AUA 2017: Comparative Assessment of Efficacies Between Two Alternative Therapeutic Sequences with Novel Androgen Receptor-axis-targeted Agents in Patients With Chemotherapy-naive Metastatic Castration-resistant Prostate Cancer

Boston, MA (UroToday.com) There is accumulating evidence suggesting that sequential treatment with androgen receptor-axis-targeted (ARAT) agents, abiraterone acetate (AA) and enzalutamide (Enz), has limited efficacy for metastatic castration-resistant prostate cancer (mCRPC) patients who have failed Docetaxel treatment. As a result, there has been a recent strong trend towards initiation of ARAT therapies in mCRPC patients prior to the introduction of docetaxel. The authors aimed to determine the optimal sequencing order of novel ARAT agents for mCRPC chemotherapy naïve patients.

In this retrospective study, 108 mCRPC patients were analyzed. All patients were chemo-naïve and received sequentially AA and Enz, in either order. Primary endpoint included PSA response, overall survival (OS), and progression-free survival (PFS) defined as the sum of PFS1 (PFS of first ARAT therapy) and PFS2 (PFS of second ARAT therapy).

Of the 108 patients, 49 and 59 received ARAT therapy with the AA-to-Enz sequence, and with the Enz-to-AA group, respectively. No significant differences in the baseline demographic and clinical characteristics were noted between the two groups. In the overall patient population, the PSA response rate to the first-line ARAT agent (58.3%) was significantly higher than that to the second line ARAT agent (21.3%). The combined PSA PFS in the AA-to-Enz group (median, 18.4 months) was significantly higher than in the Enz-to-AA group (median, 12.8 months). Furthermore, multivariate analysis identified the treatment sequence (i.e., AA-to-Enz versus Enz-to-AA group) in addition to performance status as independent predictors of combined PSA PFS in these patients. No significant OS difference was noted between the both sequencing groups.

To conclude, in mCRPC chemo-naive patients, when ARAT agents are to be introduced sequentially, it may be more beneficial to use the AA-to-Enz sequence.

Speaker: Yuto Matsushita, Hamamatsu, Japan

Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre

at the 2017 AUA Annual Meeting - May 12 - 16, 2017 – Boston, Massachusetts, USA
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