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. 2022 Feb 1;95(1130):20210718.
doi: 10.1259/bjr.20210718. Epub 2021 Dec 20.

Mathematical evaluation of post-radiotherapy salivary gland function using salivary gland scintigraphy

Tomohiro Itonaga  1 , Koichi Tokuuye  1 , Ryuji Mikami  1 , Akira Shimizu  2 , Hiroki Sato  2 , Mana Yoshimura  1 , Kiyoaki Tsukahara  2 , Kazuhiro Saito  1
Affiliations

Mathematical evaluation of post-radiotherapy salivary gland function using salivary gland scintigraphy

Tomohiro Itonaga et al. Br J Radiol. .

Abstract

Objective: Xerostomia is the most common treatment-related toxicity after radiotherapy (RT) for head and neck carcinoma, reducing the quality of life of patients due to a decrease in salivary gland function.

Methods: Salivary gland scintigraphy was performed to quantitatively evaluate the salivary gland functions in patients undergoing RT. It was done chronologically for 62 salivary glands of 31 patients before RT and retested 12 months later.

Results: The salivary gland functions of most patients deteriorated post-RT and recovered when the radiation dose to the salivary gland was not high. The mean dose to the salivary gland was found to be the most reliable factor in deteriorating salivary gland function, and the tolerance dose was determined to be 46 Gy. The recovery rate of salivary gland function after 1 year of RT was 72% in the RT alone group (n = 10), 56% in the conformal radiotherapy group (n = 15), and 44% in the bioradiotherapy group (n = 6).

Conclusion: Scintigraphy revealed that the salivary glands recovered from post-RT hypofunction when decreased doses were administered. The determined tolerance dose of 46 Gy may guide the approach to minimizing associated xerostomia in RT.

Advances in knowledge: In this study, the average tolerated dose to the salivary glands was 46 Gy.

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Figures

Figure 1.
Figure 1.
Changes in washout rates. Washout rates generally decreased in the acute phase and recovered in the late phase. Around 42.9% of salivary glands reached zero in the acute phase after a mean dose of 39.8 Gy and recovered in the late phase.
Figure 2.
Figure 2.
Receiver operating characteristic curves for dose–volume analysis. AUC data revealed that the mean dose is the most reliable method for predicting salivary gland preservation. AUC, area under the curve.
Figure 3.
Figure 3.
Scatter plot demonstrating dispersion relationship between mean doses and recovery rates. Both the acute and late recovery rates decreased as the mean dose increased. The tolerance dose was determined to be 46 Gy, with a 5% risk of salivary gland destruction in the late phase.
See this image and copyright information in PMC

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