Comparison between two different immobilization techniques in radiotherapy for breast cancer
LIU Libin;ZHANG Xiaoqing;YANG Haisong;HUANG Jiawen;NI Min;WU Junxin;Department of Radiation Therapy, Fujian Provincial Cancer Hospital;
Objective To study the set-up errors in radiotherapy with two different immobilization techniques for breast cancer via k V-cone beam computed tomography(CBCT). Methods Sixty patients with breast cancer were in cluded in this study and divided into observation group and control group. The patients in observation group were immobilized with breast bracket, while the immobilization combining immobilized carbon fiber holder, vacuum bag and thermoplastic mask was adopted in control group.CBCT scan and auto-match online were performed before the treatment to obtain the set-up errors in left-right(X), superiorinferior(Y), anterior-posterior(Z) directions, and the obtained set-up errors were analyzed with independent-samples t-test. In observation group, CBCT scan was performed once each week, last for 4 week, and SNK-q test was carried out to verify the repeatability of the 4 scans. Results The set-up errors in X, Y and Z directions were(0.27±3.61),(0.63±4.19),(-0.37±5.05) mm in observation group, and(0.64±3.25),(-2.03±4.51),(2.47±2.67) mm in control group. The t-test values in X, Y and Z directions were-0.46, 2.55 and-2.79, respectively(P=0.650, 0.014, 0.007). In observation group, no statistical significance was observed in the repeatability verification in X, Y and Z directions(P0.05). Conclusion The two immobilization techniques doesn't show any differences in X direction. In Y and Z directions, breast bracket is better than the immobilization technique combining carbon fiber holder, vacuum bag and thermoplastic mask in reducing the set-up errors. The reproducibility of using breast bracket for immobilization is relatively steady.