Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins Medicine, Johns Hopkins University, Baltimore, MD.
Br J Radiol. 2013 Nov;86(1031):20130363. doi: 10.1259/bjr.20130363. Epub 2013 Sep 12.
To describe the pattern and predictors of volumetric change of parotid glands during intensity modulated radiotherapy (IMRT) for oropharyngeal cancer.
A cohort of patients undergoing weekly CT scans during dose-painted IMRT was considered. The parotid glands were contoured at the time of treatment planning (baseline) and on all subsequent scans. For a given patient, the parotid glands were labelled as higher (H) and lower (L), based on the mean dose at planning. The volume of each gland was determined for each scan and the percent change from baseline computed. Data were fit to both linear and quadratic functions. The role of selected covariates was assessed with both logistic regression and pair-wise comparison between the sides. The analyses were performed considering the whole treatment duration or each separate half.
85 patients, 170 glands and 565 scans were analysed. For all parotids except one, the quadratic function provided a better fit than the linear one. Moreover, according to both the logistic regression and pair-wise comparison, the cumulative mean dose of radiation is independently correlated with the parotid shrinkage during the first but not the second half of the treatment. Conversely, age and weight loss are predictors of relative parotid shrinkage during the entire course of the treatment.
Parotid gland shrinkage during IMRT is not linear. Age, weight loss and radiation dose independently predict parotid shrinkage during a course of IMRT.
The present study adds to the pathophysiology of parotid shrinkage during radiotherapy.
描述调强放疗（IMRT）治疗口咽癌过程中腮腺体积变化的模式和预测因素。
考虑了一组在剂量绘制 IMRT 过程中每周进行 CT 扫描的患者。在治疗计划（基线）时以及在所有后续扫描时对腮腺进行轮廓勾画。对于给定的患者，根据计划时的平均剂量，将腮腺标记为高（H）和低（L）。为每个扫描确定每个腺体的体积，并计算相对于基线的百分比变化。数据拟合到线性和二次函数。使用逻辑回归和两侧之间的两两比较评估选定协变量的作用。在考虑整个治疗持续时间或每个单独的一半时，进行了分析。
共分析了 85 名患者、170 个腺体和 565 次扫描。除了一个腺体之外，所有腮腺的二次函数拟合都优于线性函数。此外，根据逻辑回归和两两比较，累积平均辐射剂量与治疗前半段而非后半段的腮腺收缩独立相关。相反，年龄和体重减轻是整个 IMRT 治疗过程中相对腮腺收缩的预测因素。
IMRT 过程中腮腺收缩不是线性的。年龄、体重减轻和辐射剂量独立预测 IMRT 过程中的腮腺收缩。
本研究增加了放疗过程中腮腺收缩的病理生理学知识。
