乳腺癌根治术后双弧VMAT与IMRT计划的剂量学比较

目的 比较乳腺癌根治术后双弧的容积旋转调强放射治疗(VMAT)与5野的静态调强放射治疗(IMRT)2种计划之间的剂量学差异,评估VMAT技术在乳腺癌根治术后的剂量学特点与应用能力.方法 选取28例乳腺癌根治术后患者(左侧10例,右侧18例),分别制定双90度弧段的VMAT与5野的IMRT 2种计划,主要的计划评估参数为靶区的肿瘤控制概率(TCP)、适形指数(CI)、均匀指数(HI)以及接受相应处方剂量水平照射体积百分比V₉₅、V₁₁₀,危及器官(OAR)评估包括患侧肺的正常组织并发症概率(NTCP)、D_mean、V₅、V₂₀、V₃₀,心脏的NTCP值、D_mean、V₂₅,健侧乳腺的D_mean、机器跳数(MU)以及治疗时间.结果 VMAT计划与IMRT计划的TCP值分别为(96±2)%、(90±2)%(t=-6.28,P<0.01);HI值分别为0.15±0.04,0.22±0.02(t=13.29,P<0.05);肿瘤位于左侧时,心脏NTCP值在VMAT计划与IMRT计划中分别为(1.0±0.12)%,(1.7±0.13)%(t=2.14,P<0.05);肿瘤位于右侧时,2种计划心脏的NTCP差异无统计学意义,平均剂量分别为(3.27±0.26)、(6.0±0.47)Gy(t=9.21, P<0.01);VMAT计划在MU少于IMRT计划(t=9.58,P<0.01),治疗时间短于IMRT计划(t=8.40,P<0.05).结论 乳腺癌根治术后,VMAT计划具有更强的临床应用能力,且表现出更优的剂量学特点.

Dosimetric comparison of two arcs VMAT plan and IMRT plan for breast cancer post-mastectomy

Objective To analyze the biophysical dosimetric characteristics and clinical application ability of VMAT technology for breast cancer post-mastectomy. Methods 28 patients with breast cancer (10 at left side and the other at right side) were planned in different ways respectively. One was two 90 degree arc VMAT plan and the other were 5 beam IMRT plan. The dosimetric parameters of two different plans including tumor control probability (TCP),conformity index(CI), homogeneity index(HI),V₉₅ and V₁₁₀ in target, normal tissue complication probability(NTCP),V_-5, V₂₀, V₃₀ for ipsilateral lung, NCTP, D_mean, V₂₅ for heart, D_mean for the contralateral breast in OARs, MU and times were compared. Results The average tumor control probability (TCP) in VMAT and IMRT group was(96±2)% and (90±2)% (t=-6.28, P<0.01), respectively. The PTV dose average homogeneity index (HI) of VMAT plans was better than that of IMRT plan (0.15±0.04 vs 0.22±0.02, t=13.29, P <0.01). For cancer position in left side, the mean dose of heart was decreased by 433.24 cGy in the VMAT plan. The NTCP of the hearts in VMAT plans had statistically significant difference compared with IMRT plans [(1.00±0.12)% vs (1.70±0.13)%, t=2.14,P<0.05]. For plans of right breast cancer,the average mean dose of hearts in two control group was (3.27±0.26) Gy and (6.00±0.47)Gy (t=9.21,P<0.01). The total monitor unit (MU) was 530.7 in the VMAT arm and 693.9 in the IMRT arm (t=9.58,P <0.01). The treatment time was shorter in VMAT arm (t=8.40,P<0.05). Conclusions VMAT plans have better clinical value and more superior biophysical dosimetric characteristics for breast cancer post-mastectomy.