乳腺癌固定野调强射野数目的研究

Different fixed-field intensity-modulated radiotherapy plans for breast cancer: a dosimetric comparison

目的:在乳腺癌改良根治术后放疗中,通过比较4种不同治疗计划的剂量分布,找出一种靶区覆盖率高、均匀性好、适形度高而正常组织受量少的治疗方式。方法:随机选取16例乳腺癌根治术后患者制定4、5、6野调强计划(4FIMRT、5F-IMRT、6F-IMRT)及适形混合调强治疗计划(Hybrid-IMRT),比较4种不同治疗计划的靶区和危及器官的剂量。结果:通过数据分析可以得出,Hybrid-IMRT、5F-IMRT和6F-IMRT的CI优于4F-IMRT,差异有统计学意义(P<0.05),Hybrid-IMRT、5F-IMRT和6F-IMRT之间统计无差异(P>0.05);4种计划的HI分别为:4F-IMRT(0.22)、5F-IMRT(0.22)、6F-IMRT(0.21)、Hybrid-IMRT(0.16),差异无统计学意义(P>0.05);患侧肺的V5方面,Hybrid-IMRT和4F-IMRT好于5F-IMRT、6F-IMRT,V20方面,Hybrid-IMRT优于其它3种治疗计划(P<0.05),V30方面,Hybrid-IMRT明显低于4F-IMRT和6F-IMRT(P<0.05),其余治疗计划之间差异不明显(P>0.05),Dmean方面,Hybrid-IMRT计划明显高于5F-IMRT和6FIMRT,差异具有统计学意义(P<0.05),Hybrid-IMRT和4F-IMRT计划之间统计差异不明显(P>0.05);4种计划心脏的V30、V40差异无统计学意义,Dmean方面,Hybrid-IMRT和4F-IMRT计划明显低于5F-IMRT和6F-IMRT,差异具有统计学意义(P<0.05);4种计划脊髓的Dmax之间的差异无统计学意义;在甲状腺的Dmean方面,4F-IMRT不如其它3种计划,有统计学差异(P<0.05);4种计划的机器跳数平均值,Hybrid-IMRT<5F-IMRT<4F-IMRT<6F-IMRT。结论:Hybrid-IMRT明显改善靶区剂量分布,不会增加周围正常组织的照射剂量,能够通过剂量验证,可在临床推广。

Objective To compare the dose distribution in 4 different plans for the modified radical mastectomy of breast cancer for selecting an optimal treatment strategy with a high target coverage,good homogeneity,better conformity index and less doses to the normal tissues.Methods A total of 16 patients with breast cancer after radical mastectomy were randomly selected,and 4 different treatment plans,namely 4-field(4F),5-field(5F),6-field(6F)and hybrid intensity-modulated radiotherapy(IMRT),were designed for each patient.The doses of target areas and organs-at-risk were compared among 4 different treatment plans.Results The conformity index of Hybrid-IMRT,5F-IMRT and 6F-IMRT was better than that of 4F-IMRT,with statistical differences(P<0.05),and no statistical differences were found in conformity index among Hybrid-IMRT,5F-IMRT and 6F-IMRT(P>0.05).The homogeneity index of 4F-IMRT,5F-IMRT,6F-IMRT and Hybrid-IMRT was 0.22,0.22,0.21 and 0.16,respectively,without statistical differences(P>0.05).Hybrid-IMRT and 4F-IMRT were superior to 5F-IMRT and 6F-IMRT in the V5 of ipsilateral lung,and the V20 of ipsilateral lung in Hybrid-IMRT plan were better than that in the other plans(P<0.05).The V30 of ipsilateral lung was significantly lower in Hybrid-IMRT than in 4F-IMRT and 6F-IMRT(P<0.05),but there was no significant difference among other treatment plans(P>0.05).The Dmean of ipsilateral lung in Hybrid-IMRT was significantly higher than 5FIMRT and 6F-IMRT,with statistical differences(P<0.05),and there was no statistical difference between Hybrid-IMRT and 4FIMRT plans(P>0.05).No significant differences were found among 4 plans in the V30 and V40 of heart.The Dmean of heart in Hybrid-IMRT and 4F-IMRT was lower than that in 5F-IMRT and 6F-IMRT,with statistical differences(P<0.05).No significant differences were found in the Dmax of the spinal cord among 4 plans.4F-IMRT was inferior to the other 3 plans in the Dmean of thyroid,with statistical differences(P<0.05).The monitor unit was found to be highest in 6F-IMRT,followed by 4F-IMRT,5F-IMRT and Hybrid-IMRT.Conclusion Hybrid-IMRT plan which can remarkably improve the dose distribution of target areas,without increasing the radiation dose of organs-at-risk should be further promoted in clinic.