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Title: Regional radiation dose susceptibility within the parotid gland: Effects on salivary loss and recovery

Purpose: Xerostomia is one of the most likely late toxic effects of radiotherapy treatment in patients with head-and-neck cancers. Modern treatment techniques can incorporate knowledge of complication risk into treatment plans. To this end, the authors attempt to quantify the regional radiotherapy dose-dependence of salivary output loss and recovery in a prospective study. Methods: Salivary output was collected from patients undergoing radiotherapy treatment for head-and-neck cancers at the BC Cancer Agency between February 2008 and May 2013. Regional dose-dependence (i.e., dose susceptibility) of loss and recovery is quantified using nonparametric (Spearman’s rank correlation coefficients, local linear regression) and parametric (least-sum of squares, least-median of squares) techniques. Results: Salivary flow recovery was seen in 79 of 102 patients considered (p < 0.0001, Wilcoxon sign rank test). Output loss was strongly correlated with left- and right parotid combined dose φ = min (D{sub L},  45 Gy) + min (D{sub R},  45 Gy), and can be accurately predicted. Median early loss (three months) was 72% of baseline, while median overall loss (1 yr) was 56% of baseline. Fitting an exponential model to whole parotid yields dose sensitivities A{sub 3m} = 0.0604 Gy{sup −1} and A{sub 1y} = 0.0379 Gy{sup −1}. Recovery was notmore » significantly associated with dose. Hints of lateral organ sub-segment dose–response dimorphism were observed. Conclusions: Sub-segmentation appears to predict neither loss nor recovery with any greater precision than whole parotid mean dose, though it is not any worse. Sparing the parotid to a combined dose φ of <50 Gy is recommended for a patient to keep ≈40% of baseline function and thus avoid severe xerostomia at 12 months post-treatment. It seems unlikely that a population’s mean recovery will exceed 20%–30% of baseline output at 1 yr after radiotherapy treatment using current (whole-organ based) clinical guidelines.« less
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)
  2. Oral Oncology/Dentistry, British Columbia Cancer Agency–Vancouver Centre, Vancouver, British Columbia V5Z 4E6 (Canada)
  3. Department of Radiation Medicine and Applied Sciences, University of California–San Diego, La Jolla, California 92093 (United States)
  4. Department of Medical Physics, British Columbia Cancer Agency–Vancouver Centre, Vancouver, British Columbia V5Z 4E6 (Canada)
  5. Radiation Oncology, British Columbia Cancer Agency–Vancouver Centre, Vancouver, British Columbia V5Z 4E6 (Canada)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 4; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States