Response of Multiple Recurrent TaT1 Bladder Cancer to Intravesical Apaziquone (EO9): Comparative Analysis of Tumor Recurrence Rates

Objectives: Previous studies have demonstrated that intravesical administration of apaziquone (EOquin) has ablative activity against superficial bladder cancer marker lesions with 8 out of 12 complete responses recorded. We present a comparison between the rates of tumor recurrence before and after treatment with apaziquone. 

Methods: The rate of tumor recurrence after treatment with apaziquone was compared with each patient's historical record of recurrences obtained from a retrospective analysis of the patients' case notes. The time to each recurrence event before apaziquone treatment and the time to the first recurrence after apaziquone treatment were recorded, and the data were analyzed using a population-averaged linear regression model using Stata Release, version 9.2, software. 

Results: Of the eight complete responses obtained in the Phase I study, tumor recurrence occurred in 4 patients and the remaining 4 patients remained disease free after a median follow-up of 31 months. The time to the first recurrence after apaziquone treatment was significantly longer (P <0.001) compared with the historical pattern and recurrence interval before apaziquone. Before apaziquone instillation, the mean ± SE recurrence rate and tumor rate per year was 1.5 ± 0.2 and 4.8 ± 1.2, respectively, and these decreased to 0.6 ± 0.25 and 1.5 ± 0.8, respectively, after apaziquone treatment (P <0.05). 

Conclusions: The results of this study indicate that early recurrences after treatment with apaziquone are infrequent and the interval to recurrence is significantly greater compared with the historical recurrence times for these patients. Larger prospective randomised trials are warranted to confirm these results.