Zytiga Outperforms MDV3100

This years ASCO abstracts from the meeting in Chicago show a number of new results on the clinical use of Abiraterone (Zytiga).

This abstract shows that Zytiga can work beyond MDV3100 and continues to show activity in MDV3100 relapsed patients.


Abiraterone in patients with metastatic castration-resistant prostate cancer progressing after docetaxel and MDV3100.

Abstract:

Background: Chemotherapy with docetaxel is the standard first-line treatment in patients with metastatic castration-resistant prostate cancer (mCRPC). In patients progressing after docetaxel, both abiraterone and MDV3100 have yielded improved survival for patients with mCRPC. The efficacy of abiraterone in patients pre-treated with MDV 3100 is unknown.

Methods: We investigated abiraterone-prednisone in 24 patients with cancer progression after docetaxel followed by MDV3100. All patients received abiraterone 1000 mg/day plus prednisone 10mg/day. Prostate-specific antigen (PSA) response, symptom response, and time to progression were assessed.

Results: Patient characteristics were as follows: median age: 74 years (53-84), median PSA: 108 ng/mL (2-2541), metastatic sites: bone: all 24 patients, liver/lung: 6 patients (25%), and lymph nodes : 9 patients (38%). Five patients (21%) had a PSA decrease on abiraterone-prednisone. Three patients (13%) achieved a PSA response, defined as a decrease of >50% in PSA, confirmed after≥ 4 weeks. The duration of PSA response was 2, 3 and 4.5 months. Six patients (29%) had a symptomatic response on the pain score and analgesic consumption was decreased. Treatment was well tolerated. Abiraterone-prednisone was discontinued in one patient due to edema and hypokaliemia.

Conclusions: This study shows preliminary evidence that abiraterone-prednisone yields activity in patients with mCRPC pretreated with docetaxel and MDV3100.