What is the recommended radiation therapy approach for bladder cancer irradiation?

Plan of the Day Approach in Bladder Cancer Irradiation

Simulating and treating patients with an empty bladder is the preferred standard approach for daily reproducibility in bladder cancer radiotherapy. 1

Bladder Filling Protocol

The NCCN guidelines explicitly recommend the "empty bladder" approach as the preferred method for both simulation and daily treatment delivery. 1 This approach prioritizes:

• Daily reproducibility of bladder position and volume 1
• Consistent target localization throughout the treatment course 1
• Reduced interfractional variation in organ position 1

Exception to Empty Bladder Protocol

A full bladder may be acceptable specifically for tumor boost phases when daily image guidance is utilized. 1 This exception requires:

• Mandatory use of image-guided radiation therapy (IGRT) 1
• Restriction to boost volumes only, not whole bladder treatment 1
• Verification of bladder filling consistency at each fraction 1

Daily Image Guidance Recommendations

Daily image guidance should be considered when irradiating the bladder-only or delivering bladder tumor boosts. 1 The rationale includes:

• Compensation for significant organ motion that occurs with bladder filling 2
• Reduction of treatment margins that would otherwise need to be very large (up to several centimeters without IGRT) 2
• Improved target coverage while sparing adjacent critical structures 1

Treatment Volume Approach

Whole Bladder Phase

• Treat the whole bladder with or without pelvic nodal radiotherapy to 39.6–50.4 Gy using conventional or accelerated hyperfractionation 1
• Alternative: 55 Gy in 20 fractions to the whole bladder (hypofractionated approach) 1, 2
• Empty bladder protocol is mandatory during this phase 1

Boost Phase

• Boost either whole or partial bladder to 60–66 Gy 1
• Consider simultaneous integrated boosts to sites of gross disease as an alternative to sequential boost 1
• Image guidance is particularly important during boost delivery 1

Technical Specifications

Use multiple fields from high-energy linear accelerator beams for treatment delivery. 1 Modern techniques include:

• 3D conformal radiation therapy or intensity-modulated radiotherapy (IMRT) 1
• Volumetric modulated arc therapy (VMAT) has shown good tolerability and outcomes 3
• Adaptive radiation therapy approaches are emerging, with dose escalation to 70 Gy showing acceptable toxicity 4

Common Pitfalls and Caveats

Avoid inconsistent bladder filling protocols between simulation and treatment, as this is the primary source of geometric miss. 1, 2 The empty bladder approach specifically addresses this issue by providing the most reproducible baseline state. 1

Do not use full bladder protocols without IGRT, as margins required to account for organ motion would be prohibitively large and increase toxicity to surrounding organs. 2

Precede radiation therapy by maximal transurethral resection (TUR) of the tumor when safely possible, as this improves treatment outcomes. 1

Hypofractionation Evidence

Recent evidence supports hypofractionated radiotherapy (55 Gy in 20 fractions) as superior to conventional fractionation for invasive locoregional control with similar toxicity profiles. 2 This can be considered standard of care for node-negative invasive bladder cancer when delivered with IGRT. 2