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Updated: Jun 4, 2026
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Quantification of Levator Ani Hiatus Enlargement by Magnetic Resonance Imaging in Males and Females with Pelvic Organ Prolapse
Published on: April 17, 2019
A significant decrease in rectal volume and diameter during prostate IMRT
Nicole S Anderson1, James B Yu, Richard E Peschel
1Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, USA. nanderson@lifespan.org
Summary
Rectal volume and diameter significantly decrease during prostate intensity-modulated radiotherapy (IMRT). This reduction, especially in patients with larger initial rectal volumes, may impact treatment accuracy and toxicity assessments.
Area of Science:
- Radiation Oncology
- Medical Imaging
- Prostate Cancer Treatment
Background:
- Prostate cancer radiotherapy requires precise targeting.
- Rectal volume (RV) and diameter (RD) changes during treatment can affect dose delivery.
- Understanding these changes is crucial for optimizing treatment plans and minimizing toxicity.
Purpose of the Study:
- To quantify changes in RV and RD during prostate intensity-modulated radiotherapy (IMRT).
- To assess the impact of initial RV on RV and RD changes.
- To evaluate implications for treatment planning and toxicity prediction.
Main Methods:
- Retrospective analysis of planning CT scans from 315 prostate adenocarcinoma patients undergoing IMRT.
- Measurement of RV and RD before and after 45 Gy radiation.
- Statistical comparison using paired t-tests and robust linear regression.
Main Results:
- Significant mean decreases in RV (-8.62 cm³; p<0.05) and RD (-0.19 cm³; p<0.05) were observed.
- Over 50% of patients experienced ≥10% RV decrease, and 37.1% had ≥10% RD decrease.
- Patients with larger initial RVs (>70 cm³) showed a greater propensity for significant volume reduction.
Conclusions:
- Prostate IMRT delivery leads to significant rectal shrinkage.
- Pre-treatment RV is a predictor of significant RV and RD changes during therapy.
- Current dose-volume histogram (DVH) analyses based on initial scans may overestimate rectal toxicity risk, particularly for patients with larger initial RVs.
