诱导化疗后局部晚期鼻咽癌调强放疗肿瘤靶区勾画方式改变对剂量分布和临床疗效的影响

Impact of changing gross tumor volume delineation of intensity-modulated radiotherapy on the dose distribution and clinical treatment outcome after induction chemotherapy for the primary locoregionally advanced nasopharyngeal carcinoma

背景与目的:晚期鼻咽癌诱导化疗后大体肿瘤体积(gross tumor volume,GTV)明显缩小。本研究探讨按化疗后肿瘤改变GTV勾画方式对靶区和正常组织剂量以及临床疗效的影响。方法:从2008年1月至2009年4月收治24例局部晚期鼻咽癌初治患者,采用TPF诱导化疗加同期调强放化疗方案进行治疗。调强放疗原发灶GTV分为诱导化疗后可见的肿瘤和诱导化疗后肿瘤消退区域两部分。选取10例患者,比较按诱导化疗前后肿瘤勾画GTV所做计划的剂量分布,同时观察全组患者毒副反应和近期疗效。结果:诱导化疗后和前原发灶GTV平均体积分别为25.5cm3和51.1cm3(P=0.001);颈淋巴结GTV9.1cm3和31.4cm3(P=0.035);原发灶+颈淋巴结GTV33.2cm3和82.6cm3(P=0.004),诱导化疗使肿瘤总体积减少了61%,64.6Gy等剂量线所包括的体积分别为422.9cm3和457.9cm3(P=0.003);68Gy等剂量线所包括的体积274.2cm3和334.5cm3(P=0.041)。诱导化疗后鼻咽病灶和颈部淋巴结完全缓解率达38%。同期放化疗结束后3个月鼻咽病灶和颈部淋巴结完全缓解率达100%。该模式同期放化疗毒性反应与单纯调强同期放化疗相似。经中位期9个月的随访,全组患者局部区域控制率为100%。仅1例患者在15个月出现多处远处转移。结论:鼻咽癌TPF方案诱导化疗后肿瘤体积明显缩小,按化疗后肿瘤勾画GTV的调强放疗能使高剂量区体积减少,同期放化疗毒性反应未见加重,并且具有较好的近期治疗效果。

Background and Objective. The gross tumor volume （GTV） obviously reduces after induction chemotherapy （IC） for primary Iocoregionally advanced nasopharyngeal carcinoma （NPC）. This study was to investigate the impact of changing gross tumor volume delineation on the dose distribution and clinical treatment outcome after IC. Methods： From January 2008 to April 2009, 24 patients with Stage III -IV b primary Iocoregionally advanced NPC were treated with TPF regimen IC followed by intensitymodulated radiotherapy （IMRT） with concurrent chemotherapy. The primary GTVs were delineated into two parts： the post-IC primary GTV （GTVpost-IC-NP）, and the region of pre-IC primary GTV minus GTVpost-IC-NP （GTVpre- post-IC-NP）. The dose distributions of two plans with GTVpost-IC-NP or preIC primary GTV were assessed by analyzing ten cases. The clinical treatment outcome and toxicity of all patients were observed. Results： The post-IC GTV was significantly smaller than the pre-IC GTV （primary GTV 25.5 cm^3 vs. 51.1 cm^3,p=0.001; lymph nodes GTV 9.1 cm^3 vs. 31.4 cm^3, P=0.035; primary ＋ lymph nodes GTV 33.2 cm^3 vs. 82.6 cm^3,p=0.004）, the overall GTV with an average shrinkage of 61%. The high dose region was also smaller after IC （volumes covered by 64.4 Gy were 422.9 cm^3 vs. 457.9 cm3, P=0.003＇ 274.2 cm^3 vs.334.5 cm^3 by 68 Gy, P=0.041）. The complete response rate was 38% after IC, and 100% three month after radiotherapy. The toxicity of following IMRT with concurrent chemotherapy was similar to that of IMRT with concurrent chemotherapy alone. With median follow-up of 9 months, the Iocoregionally control rate was 100% and only one patient presented metastasis 15 months after treatment. Conclusions： TPF regimen IC could significantly reduce tumor volume. The following IMRT with GTVpost- IC-NP plan reduced the high dose region, which didn＇t add toxicity while had excellent short-term treatment outcome.