Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Room 703, Building 1, Dong'an Road 270, Shanghai, 200032, China.
Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, 200032, China.
Radiat Oncol. 2022 Mar 21;17(1):57. doi: 10.1186/s13014-022-02028-z.
The aim of the study is to identify clinical and dosimetric factors that could predict the risk of hypothyroidism in nasopharyngeal carcinoma (NPC) patients following intensity-modulated radiotherapy (IMRT).
A total of 404 non-metastatic NPC patients were included in our study. All patients were treated with IMRT. The thyroid function were performed for all patients before and after radiation at regular intervals. The time onset for developing hypothyroidism was defined as the time interval between the completion of RT and the first recorded abnormal thyroid hormone test. The cumulative incidence rates of hypothyroidism were estimated using Kaplan-Meier method. Univariate and multivariate Cox regression analyses were performed to detect the most promising factors that were associated with hypothyroidism.
Median follow up was 60.6 months. The 3-, 5- and 7- year cumulative incidence rate of hypothyroidism was 39.4%, 49.1% and 54.7%, respectively. The median time to primary hypothyroidism and central hypothyroidism were 15.4 months (range 2.9-83.8 months) and 29.9 months (range 19.8-93.6 months), respectively. Univariate and multivariate analyses revealed that younger age, female gender and small thyroid volume were the most important factors in predicting the risk of hypothyroidism. Dtmean (mean dose of thyroid), V30-V50 (percentage of thyroid volume receiving a certain dose level) and VS45-VS60 (the absolute volumes of thyroid spared from various dose levels) remained statistically significant in multivariate analyses. Cutoff points of 45 Gy (Dtmean), 80% (Vt40) and 5 cm (VS45Gy) were identified to classify patients as high-risk or low-risk group.
Thyroid Vt40 highly predicted the risk of hypothyroidism after IMRT for NPC patients. We recommended plan optimization objectives to reduce thyroid Vt40 to 80%.
Retrospectively registered.
本研究旨在确定临床和剂量学因素，以预测接受调强放疗（IMRT）的鼻咽癌（NPC）患者发生甲状腺功能减退症的风险。
共纳入 404 例非转移性 NPC 患者。所有患者均接受 IMRT 治疗。所有患者在放疗前后定期进行甲状腺功能检查。甲状腺功能减退症的发病时间定义为放疗结束至首次记录异常甲状腺激素检查之间的时间间隔。采用 Kaplan-Meier 法估计甲状腺功能减退症的累积发生率。采用单因素和多因素 Cox 回归分析来检测与甲状腺功能减退症相关的最有希望的因素。
中位随访时间为 60.6 个月。3、5 和 7 年的甲状腺功能减退症累积发生率分别为 39.4%、49.1%和 54.7%。原发性甲状腺功能减退症和中枢性甲状腺功能减退症的中位发病时间分别为 15.4 个月（范围 2.9-83.8 个月）和 29.9 个月（范围 19.8-93.6 个月）。单因素和多因素分析显示，年龄较小、女性和甲状腺体积较小是预测甲状腺功能减退症风险的最重要因素。在多因素分析中，Dtmean（甲状腺的平均剂量）、V30-V50（甲状腺接受一定剂量水平的体积百分比）和 VS45-VS60（甲状腺免受各种剂量水平的绝对体积）仍然具有统计学意义。确定 45Gy（Dtmean）、80%（Vt40）和 5cm（VS45Gy）的截断值将患者分为高危或低危组。
甲状腺 Vt40 高度预测 NPC 患者接受 IMRT 后发生甲状腺功能减退症的风险。我们建议将计划优化目标设定为将甲状腺 Vt40 降低到 80%。
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