鼻咽癌IMRT靶区勾画与计划制定期间肿瘤体积的变化

目的分析在调强放疗（IMRT）靶区勾画与计划制定期间鼻咽癌肿瘤体积的变化。方法31例经病理证实的初治鼻咽癌患者接受调强放疗。对患者CT模拟定位扫描后行靶区勾画和制定IMRT计划。验证后CT校位时进行第2次CT扫描。记录两次扫描间隔时间,并将两次CT图像进行融合后测量肿瘤体积。采用配对t检验分析两次扫描肿瘤体积的变化,其变化影响因素分析采用Pearson相关分析和多重线性回归分析。结果共检测原发灶31例,淋巴结60例（其中ⅡA区淋巴结28例,ⅡB区淋巴结25例,Ⅲ区淋巴结1例,ⅤA区淋巴结6例）。两次扫描时间间隔9～27 d,中位时间18d。31例原发灶两次扫描之间差值的变化范围为-0．419～13．629 cm^3,平均值1．523 cm^3,其中3例原发灶较第1次扫描时缩小,8例无明显变化,20例较第1次扫描时增大,前后两次扫描两者体积变化有差异（P=0．009）。对于60例淋巴结,两次扫描之间差值的变化范围为0～5．659 cm^3,平均值0．399 cm^3,其中47例无明显变化,13例较第1次扫描时增大,前后两次扫描两者体积变化有差异（P=0．005）。无论原发灶、淋巴结还是单因素、多因素分析,两次测量差值与第1次扫描时大小有显著相关性,而两次扫描时间间隔无明显相关性。结论IMRT制定时间间隔对肿瘤体积大的影响较大,但是否肿瘤体积增大会影响IMRT的疗效尚需大量临床病例证实。扩大GTV与CTV的范围降低肿瘤体积增大对疗效的影响,可能会造成不必要的正常组织损伤,在IMRT计划制定期间行诱导化疗来降低影响或许是一个更好的选择。

Change of tumor target volume during waiting time for intensity-modulated radiotherapy (IMRT) in nasopharyngeal carcinoma

Objective To determine the influence of change in tumor target volume of nasopharyn- geal carcinoma(NPC)while waiting for intensity modulated radiation therapy(IMRT).Methods From March 2005 to December 2005,31 patients with nasopharyngeal carcinoma received IMBT as the initial treatment at the Cancer Hospital of Chinese Academic of Medical Sciences.The original simulation CT scan was acquired before IMRT planning.A second CT scan was acquired before the start of radiotherapy.Wait- ing time was defined as the duration between CT simulation and start of radiotherapy.CT-CT fusion was used to minimize the error of delineation between the first tumor target volume(GTV)and the second tumor target volume(sGTV).Tumor target volume was calculated by treatment planning system.T test was carried out to analyse the difference between GTV and sGTV.Pearson correlation and multivariate linear regression was used to analyse the influence factor of the change betweent GTV and sGTV.Results Median waiting time was 18 days(range,9-27 days).There were significant differences between GTV and sGTV of both primary tumor(P=0.009)and metastatic lymphoma(P=0.005).Both Pearson correlation and multivariate linear regression showed that the change of primary tumor target volume had significant correlation with the first tumor target volume but had no significant correlation with the waiting time,sex,age,T stage and N stage (1992 Chinese Fuzhou Staging Classification).Conclusions Within the range of the waiting time ob- served in our study,large volume primary tumor would have had a significant increase in volume,but wheth- er the therapeutic effect would be influenced or not would need to be proved by study of large number of cases.Patients with large volume tumor should be considered to reduce the influence of waiting time by en- larging gross target volume and clinical target volume and by neoadjuvant chemotherapy.For avoiding the un- necessary high-dose to normal tissues,the later may be necessary.