Whole Versus Partial Bladder Radiation: Use of an Image-guided Hypofractionated IMRT Bladder-preservation Protocol.

Objectives: To report our institutional experience using definitive chemoradiation via whole bladder (WB) and partial bladder (PB) treatment in muscle-invasive bladder cancer. Combining intensity-modulated radiation therapy with image-guidance can improve the therapeutic ratio.

Materials And Methods: Retrospective analysis of 26 patients with clinical stage T2-4 N0-2 M0 urothelial cancer treated in 2009 to 2012; 16 received WB radiation and 10 received PB radiation. PB/tumor boost volume included visibly thickened bladder wall or tumor localized on cystoscopy. WB radiation delivered 45 to 50.4 Gy to bladder/lymph nodes, then sequential 19.8 to 21.6 Gy tumor boost (1.8 Gy/fx). PB radiation was 45 to 50 Gy to lymph nodes (1.8 to 2 Gy/fx) and simultaneous integrated boost to 55 to 62.5 Gy to tumor only (2.2 to 2.5 Gy/fx). The primary endpoint was local control, defined as no muscle-invasive recurrence. Secondary endpoints were overall survival, toxicity, and cost.

Results: Mean age was 77 and median follow-up was 20 months. Freedom from local recurrence was 86% at 2 years (PB 100%, WB 77%). Overall survival was 80% at 1 year (PB 88%, WB 75%), and 55% at 2 years (PB 70%, WB 48%, P=0.38). Failure was predominantly distant. Toxicities were minimal (3 late grade 3 ureteral, 1 acute grade 4 renal), and all resolved. No cystectomies were performed for toxicity. Hypofractionation reduces treatment time and costs by one third.

Conclusions: Image-guided hypofractionated PB radiation provides local control with similar survival to WB therapy, with minimal toxicity. Hypofractionation also offers time and cost advantages. Our results need to be validated in a larger, multi-institutional cohort.