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Published on: June 7, 2015
Variability of marker-based rectal dose evaluation in HDR cervical brachytherapy
Zhou Wang1, Wainwright Jaggernauth, Harish K Malhotra
1Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY 14263, USA. Zhou.Wang@RoswellPark.org
Summary
Rectal marker placement in cervical cancer brachytherapy can significantly alter rectal dose estimates. Careful consideration of marker position is crucial for accurate dose assessment during high-dose-rate treatment.
Area of Science:
- Oncology
- Medical Physics
- Radiotherapy
Background:
- Film-based intracavitary brachytherapy is a standard treatment for cervical cancer.
- Accurate rectal dose estimation is vital to minimize toxicity during treatment.
Purpose of the Study:
- To analyze the variability in rectal dose estimation due to interfractional variations in rectal marker placement.
- To assess the impact of marker placement variability on cumulative rectal dose calculations in high-dose-rate brachytherapy.
Main Methods:
- Retrospective analysis of five cervical cancer patients undergoing HDR brachytherapy.
- Matching applicator orientation and cervical os point across fractions.
- Repositioning rectal dose points from all fractions into each clinical plan to recalculate doses.
Main Results:
- Maximum interfractional variation in rectal dose point distance to sources was 1.1 cm.
- Maximum interfractional rectal dose variability reached 65.5%.
- Percentage differences in cumulative rectal dose estimation ranged from 5.4% to 34.6%.
Conclusions:
- Rectal markers may not reliably represent the anterior rectal wall in brachytherapy.
- Interfractional marker placement variability significantly impacts rectal dose estimation.
- The most anterior rectal point across all fractions provides the best estimate of true rectal dose.
