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目的:比较左侧乳腺癌患者根治术后常规调强放射治疗计划(intensity modulated radiotherapy, IMRT)与电子束适形放疗(electron beam conformal radiotherapy, EBCRT)联合调强放疗计划的剂量学差异。方法:选择2018年6月至2021年10月于宁波市第一医院放化疗中心收治的20例左侧乳腺癌根治术后患者资料，计划靶区(plan target volume, PTV)包括锁骨上下淋巴结引流区域计划靶区(PTVn sc)和患侧胸壁计划靶区(PTVn cw)，处方剂量均为50 Gy/25次。所有患者均采用美国Varian Eclipse治疗计划系统(treatment planning system, TPS)设计两种放疗计划，然后对比两种放疗计划的剂量学参数差异。n 结果:所有20例患者的IMRT计划全部满足临床要求，与此同时EBCRT联合IMRT计划中有2例患者因患侧肺剂量参数超出本单位的剂量限定标准而不被临床接受，两例失败计划的胸壁最大深度分别为3.7和4.4 cm，使用的电子束能量分别为12和15 MeV。其余18例患者的胸壁深度均≤3 cm，使用9 MeV及以下能量电子束进行EBCRT联合IMRT计划设计，靶区和各危及器官剂量均满足临床要求，并与IMRT计划进行剂量学配对比较。常规IMRT的均匀性指数(HI)均优于EBCRT联合IMRT计划(n tPTVsc＝-10.20、n tPTVcw＝ -9.24, n P<0.05)；常规IMRT整体靶区适形指数(CI)与EBCRT联合IMRT计划比较差异有统计学意义(n tPTVall ＝10.39，n P<0.05)。对于危及器官(organ at risk, OARs)，EBCRT联合IMRT计划患侧肺的n V5 Gy、n V20 Gy和n Dmean均较IMRT更低，差异有统计学意义(n t＝5.98、6.30、11.30，n P<0.05)；心脏的n V25 Gy和n Dmean分别降低了8.3 %和4.79 Gy(n t ＝ 15.23、15.76，n P< 0.05)；冠状动脉左前降支(left anterior descending coronary artery, LADCA)的n Dmean降低了44.03 %(n t＝11.69, n P<0.05);健侧乳腺的n V5 Gy和n Dmean分别降低了7.9 %和0.8 Gy(n t＝3.66、4.932 n P0.05)。n 结论:对于胸壁靶区深度≤3 cm的左侧乳腺癌根治术后患者，EBCRT联合IMRT能显著降低心脏、患侧肺和健侧乳腺的剂量，有利于降低乳腺癌放疗远期并发症风险以进一步提高患者的长期总生存率。而对于胸壁较厚的患者，选择IMRT计划可满足临床要求。“,”Objective:To investigate the dosimetric differences between conventional IMRT and electron beam conformal radiotherapy (EBCRT) combined with IMRT for post-mastectomy left-sided breast cancer patients.Methods:A total of 20 post-mastectomy left-sided breast cancer patients who were treated in the Ningbo First Hospital from June 2018 to October 2021 were retrospectively studied. The planning target volume (PTV) included the supra-and infra-clavicular regions(PTVn sc)and the ipsilateral chest wall (PTVn cw), and the prescribed dose was 50 Gy/25 f. All radiotherapy plans were designed using the Varian Eclipse treatment planning system (TPS). After that, the dose distribution of the target volume and the dose exposure of organs at risk (OARs) were compared and analyzed.n Results:All the IMRT plans met the clinical requirements, yet 2/20 of the EBCRT combined with IMRT plans were not clinically accepted. For these two patients, the maximum chest wall thickness was 3.7 cm and 4.4 cm each, and the designed electron beam energy was 12 MeV and 15 MeV, respectively. The dose to the ipsilateral lung of these two patients exceeded the institution-specific dose limit standard. For the remaining 18 patients whose chest wall thickness was 3 cm or less, the designed electron beams were 9 MeV or less. All the EBCRT combined with IMRT plans were clinically accepted. The target dose distribution of the conventional IMRT was better than that of the EBCRT combined with IMRT (uniformity index (HI): PTVn sc: n t = -10.20, n P<0.05; PTVn cw: n t = -9.24, n P<0.05; conformal index (CI): PTVn all: n t = 10.39, n P <0.05). For OARs, the n V5 Gy, n V20 Gy, and n Dmean of the ipsilateral lung of EBCRT combined with IMRT were lower than those of IMRT (n t = 5.98, 6.30, 11.30, n P <0.05). Specifically, the n V25 Gy and n Dmean of heart decreased by 8.3% and 4.79 Gy, respectively (n t = 15.23, 15.76, n P<0.05), then Dmean of the left anterior descending coronary artery (LADCA) decreased by 44.03% (n t = 11.69, n P <0.05), and the n V5 Gy and n Dmean of the contralateral breast decreased by 7.9% and 0.8 Gy, respectively (n t = 3.66, 4.93, n P 0.05).n Conclusions:For post-mastectomy left-sided breast cancer patients with a chest wall thickness of less than 3 cm, EBCRT combined IMRT can significantly reduce the exposure dose to the heart, the ipsilateral lung, and the contralateral breast, which is beneficial to reducing the potential risk of long-term complications after radiotherapy and can further improve the long-term overall survival rate of patients. For patients with thick chest wall, IMRT plans are more technologically ideal.