鼻咽癌IMRT后甲状腺功能减退的相关剂量体积研究

Dosimetric predictors of hypothyroidism in nasopharyngeal cancer patients treated with intensity- modulated radiation therapy

目的 通过对原发性甲状腺功能减退危险因素分析,探寻IMRT鼻咽癌患者甲状腺功能损伤的剂量体积阈值。方法 对2008—2010年间IMRT初治鼻咽癌113例病例进行回顾分析,所有病例均有完整临床资料以及疗前和疗后2年内甲状腺功能生化检查结果。计算甲状腺和垂体不同体积剂量参数,观察IMRT治疗后甲状腺功能损伤相关剂量体积阈值以及临床影响因素。结果113例患者中位随诊期62个月,其中41例（36.3%）出现临床甲状腺功能减退,28例（24.8%）出现亚临床甲状腺功能减退（仅TSH升高）,出现时间（3-60个月,中位数12个月）。单因素分析中患者年龄、甲状腺受照Dmean、V40、V45、V50、V55、V60是放疗后甲状腺功能减退的影响因素（P均〈0.05）。多因素分析显示仅V50、年龄与甲状腺功能减退发生有关（P均=0.002）。采用ROC曲线对预测变量分析结果显示年龄〉45岁且V50〈50%时甲状腺功能减退发生率为31.8%,而V50≥50%且年龄〈45岁时甲状腺功能减退发生率为79.3%。结论 IMRT甲状腺V50〉50%是甲状腺功能减退发生的影响因素,年龄〈45岁患者IMRT时应对甲状腺限量降低。

Objective To investigate the mobidity and risk factors for primary hypothyroidism （HT） in nasopharyngeal cancer （NPC） patients treated with intensity-modulated radiotherapy （IMRT）. Methods 113 NPC patients with complete clinical information who received IMRT from 2008-2010 were retrospectively analyzed. Thyroid function assessments before and after IMRT were periodically monitored. Various clinical and dosimetric parameters were obtained including Dmin,Dmax,Dmean,V30,V35,V40,V45,V50,V55,V60,V65,V70（thyroid gland）, PDmin,PDmax,PDmean（pituitary gland）.Univariate and multivariate logistic regression analyses were performed to identify predictors of HT. Results After a median follow-up period of 62 months,41 patients （36.3%） had clinical HT,and 28 patients （24.8%） developed subclinical HT. Univariate analysis revealed that younger age,mean dose to the thyroid gland,V40,V45,V50,V55,V60 were correlated with developing HT （all P〈0.05）.On multivariate analysis including patient,tumor,and treatment variables,younger age （P=0.002） and V50（P=0.002） remained statistically significant. We found that the cutoff value of V50（50%） may be an valuable evaluation marker of HT.Combined with age to predict the HT,the area under ROC curve is 0.728.The endpoint event rate of the patients whose level of V50 is above 50% and age level below 45 years were 79.3%,whlie the date in patients whose level of V50 is below 50% and age level above 45 years was 31.8%. Conclusions Thyroid V50 above 50% is predictive of primary HT after IMRT for NPC patient,Our results suggested that restricting V50〈50% during IMRT planning may facilitate the reduction in incidence of HT for the younger patients.