Pelvic Organ Motion during Radiotherapy for Cervical Cancer: Understanding Patterns and Recommended Patient...

Area of Science:

• Radiation Oncology
• Medical Physics
• Gynecologic Oncology

Background:

• Accurate radiotherapy for pelvic cancers requires minimizing organ motion.
• Bladder and rectal filling variations can significantly impact treatment efficacy.

Purpose of the Study:

• To analyze bladder and rectal filling variations during pelvic radiotherapy.
• To identify methods for reducing organ position variability in cervical cancer patients.

Main Methods:

• Retrospective analysis of cone beam computed tomography (CBCT) scans from 10 cervical cancer patients.
• Clinician outlining of bladder, rectum, and clinical target volume (CTV) on CBCTs.
• Statistical analysis of factors affecting organ volumes and impact on CTV coverage.

Main Results:

• Bladder volume varied significantly (45-578 cm(3)) and increased with waiting time and post-chemotherapy.
• Deviations in bladder volume from planning (>130 cm(3)) reduced CTV coverage probability by 1.9% per cm(3).
• Rectal diameter correlated with volume, and larger rectal volumes increased the risk of inadequate CTV coverage.

Conclusions:

• An ideal planning bladder volume of 150-300 cm(3) is suggested.
• Optimizing waiting times, hydration, and potentially using laxatives can help standardize organ filling.
• Regular imaging remains essential for advanced radiotherapy techniques in gynecologic cancers.