A standard approach for treating aggressive prostate cancer is to give therapies that block testosterone, a tumor-stimulating hormone. Should initial hormonal therapies fail, doctors can switch to other drugs that suppress testosterone in different ways. One of them, a drug called abiraterone, has been shown to significantly extend lifespans in men who have become resistant to other hormonal treatments.
But in June, two major studies reported simultaneously that abiraterone also prolongs life in men with aggressive prostate cancer that’s been newly diagnosed. One of the studies, a phase 3 clinical trial called LATITUDE, enrolled 1,199 men with metastatic prostate cancer, or cancer that had spread to other sites in the body. The other one, called STAMPEDE, enrolled 1,917 men, half with metastatic prostate cancer and the other half with cancer that was still confined to the prostate gland. Both studies split the men in two groups: one was treated with a combination of traditional first-line hormonal therapy plus abiraterone, and another group was treated with first-line hormonal therapy by itself.
After 30 to 40 months of follow-up, both studies showed similar results: the combined treatment that included abiraterone reduced the risk of death by nearly 40%. Abiraterone treatment also prolonged the time it took for the cancers to worsen by 14 to 15 months, delayed the need for chemotherapy, slowed the increase in blood levels of prostate-specific antigen (or PSA, which is released by prostate tumors), and lessened pain.
Abiraterone does have side effects, such as high blood pressure and a drop in blood levels of potassium that can trigger heart problems. But those effects can be minimized with prednisone, a powerful anti-inflammatory agent. So the Food and Drug Administration requires that abiraterone and prednisone be given together.
Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor in chief of HarvardProstateKnowledge.org, say the evidence helps to challenge conventional wisdom that abiraterone can’t suppress testosterone to levels below those achieved with first-line hormonal treatments. “But additional research is needed to identify the patients who might benefit most from abiraterone,” he said. “Aggressive prostate cancer often strikes elderly men with additional health problems, and for some, adding abiraterone might be too burdensome. But based on the results of these studies, it’s likely that abiraterone will be prescribed to newly diagnosed men with aggressive prostate cancer more often.”