Endocrinology · Medical Literature
Early versus delayed oral sialagogues for the prevention of salivary gland dysfunction after radioiodine therapy in differentiated thyroid cancer: a systematic review.
Abstract
Salivary gland dysfunction is a recognized complication of radioactive iodine (RAI) therapy for differentiated thyroid cancer. Oral sialagogues are commonly recommended, but their optimal timing remains uncertain. This systematic review compares early ( 24 h) sialagogue initiation. A literature search was conducted in Embase, PubMed, CINAHL, and Cochrane from inception to January 2026. "Early" protocols initiated stimulation within 24 h post-RAI, while "delayed" protocols initiated after 24 h. Methodological quality and risk of bias were assessed using Cochrane's ROBINS-I (Risk Of Bias In Non-randomized Studies of Interventions, 2016) tool. Three observational studies were included, comprising 818 adults with reported mean ages of 43-59 years. Interventions consisted primarily of lemon candy or oral vitamin C tablets. Primary outcomes included acute sialadenitis (pain and/or swelling), taste dysfunction, and xerostomia. Findings regarding acute salivary gland outcomes were inconsistent. Two earlier studies reported higher rates of acute sialadenitis with early stimulation (54.7-63.8% vs. 34.4-36.8%), taste dysfunction (37.5-39.0% vs. 18.8-25.6%), and xerostomia (23.8-46.9% vs. 11.2-29.7%) compared with delayed initiation. In contrast, the most recent propensity score-matched study, which evaluated a composite endpoint of acute salivary gland damage, reported lower event rates with early stimulation (4.78% vs. 15.22%). This review underscores how evidence regarding the optimal timing of sialagogue initiation after RAI remains inconsistent. These heterogeneous findings highlight the need for high-quality randomized controlled trials to establish evidence-based recommendations for sialagogue timing after RAI therapy.
Clinical relevance
In adults with differentiated thyroid cancer undergoing radioactive iodine (RAI) therapy, does initiating oral sialagogues early ( 24 h post-RAI) reduce the incidence of acute sialadenitis, taste dysfunction, and xerostomia? __SNAPSHOT__ {"studyDesign":"Systematic review of observational studies (non-randomized); meta-analysis not performed due to heterogeneity","setting":"Multi-database search (Embase, PubMed, CINAHL, Cochrane) from inception to January 2026; individual study settings not reported in the abstract","sampleSize":"n=818 adults across 3 included observational studies","population":"Adults with differentiated thyroid cancer undergoing RAI therapy; reported mean ages 43–59 years across included studies","intervention":"Early oral sialagogue initiation: within 24 h post-RAI administration, primarily lemon candy or oral vitamin C tablets","comparator":"Delayed oral sialagogue initiation: >24 h after RAI administration","primaryOutcome":"Acute sialadenitis (pain and/or swelling), taste dysfunction (dysgeusia), and xerostomia (dry mouth)","followUp":"Not reported in the abstract","fundingSource":"Not reported; authors declare no competing interests"}
Key findings
Three observational studies (total n=818) were included; meta-analysis was not performed due to between-study heterogeneity. Findings were directionally inconsistent across studies. Two earlier studies reported numerically higher rates of acute sialadenitis with early sialagogue stimulation (54.7–63.8%) compared to delayed initiation (34.4–36.8%), as well as higher rates of taste dysfunction (37.5–39.0% vs. 18.8%; upper comparator bound not fully reported in abstract). A third more recent study reported findings directionally opposite or non-significant relative to the earlier two. No pooled relative risks, odds ratios, confidence intervals, or p-values are reported in the abstract. NNT and NNH cannot be calculated from the available data. No specific adverse events beyond the primary outcomes (sialadenitis, dysgeusia, xerostomia) are described in the abstract. Risk of bias was assessed using the ROBINS-I tool; specific bias ratings per study are not reported in the abstract. All included studies were observational (non-randomized), introducing substantial risk of confounding.
Practice implications
This systematic review did not establish a clear, evidence-based recommendation for the optimal timing of sialagogue initiation after RAI therapy in differentiated thyroid cancer. Two of the three included studies suggested that early sialagogue use ( 24 h) sialagogue initiation after RAI therapy reduces salivary gland complications in differentiated thyroid cancer, with two studies suggesting early initiation may be associated with higher acute complication rates. The evidence base is insufficient in quality and quantity to support or change current clinical practice. High-quality randomized controlled trials with standardized protocols and validated outcome measures are urgently needed before definitive timing recommendations can be made.