直肠癌腹股沟淋巴结转移术前调强放疗剂量学研究

Dosimetric study of preoperative intensity modulated radiotherapy for rectal cancer with inguinal lymph node metastasis

目的比较固定准直器调强技术(fixed-jaw technique,FJT)与常规分野调强技术(split-field technique,SFT)在直肠癌术前腹股沟淋巴结转移放疗计划中的剂量学差异。方法选取2013-06-10-2014-09-30佛山市第一人民医院10例直肠癌腹股沟淋巴结转移术前调强放疗的患者,分别设计FJT和SFT两种调强计划。计划肿瘤区(planning gross target volume,PGTV)和计划靶区(planning target volume,PTV)的处方剂量分别为50Gy/25次和45Gy/25次。比较PGTV和PTV的均匀性指数(heterogeneity index,HI)和适形性指数(conformity index,CI),以及小肠、股骨头、骨髓、膀胱和正常组织的受照体积(V10、V15、V20、V30和V40分别表示接受10、15、20、30和40Gy的照射体积占整个体积的百分比)、机器跳数(monitor unit,MU)和治疗时间。结果 FJT和SFT两种调强计划,PGTV的HI分别为0.048±0.004和0.048±0.003,CI分别为0.918±0.019和0.917±0.024;PTV的HI分别为0.107±0.095和0.105±0.085,CI分别为0.781±0.032和0.786±0.029,差异均无统计学意义,P值均>0.05。FJT计划小肠的V15为(71.68±7.97)%,左右侧股骨头的V30分别为(29.52±11.51)%和(27.79±9.83)%,骨髓的V10和V20分别为(86.39±3.12)%和(73.29±1.71)%,正常组织的V10、V20和V30分别为(78.68±3.02)%、(57.04±3.33)%和(30.87±2.91)%,分别低于SFT计划的(72.73±7.37)%、(50.02±13.25)%、(46.24±13.03)%、(87.03±3.56)%、(74.62±2.10)%、(79.80±2.86)%、(60.32±3.41)%和(34.36±3.60)%,差异有统计学意义,P值均<0.05。FJT计划骨髓和正常组织的V40分别为(27.81±5.41)%和(8.56±0.98)%,高于SFT计划的(25.76±5.53)%和(8.15±0.86)%,差异有统计学意义,P值均<0.05。两种技术小肠的V40、膀胱的V30和V40、左右侧股骨头的V40以及骨髓的V30,差异无统计学意义,P值均>0.05。FJT计划相对于SFT计划,MU和治疗时间分别减少了19%和27%,差异有统计学意义,P值均<0.05。结论相对于SFT,FJT更适合直肠癌腹股沟淋巴结转移术前调强治疗。

OBJECTIVE To compare the dosimetric difference of fixed-jaw technique （FJT） with split- field tech nique （SFT） in preoperative intensity modulated radiotherapy （IMRT） plans for rectal cancer with inguinal lymph node metastasis. METHODS Ten patients of rectal cancer with the inguinal nodes metastasis who received preoperative IMRT between June 10, 2013 and September 30, 2014 were selected. FJT IMRT and SFT IMRT plans were made for every pa- tient respectively. The prescribed dose was 50 Gy for planning gross target volume （PGTV） and 45 Gy for planning target volume （PTV） in 25 fractions. Heterogeneity index（ HI）, conformity index（CI） of PGTV and PTV, the volume irradiated of small bowel, bone marrow, femoral heads, bladder and the normal tissue （Vlo , Via , V20 , V30 , V40 , representing the pro- portion of the volume involved by 10 Oy, 15 Oy, 20 Gy, 30 Oy, 40 Oy to the total volume）, the monitor units （MU） and the treatment time were evaluated. RESULTS The HI of PGTV were 0. 048±0. 004 and 0. 048±0. 003, the CI of PGTV were0.918±0.019 and 0. 917±0. 024, the HI of PTV were 0. 107±0. 095 and 0. 105±0. 085, the CI of PTV were 0. 781±0. 032 and 0. 786±0. 029 for FJT and SFT plans, respectively. There were no significant differences between the two plans （P）0.05）. The V10 of small bowel, the V10 of the left and right femoral head, the V10 and V20 of bone mar row, the V10 and V20, V30 of normal tissue for FJT plan were （71.68±7.97）%, （29. 52±11. 51）% , （27.79±9.83）%, （86.39±3. 12）%, （73. 29±1. 71）%, （78. 68±3. 02）%, （57. 04±3. 33）%, （30. 87±2. 91）%, respectively,which was less than that in the plan of SFT（P〈0. 05）, the dose for SFT were （72. 73 ± 7. 37）%, （50. 02±13. 25）%, （46.24±13.03）% , （87.03±3.56）%, （74.62±2.10）%, （79.80±2.86）%o, （60.32±3.41）%, （34.36±3.60）%, respec- tively. The V40 of bone marrow and normal tissue for FJT and SFT plans were （27. 81 ± 5. 41）% and （25. 76 ± 5. 53）%, （8.56±0.98） % and （8.15±0.86）%, respectively （P〈0.05）. There were no significant differences in the V40 of small bowel, the V30 and of V40 of bladder, the V10 of the left and the right femoral head, the V30 of bone marrow between the two plans（P〉 0. 05）. Compared with SFT plan, the total MU and the treatment time for FJT plan were significantly reduced by 19 % and 27 %, and the differences were significant （P〈0.05）. CONCLUSION FJT is a more suitable for the preoperative intensity modulated radiotherapy for rectal cancer with inguinal lymph node metastasis than SFT.