INTRODUCTION
Patients may be diagnosed to have metastatic prostate cancer that has spread to other parts of the body such as the bones, lymph nodes and abdominal organs. For many years, the first line treatment for these patients has been hormonal therapy, in which the production of testosterone from the testicles is stopped, either by medication or by surgical removal of the testicles. The cancer is dependent on testosterone to survive and will regress when testosterone levels are low.
However standard hormonal therapy does not completely eliminate the testosterone circulating in the body. This is because the adrenal glands also produce a small amount of testosterone. Prostate cancer cells may also start producing testosterone after a while. Eventually, the cancer develops resistance to hormonal therapy, and this may lead to worsening of disease and death.
In 2015, it was found that patients with aggressive metastatic cancer would have better control of their disease and survive longer by going for both chemotherapy and hormonal therapy. However chemotherapy can have serious side effects and some patients who are elderly or unfit will not be suitable for chemotherapy. Even patients who are suitable for chemotherapy may be fearful of going for this treatment.
NEW DRUGS THAT BLOCK PRODUCTION OF TESTOSTERONE
Recent years have seen the introduction of drugs which are very effective in blocking the production of testosterone. Examples of these drugs are abiraterone (trade name Zytiga) and enzalutamide (trade name Xtandi). They have been used as second-line treatment for metastatic prostate cancer that has become resistant to standard hormonal therapy. Now there is evidence that these drugs are effective in the first-line treatment of the disease.
Two trials published in June 2017 in the New England Journal of Medicine have shown that patients with newly diagnosed metastatic prostate cancer, who received abiraterone in addition to standard hormonal therapy had significantly better outcomes compared to patients who were treated with standard hormonal therapy alone. In one of the trials, the patients who were on abiteratone and standard hormonal therapy had a 38% lower risk of death and 53% lower risk of progression compared to those on hormonal therapy alone.
Rise in blood pressure, low potassium levels and liver enzymes abnormalities are the more common side effects of abiraterone. However because the side effects of abiraterone are less serious than those of chemotherapy, it is likely that this drug will be used more often in the treatment of newly diagnosed metastatic prostate cancer.
The downside of abiraterone is that it is an expensive medication, and the use of this drug may be determined by whether patients can afford it or have the necessary insurance to cover the cost.
