Evaluation of submandibular gland function using quantitative 99mTc-pertechnetate scintigraphy in submandibular gland sparing radiotherapy for head-neck cancers, a prospective longitudinal study

Abstract

Purpose

This study evaluates the efficacy of submandibular gland sparing radiotherapy in reducing salivary dysfunction using dynamic ^99mTechnetium pertechnetate scintigraphy.

Materials and Methods

Adults with head and neck squamous cell carcinoma planned for radical radiation using volumetric modulated arc radiotherapy were recruited in the study. The salivary function was assessed using ^99mTechnetium pertechnetate scintigraphy at baseline, 3-, 6-, and 12 months post-radiation. Maximum Uptake (Umax), Salivary Excretion Fraction (SEF), relative change in SEF (rSEF), and SEF ratio were calculated and compared at different time points.

Results

Between June 2022 and January 2024, 113 patients were recruited, with scintigraphy data available for 27 patients with spared and 53 with unspared submandibular glands. At baseline, the mean Umax was 82.7 counts/second (cps) (spared) versus 81.5 cps (unspared). There was a decline at 3 months (66.5 cps vs. 72.7 cps), with significantly greater recovery by 12 months in the spared glands (81.2 cps vs. 54.8 cps; p = 0.035). SEF values at 3, 6, and 12 months respectively were 27.6 (IQR 19.6–42.1), 23.9 (IQR 17.7–31.2), and 29.9 (IQR 18.3–34.7) in spared glands compared to 2.8 (IQR −2.9–6.9), 4.4 (IQR 1.8–9.1), and 5.8 (IQR 2.6–7.6; p < 0.01 at all timepoints) in the unspared glands. At 3, 6, and 12 months, spared glands retained 78.5 %, 89.6 %, and 87.0 % function, compared to 10.5 %, 17.4 %, and 14.0 % in unspared glands (p < 0.01 at all time points). No recurrences occurred near the spared glands during the study period.

Conclusion

Submandibular gland sparing is safe and significantly reduces radiation-induced salivary dysfunction. Dynamic 99mTc-pertechnetate scintigraphy is a reliable, minimally invasive method for evaluating gland function.