Aim : The purpose of the current study was to compare between deep inspiration breath-hold (DIBH) and free-breathing (FB) method in the setup reproducibility and to perform a dosimetric comparison between both methods in left-sided breast cancer patients who undergo the UK FAST trial. Materials and methods : The online matching correction data were retrospectively collected for 50 patients treated with the FAST trial. They were equally divided into DIBH and FB groups to compare between both methods in the setup reproducibility and create the appropriate planning target volume (PTV) margin. Ten patients out of the fifty were scanned in DIBH and FB to perform a dosimetric comparison with the strict acceptance criteria of the FAST trial. Results : All heart dosimetric parameters of the DIBH was significantly lower than that of FB (p < 0.001), and the lung V_30% of DIBH plans was significantly lower than FB plans (p=0.03). There was no statistically significant difference between the two methods in the other organs at risk doses. To fulfill the heart and lung constraints in FB plans, the PTV V_90% was reduced by 3.4%, and three plans would not attain the PTV acceptance criteria. There was no significant difference between the systematic or random setup errors between both methods except the left-right random shift was significantly lower in DIBH cases (p=0.004). The calculated PTV margins were (4 mm, 3 mm, and 4 mm) for DIBH group, and (5 mm, 6 mm, and 8 mm) for FB group in the anterior-posterior, superior-inferior, and left-right shifts, respectively. Conclusion : It is highly warranted to treat left-sided breast cancer patients with the DIBH technique when the UK FAST trial is employed for treatment.

目的 ：本研究的目的是比较深吸气屏气 (DIBH) 和自由呼吸 (FB) 方法在设置重现性方面的差异，并在接受治疗的左侧乳腺癌患者中对两种方法进行剂量学比较。英国 FAST 试验。材料和方法：回顾性收集了 50 名接受 FAST 试验治疗的患者的在线匹配校正数据。他们被平均分为 DIBH 和 FB 组，以比较两种方法的设置可重复性并创建适当的计划目标体积 (PTV) 边界。五十名患者中有十名在 DIBH 和 FB 中进行了扫描，以与 FAST 试验的严格接受标准进行剂量学比较。结果 ：DIBH 的所有心脏剂量学参数均显着低于 FB (p < 0.001)，并且DIBH 计划的肺 V _30%显着低于 FB 计划 (p=0.03)。在危险剂量的其他器官中，两种方法之间没有统计学上的显着差异。为了满足 FB 计划中的心肺限制，PTV V _90%减少了 3.4%，三个计划未达到 PTV 验收标准。两种方法之间的系统或随机设置误差之间没有显着差异，只是左右随机偏移在 DIBH 情况下显着降低（p = 0.004）。计算出的 PTV 边缘为 DIBH 组（4 毫米、3 毫米和 4 毫米），FB 组的前-后、上-下和左右移位的 PTV 边缘为（5 毫米、6 毫米和 8 毫米） ， 分别。结论：当采用英国 FAST 试验进行治疗时，采用 DIBH 技术治疗左侧乳腺癌患者是非常有必要的。