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Sub-category:
Prostate
Category:
Genitourinary Cancers
Meeting:
2008 Genitourinary Cancers Symposium
Abstract No:
3
Author(s):
D. C. Danila, D. Rathkopf, M. Fleisher, S. Slovin, M. Morris, D. Solit, E. Tanaka, A. Anand, C. Haqq, G. Lee, H. I. Scher
Abstract:
Background: Prostate tumors progressing despite androgen depletion often continue to express functional androgen receptor. Abiraterone acetate (CB7630) inhibits 17 a-hydroxylase and C17,20-lyase, and has been demonstrated to decrease serum androgen to undetectable levels. Methods: The anti-tumor effects of abiraterone acetate were studied in patients with castration resistant metastatic prostate cancer who had progressed on docetaxel based chemotherapy, with rising PSA levels. Abiraterone acetate was given orally at the dose of 1,000 mg daily for 28 day cycles, alone in the first 10 patients or in combination with prednisone orally 5 mg twice daily in the next 37 patients. The primary objective was to determine the proportion of patients achieving PSA decline of >50% according to PSAWG criteria (PSA response). Metastatic bone and soft tissue involvement was evaluated by radiologic imaging. Correlative studies of circulating tumor cells enumeration were also performed. Results: Forty-seven patients have been treated to date. The median age was 72 years (IQR 63-78), median PSA was 115 ng/mL (IQR 39.4-328.6 ng/mL), while median baseline circulating tumor cell counts were 14 (IQR 4-43) cells/7.5 mL of blood. Evaluation at 12 week time point of 29 patients showed 12 (41%) patients continued to have 50% or more decline in PSA from baseline, whereas 3 and 8 patients have radiologic partial response or stable disease, respectively (data to be updated at the time of presentation). The adverse event profile has been acceptable for this group of pretreated patients. Changes in circulating tumor cell number have tracked well with post-therapy PSA and radiographic changes. Conclusion: Significant response to treatment with abiraterone acetate, an investigational androgen synthesis inhibitor, suggests that the hormone-refractory classification in patients with progressive castration resistant metastatic disease following chemotherapy is not only a misnomer, but has the potential to deny patients potentially effective treatments. Associations between circulating tumor cell number and outcome will be explored. (Supported by Cougar Biotechnology)
Abstract Disclosures
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy
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 Associated Presentation(s):
Other Abstracts in this Sub-Category:
Abstracts by D. C. Danila:
Presentations by D. C. Danila:
Educational Book Manuscripts by D. C. Danila:
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