不同靶区边缘参数对乳腺癌根治术后容积弧形调强放射治疗计划质量的影响

The Influence of Different Target Margin Parameters on the Quality of Volumetric Modulated Arc Therapy Plan after Radical Surgery for Breast Cancer

目的探讨不同靶区边缘参数对乳腺癌根治术后容积弧形调强放射治疗(VMAT)计划质量的影响。方法回顾性分析2021年1月至2022年12月于医院行VMAT的14例乳腺癌根治术后患者的临床资料。所有患者均采用Monaco计划系统设计Tight组、Narrow组、Normal组3组不同靶区边缘参数的VMAT计划,并比较3组靶区剂量学指标[PTV的平均剂量(D_(mean))、最大剂量(D_(max)),2%PTV体积受照射剂量(D_(2%))、98%PTV体积受照射剂量(D_(98%))、50%PTV体积受照射剂量(D_(50%)),适形度指数(CI)、均匀性指数(HI)、剂量梯度指标(GI)]、危及器官(OARs)剂量学指标[患侧肺体积百分比(V_(5)、V_(20)、V_(30))和平均剂量(D_(mean)),健侧肺体积百分比(V_(5))和平均剂量(D_(mean)),心脏体积百分比(V_(5))和平均剂量(D_(mean)),脊髓最大剂量(D_(max))及健侧乳腺平均剂量(D_(mean))]及计划参数[计划控制点数(CP)、机器跳数(MU)和出束时间(T)]。结果Tight组的D_(mean)、D_(max)、D_(2%)、D_(50%)、HI、GI均低于Narrow组和Normal组,且Narrow组的D_(mean)、D_(2%)、D_(50%)、HI、GI均低于Normal组,差异有统计学意义(P<0.05);Narrow组和Normal组的D_(max)比较,差异无统计学意义(P>0.05);Tight组的D_(98%)和CI均高于Narrow组和Normal组,且Narrow组的D_(98%)高于Normal组,差异有统计学意义(P<0.05);Narrow组和Normal组的CI比较,差异无统计学意义(P>0.05)。Tight组的心脏V_(5)、D_(mean)和脊髓D_(max)均低于Narrow组和Normal组,且Narrow组低于Normal组,差异有统计学意义(P<0.05);Tight组和Narrow组的健侧乳腺D_(mean)均低于Narrow组,差异有统计学意义(P<0.05);3组其他OARs剂量学指标比较,差异均无统计学意义(P>0.05)。Tight组的CP、MU和T均高于Narrow组和Normal组,且Narrow组高于Normal组,差异有统计学意义(P<0.05);Tight组的MU高于Narrow组和Normal组,差异均有统计学意义(P<0.05);Narrow组和Normal组的MU比较,差异无统计学意义(P>0.05)。结论设计乳腺癌根治术后VMAT计划时,合理设置靶区边缘参数可改善剂量学特性,有助于提高放射治疗的精准性和治疗效果。

Objective To explore the influence of different target edge parameters on the quality of volume arc intensity modulated radiotherapy(VMAT)plan after radical surgery for breast cancer.Methods With the retrospective analysis of the clinical data of 14 patients with breast cancer who underwent VMAT in hospital from January 2021 to December 2022,three sets of VMAT plans with different target area margin parameters were designed using the Monaco planning system for each patient.The dosimetric indices of the three target areas[average dose of PTV(D_(mean)),maximum dose(D_(max)),2%volume exposure dose of PTV(D_(2%)),98%volume exposure dose of PTV(D_(98%)),50%volume exposure dose of PTV(D_(50%)),Conformity Index(CI),Heterogeneity Index(HI),dose gradient index(GI)],organ at risk(OARs)dosimetry index[percentage of lung volume on the affected side(V_(5),V_(20),V_(30))and mean dose(D_(mean)),percentage of lung volume on the healthy side(V_(5))and mean dose(D_(mean)),Percentage of cardiac volume(V_(5))and mean dose(D_(mean)),maximum dose of spinal cord(D_(max))and mean dose of healthy mammary gland(D_(mean)),and planning parameters[planned control points(CP),monitor unit(MU)and beam exit time(T)]were compared.Results The D_(mean),D_(max),D_(2%),D_(50%),HI,and GI of the Tight group were lower than those of the Narrow group and the Normal group,and the D_(mean),D_(2%),D_(50%),HI,and GI of the Narrow group were lower than those of the Normal group,with statistical significance(P<0.05);There was no statistically significant difference in D_(max) between the Narrow group and the Normal group(P>0.05);The D_(98%)and CI of the Tight group were higher than those of the Narrow group and the Normal group,and the D_(98%)of the Narrow group was higher than that of the Normal group,with statistical significance(P<0.05);There was no statistically significant difference in CI between the Narrow group and the Normal group(P>0.05).The cardiac V_(5),D_(mean),and spinal D_(max) of the Tight group were lower than those of the Narrow group and the Normal group,and the Narrow group was lower than the Normal group,with statistical significance(P<0.05);The D_(mean) of the healthy breast in the Tight and Narrow groups was lower than that in the Narrow group,and the difference was statistically significant(P<0.05);There were no statistically significant differences in the dosimetric indicators of other OARs among the three groups(P<0.05).The CP,MU,and T of the Tight group were higher than those of the Narrow and Normal groups,and the Narrow group was higher than the Normal group,with statistical significance(P<0.05);The MU of the Tight group was higher than that of the Narrow and Normal groups,and the differences were statistically significant(P<0.05);There was no statistically significant difference in MU between the Narrow group and the Normal group(P>0.05).Conclusion When the VMAT plan is designed after radical surgery for breast cancer,the reasonable setting of target edge parameters can improve the dosimetry characteristics and help to improve the accuracy and therapeutic effect of radiotherapy.