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Bladder movement during radiation therapy for bladder cancer: implications for treatment planning
S L Turner1, R Swindell, N Bowl
1Department of Clinical Oncology (Radiotherapy), Christie Hospital, Manchester, UK.
International Journal of Radiation Oncology, Biology, Physics
|October 6, 1997
Summary
Bladder movement during radiation therapy (RT) is significant and unpredictable. A minimum 2.0 cm margin is recommended for tumor-bearing bladder regions to ensure adequate treatment coverage.
Area of Science:
- Radiation Oncology
- Medical Imaging
- Urological Oncology
Background:
- Bladder movement during radiation therapy (RT) can impact treatment accuracy.
- Quantifying bladder position changes is crucial for optimizing planning target volume (PTV) margins.
- Understanding factors influencing bladder displacement aids in predicting and managing positional variations.
Purpose of the Study:
- To quantify bladder movement during radical radiation therapy (RT).
- To identify predictors of significant bladder position alterations.
- To inform the definition of adequate planning target volume (PTV) margins.
Main Methods:
- Prospective study of 30 bladder cancer patients undergoing radical RT.
- Weekly CT scans were performed to assess bladder dimensions and position relative to the 95% isodose line.
- Patient data, including symptoms and tumor characteristics, were recorded for correlation analysis.
Main Results:
- 60% of patients (18/30) experienced significant bladder wall movement (>1.5 cm).
- Margin reduction occurred in 33% of patients (10/30), with 2 requiring replanning.
- Posterior wall movement correlated with rectal diameter changes; larger residual tumors showed a trend towards more movement.
Conclusions:
- Bladder movement during RT is clinically relevant, random in time and direction.
- A minimum planning target volume (PTV) margin of 2.0 cm is recommended for tumor-bearing bladder regions.
- Further research may refine strategies for managing bladder motion in RT.