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Dosimetric Planning Comparison for Left-Sided Breast Cancer Radiotherapy: 4DCT Vs Deep-Inspiration Breath-Hold

O Chau*1,2, H Fakir1,2, M Lock1,2, R Dinniwell1,2, F Perera1,2, A Erickson1, S Gaede1,2,(1) London Regional Cancer Program, London, ON,CA,(2) Western University, London, ON, CA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Background: Adjuvant whole breast radiotherapy (RT) is a standard of care after breast cancer conserving surgery. Techniques including intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) have been shown to provide better target coverage and critical organs sparing compared to 3D-conformal-RT. However, some breast cancer survivors develop radiation-induced cardiac disease. Hence, deep-inspiration breath-hold (DIBH) has been implemented at centres to further reduce cardiac exposure but require compliance. The Raystation treatment planning system (RaySearch Laboratories) 4D-CT robust optimization can account for heart intrafractional motion per breathing phase and not been explored in breast RT cardiac sparing. To provide patients with optimal treatment approach, various heart sparing techniques need to be evaluated for statistical and clinical significance.
Purpose: This retrospective study aimed to provide an extensive dosimetric heart sparing comparison among left-sided breast cancer radiotherapy treatment planning techniques including: DIBH, forward and inverse-IMRT, VMAT and robust optimization.
Methods: 10-early-stage left-sided breast cancer standard treatment plans were selected. Tumour, left anterior descending artery (LAD), left ventricle (LV), and the whole heart were contoured using Raystation7 software. Each treatment plan was optimized using forward/inverse-IMRT and VMAT on the following CT datasets: DIBH, average 4D-CT and entire 4D-CT needed for robust optimization. Dose-volume histograms were used to compare V5Heart, mean(heart), mean(LAD), and mean(LV) dose.
Results: Kruskal-Wallis test showed a statistically significant difference in mean(heart), mean(LAD), mean(LV) dose, and V5Heart among treatment techniques, p=0.03. Mann-Whitney test showed that forward and inverse-IMRT considered statistically equal for all parameters. IMRT-DIBH achieved the optimal cardiac sparing among treatment plans with a mean dose to heart: 72.55±39cGy, LAD: 272.93±362cGy, LV: 102.65±78cGy and V5Heart: 1.61±2.28%.
Conclusion: This study demonstrated that IMRT-DIBH technique was dosimetrically advantageous in heart sparing in treating early-stage left-sided breast cancer patients compared to standard 4D-CT and DIBH-based VMAT, 4D-CT robust optimization, and other IMRT treatment techniques.


Treatment Planning, Radiation Dosimetry, Breast


IM- Radiation Dose and Risk: General (Most Aspects)

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