151 - Bladder Only vs. Whole Pelvis Radiotherapy in Trimodality Treatment for Lymph Node Negative Urothelial Muscle-Invasive Bladder Cancer: A Systematic Review and Meta-Analysis

Purpose/Objective(s): The optimal radiotherapy target volume for muscle-invasive bladder cancer (MIBC) remains unclear, whether elective pelvic lymph node irradiation provides additional benefit in node-negative disease. This issue is widely debated in bladder-preserving approaches worldwide. This study aimed to compare the efficacy and toxicity of bladder-only radiotherapy (BO-RT) versus whole pelvis radiotherapy (WP-RT) in patients with lymph node-negative MIBC undergoing trimodality treatment (TMT). It is hypothesized that including pelvic lymph nodes in the radiation field improve oncologic outcomes by addressing potential micrometastases.

Materials/Methods: A systematic review and meta-analysis was conducted following PRISMA 2020 guidelines. PubMed/MEDLINE, Google Scholar, ScienceDirect and HERDIN databases were searched for studies from 2012-2024. Six studies (3 randomized controlled trials and 3 retrospective studies) with 3,655 patients were included. Primary outcomes assessed were overall survival (OS), disease-free survival (DFS), cancer-specific survival (CSS), and acute/late gastrointestinal (GI) and genitourinary (GU) toxicities. The Cochrane RoB 2 tool (for RCTs) and RoBINS-I tool (for non-RCTs) were used for quality assessment. Data were analyzed using Review Manager 5.4 with random or fixed effects models based on heterogeneity. This review was registered on PROSPERO, number: CRD42024580985.

Results: WP-RT demonstrated significantly better OS compared to BO-RT (OR 0.76, 95% CI: 0.66-0.89, p=0.0004) and improved CSS (OR 0.70, 95% CI: 0.50-0.98, p=0.04). No significant difference was observed in DFS between the approaches (OR 0.99, 95% CI: 0.62-1.57, p=0.96). For toxicity outcomes, BO-RT showed a trend toward lower acute GI toxicity (OR 0.45, 95% CI: 0.20-1.05, p=0.06), though not statistically significant. No significant differences were found in acute GU toxicity (OR 0.85, 95% CI: 0.45-1.60, p=0.62), late GI toxicity (OR 0.38, 95% CI: 0.09-1.68, p=0.20), or late GU toxicity (OR 0.85, 95% CI: 0.36-2.01, p=0.72).

Conclusion: Whole pelvis radiotherapy provides significant survival benefits over bladder-only radiotherapy in patients with lymph node-negative MIBC undergoing trimodality treatment. The survival advantage of WP-RT should be balanced against the trend toward increased acute GI toxicity. These findings support a personalized treatment approach based on patient risk factors, preferences, and quality of life considerations. Future research should focus on identifying patient subgroups most likely to benefit from each approach through molecular markers and advanced imaging techniques.