Patients who have been treated for localized prostate cancer and are now seeing their PSA rise rapidly are at high risk of metastasis and of death from prostate cancer. Now, patients and their doctors have a new treatment option that decreases these risks.
The FDA has approved enzalutamide alone OR in combination with hormone therapy (such as leuprolide) for patients with high-risk biochemical recurrence. This approval is based on the results of a large randomized clinical trial called EMBARK.
Who is eligible for this treatment?
Eligible patients have been treated for localized prostate cancer (usually with surgery or radiation therapy) and are now experiencing high-risk biochemical recurrence. In general, this means patients with a rapidly rising PSA and no metastases seen on imaging scans. Additionally, patients are not being treated with hormone therapy. Patients with a PSA doubling time of 9 months or less are at high risk of metastasis and death from prostate cancer.
What is the treatment?
Enzalutamide is a newer form of treatment for prostate cancer called an androgen receptor pathway inhibitor. It is an oral pill taken daily. It was already approved and in use to treat advanced prostate cancer. Under this approval, patients can take enzalutamide alone OR with standard hormone therapy such as leuprolide.
What benefit was shown in the clinical trial?
The EMBARK trial made two separate comparisons:
- Enzalutamide + leuprolide vs leuprolide alone
- Enzalutamide alone vs leuprolide alone
Both enzalutamide treatment regimens were superior to leuprolide alone.
The trial evaluated “metastasis-free survival,” meaning the number of patients in each treatment group who remained alive and free from metastases. After 5 years of follow-up, 87% of patients treated with enzalutamide + leuprolide had no metastases, compared with 80% of patients treated with enzalutamide alone and 71% of patients treated with leuprolide alone.
In other words, patients treated with the combination had a 58% lower risk of developing metastases or death vs. patients treated with leuprolide alone. Patients treated with enzalutamide alone had a 37% lower risk vs. patients treated with leuprolide alone.
What are the side effects?
Enzalutamide has known side effects, including hot flashes and fatigue. The side effect profile was as expected, in that no new safety issues were seen in the trial. Certain side effects were more common in the combination group, including fractures and cognitive/ memory impairment. More patients in the combination group (21%) discontinued treatment due to adverse events compared with 10% in the leuprolide-alone group and 18% in the enzalutamide-alone group.
What does this mean for patients?
If your PSA is rising after treatment for localized prostate cancer, talk to your doctor about any additional testing you should have and about your treatment options, including potential benefits, risks, and side effects.