Abiraterone Approval Extended to Treat Late-Stage Prostate Cancer ► NCI Cancer Bulletin for December 11, 2012 - National Cancer Institute

NCI Cancer Bulletin for December 11, 2012 - National Cancer Institute

Abiraterone Approval Extended to Treat Late-Stage Prostate Cancer

Men with castration-resistant prostate cancer that has spread can now be treated with abiraterone acetate (Zytiga) before receiving chemotherapy. The Food and Drug Administration (FDA) expanded the approved use of abiraterone on December 10.
The FDA initially approved abiraterone in April 2011 for use in patients whose prostate cancer had progressed after treatment with the chemotherapy docetaxel. Abiraterone is a pill that reduces testosterone production.
Testosterone stimulates the growth of prostate tumors, so drugs or surgery that reduce testosterone production or block testosterone’s effects are used to slow the growth of prostate cancer. However, most prostate cancers eventually become resistant to these treatments. These castration-resistant cancers continue to grow even when levels of testosterone are very low. Abiraterone is designed to treat these tumors by inhibiting the production of androgen in the testes, adrenal glands, and prostate cancer tumors themselves.
Abiraterone’s safety and effectiveness for its expanded use were established in a clinical study of 1,088 men with late-stage castration-resistant prostate cancer who had not previously been treated with chemotherapy. Participants received either abiraterone or a placebo (both in combination with the corticosteroid prednisone).
The study was designed to measure the length of time a patient lived before death (overall survival) and the length of time a patient lived without further tumor growth as assessed by imaging studies (radiographic progression-free survival, or rPFS).
Patients who received abiraterone had a 25 percent decrease in the risk of death. Study results also showed abiraterone improved rPFS. The median rPFS was 16.5 months for patients treated with abiraterone versus 8.3 months in the placebo group.
The most common side effects reported included fatigue, joint swelling or discomfort, swelling caused by fluid retention, hot flashes, diarrhea, vomiting, cough, high blood pressure, shortness of breath, urinary tract infection, and bruising.
The most common laboratory abnormalities included low red blood cell count; high levels of the enzyme alkaline phosphatase, which can be a sign of other serious medical problems; high levels of fatty acids, sugar, and liver enzymes in the blood; and low levels of lymphocytes, phosphorous, and potassium in the blood.