Three-dimension anatomy-based planning optimization for high dose rate vaginal vault brachytherapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Gynecologic Oncology

Background:

• High-dose-rate brachytherapy is a key treatment for gynecologic cancers.
• Conventional planning methods may not fully optimize dose distribution.
• Three-dimensional (3D) inverse planning offers potential for improved treatment precision.

Purpose of the Study:

• To compare the efficacy of 3D inverse planning with two conventional methods for vaginal vault high-dose-rate brachytherapy.
• To evaluate dose coverage of the clinical target volume and sparing of organs at risk.

Main Methods:

• Retrospective analysis of 26 endometrium cancer patients treated with external beam radiotherapy and brachytherapy.
• Dose-volume-histograms were analyzed for three planning protocols: 0.5 cm from applicator tip, 0.5 cm along applicator surface, and inverse planning.
• Data collected between July 2010 and October 2011 at King Abdulaziz University Hospital, Jeddah.

Main Results:

• 3D inverse planning achieved significantly higher clinical target volume dose coverage (68.6%+/-7.5%) compared to conventional methods (26.7%+/-5.4% and 48.5%+/-6.7%; p<0.001).
• Inverse planning demonstrated improved sparing of organs at risk, including the rectum, sigmoid, and bladder, with significantly lower doses received by 2 cm3 volumes (p<0.001).
• Significant differences (p<0.001) were observed across all planning methods for target coverage and organ-at-risk doses.

Conclusions:

• 3D inverse planning effectively balances target dose coverage and organ-at-risk sparing in vaginal vault brachytherapy.
• Using CT scans solely for the initial fraction in 3D inverse planning is a feasible approach with minimal dosimetric impact.
• This study supports the adoption of 3D inverse planning for optimizing high-dose-rate brachytherapy in gynecologic cancers.