Expression of Androgen Receptor Splice Variant 7 or 9 in Whole Blood Does Not Predict Response to Androgen-Axis –targeting Agents in Metastatic Castration-resistant Prostate Cancer

Publication date: June 2018 Source:European Urology, Volume 73, Issue 6 Author(s): Sarah Q. To, Edmond M. Kwan, Heidi C. Fettke, Andrew Mant, Maria M. Docanto, Luciano Martelotto, Patricia Bukczynska, Nicole Ng, Lisa-Jane K. Graham, Phillip Parente, Carmel Pezaro, Kate Mahon, Lisa Horvath, Tilman Todenhöfer, Arun A. Azad In 2014, a landmark study was published demonstrating that the expression of androgen receptor splice variant (AR-V) 7 was a negative predictive biomarker for response to abiraterone acetate and enzalutamide in metastatic castration-resistant prostate cancer (mCRPC) patients. However, these results were not supported by the recently reported ARMOR3-SV phase III clinical trial, which employed an identical circulating tumour cell assay to assess AR-V7 expression. Therefore, the predictive utility of AR-V7 expression in mCRPC remains uncertain, as does any potential association between other AR-Vs and treatment response. To further investigate, we designed a highly sensitive and specific whole blood assay for detecting AR-V7 and AR-V9. We then examined for a correlation between baseline AR-V7/V9 status and treatment outcome in 37 mCRPC patients commencing abiraterone or enzalutamide. Of the patients, 24% (9/37) were AR-V–positive. Notably, prostate-specific antigen (PSA) response rates did not significantly differ between AR-V–positive (6/9) and AR-V–negative (18/28) patients (66% vs 64%, p =0.9). Likewise, median PSA progression-free sur...
Source: European Urology - Category: Urology & Nephrology Source Type: research