The influence of regional dose sensitivity on salivary gland loss and recovery in the parotid gland
Channel: haldclark
Date: 2014-10-28

Video footage of a presentation I (Hal Clark) gave at the Canadian Organization of Medical Physicists (COMP) Annual General Meeting in Banff on 20140711 (July 11th, 2014). The title is "The influence of regional dose sensitivity on salivary gland loss and recovery in the parotid gland."

An accompanying three page abstract was provided for peer review and is available upon request. A short abstract was indexed and is available at: http://dx.doi.org/10.1118/1.4894953 .

Abstract:
Purpose: The Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC 2010) survey of radiation dose-volume effects on salivary gland function has called for improved understanding of intragland dose sensitivity and the effectiveness of partial sparing in salivary glands. Regional dose susceptibility of sagittally- and coronally-sub-segmented parotid gland has been studied. Specifically, we examine whether individual consideration of sub-segments leads to  improved prediction of xerostomia compared with whole parotid mean dose.
Methods: Data from 102 patients treated for head-and-neck cancers at the BC Cancer Agency were used in this study. Whole mouth stimulated saliva was collected before (baseline), three months, and one year after cessation of radiotherapy. Organ volumes were contoured using treatment planning CT images and sub-segmented into regional portions. Both non-parametric (local regression) and parametric (mean dose exponential fitting) methods were employed. A bootstrap technique was used for reliability estimation and cross-comparison.
Results: Salivary loss is described well using non-parametric and mean dose models. Parametric fits suggest a significant distinction in dose response between medial-lateral and anterior-posterior aspects of the parotid (p less than 0.01). Least-squares and least-median squares estimates differ significantly (p less than 0.00001), indicating fits may be skewed by noise or outliers. Salivary recovery exhibits a weakly arched dose response: the highest recovery is seen at intermediate doses.
Conclusions: Salivary function loss is strongly dose dependent. In contrast no useful dose dependence was observed for function. Regional dose dependence was observed, but may have resulted from a bias in dose distributions.