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KMID : 1164220190310020051
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Journal of Korean Society for Radiotherapeutic Technology
2019 Volume.31 No. 2 p.51 ~ p.63
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Dosimetric Comparison of Left-sided Whole Breast Irradiation using a Virtual Bolus with VMAT and static IMRT
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Lim Kyeong-Jin
Kim Tae-Woan
Jang Yo-Jong
Yang Jin-Ho
Lee Seong-Hyeon
Yeom Du-Seok
Kim Seon-Yeong
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Abstract
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Purpose: Radiation therapy for breast cancer should consider the change in breast shape due to breathing and swelling. In this study, we evaluate the benefit of using virtual bolus for IMRT of left breast cancer.
Materials and methods: 10 patients with early breast cancer who received radiation therapy after breastconserving surgery compared the VMAT and IMRT plans using the virtual bolus method and without using it. The first analysis compared the V95%, HI, CI of treatment volume, Dmean, V5, V20, V30 of ipsilateral lung, and Dmean of heart in VMAT plan made using the virtual bolus method(VMAT_VB) to the plan without using it(VMAT_NoVB) in case there is no change in the breast. In IMRT, the same method was used. The second analysis compared TCP and NTCP based on each treatment plan in case there is 1cm expansion of treatment volume.
Result: If there is no change in breast, V95% in VB Plan(VMAT_VB, IMRT_VB) and NoVB Plan(VMAT_NoVB, IMRT_NoVB) is all over 99% on each treatment plan. V95% in VMAT_NoVB and VMAT_VB is 99.80±0.17% and 99.75±0.12%, V95% in IMRT_NoVB and IMRT_VB is 99.67±0.26% and 99.51±0.15%. Difference of HI, CI is within 3%. OAR dose in VB plan is a little high than NoVB plan, and did not exceed guidelines. If there is 1cm change in breast, VMAT_NoVB and IMRT_NoVB are less effective for treatment. But VMAT_VB and IMRT_VB continue similar treatment effect compared in case no variation of breast.
Conclusion: This study confirms the benefit of using a virtual bolus during VMAT and IMRT to compensate potential breast shape modification.
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KEYWORD
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Virtual bolus, Left breast, VMAT, IMRT, Edema
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