Randomized Phase III Trial of Piroxicam in Combination with Mitoxantrone or Carboplatin for First‐Line Treatment of Urogenital Tract Transitional Cell Carcinoma in Dogs

Background Reported response rates of transitional cell carcinoma ( TCC ) in dogs to piroxicam in combination with either mitoxantrone or carboplatin are similar; however, it is unknown whether either drug might provide superior duration of response. Hypothesis/Objectives To determine if the progression‐free interval ( PFI ) of dogs with TCC treated with mitoxantrone and piroxicam was different than that of dogs receiving carboplatin and piroxicam. The hypothesis was that the efficacy of mitoxantrone is no different from carboplatin. Animals Fifty dogs with TCC without azotemia. Methods Prospective open‐label phase III randomized study. Either mitoxantrone or carboplatin was administered every 3 weeks concurrently with piroxicam with restaging at 6‐week intervals. Twenty‐four dogs received carboplatin and 26 received mitoxantrone. Results Response was not different between groups ( P  =   .56). None of the dogs showed complete response. In the mitoxantrone group, there were 2 (8%) partial responses ( PR ) and 18 (69%) dogs with stable disease ( SD ). In the carboplatin group, there were 3 PR (13%) and 13 (54%) dogs with SD . The PFI was not significantly different between groups (mitoxantrone = 106 days; carboplatin = 73.5 days; P  =   .62; hazard ratio 0.86; 95% confidence interval 0.47–1.56). Dogs with prostatic involvement experienced a shorter survival (median, 109 days) compared to dogs with urethral, trigonal, or apically located tumors; this difference was significant (median 300, 190, and 645 days, respectively; P  =   .005). Conclusions and Clinical Importance This study did not detect a different in outcome in dogs with TCC treated with either mitoxantrone or carboplatin in combination with piroxicam.