Metastatic Prostate Cancer Update - Episode 6
The phase III COU-AA-302 trial enrolled patients who reported little to no pain associated with their castration-resistant prostate cancer (CRPC) and excluded those who were on opiates at the time of enrollment. A secondary endpoint of the study assessed the amount of time to first opiate use, explains Charles J. Ryan, MD.
In general, patients receiving treatment with abiraterone acetate in the trial went 1 year longer without requiring opiate analgesics than patients in the placebo arm. This delay in the need for an opiate is a clinically useful and very meaningful finding, since the development of pain is a major landmark in metastatic CRPC, Ryan notes.
With regard to the long-term toxicity of abiraterone, the final analysis showed no new safety signals after year 2 and year 3 of follow up. There were corticosteroid-related toxicities that were shown to occur at the outset of therapy. However, data presented at the 2015 AUA Annual Meeting showed that the cumulative toxicities of corticosteroids with abiraterone were less than expected. Overall, the safety profile for abiraterone plus prednisone was not that different than what is seen using prednisone 10 mg daily, says Ryan.
In terms of the ideal time to stop abiraterone, patients in the 302 trial did not discontinue therapy when their PSA levels began to increase. Ryan advises against this and believes, based on the 302 study data, that continuing therapy will slow down the progression of CRPC. Before deciding whether to stop therapy, the type of progression should be assessed. For patients with globally progressing disease, new symptom development, and new lesions on bone scan, it is clinically prudent to discontinue abiraterone. However, for progressive disease in isolated sites, radiotherapy such as focal therapy can be used to treat those lesions, explains Ryan.