早期乳腺癌保乳术后4种放疗技术的剂量参数比较

目的：比较早期乳腺癌保乳术后常规切线野（TW）、野中野调强（FIF - IMRT）、切线逆向调强（T -IMRT）和容积调强（VMAT）4种放射治疗技术的靶区和危及器官的剂量参数。方法：15例左侧早期（pT1-2 N0 M0）乳腺癌患者保乳术后接受放疗。CT 模拟定位扫描后勾画靶区和危及器官，在同一患者 CT 影像上分别做 TW、FIF - IMRT、T - IMRT 和 VMAT 4种治疗计划设计。PTV 剂量为50Gy，V47.5≥95%。4种计划的剂量限制相同。在剂量-体积直方图中读取4种计划靶区剂量的分布参数，心脏、双侧肺脏及对侧乳腺受照剂量和体积，对各参数的均数进行比较，并比较4组平均机器跳数差异。结果：4种计划都满足 V47.5≥95%。VMAT 与 T - IMRT、FIF - IMRT 和 TW 计划相比，明显提高了靶区适行指数（CI，P ﹤0.05）。VMAT、T - IMRT和 FIF - IMRT 与 TW 相比，明显改善了靶区均匀性指数（HI，P ﹤0.05）。VMAT 增加了危及器官（心脏和同侧肺脏）V 5、V10和 V20的受照射体积，但是没有增加﹥ V30的照射体积。VMAT 明显增加了右侧乳腺和右侧肺脏照射剂量（P ﹤0.05），T - IMRT 和 FIF - IMRT 明显降低了右侧乳腺和右侧肺脏照射剂量（P ﹤0.05）。VMAT 与T - IMRT、FIF - IMRT 和 TW 相比，明显增加了机器跳数（P ﹤0.05）。结论：早期乳腺癌保乳术后放射治疗4种计划比较，VMAT 明显提高了靶区的适行性和均匀性，增加了正常组织的受照射剂量和机器跳数，延长了治疗时间。T - IMRT 和 FIF - IMRT 也提高了靶区的适行性和均匀性，降低了正常组织的受照射剂量。

A comparison of dose parameters for early stage breast cancer after breast - conserving surgery using four different radiotherapy techniques

Objective:To compare the dose parameter for breast - conserving surgery in breast cancer treatment u-sing four different radiotherapy techniques. Methods:Fifteen patients with left side breast cancer were treated with conservative surgery followed by radiotherapy. After target definition,the treatment planning was performed by conven-tional tangential wedge - based fields(TW),field - in - field intensity - modulated radiation therapy(FIF - IMRT), tangential inverse planning intensity - modulated radiation therapy(T - IMRT)and volumetric modulated arc therapy (VMAT)respectively on the same CT scan. The PTV dose was prescribed with 50Gy and V47. 5 ≥ 95% . Same dose constraint was used in all four plans. The target dose distribution,irradiation doses and volumes for the lung,heart,and contralateral breast were read in the dose volume histogram(DVH),which compared for four different radiotherapy techniques. The monitor units were also compared. Results:Four plans were able to meet the V95%(V47. 5 ). VMAT im-proved significantly the dose conformity index of target volume(CI,P ﹤ 0. 05),as compared with TW,FIF - IMRT and T - IMRT. VMAT and T - IMRT improved significantly the dose homogeneity index of target volume(HI,P ﹤ 0. 05), as compared with TW,FIF - IMRT. VMAT increased the V5 ,V10 and V20 of organs at risk(heart and ipsilateral lung), but didn’ t increase V30 . VMAT increased significantly the irradiation doses of right breast and right lung(P ﹤ 0. 05), T - IMRT and FIF - IMRT decreased significantly the irradiation doses of right breast and right lung(P ﹤ 0. 05). VMAT decreased significantly MU(P ﹤ 0. 05),as compared with TW,FIF - IMRT and T - IMRT. Conclusion:As compared four radiotherapy plans for early stage breast cancer after breast - conserving surgery,VMAT improved significantly CI and HI of target volume,increased the irradiation doses of normal tissues and MU,prolonged the treat-ment time;T - IMRT and FIF - IMRT improved CI and HI of target volume,decreased the irradiation doses of organs at risk.