VMAT与IMRT在局部晚期宫颈癌放疗中的剂量学差异

魏纯霄; 田含含; 韩济华

doi:10.3760/cma.j.cn121381-202208015-00325

VMAT与IMRT在局部晚期宫颈癌放疗中的剂量学差异

Dosimetric comparison of volumetric intensity modulated arc therapy and intensity-modulated radiation therapy in locally advanced cervical cancer

摘要

摘要:
目的比较分析容积弧形调强放射治疗（VMAT）与固定野调强适形放射治疗（IMRT）在局部晚期宫颈癌延伸野放疗计划中的剂量学差异。
方法回顾性分析2019年1月至2021年12月南京医科大学附属淮安第一医院收治的20例宫颈癌患者的临床资料，患者年龄（56.3±9.1）岁，范围39~78岁，均行CT扫描，对所有患者进行计划靶区（PTV）、转移淋巴结计划靶区（PGTV_nd）以及膀胱、直肠、双侧股骨头、肝、双肾、小肠、脊髓等危及器官的勾画。按照随机数字表法将患者分为IMRT 组和VMAT组，每组10例，分别进行IMRT 和VMAT的放疗计划；其中IMRT 组患者年龄（54.1±7.1）岁，VMAT组患者年龄（58.1±10.8）岁。比较2组患者靶区的剂量参数、危及器官的剂量参数以及机器总跳数、有效治疗时间。计量资料的组间比较采用t检验。
结果在PTV中，VMAT组的适形指数（0.81±0.03）高于IMRT组（0.79±0.23），且差异有统计学意义（t=−2.190，P=0.035）。在PGTV_nd中，VMAT组的均匀性指数（0.06±0.01）低于IMRT组（0.07±0.01），且差异有统计学意义（t=−2.315，P=0.026）。在膀胱受照射剂量中，VMAT组的V_{20 Gy}（V_{x Gy}表示接受≥x Gy照射的体积占总体积的百分比）为（92.64±2.29）%，低于IMRT组的（93.98±1.47）%，且差异有统计学意义（t=2.220，P=0.032）。在直肠受照射剂量中，VMAT组的V_{20 Gy}为（92.20±2.21）%，低于IMRT组的（93.68±1.88）%，且差异有统计学意义（t=2.282，P=0.028）。在肝受照射剂量中，VMAT组的V_{10 Gy}、V_{20 Gy}分别为（7.73±0.39）%、（5.14±0.68）%，均低于IMRT组的V_{10 Gy}（7.93±0.10）%、V_{20 Gy}（5.51±0.16）%，且差异均有统计学意义（t=2.372、2.367，P=0.023、0.023）。在小肠受照射剂量中，VMAT组的V_{20 Gy}、V_{30 Gy}、V_{40 Gy}和平均剂量（D_mean）分别为（77.67±4.64）%、（39.21±1.10）%、（18.35±3.05）%和（30.36±3.46） Gy，均低于IMRT组的V_{20 Gy}（80.24±1.05）%、V_{30 Gy}（42.34±6.00）%_、V_{40 Gy}（22.34±6.01）%和D_mean（34.23±6.71） Gy，且差异均有统计学意义（t=2.228~2.628，均P<0.05）。在脊髓受照射剂量中，VMAT组的V_{20 Gy}和D_mean分别为（38.81±2.33）%和（11.46±4.26） Gy，均低于IMRT组的V_{20 Gy}（42.88±6.19）%和D_mean（17.97±7.40） Gy，且差异均有统计学意义（t=2.752、3.410，P=0.009、0.002）。在左肾受照射剂量中，VMAT组的V_{20 Gy}和D_mean分别为（11.67±2.36）%和（10.02±2.19） Gy，均低于IMRT组的V_{20 Gy}（15.56±7.50）%和D_mean（14.06±7.29） Gy，且差异均有统计学意义（t=2.216、2.375，P=0.033、0.023）。在右肾受照射剂量中，VMAT组的V_{20 Gy}和D_mean分别为（11.72±2.31）%和（10.07±2.15） Gy，均低于IMRT组的V_{20 Gy}（16.67±6.92）%和D_mean（13.92±7.17） Gy，且差异均有统计学意义（t=3.030、2.295，P=0.004、0.027）。在左股骨头受照射剂量中，VMAT组的 V_{10 Gy}、V_{20 Gy}、V_{30 Gy}、V_{40 Gy}、V_{50 Gy}及D_mean均低于IMRT组（74.77±2.33）%对（78.51±7.46）%、（34.37±2.74）%对（38.91±7.20）%、（14.77±2.33）%对（18.51±7.46）%、（2.99±1.03）%对（4.98±3.73）%、（0.48±0.22）%对（0.99±0.65）%、（34.32±2.79） Gy对（38.41±6.67） Gy，且差异均有统计学意义（t=2.147~3.359，均P<0.05）。在右股骨头受照射剂量中，VMAT组的 V_{50 Gy}为（0.02±0.01）%，低于 IMRT组的V_{50 Gy}0.03±0.01%，且差异有统计学意义（t=2.997，P=0.005）。VMAT组的机器总跳数为（536.16±42.37），低于IMRT组的（614.44±59.44），且差异有统计学意义（t=−5.362，P<0.001）；VMAT组的有效治疗时间为（152.23±0.31） min，短于IMRT组的（453.88±9.94） min，且差异有统计学意义（t=−151.708，P<0.001）。
结论对于局部晚期宫颈癌，VMAT计划的适形度及均匀性较好，更能保护危及器官，且可减少机器跳数，缩短治疗时间。

Abstract:
Objective To analyze and compare the dosimetric difference between volumetric intensity modulated arc therapy (VMAT) and conformal intensity-modulated radiation therapy (IMRT) in the extended field radiotherapy plan for locally advanced cervical cancer.

Methods Retrospective analysis was carried out on the clinical data of 20 patients with cervical cancer admitted to the Affiliated Huaian NO.1 People's Hospital of Nanjing Medical University from January 2019 to December 2021. Patients aged (56.3±9.1) years and ranging from 39 to 78 years old were included. Each patient underwent CT scanning, and the delineations of the planning target volume (PTV), planning gross target volume for lymph node lesion (PGTV_nd), and organs at risk such as bladder, rectum, bilateral femoral heads, liver, kidneys, small intestine, and spinal cord were outlined. All patients were divided into the IMRT and VMAT group by using a random number table method with 10 patients in each group. The IMRT and VMAT radiotherapy plans were conducted separately. The patients in the IMRT group were aged (54.1±7.1) years, while those in the VMAT group were aged (58.1±10.8) years. The relevant dosimetric parameters of the target volume and the organs at risk, total machine hops, and total treatment time were compared between the two groups. The t-test was used for inter-group comparison of measurement data.

Results In PTV, the conformity index of VMAT was significantly higher than that of IMRT ((0.81±0.03) vs. (0.79±0.23), t=−2.190, P=0.035). In PGTV_nd, the homogeneity index of VMAT was significantly lower than that of IMRT ((0.06±0.01) vs. (0.07±0.01), t=−2.315, P=0.026). In the bladder irradiation dose, the V₂₀ _Gy (V_{x Gy} indicates the percentage of volume irradiated with ≥ x Gy to total volume) in the VMAT plan was significantly lower than that in the IMRT group ((92.64±2.29)% vs. (93.98±1.47)%, t=2.220, P=0.032). In the rectal irradiation dose, the V_{20 Gy} in the VMAT group was significantly lower than that in the IMRT group ((92.20±2.21)% vs. (93.68±1.88)%, t=2.282, P=0.028). In the liver irradiation dose, the V_{10 Gy} and V_{20 Gy} in the VMAT group were (7.73±0.39)% and (5.14±0.68)%, respectively, which were lower than the V_{10 Gy} ((7.93±0.10)% ) and V_{20 Gy} ((5.51±0.16)%) in the IMRT group, and the differences were statistically significant (t=2.372, 2.367, P=0.023, 0.023). In the small intestine irradiation dose, V_{20 Gy}, V_{30 Gy}, V₄_{0 Gy}, and D_mean in the VMAT group were (77.67±4.64)%, (39.21±1.10)%, (18.35±3.05)%, and (30.36±3.46) Gy, respectively, which were significantly lower than the V_{20 Gy} ((80.24±1.05)%), V_{30 Gy} ((42.34±6.00)%), V₄_{0 Gy} ((22.34±6.01)%), and D_mean ((34.23±6.71) Gy) in the IMRT group (t=2.228–2.628, all P<0.05). In the spinal cord irradiation dose, the V_{20 Gy} and D_mean in the VMAT group were (38.81±2.33)% and (11.46±4.26) Gy, respectively, which were significantly lower than the V₂₀ _Gy ((42.88±6.19)%) and D_mean ((17.97±7.40) Gy) in the IMRT group (t=2.752, 3.410, P=0.009, 0.002). In the left kidney irradiation dose, the V_{20 Gy} and D_mean in the VMAT group were (11.67±2.36)% and (10.02±2.19) Gy, respectively, which were significantly lower than the V_{20 Gy} ((15.56±7.50)% ) and D_mean ((14.06±7.29) Gy) in the IMRT group (t=2.216, 2.375, P=0.033, 0.023). In the right kidney irradiation dose, the V_{20 Gy} and D_mean in the VMAT plan were (11.72±2.31)% and (10.07±2.15) Gy, respectively, which were significantly lower than the V_{20 Gy} ((16.67±6.92)%) and D_mean ((13.92±7.17) Gy) in the IMRT group (t=3.030, 2.295, P=0.004, 0.027). In the left caput femoris irradiation dose, significant differences were observed in the V_{10 Gy} ( (74.77±2.33)% vs. (78.51±7.46)%), V_{20 Gy} ((34.37±2.74)% vs. (38.91±7.20)%), V_{30 Gy} ((14.77±2.33)% vs. (18.51±7.46)%), V_{40 Gy} ((2.99±1.03)% vs. (4.98±3.73)%), V_{50 Gy} ((0.48±0.22)% vs. (0.99%±0.65)%), and D_mean ((34.32±2.79) Gy vs. (38.41±6.67) Gy) in the VMAT plan compared with the IMRT group (t=2.147–3.359, all P<0.05). In the right caput femoris irradiation dose, the V₅_{0 Gy} in the VMAT group was (0.02±0.01)%, which was significantly lower than the V₅_{0 Gy} ((0.03±0.01)%) in the IMRT group (t=2.997, P=0.005). The total machine hop of VMAT group was significantly lower than that of the IMRT group ((536.16±42.37) vs. (614.44±59.44), t=−5.362, P<0.001). The effective treatment time of VMAT group was significantly lower than that of the IMRT group ((152.23±0.31) min vs. (453.88±9.94) min, t=−151.708, P<0.001).

Conclusion VMAT has good plan conformation and uniformity, can effectively protect the organs at risk, and can reduce the number of machine hops, and can shorten the treatment time.

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