Dosimetric Evaluation of the Feasibility of Utilizing a Reduced Number of Interstitial Needles in Combined Intracavitary and Interstitial Brachytherapy for Cervical Cancer
D Jahan*, S Ahmad, S Thompson, E Schnell, Oklahoma University Health Sciences Center, Oklahoma City, OK
Presentations
PO-BPC-Virtual-36 (Saturday, 4/17/2021) [Eastern Time (GMT-4)]
Purpose: To evaluate the ability of the Venezia?? advanced multi-channel tandem and ring applicator to consistently produce dosimetrically comparable plans utilizing a reduced number of needle channels, to reduce the risk of secondary complications when boosting cervical cancer treatments with HDR brachytherapy.
Methods: We evaluated 26 fractions from 13 patients who were treated with HDR brachytherapy using the Venezia?? applicator. The original plans included a full load of 12-16 needles, including both parallel and 30° oblique needles. We replanned each original to 9 new configurations, each with a reduced number of needles. Comparisons included differences in percentage dose coverage to 90% of the high-risk CTV (HRCTV), and percentage dose to 2 cm³ of the bladder, rectum, sigmoid, and bowel. We considered new plans “passing” if they remained within our standards (D90 > 100%, D2 cm³ < 85% bladder, < 65% rectum, sigmoid, bowel), or did not perform worse than original.
Results: Removing only the two most anterior needles showed a 80.8% passing rate. Removing only the most posterior two needles from both sides, or the most anterior and posterior four needles together, both showed a 65.4% passing rate. Removing all oblique needles showed a 19.2% passing rate. Removing only left-sided or only right-sided oblique needles showed 46.2% and 23.1% passing, respectively. Removing only right-sided or only left-sided parallel needles separately showed 19.2% and 34.6% passing, respectively. Removing all parallel needles showed a 11.5% passing rate.
Conclusion: As only two replans required a full needle load to maintain dosimetric quality and 40, 36, 18, and 10 replans passed with 2, 3, 4, and 6 needles removed respectively, this indicates the potential for using a lesser number of interstitial needles during combined intracavitary and interstitial HDR brachytherapy while maintaining dosimetric quality.
Keywords
Interstitial Brachytherapy, HDR, Dosimetry
Taxonomy
TH- Brachytherapy: HDR Brachytherapy
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