(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Evaluate and examine the feasibility of using external beam radiation therapy (EBRT) techniques with C- arm and tomotherapy linear accelerators to create alterative plans for high dose rate (HDR) vaginal cylinder brachytherapy (VCBT) boosts in the treatment of endometrial cancer.
Methods: CT images for several female patients who had endometrial cancer treated with HDR VCBT were selected for this study. A 0.5 cm thick shell around the cylinder applicator was used as the target volume in order to compare plans. The HDR VCBT plans were made based on clinical protocol of 5 Gy given at a depth of 0.5 cm from the surface of the vaginal cylinder. The EBRT plans were generated using volumetric modulated arc therapy (VMAT) and helical tomotherapy for a treatment length of 5 cm and different cylinder diameters, with a prescription dose of 6 Gy in 3 fractions. Dose to target metrics included mean dose, the dose covering 90% of the target volume (D90) and the percentage of the target volume covered by 18 Gy the prescription dose (V18) were used to evaluate and compare plans. Organs at risk (OARs) were also contoured and used in dose evaluation.
Results: Comparison plans for EBRT had more dose homogeneity and increased coverage as shown by the D90 average values VMAT EBRT 17.9 Gy, TOMO EBRT 18.0 Gy, HDR 15.5 Gy, and PTV mean values VMAT EBRT 18.6 Gy, TOMO EBRT 18.2 Gy, HDR 19.1 Gy in comparison to HDR plans. The D0.1cc, D1.0cc, and D2.0cc does to OARs for bladder and rectum were on average 20% higher for the EBRT plans than HDR.
Conclusion: Due to the nature of EBRT and HDR, comparison plans for EBRT had more dose homogeneity and increased coverage in comparison to HDR plans.
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