Abstract
The purpose of this study was to assess the feasibility of using a multiple partial volumetric‐modulated arcs therapy (MP‐VMAT) technique on the left breast irradiation and to evaluate the dosimetry and treatment efficiency. Ten patients with left‐sided breast cancer who had been treated by whole breast irradiation were selected for the treatment plan evaluation by using six partial volumetric modulated arcs. Each arc consisted of a 50° gantry rotation. The planning target volumes and the normal organs, including the right breast, the bilateral lungs, left ventricle, heart, and unspecified tissue, were contoured on the CT images. Dose‐volume histograms were generated and the delivery time for each arc was recorded. The PTV received greater than 95% of the V95 for all cases, and the maximum dose was within ±1% of 110% of the prescription dose. The mean homogeneity index (HI) was 10.61±0.99, and mean conformity index (CI) was 1.21±0.03. The mean dose, V5, V10, V25, and V30 of the heart were 7.61±1.38 Gy, 59.73% ±15.87%, 24.39% ±6.82%, 2.52% ±1.11%, and 1.57% ±0.71%, respectively. The volume of the left ventricle receiving 25 Gy was 5.15% ±2.23%. The total lung mean dose was 5.57±0.36 Gy, with V5 of 25.39% ±3.88% and V20 of 5.66% ±0.89%. The right breast received a mean dose of 2.13±0.22 Gy, with V5 of 1.83% ±1.22% and V10 of 0.04% ±0.12%. The mean dose of unspecified tissue was 5.34±0.37 Gy and V5 was 22.23% ±1.57%. The volume of the unspecified tissue receiving 50 Gy was 0.50% ±0.14%. The mean delivery time for each arc was 13.9 seconds. The average MU among ten patients was 511 MU (range 443 to 594 MUs). The MP‐VMAT technique for the left‐sided breast cancer patients achieved adequate target dose coverage while maintaining low doses to organs‐at‐risk, and therefore reduced the potential for induction of second malignancy and side effects. The highly efficient treatment delivery would be beneficial for improving patient throughput, providing patient comfort, and achieving precise treatment with the breathing control system.PACS number: 87.55.‐x, 87.55.D‐, 87.55.dk
Highlights
63 Tsai et al.: Volumetric-modulated arc therapy for breast cancer breast-conserving surgery
The tangential field technique achieved a good local control rate in breast cancer patients, an increased risk of acute radiation dermatitis,(2) late cardiac,(3-6) pulmonary toxicity,(7-9) and secondary breast cancer on the contralateral breast[10,11,12] were shown, mainly caused by the inhomogeneous radiation distributed within the breast, the substantial lung and heart volumes still in the high-dose region, and some doses given to the contralateral breast
The RapidArc technique is capable of modulating gantry speed, multileaf collimator (MLC) speed, and dose rate while the gantry is in rotation
Summary
63 Tsai et al.: Volumetric-modulated arc therapy for breast cancer breast-conserving surgery. The tangential field technique achieved a good local control rate in breast cancer patients, an increased risk of acute radiation dermatitis,(2) late cardiac,(3-6) pulmonary toxicity,(7-9) and secondary breast cancer on the contralateral breast[10,11,12] were shown, mainly caused by the inhomogeneous radiation distributed within the breast, the substantial lung and heart volumes still in the high-dose region, and some doses given to the contralateral breast Many advanced techniques, such as fixed-beam intensity-modulated radiation therapy (IMRT)(13-15) and helical tomotherapy,(16-18) have been used to provide a better dosimetric result. Some recent publications[19,22] have investigated the potential of using the VMAT technique on whole breast irradiation
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