitted to the US Food and Drug Administration for approval. Enzalutamide already benefits from FDA approval for the treatment of metastatic prostate cancer, but the drug makers hope to now expand the approved use.