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A Novel Two-Step Optimization Scheme for Tandem and Ovoid (T&O) HDR Brachytherapy Treatment for Locally Advanced Cervical Cancer

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M Sharma

M Sharma1*, E Fields2 , D Todor3 , (1) Virginia Commonwealth University, Richmond, VA, (2) Virginia Commonwealth University, Richmond, Virginia, (3) Virginia Commonwealth University, Richmond, VA


SU-E-T-23 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To present a novel method allowing fast, true volumetric optimization of T&O HDR treatments and to quantify its benefits.

Materials and Methods: 27 CT planning datasets and treatment plans from six consecutive cervical cancer patients treated with 4-5 intracavitary T&O insertions were used. Initial treatment plans were created with a goal of covering high risk (HR)-CTV with D90 >90% and minimizing D2cc to rectum, bladder and sigmoid with manual optimization, approved and delivered. For the second step, each case was re-planned adding a new structure, created from the 100% prescription isodose line of the manually optimized plan to the existent physician delineated HR-CTV, rectum, bladder and sigmoid. New, more rigorous DVH constraints for the critical OARs were used for the optimization. D90 for the HR-CTV and D2cc for OARs were evaluated in both plans.

Results: Two-step optimized plans had consistently smaller D2cc’s for all three OARs while preserving good D90s for HR-CTV. On plans with “excellent” CTV coverage, average D90 of 96% (range 91-102), sigmoid D2cc was reduced on average by 37% (range 16-73), bladder by 28% (range 20-47) and rectum by 27% (range 15-45). Similar reductions were obtained on plans with “good” coverage, with an average D90 of 93% (range 90-99). For plans with inferior coverage, average D90 of 81%, an increase in coverage to 87% was achieved concurrently with D2cc reductions of 31%, 18% and 11% for sigmoid, bladder and rectum.

Conclusions: A two-step DVH-based optimization can be added with minimal planning time increase, but with the potential of dramatic and systematic reductions of D2cc for OARs and in some cases with concurrent increases in target dose coverage. These single-fraction modifications would be magnified over the course of 4-5 intracavitary insertions and may have real clinical implications in terms of decreasing both acute and late toxicity.

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