Gabryś Hubert Szymon, Buettner Florian, Sterzing Florian, Hauswald Henrik, Bangert Mark
a Department of Medical Physics in Radiation Oncology , German Cancer Research Center (DKFZ) , Heidelberg , Germany.
b Heidelberg Institute for Radiation Oncology (HIRO) , Heidelberg , Germany.
Acta Oncol. 2017 Sep;56(9):1197-1203. doi: 10.1080/0284186X.2017.1324209. Epub 2017 May 13.
Xerostomia is a common side effect of radiotherapy resulting from excessive irradiation of salivary glands. Typically, xerostomia is modeled by the mean dose-response characteristic of parotid glands and prevented by mean dose constraints to either contralateral or both parotid glands. The aim of this study was to investigate whether normal tissue complication probability (NTCP) models based on the mean radiation dose to parotid glands are suitable for the prediction of xerostomia in a highly conformal low-dose regime of modern intensity-modulated radiotherapy (IMRT) techniques.
We present a retrospective analysis of 153 head and neck cancer patients treated with radiotherapy. The Lyman Kutcher Burman (LKB) model was used to evaluate predictive power of the parotid gland mean dose with respect to xerostomia at 6 and 12 months after the treatment. The predictive performance of the model was evaluated by receiver operating characteristic (ROC) curves and precision-recall (PR) curves.
Average mean doses to ipsilateral and contralateral parotid glands were 25.4 Gy and 18.7 Gy, respectively. QUANTEC constraints were met in 74% of patients. Mild to severe (G1+) xerostomia prevalence at both 6 and 12 months was 67%. Moderate to severe (G2+) xerostomia prevalence at 6 and 12 months was 20% and 15%, respectively. G1 + xerostomia was predicted reasonably well with area under the ROC curve ranging from 0.69 to 0.76. The LKB model failed to provide reliable G2 + xerostomia predictions at both time points.
Reduction of the mean dose to parotid glands below QUANTEC guidelines resulted in low G2 + xerostomia rates. In this dose domain, the mean dose models predicted G1 + xerostomia fairly well, however, failed to recognize patients at risk of G2 + xerostomia. There is a need for the development of more flexible models able to capture complexity of dose response in this dose regime.
口干症是放疗常见的副作用，由唾液腺受到过度照射所致。通常，口干症通过腮腺的平均剂量反应特性来建模，并通过对同侧或双侧腮腺的平均剂量限制来预防。本研究的目的是调查基于腮腺平均辐射剂量的正常组织并发症概率（NTCP）模型是否适用于预测现代调强放疗（IMRT）技术高适形低剂量方案中的口干症。
我们对153例接受放疗的头颈癌患者进行了回顾性分析。采用莱曼·库彻·伯曼（LKB）模型评估治疗后6个月和12个月时腮腺平均剂量对口干症的预测能力。通过受试者操作特征（ROC）曲线和精确召回率（PR）曲线评估模型的预测性能。
同侧和对侧腮腺的平均平均剂量分别为25.4 Gy和18.7 Gy。74%的患者符合QUANTEC限制。6个月和12个月时轻度至重度（G1+）口干症患病率均为67%。6个月和12个月时中度至重度（G2+）口干症患病率分别为20%和15%。G1+口干症预测效果较好，ROC曲线下面积在0.69至0.76之间。LKB模型在两个时间点均未能提供可靠的G2+口干症预测。
将腮腺平均剂量降低至低于QUANTEC指南会导致低G2+口干症发生率。在该剂量范围内，平均剂量模型对G1+口干症预测效果较好，但未能识别有G2+口干症风险的患者。需要开发更灵活的模型，以捕捉该剂量方案中剂量反应的复杂性。
