Uro-Oncology Fellow Dept. of Urology, Rabin Medical Center, Tel Aviv University
Introduction: Radiation-based therapy (RT) is an acceptable bladder-preserving treatment for selected patients with muscle-invasive bladder cancer (MIBC). Real-world outcomes of RT-based therapy for histologic variants are lacking. Our objective was to compare oncological outcomes between pure urothelial carcinoma (PUC) and variant urothelial carcinoma (UC-HV) patients with MIBC treated with RT-based therapy. Methods: A collaborative Canadian multicenter retrospective study of 864 patients with MIBC who underwent curative-intent bladder-sparing RT for T2-4a N0-3 M0 MIBC between 2001-2018. Tumours were classified based on the presence of non-urothelial components as either PUC or UC-HV. A complete response (CR) was defined by a negative tumour bed biopsy and/or the combination of a negative urine cytology, negative cystoscopy and normal imaging post-RT. Loco-regional disease-free survival (LR-DFS), disease-free survival (DFS), metastasis-free survival (MFS), cancer-specific survival (CSS) and overall survival (OS) were calculated using Kaplan-Meier method. Cox regression models were used to estimate the effect of UC-VH on oncologic outcomes for patients with MIBC treated with RT-based therapy. Results: Of 864 patients treated with RT-based therapy, 123 (14.2%) had UC-HV. Seventy-five (61%) had UC-HV with squamous and/or glandular differentiation and 48 (39%) had other variants. A CR after RT-based therapy was confirmed in 69.1% of patients with PUC and 63.4% with UC-HV (p=0.266). The 5-yr CSS was 62.0% in PUC vs. 66.8% in UC-HV. The 5-yr OS was 47.7% in PUC and 53.3% in UC-HV. Rates of LR-DFS, DFS and MFS at 5 years were not statistically different between the groups. Salvage cystectomy (sRC) rates were similar (p=0.781). In the univariate Cox regression analyses, UC-HV status was not associated with inferior LR-DFS, DFS, MFS, CSS, and OS. Conclusions: Variant histology of urothelial carcinoma responded to RT-based therapy with no significant difference in CR, LR-DFS, DFS, MFS, CSS, OS, or rates of salvage cystectomy compared to PUC. The presence of variant histology in MIBC does not confer resistance to RT-based therapy and these patients should not be excluded from bladder preservation treatment. SOURCE OF Funding: None
