Long-term single-institute experience with trimodal bladder-preserving therapy with proton beam therapy for muscle-invasive bladder cancer

Abstract

Objective: We retrospectively elucidated the oncological outcomes, prognostic factors and toxicities of proton beam therapy in trimodal bladder-preserving therapy for muscle-invasive bladder cancer at our institution. Methods: From 1990 to 2015, 70 patients with cT2-3N0M0 muscle-invasive bladder cancer underwent trimodal bladder-preserving therapy consisting of maximal transurethral resection of the bladder tumor, small pelvis photon irradiation, intra-arterial chemotherapy and proton beam therapy. The overall survival rate, progression-free survival rate, time to progression, predictive factors for progression and toxicities were analyzed. Progression was defined as when muscleinvasive recurrence, distant metastasis or upper urinary tract recurrence was observed. Results: The patients' median age was 65 (range 36-85) years. The median follow-up period was 3.4 (range 0.6-19.5) years. The 5-year cumulative overall survival rate, progression-free survival rate and time to progression rate were 82%, 77%, and 82%, respectively. In univariate and multivariate analyses, tumor multiplicity and tumor size (≥5 cm) were significant and independent factors associated with progression (hazard ratio 3.5, 95% confidence interval 1.1-12; hazard ratio 5.0, 95% confidence interval 1.3-17; P < 0.05 for all). As for toxicity, 26 (18%) patients had grade 3-4 acute hematologic toxicities and 2 (3%) patients had grade 3 late genitourinary toxicity. No patient had to discontinue the treatment due to acute toxicity. Conclusions: Our bladder-preserving therapy with proton beam therapy was well tolerated and achieved a favorable mortality rate. Tumor multiplicity and tumor size were important risk factors for progression. Our findings indicate that this therapy can be an effective treatment option for selected muscle-invasive bladder cancer patients.