Cabazitaxel in patients with locally advanced or metastatic transitional cell carcinoma who developed disease progression within 12 months of platinum based chemotherapy: Results of a phase II trial—CAB-B1.

4542 Background: There is a paucity of chemotherapy options for the treatment of patients who have relapsed following platinum based chemotherapy (CT). Cabazitaxel is a new taxane that showed in-vivo antiproliferative activity on resistant cell lines. Methods: CAB-B1 was a single centre phase II randomised controlled trial of Cabazitaxel (CAB; 25mg/m2 q3 week for 6 cycles) versus best supportive care (BSC) in patients (pts) with histologically proven transitional cell carcinoma (TCC), locally advanced or metastatic, who had received platinum based treatment and recurred within 12 months of the last cycle of CT. Primary outcome was overall response rate (ORR) using RESIST. Secondary outcomes were Progression Free Survival (PFS), Overall Survival (OS), Quality of Life assessment, safety and tolerability. A total of 96 pts required to detect differences in ORR from 5% to 30%; 80% power; 5% alpha level; 10% dropouts. Stopping rules, using Simon’s two stage optimal design to assess the individual effectiveness of CAB, required at least 1 ORR from 10 pts on CAB during 1st stage (i.e. total of 20 pts randomised) and 4 from 29 CAB pts in 2nd stage (assuming lower ORR limit of 0.05, target ORR of 0.20, 80% power, 5% alpha level). The trial was supported by grant from Sanofi. Results: Between January 2013 and October 2016, 20 pts were randomised (10 on each arm). 75% males; median age 68 years; 65% had recurred within 6 months of previous CT. BSC included paclitaxel CT for 9 pts and radiotherapy for 1 pt. 8 pts completed 6 cycles of CT (3 on CAB; 5 on BSC). 6 pts on each arm were evaluated for response after having 2/3 cycles; 2 pts had an ORR on CAB and 1 pt on BSC. 14 pts have died of disease (8 on CAB; 6 on BSC).Median OS was 5.6 months (95% confidence interval (CI) 0.7-15.2) for CAB pts and 8.2 months (95% CI 1.0-8.8) for BSC pts. Median PFS was 4.4 months (95% CI 0.7-9.4) for CAB pts and 4.1 months (95% CI 1.0-6.8) for BSC pts. Conclusions: It has been hard to recruit these poorly patients within a single centre, but CAB-B1 successfully reached the efficacy target for the 1st stage, showing that there could be a role for CAB in these pts. Clinical trial information: NCT01668459.