左乳癌根治术后胸壁3DCRT与3DCRT加电子线混合照射的剂量学研究

Dosimetric Study on the 3DCRT and the Mixed Irradiation of Electron Beam and 3DCRT on the Chest Wall after Left-sided Radical Mastectomy

目的:探讨左乳癌改良根治术后胸壁三维适形照射和三维适形加电子线照射的剂量学特点。方法:选取左乳癌改良根治术后10例患者,采用pinnacle3 9.10计划系统分别设计胸壁三维适形照射和三维适形加电子线照射计划,比较两种计划的剂量学参数。结果:Dmax、Dmix、Dmean、V90、3DCRT较3DCRT+E升高,差异均有统计学意义(P<0.05);V95、V100、3DCRT略低于3DCRT+E,差异无统计学意义(P>0.05);V105、V110、3DCRT较3DCRT+E高,其中V105差异有统计学意义(P<0.05);CI和D53DCRT+E较3DCRT高,3DCRT+E优于3DCRT,差异有统计学意义(P<0.05);HI和D95差异无统计学意义(P>0.05)。危及器官左肺V5、V10、V15、V20、V30、V40和Dmean3DCRT+E较3DCRT总体升高,除V40差异无统计学意义外(P>0.05),其余参数差异均有统计学意义(P<0.05),右肺Dmean3DCRT+E稍高,差异无统计学意义(P>0.05);心脏受照剂量3DCRT+E总体呈升高趋势,其中V5、V10、V15和V40差异均有统计学意义(P<0.05)。结论:总体上靶区剂量分布3DCRT优于3DCRT+E,但3DCRT+E适形度、靶区高剂量D5和高剂量体积V105和V110优于3DCRT;3DCRT+E对危及器官剂量左肺和心脏的保护并不优于3DCRT。可能是0.5 cm厚的等效填充物不能有效的降低9Me V电子线等对左肺和心脏表面剂量所致。因此、建议每一个患者在治疗前应该选择最佳厚度等效填充物和电子线能量、混合射线的剂量比例等,并通过放射治疗计划系统下制定个体化的治疗方案。

Objective To compare the dosimetric characteristics of the three dimensional conformal radiation therapy（3 DCRT） irradiation and the mixed irradiation of electron beam and 3 DCRT on the chest wall for the patients receiving left-sided modified radical mastectomy. Method 10 patients who had received left-sided modified radical mastectomy were enrolled. The pinnacle3 9. 10 planning system was adopted to design two treatment plans,respectively,which were the 3 DCRT irradiation（3 DCRT plan） and the mixed irradiation of 3 DCRT and electron beam（3 DCRT ＋ E plan）. Results In the 3 DCRT plan,the maximum dose（Dmax）,minimal dose（Dmin）,mean dose（Dmean）,the Dmeanand percentage of volume receiving more than 90 Gy（V90） were obviously higher than those of 3 DCRT ＋ E group,the differences were statistically significant（P〈0. 05）; the Dmeanand percentage of volume receiving more than 95 Gy（V95） and 100 Gy（V100） irradiation in 3 D-CRT group were slightly lower than those in 3 DCRT ＋ E radiotherapy and there were no statistical significances（P〈0. 05）; the Dmeanand percentage of volume receiving more than 105 Gy（V105） and 110 Gy（V110） in 3 DCRT were superior to those in 3 D-CRT ＋ E,among which,the differences in the V105 was of statistical significance（P〈0. 05）. The conformity index（CI） and the dose of 5% CTV（D5）in 3 DCRT ＋ E,the differences were of statistical significance（P〈0. 05）. But the difference of the homogeneity index（HI） and the dose of 5% CTV（D5） between two groups were of no statistical significance（P〈0. 05）. Regarding the organs at risk,the V5、V10、V15、V20、V30、V40 and Dmeanof the left lung in 3 DCRT ＋ E were increased,and the differences were statistically significant（P〈0. 05） except for V40. The Dmeanof right lung in 3 DCRT ＋ E was higher than that of 3 DCRT,the differences were not statistically significant（P〈0. 05）. The irradiation dose of heart in the 3 DCRT group showed a increasing trend on the whole,among which,the differences in the V5,V10,V15 and V40 were of statistical significance（P〈0. 05）. Conclusion The 3 DCRT group has more significant advantages over the 3 DCRT ＋ E on the distribution of target volume. The conformal degree,D5,V105 and V110 in3 DCRT ＋ E are superior to those in 3 DCRT; but the protection to organs at risk in 3 DCRT ＋ E,such as the left lung and heart,is not superior to that of 3 DCRT. This might be caused by using the 0. 5 cm-in-thickness equivalent filler upon the chest wall,which could not decrease the dose of left lung and heart efficiently. Therefore,we suggest that patients should choose the equivalent filler with optimal thickness,the appropriate electron energy and the best dose rate of mixed ray before iradidation,and doctors should use the radiotherapy treatment planning system to design the therapeutic individuation program for each person.