The initial report of RTOG 0524: Phase I/II trial of a combination of paclitaxel and trastuzumab with daily irradiation or paclitaxel alone with daily irradiation following transurethral surgery for noncystectomy candidates with muscle-invasive bladder cancer.

Abstract

LBA287 Background: Most patients (pts) with muscle-invasive bladder urothelial carcinoma (UC) undergo definitive local treatment with radical cystectomy. Up to 50% of pts with UC overexpress HER2/neu, which may be associated with reduced responsiveness to chemoradiation and reduced survival. Many pts with UC have comorbidities that preclude surgery, creating a traditionally underserved population with worse outcomes. RTOG 0524 evaluated the safety and efficacy of trimodality, organ-preserving therapy in pts not suitable for cystectomy. Methods: Pts with invasive bladder UC (stages T2-T4a, N0-1, M0) underwent cystoscopic tumor resection. Tumors were analyzed by HER2/neu immunohistochemistry (IHC) and assigned to chemotherapy group I (IHC 2+ or 3+; paclitaxel and trastuzumab) or II (IHC negative or 1+; paclitaxel alone). Concurrent weekly paclitaxel (50 mg/m2), weekly trastuzumab (group I only) and daily radiation (64.8 Gy total in 36 fractions) were given for seven consecutive weeks. Results: 21 eligible patients were entered in group I and 47 in group 2, with median ages of 80 and 73, respectively. The primary endpoint was acute protocol-defined toxicity related to treatment. Acute toxicity was observed in 7/21 pts (33%) in group I and 14/47 pts (30%) in group II. Most common grade > 3 adverse events in groups I and II were marrow suppression (43% and 17%), diarrhea (33% and 30%), and hyponatremia (14% and 4%). Three deaths on study were attributed to colonic perforation, pneumonia, and sudden death. Radiation completion rates were 72% and 85% in the two groups, and full-dose chemotherapy completion rates were 52% and 51%. Evaluation by cystoscopy and/or tumor biopsy at 12 weeks noted complete response in 9/13 pts (69%) in group I, in 19/33 pts (58%) in group II, and was not performed in the remaining pts. Conclusions: Trimodality bladder-preserving therapy is an appropriate treatment in noncystectomy candidates with invasive UC. The response rate for HER2/neu-targeted therapy is encouraging but may increase certain adverse events in this challenging population. Clinical trial information: NCT00238420.