H Liu*, J Sohn, Y Zhang, E Fields, D Todor, Virginia Commonwealth University, Richmond, VA

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  H Liu

PO-GePV-T-33 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: This study analyzes the impact of integrating free needles into tandem and ovoid (T&O) HDR-brachytherapy treatment on consecutive women with locally advanced cervical cancer. Optimization algorithm based on TG-43 were used. Re-optimized plans only used T&O applicators, while matching dose coverage (D90) to the high-risk CTV (HR-CTV), or dose to adjacent OARs. Dosimetric distribution were examined, together with the volume of HR-CTV and the volume encompassed by prescription dose (PD) per fraction.

Methods: 29 patients with cervical cancers (FIGO stage IB-IIIC2) were treated with 125 fractions. HR_CTV and OARs (bladder, rectum, sigmoid) were contoured by one physician. All plans were optimized using a ‘two-step’ optimization procedure, previously described with the goal of maximizing D90(HR-CTV), minimizing dose to OARs, while maintaining the pear aspect of the PD iso-surface. Two re-optimized plans without needles were generated. The first re-optimization kept D90 to HR-CTV, while the second matched D2cc to OARs. Dosimetric information were extracted from TPS and evaluated using distribution histogram and student t-test.

Results: With comparable dose coverage, mean D2cc calculated from plans without integrated free needles is higher than those from original plans by 29%, 22%, 27% for bladder, rectum and sigmoid, respectively. Corresponding t-test shows p-values < 0.00006. With matching toxicity, mean D90(HR-CTV) in plans without needles is 21% lower than original plans with p-value < 2.2e-16.

Conclusion: Based on our clinical data, we believe that integrating free needles and optimization methods into traditional T&O cervical cancer brachytherapy treatment is beneficial for controlling organs-at-risk toxicities while achieving satisfying coverage for HR-CTV. The finding suggest that the use of free needles should be considered as larger volume of HR-CTV is presented. We recommend adding free needles and optimization to T&O treatment in High Dose Rate brachytherapy for cervical cancer to ensure the best dosimetric outcomes for our patients.

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