The Effect of Bladder and Rectum Volume Changes on Exposed Organ Volume During Intensity-Modulated Radiotherapy for...

Area of Science:

• Radiation Oncology
• Medical Physics
• Gynecologic Oncology

Background:

• Intensity-modulated radiotherapy (IMRT) for cervical cancer requires precise targeting to minimize damage to surrounding organs.
• Understanding organ motion, particularly bladder and rectal filling variations, is crucial for effective treatment planning.

Purpose of the Study:

• To investigate changes in bladder and rectal volumes during IMRT for cervical cancer.
• To determine the impact of organ filling states on themselves and adjacent structures.
• To provide data for reducing organ damage risks during cervical cancer radiotherapy.

Main Methods:

• Retrospective analysis of 24 cervical cancer patients undergoing IMRT.
• Utilized interactive cone-beam computed tomography (iCBCT) for delineating bladder, rectum, and small intestine.
• Recorded organ filling degrees and their intersection with the planned target volume.

Main Results:

• 83.44% of patients showed reduced bladder volume during treatment.
• Bladder volume changes were minimized when planned volume was 400-500 cc (P < .001).
• Increased bladder volume correlated with decreased small intestine exposure (r = -.674, P < .01).
• Rectal volume increased in 45.83% of patients, with increased exposure (P < .01).

Conclusions:

• Standard bladder and rectal preparation may not ensure stability during IMRT.
• Targeting a bladder volume of 400-500 cc can minimize intrafraction variability.
• Optimizing bladder filling is a potential strategy to reduce small intestine exposure.