诱导化疗对鼻咽癌调强放疗靶区和剂量分布的影响研究

目的分析诱导化疗前后鼻咽癌肿瘤体积的变化,及靶区和正常组织剂量分布的变化。方法自2009年3月至2010年8月收治12例经病理证实的初治局部晚期鼻咽癌患者,调强放疗前接受PF方案诱导化疗2周期。对患者诱导化疗前作CT模拟定位扫描后行靶区勾画和制定诱导化疗前调强放疗(IMRT)计划。2周期诱导化疗后进行第2次CT扫描,并将两次CT图像进行融合后测量肿瘤体积和制定诱导化疗后IMRT计划。采用配对t检验分析诱导化疗前后扫描肿瘤体积的变化,及靶区和正常组织剂量分布的变化。结果诱导化疗前和后原发灶GTVnx平均体积分别为(39.75±19.17)cm3和(25.65±15.11)cm3(t=4.203,P=0.001);颈淋巴结GTVnd(33.78±28.9)cm3和(15.56±14.91)cm3(z=2.94,P=0.003);原发灶+颈淋巴结GTV(73.53±31.55)cm3和(41.2±24.06)cm3(t=4.753,P=0.001);诱导化疗使肿瘤总体积减少了52.9%。66.5 Gy等剂量线所包括的体积分别为(302.0±110.3)cm3和(248.4±79.0)cm3(P=0.023),63 Gy等剂量线所包括的体积分别为(413.2±117.4)cm3和(409.1±115.1)cm3(P=0.097)。诱导化疗使T和N分期降低达33.3%和50%。结论诱导化疗前后肿瘤体积变化较大,按化疗后肿瘤勾画GTV的调强放疗能使高剂量区体积减少。

Effect of induction chemotherapy on target volume and dose distribution of intensity-modulated radiotherapy of nasopharyngeal carcinoma

Objective To analyze the changes of tumor volume（GTV） and dose distribution after induction chemotherapy（IC） for primary regional advanced nasopharyngeal carcinoma（NPC）.Methods From March 2009 to August 2010,12 patients with Ⅲ-Ⅳa primary regional advanced NPC were treated with PF regimen IC followed by intensity-modulated radiotherapy（IMRT）.The simulation CT scan was acquired before IC to plan the primary IMRT（pIMRT）.A second CT scan was acquired after 2 cycles of IC to plan the second IMRT（sIMRT）.The two CT-images were merged to minimize the error of definition between the primary tumor target volume（pGTV） and the second target volume（sGTV）.T test was used to analyze the difference between pGTV and sGTV,and dose distribution between pIMRT and sIMRT.Results The pGTV was significantly bigger than the sGTV（primary GTV 39.75±19.17cm3 vs 25.65±15.11 cm3,P=0.001;cervical lymph nodes GTV 33.78±28.9 cm3 vs 15.56±14.91 cm3,P=0.003;primary focus＋ lymph nodes GTV 73.53 ±31.55 cm3 vs 41.2 ±24.06 cm3,P=0.001）.The overall GTV was reduced by 52.9% after IC.The high dose region was also bigger before IC（volumes covered by 66.5 Gy were 302.0±110.3 cm3 vs 248.4±79.0 cm3,P=0.023;the volumes covered by 63 Gy were 413.2±117.4 cm3vs 409.1±115.1 cm3,P=0.097）.IC caused down-staging of T stage by 33.3% and down-staging of N stage by 50%.Conclusions PF regimen IC could siginificantly reduce tumor volume.The sIMRT with sGTV plan reduced the volume at high dose region.