Dosimetric evaluation of adaptive planning for five-fraction gynecologic template-based interstitial brachytherapy

Area of Science:

• Radiation Oncology
• Gynecologic Oncology
• Medical Physics

Background:

• Template-based interstitial brachytherapy (TISB) is a key treatment for gynecologic cancers.
• Adherence to clinical planning objectives is crucial for optimal treatment outcomes.
• Inter-fraction anatomical variations can challenge treatment delivery accuracy.

Purpose of the Study:

• To evaluate if inter-fraction imaging and replanning improve treatment delivery adherence to planning objectives.
• To assess the impact of replanning on target coverage and organ-at-risk doses in a 5-fraction TISB regimen for gynecologic cancer.

Main Methods:

• Retrospective analysis of 19 patients undergoing 5-fraction TISB using the Syed-Neblett template.
• Verification CT scans acquired before each fraction for applicator assessment.
• Replanning involved contour updates, catheter digitization, and dose optimization; nonadapted doses were compared to adapted doses.

Main Results:

• Replanning significantly improved high-risk clinical target volume (HR-CTV) coverage (D90% and D98%).
• Dose changes to organs at risk (bladder, bowel, rectum, sigmoid) were not statistically significant.
• Fraction 3 was most frequently identified as requiring replanning.

Conclusions:

• Replanning during template-based interstitial brachytherapy enhances target volume coverage.
• This adaptive approach improves adherence to treatment planning goals in gynecologic brachytherapy.