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Journal SAM 43-1: Radiation therapy of synchronous bilateral breast carcinoma (SBBC) using multiple techniques

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CEUs: 2.5

Available Until: 2/28/2019

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Journal SAM 43-1: Radiation therapy of synchronous bilateral breast carcinoma (SBBC) using multiple techniques

Sung Jin Kim, M.S.,*,† Mi Jo Lee, MD, Ph.D.,* and Seon Min Youn, MD, Ph.D.*

*Department of Radiation Oncology, Eulji University Hospital, Eulji University, College of Medicine, Daejeon, Republic of Korea; and †Department of Physics, Yeung Nam University, Daegu, Republic of Korea

The purpose of this study was to establish intensity-modulated radiation therapy(IMRT) and volumetric-modulated arc therapy (VMAT) treatment plans for synchronous bilateral breast cancer (SBBC) and to compare those plans with the previous treatment plans using 3D conformal radiation therapy (3DCRT). The differences among the treatments were also statistically compared regarding dosimetry distribution and treatment efficiency. The research was conducted with 10 SBBC patients. The study established IMRT (12 fields with a single isocenter) and VMAT (2 partial arcs with a single isocenter) treatment plans for SBBC patients and then compared those plans with 3DCRT (8 fields with multiple isocenters). The plans were evaluated based on a dose-volume histogram analysis. For planning target volumes (PTVs), the mean doses and the values of V95%, V105%, conformity index, and homogeneity index were reported. For the organs at risk, the analysis included the mean dose, maximum dose, and VXGy, depending on the organs (lungs, heart, and liver). To objectively evaluate the efficiency of the treatment plans, each plan’s beam times, treatment times (including set-up time), and monitor units were compared. Tukey test and one-way analysis of variance were used to compare the PTV and organs at risk values of the 3 techniques. Additionally, the independent samples t-test was used to compare the 2 techniques (IMRT and VMAT) based on the values of Rt. PTV and Lt. PTV (p<0.05). For PTV dose distribution, IMRT showed increases of approximately   1.2% in Dmean and of approximately 5.7% in V95% dose distribution compared with 3DCRT. In comparison to VMAT, 3DCRT showed about 3.0% higher dose distribution in Dmean and V95%. IMRT was the best in terms of conformity index and homogeneity index (p<0.05), whereas 3DCRT and VMAT did not significantly differ from each other. In terms of dose distribution on lungs, heart, and liver, the percentage of volume at high doses such as V30Gy and V40Gy was approximately 70% lower for IMRT and approximately 40% lower for VMAT than for 3DCRT. For distribution volumes of low doses such as V5% and V10%, that for 3DCRT was approximately 60% smaller than for IMRT and approximately 70% smaller than for VMAT. Comparison between IMRT and VMAT showed that the IMRT was superior in all distribution factors. VMAT showed better treatment efficiency than 3DCRT or IMRT. Among the SBBC radiotherapy treatment plans, IMRT was superior to 3DCRT and VMAT in terms of PTV dose distribution, whereas VMAT showed the most outstanding treatment efficiency.

Learner Outcomes:

1. Gain an understanding of how 3DCRT, IMRT, and VMAT can each be used in the treatment of synchronous bilateral breast cancer (SBBC).

2. Learn the dosimetric advantages and limitations of each technique in the setting of SBBC treatment, including constraints imposed by anatomy, target shape, and delivery system capabilities.

3. Improve understanding of how to calculate and compare plan quality metrics such as homogeneity index, conformity index, and dose volume histogram goals.

4. Improve understanding of how non-dosimetric criteria such as treatment time and planning software capabilities can influence the selection of treatment techniques.