Background: In the TROPIC study, Cbz was shown to improve overall survival in mCRPC pts post-docetaxel, however none of these pts had prior exposure to Abi. To better understand the impact of prior Abi treatment on Cbz efficacy and QoL, we evaluated Canadian pts enrolled in the International Phase IIIb/IV single arm Cbz study. Methods: In total 61 pts were enrolled from 9 centers (May 2011 to February 2012). Cbz efficacy (PSA Response Rate (RR, decline ≥50%)) and impact on QoL were analyzed as a function of prior Abi use. Results: Baseline and disease characteristics were similar between NoPriorAbi (n=35, 57%) and PriorAbi (n=26, 43%) groups, except for age and time between last docetaxel dose and progression (Table). Pts received a median of 9 cycles of prior docetaxel. 92% of pts were ECOG 0/1, with 88% having bone metastases and 25% visceral metastases. 31% of pts received prophylactic G-CSF. Median number of Cbz cycles received was similar between groups (NoPriorAbi= 6, PriorAbi= 7) as were PSA RR (NoPriorAbi= 42.4%, PriorAbi= 47.6%, p=0.78). QoL and pain were improved in Cbz pts with no significant difference observed based on prior Abi use (Table). Overall, treatment discontinuation was mainly due to progression (45.9%) and adverse events (32.8%). Most frequent grade 3/4 toxicities were anemia and fatigue (9.8%), with diarrhea, neutropenia and febrile neutropenia each observed in 8.2% of pts. Conclusions: Cbz efficacy and impact on QoL were not affected by prior Abi use. In routine clinical practice, toxicity rates observed were similar to the TROPIC study. Clinical trial information: NCT01254279.

* as defined in TROPIC (de Bono 2010). ǂ Minimal clinically important difference observed on 2 consecutive cycles.