#GU15 - Association between PSA declines at 4 weeks and OS in patients treated with abiraterone acetate (AA) for metastatic castration resistant prostate cancer (mCRPC) after docetaxel - Session Highlights

ORLANDO, FL, USA (UroToday.com) - Pasquale Rescigno and colleagues identified a need for intermediate endpoints of OS benefit in patients treated for mCRPC, given the current standard of PSA decline of 50% at 12 weeks. The group retrospectively evaluated 124 post-docetaxel mCRPC patients treated with abiraterone for the effect of PSA decline at 4 weeks on survival. PSA responses were stratified by 30% decline (PSA4w30) and 50% decline (PSA4w50) from baseline.

gucancerssympaltThe investigators found that PSA4w30 was associated with longer OS (17.6 vs 9.4 months, HR 0.5, p=0.004). Interestingly, PSA4w50 was not associated with OS. The current standard of 50% PSA decline at 12 weeks was associated with OS (18.9 vs 10.4 months, HR 0.49, p=0.005). Lack of PSA response at 4 weeks correlated well with lack of response at 12 weeks with a sensitivity of 84.9%, and specificity of 86.5%. 89.8% of patients with no 30% response at 4 weeks showed no 50% response at 12 weeks. Multivariable model including PSA baseline and response, ECOG PS, albumin, LDH, and hemoglobin demonstrated that PSA4w30 was associated with OS (p < 0.001) when controlling for other known prognostic factors.

The authors concluded that lack of PSA response at 4 weeks might have utility in identifying patients who are unlikely to benefit from further abiraterone therapy.

Presented by Pasquale Rescigno, David Lorente, Roberta Ferraldeschi, Diletta Bianchini, Spyridon Sideris, Zafeiris Zafeiriou, Alan David Smith, Niven Mehra, Emily Grist, Anuradha Jayaram, Michael Paul Kolinsky, Raquel Perez Lopez, Joaquin Mateo, Chris Parker, David Paul Dearnaley, Emma Hall, Nina Tunariu, Gerhardt Attard, and Johann Sebastian De Bono at the 2015 Genitourinary Cancers Symposium - "Integrating Biology Into Patient-Centric Care" - February 26 - 28, 2015 - Rosen Shingle Creek - Orlando, Florida USA

The Institute of Cancer Research, The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom; The Institute of Cancer Research, The Royal Marsden NHS Foundation Trust, London, United Kingdom; The Institute of Cancer Research, The Royal Marsden Hospital NHS Foundation Trust, Sutton, United Kingdom; The Institute of Cancer Research, Sutton, United Kingdom

Reported by Nikhil Waingankar, MD, medical writer for UroToday.com