Systematic review and meta-analysis of radiation therapy for high-risk non-muscle invasive bladder cancer

Introduction: Radiation therapy (XRT) has been investigated as a possible treatment for high-risk non-muscle invasive bladder cancer (NMIBC) with the goal of bladder preservation, especially with the ongoing Bacillus Calmette-Guerin (BCG) shortage. Yet, little is known about the clinical efficacy and the quality of evidence supporting XRT for NMIBC. Herein, we performed a systematic review and meta-analysis to evaluate XRT in the treatment of patients with high-risk NMIBC.

Methods: Cochrane Central Register of Controlled Trials, EMBASE, MEDLINE, and Web of Science were searched for high-risk NMIBC (high grade T1, T1/Ta with associated risk features: carcinoma in-situ (CIS), multifocality, > 5cm in diameter, and/or multiple recurrences) treated with primary XRT. Outcomes evaluated were recurrence-free survival (RFS), cancer-specific-survival (CSS), overall survival (OS), and salvage cystectomy and progression to metastatic disease rates. A meta-analysis was performed to assess outcomes for XRT in NMIBC.

Results: Overall,13 studies including 746 patients met the search criteria. The 5-year rates of RFS, CSS and OS were 54% (95% CI = 38% - 70%), 86% (95% CI = 80% - 92%), and 72% (95% CI = 64% - 79%). Notably, 13% of patients proceeded to salvage radical cystectomy and 9% developed metastatic disease. All studies were of poor quality, comprising single institution and retrospective studies with only one clinical trial.

Conclusion: XRT for high-risk NMIBC provides some degree of oncologic control, although distant progression was noted. In the setting of the low-quality evidence, a prospective clinical trial is needed to clearly define the risks and benefits of this approach.