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Posted by on Mar 14, 2013 in Prostate cancer | 0 comments

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In a nutshell

The present study evaluated the effect of Abiraterone acetate (AbAc) on survival and disease progression, when given to patients with metastatic prostate cancer (mPC) that is resistant to hormone therapy (castration-resistant).

Some background

Prostate cancer (PCa) growth is fueled by male hormones like testosterone. By reducing the amount and activity of testosterone PCa growth is slowed. Anti-testosterone (known as androgen deprivation therapy, or ADT) therapy is the main treatment for advanced PCa (that has spread to lymph nodes or distant organs). However, eventually most prostate cancers stop responding to ADT (thereafter defined as castration-resistant PCa). These patients may then benefit from chemotherapy (Docetaxel). However, in some patients the cancer continues to grow despite all these therapies. For these patients new medications are being researched in order to prolong survival and delay disease progression. Abiraterone acetate (Zytiga) is a new drug approved by the FDA for the treatment of castration-resistant mPCa. Abiraterone is given in conjunction with a steroid called prednisone.

Methods & findings

The study included 1195 PCa patients previously treated with Docetaxel. Patients received either AbAc with prednisone (797 patients), or placebo (a substance that has no medical effect, used as a control in testing new drugs) with prednisone (398 patients). Parameters measured included overall survival (the percentage of patients who have survived for a defined period of time), progression-free survival, or PFS (the percentage of patients who have survived for a defined period of time, without progression of their cancer), PSA (Prostate Specific Antigen, a protein found in the prostate that rises in prostate disease) response to treatment (a decline in the PSA blood level) and PSA progression (a rise in the PSA blood level) rates.

The study found that treatment with AbAc plus prednisone resulted in a 35.4% reduction in the risk of death compared to placebo plus prednisone. There was a median overall survival of 14.8 months in the AbAc group compared to 10.9 months in the placebo group. The study also showed some benefit in PSA response in favor of AbAc (29% versus 6% in the placebo group) with a median duration of 10.2 months without PSA progression compared to 6.6 months with placebo. There was an improvement in PFS (5.6 vs. 3.6 months) in favor of AbAc with a 33% or 42% reduction in the risk of disease progression, evaluated by radiographic imaging or PSA level, respectively. Side effects like fluid accumulation, elevated blood pressure and low potassium levels were more frequent in the AbAc group compared to placebo.

The bottom line

In this study, patients with castration-resistant mPC who previously failed on chemotherapy, demonstrated improved survival rates and delayed disease progression under Abiraterone treatment, with a low frequency of treatment-related side effects.

The fine print

The results of this study served as grounds for the approval of Abiraterone acetate with prednisone by the US FDA.

Published By :

The New England Journal of Medicine

Date :

May 26, 2011

Original Title :

Abiraterone and Increased Survival in Metastatic Prostate Cancer

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