Testosterone drives the growth of prostate cancer cells. Androgen deprivation therapy (ADT) stops the testicles from making testosterone and other male hormones, thus slowing the growth of prostate cancer cells. However, the prostate gland and other organs still produce small amounts of testosterone, even if a man is on ADT.
The drug abiraterone (Zytiga) is an oral medication that interrupts the androgen-making process at three sources: the testes, the adrenal glands, and in the prostate tumor. Abiraterone is currently approved for use in men with metastatic castration-resistant prostate cancer—cancer that continues to get worse after men are on ADT. The drug is taken in combination with prednisone.
Now, new results from two randomized clinical trials suggest that men diagnosed with advanced prostate cancer could benefit from taking abiraterone at the same time they start hormonal therapy, instead of waiting until the disease becomes castration- resistant.
The STAMPEDE trial showed that adding abiraterone to standard treatment for high-risk, advanced prostate cancer lowered the relative risk of death by 37%. The 3-year survival rate was 83% for men who added abiraterone to standard therapy, compared to 76% for men on standard therapy alone.
Abiraterone also lowered the relative chance of relapse by 70% compared to standard therapy.
The study included almost 2,000 men. Standard therapy was defined as being on ADT for at least 2 years. Some patients in the study with locally advanced cancer also received radiation therapy.
Similar to STAMPEDE, the LATITUDE trial showed that adding abiraterone to hormonal therapy lowered the chance of death by 38% in men newly diagnosed with high-risk, metastatic prostate cancer. Abiraterone also delayed cancer growth by a median of 1.5 years.
The study included approximately 1,200 men.
The future of managing advanced cancer
Previous study results showed that adding docetaxel (Taxotere), a chemotherapy drug, similarly increased the chances of survival for men with metastatic prostate cancer. Now, the authors of both the STAMPEDE and LATITUDE trials said that future studies are needed to examine whether adding both abiraterone and docetaxel to hormonal therapy could further benefit men diagnosed with advanced prostate cancer.
For details on the docetaxel studies, go to www.drcatalona.com and search “docetaxel.”
The American Society of Clinical Oncology (ASCO) 2017 Annual Meeting was held June 2-6, 2017 in Chicago.