早期乳腺癌保乳术后全乳调强放射治疗与常规切线野放疗的剂量学比较

目的探讨早期乳腺癌保乳术后全乳调强放射治疗(intensity-modulated radiotherapy,IMRT)的剂量学优势。方法选择6例接受保乳手术的T1N0M0早期乳腺癌病例,其中左侧乳腺癌4例,右侧乳腺癌2例,应用三维调强治疗计划系统为每例患者设计常规切线野与IMRT2种全乳放射治疗计划,处方剂量均为50Gy/25次。用剂量体积直方图(dose volume histograms,DVH)来比较2种计划中计划靶体积(planning target volume,PTV)、危及器官(organs at risks,OARs)的剂量学差异。结果在2种计划中,95%PTV均接受50Gy,99%PTV均接受95%的处方剂量;但在IMRT计划组V110%(接受大于110%处方剂量体积占PTV的百分比)下降了9.1%(46.3%比37.2%,P<0.05);同侧肺的V20(至少接受20Gy照射的肺体积占同侧肺体积的百分比)下降了7.2%(26.8%比18.0%,P<0.05);同侧肺的V30下降了12.0%(23.2%比11.2%,P<0.05);4例左侧乳腺癌患者的心脏V30下降了3.8%(7.0%比3.2%,P<0.05)。结论全乳IMRT在保证靶区覆盖率的前提下,改善了靶区内剂量的均匀性,降低了危及器官的受照剂量及缩小了危及器官的照射体积,尤其是同侧肺、心脏的照射体积,降低放射性肺炎及心血管事件发生的可能。

A Dosimetric Comparison of Intensity-modulated Radiotherapy Versus Conventional Tangential Irradiation for the Early Stage Breast Cancer after Breast-Conserving Surgery

Objective To evaluate the dosimetric benefits of intensity-modulated radiotherapy(IMRT)for the early stage breast cancer after breast-conserving surgery.Methods Six patients with stage T1N0M0 breast cancer receiving breast-conserving surgery were selected for this study.A dosimetric comparison of IMRT with conventional wedged tangential technique was performed on each patient using three dimensional treatment planning.The total prescribed dose for both plans was 50 Gy/25 fractions.Dose volume histograms(DVH)were used to compare the planning target volume(PTV)and organs at risks(OARs)such as ipsilateral lung,and heart for the four left sided patients.Results The percentage of PTV receiving more than 95% prescribed dose(V95%)was 99%;More than 95% of PTV received the total prescribed dose;The percentage of PTV receiving more than 110% prescribed dose(V110%)decreased from 46.3% to 37.2%.The percentage of volume receiving more than 20 Gy(V20)of ipsilateral lung decreased from 26.8% to 18.0%,and V30 from 23.2% to 11.2%;The percentage of V30 of heart for the four left sided patients decreased from 7.0% to 3.2%.Conclusion A better dose uniformity throughout the whole breast was achieved by IMRT plan while the PTV coverage in IMRT plan was similar to that of the conventional plan and obvious reduction in the doses to OARs was achieved by IMRT plan.