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Evaluation of optimal treatment planning for radiotherapy of synchronous bilateral breast cancer including regional lymph node irradiation

 Yeona Cho  ;  Yoon Jin Cho  ;  Won Suk Chang  ;  Jun Won Kim  ;  Won Hoon Choi  ;  Ik Jae Lee 
 RADIATION ONCOLOGY, Vol.14(1) : 56, 2019 
Journal Title
Issue Date
Breast Cancer ; Organs at risk ; Radiotherapy dosage ; Volumetric-modulated arc therapy
BACKGROUND: We evaluated the optimal radiotherapy (RT) plan for synchronous bilateral breast cancer (SBBC), especially treatment plans including the regional lymph node (LN) area.

METHODS: This study was conducted using 15 patients with SBBC (5 with small breasts, 5 with large breasts, and 5 who underwent a left total mastectomy). The clinical target volume (CTV) was defined as the volume enveloping the bilateral whole breasts/chest wall and left regional LN area. We established the following plans: 1) volumetric-modulated arc therapy (VMAT)-the only plan using two pairs of partial arcs for the whole target volume, 2) VMAT using one partial arc for the left CTV followed by a 3D tangential technique for the right breast (primary hybrid plan), and 3) VMAT for the left CTV followed by a tangential technique using an automatically calculated prescription dose for the right breast, considering the background dose from the left breast VMAT plan (modified hybrid plan). The Tukey test and one-way analysis of variance were used to compare the target coverage and doses to organs at risk (OARs) of the three techniques.

RESULTS: For target coverage, the VMAT-only and modified hybrid plans showed comparable target coverage in terms of Dmean (50.33 Gy vs. 50.53 Gy, p = 0.106). The primary hybrid plan showed the largest distribution of the high-dose volume, with V105% of 25.69% and V110% of 6.37% for the planning target volume (PTV) (p < 0.001). For OARs including the lungs, heart, and left anterior descending artery, the percentages of volume at various doses (V5Gy, V10Gy, V20Gy, V30Gy) and Dmean were significantly lower in both the primary and modified hybrid plans compared to those of the VMAT-only plan. These results were consistent in subgroup analyses of breast size and morphological variation.

CONCLUSIONS: The modified hybrid plan, using an automatically calculated prescription dose for the right breast and taking into consideration the background dose from the left breast VMAT plan, showed comparable target coverage to that of the VMAT-only plan, and was superior for saving OARs. However, considering that VMAT can be adjusted according to the physician's intention, further evaluation is needed for developing a better plan.
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1. College of Medicine (의과대학) > Dept. of Radiation Oncology (방사선종양학교실) > 1. Journal Papers
Yonsei Authors
Kim, Jun Won(김준원) ORCID logo https://orcid.org/0000-0003-1358-364X
Lee, Ik Jae(이익재) ORCID logo https://orcid.org/0000-0001-7165-3373
Jang, Won Seok(장원석)
Cho, Yeona(조연아) ORCID logo https://orcid.org/0000-0002-1202-0880
Cho, Yoon Jin(조윤진)
Choi, Won Hoon(최원훈)
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