Predictive value of dual ¹³¹I WBS for impairment of salivary gland function in DTC patients after ¹³¹I treatment

Objective To investigate the relationship between salivary gland ¹³¹I decay metabolic rate (DMR) and radiation-induced salivary dysfunction, and to evaluate the predictive value of dual-phase ¹³¹I whole-body scintigraphy (WBS) for assessing post-radioiodine sialadenitis in postoperative differentiated thyroid carcinoma (DTC) patients.

Methods  This retrospective study analyzed 60 postoperative DTC patients (19 males, 41 females; mean age 45.6±12.6 years) without sialadenitis symptoms undergoing initial ¹³¹I therapy at Baoding First Central Hospital (2020-2023). All patients underwent pretreatment salivary gland scintigraphy (SGS) and completed MSGS-Q3 questionnaires. After 3-week levothyroxine withdrawal and low-iodine diet with TSH >30 mU/L, patients received ¹³¹I therapy followed by whole-body scintigraphy (WBS) on days 2 and 4, with identical secondary therapy 3−6 months later. Two months post-therapy, MSGS-Q3 questionnaires stratified patients into symptomatic/asymptomatic groups. Bilateral salivary gland radioactive counts from serial ¹³¹I WBS ROI analyses determined ¹³¹I DMR values. Statistical analyses included Mann-Whitney U tests, ROC curve analysis (AUC calculation) of parotid/submandibular ¹³¹I DMR for predicting salivary dysfunction, and Spearman correlation between MSGS-Q3 scores and salivary ¹³¹I DMR.

Results  Comparative analysis revealed significantly depressed ¹³¹I DMR values in symptomatic versus asymptomatic cohorts for both parotid (83.99±9.76% vs 91.18%IQR: 86.19−94.83, Z=−2.113, P=0.034) and submandibular glands (77.4±10.68% vs 87.65%IQR: 83.11−91.03, Z=−3.049, P=0.002). Diagnostic performance analysis demonstrated parotid DMR AUC=0.673(95%CI: 0.523−0.823) with optimal cutoff 84.86%(sensitivity 80.95%, specificity 44.44%), while submandibular DMR showed superior discrimination (AUC=0.7500.601−0.899, cutoff 77.91%, sensitivity 83.33%, specificity 61.11%). Secondary therapy analysis showed nonsignificant DMR differences (all P>0.05). Significant inverse correlation was observed between MSGS-Q3 scores and DMR values.

Conclusions  Based on the dual ¹³¹I-WBS findings, the DMR can be utilized to predict salivary gland damage in patients with DTC following ¹³¹I treatment. However, the DMR from the initial treatment did not demonstrate clinical significance in predicting salivary gland injury after subsequent treatment.