Men with advanced prostate cancer may have just received an early Christmas present. A newly developed anti-testosterone pill, combined with conventional hormone therapy, may obviate their need for chemotherapy.
A study has proclaimed that the new drug, abiraterone, lowers patients' risk of death by nearly 40 percent when added to standard androgen deprivation therapy (ADT). It also appears to more than double the average time it takes for prostate cancer to progress.
Prostate cancer that has metastasized is very frequently treated withthe chemotherapy drug docetaxel along with ADT. Abiraterone would take the place of the chemo, bringing vastly fewer side effects to the table.
Three percent of the 161,000 prostate cancer cases expected to be diagnosed in the U.S. this year will be found to be metastatic.
The reason why ADT works to begin with is because testosterone ignites prostate cancer growth. But ADT only prevents the testicles from making testosterone; adrenal glands and the prostate cancer cells themselves also manufacture the hormone, albeit in smaller amounts.
This is where abiraterone comes in. The drug, taken daily, halts all production of testosterone everywhere in the body. It does this by blocking an enzyme that converts other hormones to testosterone.
Two clinical trials have already been held. The first focused upon 1,200 patients who had been just recently diagnosed with high-risk prostate cancer. The men all shared at least two of three risk factors -- an aggressive prostate tumor, three or more bone tumors, or three or more tumors in other organs. The men were divided into one group that received abiraterone and another, control, group that received a placebo. Both the abiraterone and the placebo were given alongside ADT. After 30 months, the researchers found that the abiraterone group had a 38 percent lower risk of death than those who got a placebo, and had a 53 percent lower risk of their cancer getting worse.
The second trial involved nearly 2,000 men with advanced prostate cancer who were starting hormone therapy. Over the course of three years, the overall survival rate was 83 percent in men taking abiraterone compared to 76 percent in men receiving standard ADT. Looking ahead, the researchers anticipate that the average survival will be about 6.5 years in abiraterone patients compared with 3.5 years for all the advanced prostate cancer patients.
There are still a few kinks, in the form of side effects. High blood pressure occurred in 20 percent of patients treated with abiraterone, compared to 10 percent of placebo patients in the first trial. Low potassium and some liver abnormalities were also reported.
The studies were presented at the 2017 American Society of Clinical Oncology annual meeting.