Related Experiment Video
Updated: May 12, 2026
Stereotactic Radiosurgery for Gynecologic Cancer
Published on: April 17, 2012
A dosimetric evaluation of using a single treatment plan for multiple treatment fractions within a given applicator
Dilini S Pinnaduwage1, J Adam Cunha, Vivian Weinberg
1Department of Radiation Oncology, University of California San Francisco, San Francisco, CA.
Purpose:
To evaluate the dosimetric impact of using one treatment plan for multiple fractions from a single tandem and ring applicator insertion of high-dose-rate brachytherapy for cervical cancer.
Methods And Materials:
Thirteen cervical cancer patients undergoing high-dose-rate brachytherapy were followed. Patients received the total dose from a single applicator insertion in two fractions, given with at least 6 hours apart within 24 hours. The treatment plan was based on a CT scan taken before the first treatment fraction. A second CT was obtained before the second treatment fraction. The co-registered image series were used to evaluate the dosimetric impact of using a single treatment plan for both fractions. Applicator and catheters were measured to quantify interfraction displacement.
Results:
When the Day 1 plan was applied to the Day 2 images, high-risk clinical target volume (HR-CTV) coverage was reduced by as much as 17.4 percentage points. The mean decrease was 9.4 ± 5.0 percentage points (p < 0.0001). The rectum V75 increase was significant (p = 0.03), whereas the bladder V75 increase was not significant (p = 0.28). Volume changes in the HR-CTV contour from Day 1 to Day 2 were also observed (p = 0.29). Maximum applicator and catheter displacements of 10-30mm were seen, from Day 1 to Day 2.
Conclusions:
When the Day 1 plan was used on the Day 2, the HR-CTV coverage decreased significantly (p < 0.0001). Our study establishes the need for institutions to evaluate the necessity for replanning based on imaging obtained before each treatment fraction for their gynecologic brachytherapy techniques.
