Does lemon candy decrease salivary gland damage after radioiodine therapy for thyroid cancer?

UNLABELLED: Salivary gland dysfunction is one of the common side effects of high-dose radioiodine therapy for thyroid cancer. The purpose of this study was to determine whether an early start of sucking lemon candy decreases salivary gland injury after radioiodine therapy.

METHODS: The incidence of the side effects of radioiodine therapy on the salivary glands was prospectively and longitudinally investigated in 2 groups of patients with postsurgical differentiated thyroid cancer with varying regimens for sucking lemon candy. From August 1999 to October 2000, 116 consecutive patients were asked to suck 1 or 2 lemon candies every 2-3 h in the daytime of the first 5 d after radioiodine therapy (group A). Lemon candy sucking was started within 1 h after radioiodine ingestion. From November 2000 to June 2002, 139 consecutive patients (group B) were asked to suck lemon candies in a manner similar to that of group A. In the group B, lemon candies were withheld until 24 h after the ingestion of radioiodine. Patients with salivary gland disorders, diabetes, collagen tissue diseases, or a previous history of radioiodine therapy or external irradiation to the neck were excluded. Thus, 105 patients in group A and 125 patients in group B were available for analysis. There were no statistical differences in the mean age (55.2 y vs. 58.5 y), average levels of serum free thyroxine (l-3,5,3',5'-tetraiodothyronine) (0.40 ng/dL vs. 0.47 ng/dL), and the mean dose of (131)I administered (3.96 GBq vs. 3.87 GBq) between the 2 groups. The onset of salivary side effects was monitored during hospital admission and regular follow-up on the basis of interviews with patients, a visual analog scale, and salivary gland scintigraphy using (99m)Tc-pertechnetate. When a patient showed a persistent (>4 mo) dry mouth associated with a nonfunctioning pattern on salivary gland scintigraphy, a diagnosis of xerostomia was established.

RESULTS: The incidences of sialoadenitis, hypogeusia or taste loss, and dry mouth with or without repeated sialadenitis in group A versus group B were 63.8% versus 36.8% (P < 0.001), 39.0% versus 25.6% (P < 0.01), and 23.8% versus 11.2% (P < 0.005), respectively. Permanent xerostomia occurred in 15 patients in group A (14.3%) and 7 patients in group B (5.6%) (P < 0.05). In both groups, bilateral involvement of the parotid gland was the most frequently seen and was followed by bilateral involvement of the submandibular gland.

CONCLUSION: An early start of sucking lemon candy may induce a significant increase in salivary gland damage. Lemon candy should not be given until 24 h after radioiodine therapy.