Vaginal Dose Reduction by Changing the Ovoid Loading Pattern in Image Guided Intracavitary Brachytherapy of Cervix

Area of Science:

• Oncology
• Radiation Oncology
• Medical Physics

Background:

• Locally advanced cervical cancer treatment often involves radiotherapy (external beam and brachytherapy).
• Radiotherapy can cause significant vaginal morbidity, a major clinical concern.
• Optimizing brachytherapy dosimetry is crucial for balancing treatment efficacy and side effects.

Purpose of the Study:

• To investigate the dosimetric impact of reducing ovoid loading in intracavitary brachytherapy for cervical cancer.
• To evaluate if decreased ovoid loading affects the dose delivered to the clinical target volume (CTV).
• To assess the potential for reducing radiation dose to organs at risk, specifically the rectum and vagina.

Main Methods:

• Analysis of 45 CT-based intracavitary brachytherapy plans from 15 patients.
• Comparison of three loading strategies: standard ovoid loading (A), reduced ovoid loading (B), and tandem-only loading (C).
• Generation of Dose-Volume Histograms and recording of dose-volume parameters for CTV, bladder, sigmoid, and rectum.

Main Results:

• No significant difference in D90 for the Clinical Target Volume (CTV) across all plan types (p=0.20).
• Statistically significant reductions in D2cc for the rectum (p<0.001) and vaginal dose points (p<0.001) with reduced ovoid loading (Plan B) and tandem-only (Plan C).
• No significant differences observed for D2cc bladder (p=0.09) or D2cc sigmoid (p=0.43).

Conclusions:

• Reducing ovoid loading in brachytherapy effectively lowers rectal and vaginal doses.
• This modification does not compromise the prescribed dose to the CTV, maintaining treatment efficacy.
• Tandem-only or reduced ovoid loading may be considered in select cervical cancer cases to mitigate vaginal morbidity.