Program Information
Application of Fixed Collimator Technique in the Treatment of Breast Cancer After Radical Mastectomy with Intensity- Modulated Radiotherapy
G Zhang1*, J Lu2 , C Ma3 , T Sun4 , Y Yin5 , (1) ,,,(2) Shandong Cancer Hospital Affiliated to Shandong, Jinan, Shandong, (3) Shandong Cancer Hospital and Institute, Jinan, Shandong Province, (4) Shandong Cancer Hospital Affiliated to Shandong, Jinan, Shandong, (5) Shandong Cancer Hospital and Institute, Jinan, Shandong Province
Presentations
SU-I-GPD-T-409 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To evaluate the dosimetric impact of fixed the position of two-degrade collimators in the treatment of breast cancer after radical mastectomy using intensity-modulated radiotherapy techniques.
Methods: Ten patients with breast cancer were treated with radical mastectomy and radiotherapy sequaciously involving the supraclavicular region and the chest wall.Two different IMRT treatment plans were designed for each patient： 0°、40° and two tangential fields, there were no restriction on the position of two-degrade collimators（IMRT-1）；the beam angles and the parameters were as same as IMRT-1, but fixed the position of the two-degrade collimators of 0° and 40° at the inferior border of the supraclavicular（IMRT-2）. The prescription dose was 50 Gy in 25 fractions.The dose distribution of target volume and normal tissues, conformal index (CI), and heterogeneous index (HI) were estimated with the dose volume histogram（DVH）for the two intensity modulated modes.
Results: The conformal indices(CI) were 0.79 and 0.73 (Z=-2.316, P < 0.05)，the heterogeneous index (HI) of the IMRT-2 plans was not different from IMRT-1.Considering the dose volumes of ipsilateral lung in two plans，the values of V5，V10，Dmean of IMRT-2 were significantly less than those of IMRT- 1(Z=-2.805、-2.812，-2.521．P < 0.05). Meanwhile，the Dmean of contralateral lung and Dmean of heart from the IMRT-2 were all lower than those of IMRT-1（Z=-2.666，-2.701，P＜0.05）.There were not significant difference in the values of V20，V30 of ipsilateral lung，V30 of heart and Dmean of contralateral breast between IMRT1 and IMRT2.
Conclusion: Compared with IMRT-1, IMRT-2 fixed the position of the two-degrade collimators can significantly reduce the low dose region of the lung and heart. It may be used as an effective alternative for breast cancer after radical mastectomy irradiation.
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