Overview of the latest treatments for patients with castration-resistant prostate cancer.

In the past several years, the treatment of prostate cancer has made significant progress. In this study, researchers reviewed recent studies evaluating treatments for patients with prostate cancer.

Prostate cancer progression is usually measured by blood levels of a protein called prostate-specific antigen (PSA) in a patient’s body. This is a protein produced by the prostate gland whose levels rise in case of prostate disease such as prostate cancer. Androgen hormones, such as testosterone, cause prostate cells to grow, thus fuelling the growth of prostate cancer. Androgen deprivation therapy (ADT) reduces these androgen hormones, therefore stopping or shrinking the cancer. After ADT, PSA levels should drop. If PSA levels do not decline, the cancer is said to be castration resistant prostate cancer (CRPC). CRPC can range in severity from no symptoms at all to very aggressive cancers with metastases (cancers that have spread to other organs).

To review treatments for CRPC, the authors of this study summarized research data published until March 2013. Categories of CRPC treatment fall into four categories: drugs that interfere with the androgen receptor or AR (a protein found on prostate cancer cells to which androgens bind to exhibit their action), immunotherapy (drugs that stimulate the body’s own immune system to fight cancer), whole body (systemic) chemotherapy, and bone-targeting therapy.

Within these categories, there are four new drugs that improve survival in CRPC patients. The first two are abiraterone acetate (Zytiga) and enzalutamide (Xtandi), both of which are AR-interfering. By preventing any androgens from binding to receptors, the androgens cannot stimulate prostate cells to grow. The third drug discussed here is cabazitaxel (Jevtana), a systemic chemotherapy agent. Cabazitaxel can be used as a second-line chemotherapy drug if the cancer becomes resistant (does not respond) to the first-line drug docetaxel (Taxotere). Finally, radium-223 is a bone-targeting treatment that targets areas of high bone turnover (a process in which mature bone tissue is removed and replace with new bone). These regions are the most likely to become metastases. Radium-223 has been shown to increase survival as well as reduce the frequency of bone fractures, a common side effect of prostate cancer.

Existing CRPC therapies include several immunotherapy drugs and the bone-targeting therapy denosumab (Xgeva). Current immunotherapy drugs include two vaccines which have been shown to improve survival in CRPC patients: Sipuleucel-T (Provenge) targets prostate cancer cells and PROSTVAC-V/F (currently in clinical trials) targets a protein, the prostatic acid phosphatase, which is over-produced in patients with prostate cancer. Denosumab is a drug that helps to reduce the bone loss frequently associated with prostate cancer treatments. Patients treated with denosumab are less likely to suffer fractures and bone metastases, but this medication has not proven effects in increasing survival in prostate cancer patients.

In summary, several new therapies, including abiraterone acetate, enzalutamide, cabazitaxel, and radium-223, as well as older treatments, are available for the treatment of patients with CRPC.

Ask your doctor which treatment is the most appropriate in your situation.