PCCN News Article - Abiraterone Acetate Approved as Late-Stage Cancer Treatment
Abiraterone (Zytiga®) is a new antihormonal treatment which is taken by mouth. It blocks the enzyme CYP17 that controls two steps in the formation of male hormones (androgens). Androgens stimulate the growth of prostate cancer and may be necessary for the survival of prostate cancer cells.
While androgens were thought to be produced largely in the adrenal gland, in the testicles and in fatty tissue, it is now appreciated that they can be produced by prostate tumour cells, which thereby facilitate their own growth. Abiraterone inhibits the synthesis of androgens in all sites and thereby inhibits the growth of prostate cancer, and may cause death of existing prostate cancer cells leading to shrinkage of disease and a fall in PSA levels.
Abiraterone was studied initially in a large clinical study which included 1195 men who had received prior chemotherapy (docetaxel) for prostate cancer. The group of men who received abiraterone lived on average about 4 months longer than the group of patients who only received prednisone. The men receiving abiraterone also experienced substantial improvement in pain and their quality of life. Generally, abiraterone is well tolerated. Side effects include hypertension, decrease of potassium in the blood and increase of liver function tests. In rare cases cardiac disorders were attributed to abiraterone. Abiraterone tablets are normally taken once daily at least two hours after a meal and at least one hour prior to a meal. Approval and coverage by OHIP for abiraterone in patients who have received chemotherapy is expected in the near future.
Encouraged by the results of abiraterone in patients who had received prior chemotherapy it was also studied in patients who had not yet received chemotherapy. Abiraterone had a substantial effect to delay worsening of the disease and also led to prolonged survival; the study confirmed that it is well tolerated with only rare side effects. As the final results of this study have not been published, abiraterone is not yet regarded as standard for patients who have not received chemotherapy and is not reimbursed by OHIP.