左侧乳腺癌保乳术后3种放疗技术在同步推量中的剂量学研究

目的 探讨左侧乳腺癌保乳术后半弧容积动态旋转调强(VMAT)放疗、切线弧VMAT放疗和逆向调强放疗(IMRT)3种放疗技术在同步推量中的剂量学差异.方法 选取10例左侧乳腺癌保乳术后患者,使用MONACO 5.1计划系统,分别采用半弧VMAT、切线弧VMAT和IMRT三种放疗技术,处方剂量均为计划靶区(PTV)50 Gy/25 f、计划肿瘤靶区(PGTV)60 Gy/25 f,评估3种计划靶区剂量适形度指数(CI)、均匀性指数(HI)以及周围正常组织器官的受照剂量.结果 半弧VMAT的PGTV靶区CI优于IMRT(P﹤0.05).切线弧VMAT放疗技术较IMRT放疗技术降低了左侧乳腺癌保乳术后患者患侧肺组织V10的照射范围(P=0.04).切线弧VMAT放疗技术较半弧VMAT放疗技术降低了左侧乳腺癌保乳术后患者健侧肺组织V5(P﹤0.001)、V10(P=0.04)、心脏的V10(P=0.01)、Dmean(P=0.01)及健侧乳腺组织V5(P﹤0.01)的剂量范围.而IMRT放疗技术降低了左侧乳腺癌保乳术后患者健侧肺组织V5、V10的剂量范围(P﹤0.05).结论 对于左侧乳腺癌保乳术后患者的同步推量放疗,VMAT放疗技术尤其是半弧VMAT放疗技术具有更好的靶区适形性;切线弧VMAT放疗技术可以降低周围大部分正常组织器官的照射剂量.

Dosimetric comparison for three different radiotherapy techniques in the treatment of left breast cancer after breast-conserving therapy

Objective To analyze the differences in dosimetric characteristics and protection of organs at risk (OAR) between half-arc VMAT (volumetric modulated), tangent-arc VMAT and intensity-modulated radiation therapy (IMRT) in the treatment of breast cancer patients after breast-conserving therapy. Method 10 patients with left breast cancer were included in the study, and MONACO 5.1 planning system was applied to determine the target volume of the three re-gimes, which were half-arc VMAT, tangent-arc VMAT and IMRT, with prescribed dose of PTV was 50 Gy/25 f, and 60 Gy/25 f for PGTV. The dosimetric parameters of three different plans including dose conformity index (CI) and homo-geneity index (HI), as well as the radiation dose of OAR were assessed for the three regimens. Result The CI for PGTV of half-arc VMAT was superior to that in IMRT (P<0.05). Compared to IMRT group, the radiation volume of L-lung V10 was significantly reduced in tangent-arc VMAT group (P=0.04). Furthermore, the technology of tangent-arc VMAT had a lower dose-ranging of R-lung V5 (P<0.001), R-lung V10 (P=0.04), heart V10 (P=0.01), Dmean (P=0.01) and contralateral breast V5 (P<0.01) than half-arc VMAT. Besides, the dose-ranging of R-lung V5 and V10 in IMRT group were significant-ly decreased (P<0.05). Conclusion The technology of tangent-arc VMAT offers superior conformity index when admin-istered for the concurrent booster radiotherapy of left breast cancer after breast conserving surgery, besides, it may also re-duce the radiation dose of most OAR.