FDA Approval of Xtandi Offers Earlier Treatment Option for High-Risk Prostate Cancer

The recent approval by the Food and Drug Administration (FDA) of androgen receptor signaling inhibitor Xtandi (enzalutamide) for non-metastatic castration-sensitive prostate cancer (nmCSPC) with biochemical recurrence at high risk for metastasis (high-risk BCR) signaled a sea change for patients with earlier stages of the prostate cancer more than a decade after the FDA’s approval of Xtandi for metastatic castration-resistant prostate cancer in 2012.

Prostate-specific antigen (PSA) is a protein associated with the presence of prostate cancer in the body and is potentially indicative of which patients are at higher risk for a shorter time until prostate-specific antigen recurrence and failure.

Xtandi is the first androgen receptor signaling inhibitor approved by the FDA for the treatment of patients with ncCSPC who are at high risk for biochemical recurrence, which is determined by rising prostate-specific antigen (PSA) levels.

PSA, a protein that is associated with the presence of prostate cancer in the body, is one of the factors recently identified by researchers as potentially indicative of which patients with prostate cancer are at high risk for a shorter time until prostate-specific antigen recurrence and failure.

LEARN MORE: What is Prostate-Specific Antigen and Why Is It Important For Patients with Prostate Cancer?

“Traditionally, we would maybe incorporate radiation treatments when the PSA is starting to rise, we could actually use observation, we have some genetic testing that we could do for risk scores that are being used now, or just the hormone therapy alone,” explained Dr. Stephanie Berg, a medical oncologist for the Dana-Farber Cancer Institute’s Lank Center of Genitourinary Oncology and an instructor of medicine at Harvard Medical School. “So, this (approval) was really (playing) an important role of bringing this medication that was common in later lines of treatment earlier, as an option for men with this situation.”

Berg explained the science behind Xtandi, and how it differs from other, similar treatments that are currently available.

“It's a little bit different from the traditional hormone therapies that you might have heard of called androgen deprivation therapies,” Berg said. “For instance, Lupron (leuprolide) is the most common one that actually blocks the hormones, the testosterone production, from the testicles. But (Xtandi) is something where it actually blocks how testosterone or androgens bind in the prostate cancer cell … and what this may do, and they see this in the lab, (is) that it can lead to prostate cancer cell death and prostate cancer tumor volume reduction.”

The approval was based on the results of the EMBARK phase 3 trial, results of which were published in The New England Journal of Medicine. In the trial, 1,068 patients were treated with Xtandi plus Lupron, placebo plus Lupron or Xtandi as a monotherapy.

After five years, metastasis-free survival was 87.3% for patients in the combination treatment group, 71.4% for those treated with Lupron and placebo and 80% for the monotherapy cohort.

While no new safety signals were noted, researchers also reported that there were “no substantial between-group differences in quality-of-life measures” — something Berg said patients should keep in mind when discussing treatment options with their care team.

“When this trial had three different treatment arms, there really wasn't an improvement in quality-of-life, they just said there are no new safety or side effects noted,” Berg said. “But they didn't really say that men were maybe living better, they all kind of had the same symptoms, especially fatigue, which is a big one.

“So, I know especially with us at Dana Farber, a lot of our investigators are really looking at how we can improve fatigue using exercise, diet (and) other strategies, which I think are going to be really important to see that type of improvement as well because we know these therapies aren't lasting forever. But, when you go through it and you have a lot of these side effects, even with or without the Lupron, we really want to see how we can improve that in addition to living longer and cancer not coming back.”

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