Application of liner-accelerator two-degrade collimator in the treatment of breast cancer after radical mastectomy with intensity-modulated radiotherapy / 中华放射医学与防护杂志

ABSTRACT

Objective To evaluate the dosimetric imnpact of the fixed position of two-degrade collimator in the treatment of breast cancer after radical mastectomy using intensity-modulated radiotherapy (IMRT) technique.Methods A total of 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 field.There was no restriction on the position of two-degrade collimator(IMRT-1) (P ＞ 0.05).The beam angles and the parameters were as same as IMRT-1,but fixed the position of the two-degrade collimator of 0° and 40° at the inferior border of the supraclavicular (IMRT-2).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 CI were 0.79 and 0.73 (Z =-2.316,P＜0.05),and the HI of the IMRT-2 plans was not different from IMRT-1 (P ＞ 0.05).Considering the dose volunes of the ipsilateral lung in two plans,the values of V5,V10,D of IMRT-2 were significantly less than those of IMRT-1 (Z =-2.805,-2.812,-2.521,P ＜ 0.05).Meanwhile,the D of the contralateral lung,D of heart and D of the contralateral breast from the IMRT-2 were all lower than those oflMRT-1 (Z=-2.666,-2.701,-2.310,P＜0.05).There was no significant difference in the values of V20,V30 of the ipsilateral lung,V30 of heart and between IMRT-1 and IMRT-2 (P ＞0.05).Conclusions Compared with IMRT-1,IMRT-2 with fixed position of the two-degrade collimator could 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.