Comparison of setup errors between deep inspiration breath hold and free breathing for whole breast irradiation / 中华放射肿瘤学杂志

ABSTRACT

Objective:To compare the setup errors between deep inspiration breath hold (DIBH) and free breathing (FB) for breast cancer patients who were treated with whole breast irradiation (WBI) after breast conserving surgery (BCS).Methods:In this retrospective analysis, 30 breast cancer patients receiving WBI following BCS using DIBH in National Cancer Center/ Chinese Academy of Medical Sciences, an 30 patients treated with WBI using FB were enrolled as comparator.The kilovoltage cone-beam computed tomography (CBCT) was performed to evaluate and reduce setup errors. The optimal margins from clinical target volume (CTV) to planning target volume (PTV) for DIBH were estimated. The differences of setup errors between two techniques were compared using independent two-sample t-test. Results:A total of 318 sets of CBCT images were acquired, with (5.1±1.1) sets per patient on average. The setup errors along the three translational directions (laternal, longitudinal and vertical) were (2.1±1.6) mm, (2.6±1.7) mm and (2.5±2.1) mm for DIBH, and (2.2±1.7) mm, (3.1±2.5) mm and (3.3±2.3) mm for FB, respectively. Compared with FB, DIBH significantly reduced setup errors in the longitudinal ( P=0.015) and vertical ( P=0.004) directions, whereas the setup errors in the lateral direction did not significantly differ ( P=0.294). The optimal margins from CTV to PTV using DIBH were 6.2 mm, 7.3 mm and 7.8 mm, respectively. In the DIBH group, treatment fractions at the beginning and higher body mass index (BMI) did not associate with larger set-up deviation. Conclusions:DIBH technique yields less setup errors than FB for breast cancer patients treated with WBI after BCS. The CTV-PTV margins of 6-8 mm are recommended for DIBH.