In advanced prostate cancer, androgen deprivation therapy (ADT) has been a mainstay of treatment for more than fifty years. The details of ADT are discussed here if you'd like to learn more. In the past decade or so, physicians who treat advanced prostate cancer have come to understand that, in a variety of clinical scenarios, ADT alone is not enough. As a result, treatment intensification has become common. While chemotherapy was the first treatment intensification approach to be adopted, it has been supplanted by so-called novel hormonal therapies (NHTs; also known as androgen receptor-axis-targeted therapies (ARATs)) for most patients. While ADT effectively decreases the testosterone within the body that drives prostate cancer growth, the success of these treatments clearly shows that targeting of testosterone-driven pathways has benefit in advanced prostate cancer.
The first NHT to have proven benefit was abiraterone acetate. Abiraterone is a “androgen biosynthesis inhibitor”. It acts to block one of the key enzymes in the testicles, adrenal glands, and prostate cancer cells necessary to produce testosterone. Because the production pathway of testosterone is shared with other important hormones in the body, patients who receive abiraterone acetate also take a corticosteroid (prednisone, prednisolone, etc) to prevent a deficiency of these other hormones.
Who might be prescribed Abiraterone Acetate?
Abiraterone is approved, and has demonstrated survival benefits, for men with metastatic castration sensitive prostate cancer (mCSPC; where abiraterone will be started concurrently or shortly after ADT) and in metastatic castration resistant prostate cancer (mCRPC; which abiraterone will be started as a result of disease progression while on ADT). Patients receiving abiraterone for metastatic castration resistant prostate cancer may or may not have previously received chemotherapy. In the mCSPC disease space, the LATITUDE and STAMPEDE trial showed that men receiving ADT + abiraterone had a 38% and 37%, respectively, decreased risk of death compared to men receiving ADT alone. Among men with mCRPC that had not previously received chemotherapy in the COU-AA-302 trial, men receiving abiraterone had a 25% decreased risk of death compared to men receiving placebo + prednisone. Among men with mCRPC that had previously received chemotherapy in the COU-AA-301 trial, men receiving abiraterone had a 35% decreased risk of death compared to men receiving placebo + prednisone.
Patients who should not take Abiraterone
There are limited reasons why patients should not take abiraterone. Patients with an allergy or hypersensitivity to abiraterone should not receive it. Similarly, those with severe liver disease, an excess or deficiency of hormones in the pathway that abiraterone affects (mineralocorticoid excess or adrenocorticoid insufficiency), severe heart disease, and those with low blood potassium (hypokalemia) should take abiraterone with caution.
Instructions for taking Abiraterone
Abiraterone acetate is prescribed at four tablets to be taken each day. These should be taken by mouth on an empty stomach, either 1 hour before or two hours after eating food, to maximize absorption. Additionally, as mentioned before, you will be prescribed a corticosteroid to be taken either one or twice daily.
Abiraterone is metabolized by specific enzymes in the liver. As a result, there may be interactions between abiraterone and medications that block these enzymes (including ketoconazole, itraconazole, clarithromycin, atazanavir, nefazodone, saquinavir, telithromycin, ritonavir, indinavir, nelfinavir, voriconazole) or increase their activity (including phenytoin, carbamazepine, rifampin, rifabutin, rifapentine, phenobarbital).
As your physician discusses treatment options for advanced prostate cancer, ensure that they are aware of all of the other medications that you are taking. Further, a cancer pharmacist can be very helpful in ensuring that there are not harmful interactions between medications.
Side effects of Abiraterone
The most common side effects of abiraterone relate to its action stopping the production not just of testosterone but of other related hormones – these include high blood pressure, low blood potassium (hypokalemia), and swelling of the hands or legs (peripheral edema). Other common side effects include urinary tract infections, diarrhea, rash, and increases in liver enzymes. Numerous other side effects are possible and may be related to abiraterone treatment.
As always, the articles on this site should not constitute specific medical advice. Discuss the specifics of your clinical situation and your treatment options with your physician.