摘要目的:探究左侧乳腺癌保乳术后基于内缘切线野（IETF）的调强放疗（IMRT）与容积弧形调强放疗（VMAT）的剂量学差异。方法:选取2022年6月至2023年6月收治于云南省肿瘤医院放射治疗科的35例左侧乳腺癌保乳术后行IMRT患者的定位CT和靶区危及器官（OAR）等资料，针对同一患者分别设计基于IETF的IMRT和VMAT两种放疗计划，IETF-IMRT和IETF-VMAT；对两种放疗计划的靶区和OAR剂量及计划执行时间进行比较。结果:靶区剂量：IETF-IMRT和IETF-VMAT两种放疗计划靶区的D 98%分别为（47.92±0.51）、（48.21±0.33）Gy，D 50%分别为（52.04±0.22）、（51.91±0.26）Gy，D 2%分别为（53.93±0.36）、（53.62±0.41）Gy，适形指数分别为0.84±0.03、0.87±0.02，均匀性指数分别为0.12±0.01、0.10±0.01，差异均有统计学意义（ t=-3.87， P<0.001； t=3.53， P=0.001； t=5.30， P<0.001； t=-13.60， P<0.001； t=6.24， P<0.001）。OAR剂量：IETF-IMRT和IETF-VMAT两种放疗计划左肺V 5分别为（31.91±6.28）%、（33.99±6.31）%，V 20分别为（11.71±2.06）%、（9.73±2.12）%，差异均有统计学意义（ t=-4.18， P<0.001； t=12.40， P<0.001）；右肺V 5分别为（0.11±0.08）%、（7.13±3.12）%，D mean分别为（1.05±0.12）、（2.71±0.27）Gy，差异均有统计学意义（ t=-33.62， P<0.001； t=-13.30， P<0.001）；脊髓D 2%分别为（1.08±0.11）、（4.83±1.40）Gy，差异有统计学意义（ t=-15.99， P<0.001）。左肺D mean分别为（7.45±1.08）、（7.37±1.03）Gy，心脏D mean分别为（4.21±0.96）、（4.41±0.48）Gy，右侧乳腺D mean分别为（3.74±1.52）、（3.48±1.11）Gy，差异均无统计学意义（ t=1.16， P=0.253； t=-1.76， P=0.088； t=1.41， P=0.169）。计划执行时间：IETF-IMRT和IETF-VMAT两种放疗计划执行时间分别为（10.73±1.21）、（2.18±0.17）min，差异有统计学意义（ t=44.71， P<0.001）。 结论:IETF-IMRT和IETF-VMAT均能满足临床要求，但两种技术各有特点。靶区适形性和均匀性方面，IETF-VMAT略优；两种计划的OAR剂量均显著低于乳腺癌术后放疗剂量限值，其中，IETF-IMRT计划的左肺V 5，右肺V 5、D mean和脊髓D 2%略低，IETF-VMAT计划的左肺V 20略低。IETF-VMAT较IETF-IMRT显著缩短了计划执行时间，可极大地降低患者体位变化引起的剂量偏差，明显提高患者放疗体验感和舒适度；综合考虑，左侧乳腺癌保乳术后放疗IETF-VMAT较IETF-IMRT更具优势。

abstractsObjective:To explore the dosimetry difference between intensity-modulated radiotherapy (IMRT) and volumetric intensity modulated arc therapy (VMAT) based on the inner edge tangent field (IETF) after left-sided breast conserving surgery.Methods:The localization CT and target organ at risk (OAR) data of 35 patients with left-sided breast cancer treated with IMRT after breast conserving surgery at Department of Radiotherapy in Yunnan Cancer Hospital from June 2022 to June 2023 were selected. The IETF-IMRT and the IETF-VMAT plans were designed for the same patient based on IETF, the dosimetry differences of target areas and OAR, as well as the planned execution time were compared between the two groups.Results:Dosimetry of target areas: for IETF-IMRT and IETF-VMAT, the D 98% of the planning target volume were (47.92±0.51) and (48.21±0.33) Gy, respectively, while the D 50% were (52.04±0.22) and (51.91±0.26) Gy, respectively, and the D 2% were (53.93±0.36) and (53.62±0.41) Gy, respectively, the conformity index were 0.84±0.03 and 0.87±0.02, respectively, while the homogeneity index were 0.12±0.01 and 0.10±0.01, respectively, with statistically significant differences ( t=-3.87, P<0.001; t=3.53, P=0.001; t=5.30, P<0.001; t=-13.60, P<0.001; t=6.24, P<0.001). Dosimetry of OAR: for IETF-IMRT and IETF-VMAT, the left lung V 5 were (31.91±6.28) % and (33.99±6.31) %, respectively, and the V 20 were (11.71±2.06) % and (9.73±2.12) %, respectively, with statistically significant differences ( t=-4.18, P<0.001; t=12.40, P<0.001). The right lung V 5 were (0.11±0.08) % and (7.13±3.12) %, respectively, and the D mean were (1.05±0.12) and (2.71±0.27) Gy, respectively, with statistically significant differences ( t=-33.62, P<0.001; t=-13.30, P<0.001). The spinal cord D 2% were (1.08±0.11) and (4.83±1.40) Gy, respectively, with a statistically significant difference ( t=-15.99, P<0.001). The left lung D mean were (7.45±1.08) and (7.37±1.03) Gy, the heart D mean were (4.21±0.96) and (4.41±0.48) Gy, and the right-sided breast D mean were (3.74±1.52) and (3.48±1.11) Gy, respectively, with no statistically significant difference ( t=1.16, P=0.253; t=-1.76, P=0.088; t=1.41, P=0.169). Planned execution time: the execution time of IETF-IMRT and IETF-VMAT was (10.73±1.21) and (2.18±0.17) min, respectively, with a statistically significant difference ( t=44.71, P<0.001) . Conclusion:Both IETF-IMRT and IETF-VMAT can meet clinical requirements, however the two techniques have their own characteristics. IETF-VMAT has better conformity and homogeneity of target region. The planned OAR dosimetry in both plans are significantly lower than the dose limit of postoperative radiotherapy for breast cancer, among which the left lung V 5, the right lung V 5, D mean and spinal cord D 2% of IETF-IMRT are slightly lower, the left lung V 20 of IETF-VMAT is slightly lower. IETF-VMAT significantly reduces the planned execution time compared with IETF-IMRT, thus can greatly reduce the dose deviation caused by patient position change, and significantly improve patients experience and comfort of radiotherapy. Taken together, IETF-VMAT has advantages over IETF-IMRT in radiotherapy after breast conserving surgery of left-sided breast cancer.