Changes of salivary glands after radioiodine retreatment for differentiated thyroid cancer by ultrasonography

Objectives: To study changes over time of major salivary gland in patients with differentiated thyroid cancer (DTC) after post-operative radioactive iodine ablation (RIA) retreatment by ultrasonography (US), and to analyze the influencing factors.

Methods: Retrospectively analyzed data of consecutive patients with DTC who underwent total or near-total thyroidectomy,RIA treatment and repeated neck US in our hospital from January 2014-December 2015. 432 patients were divided into test and control group according to their treatment times. Generalized estimation equation was the main statistical method.

Results: 432 patients (mean age 38.77 ± 13.18 years, 313 female) completed five or more follow-up visits(mean 41.72 ± 8.09 months). For 25 of the 92 patients (27.2%) in control group and 110 of the 340 patients (32.4%) in test group, US revealed changes in the major salivary glands after RIA, which had no statistically significant difference (χ2 = 0.904, P = 0.342). Post-RIA changes on follow-up ultrasonography before the 5th (mean 33 months) follow-up increased with the number of follow-ups (P<0.001) , and there was no significant difference after the 5th (P> 0.05). Females had post-RIA changes more than males (OR = 0.204, P <0.001). Post-RIA changes increased with age (OR = 0.944, P = 0.044), the first dose and the second dose (OR = 1.010, 1.014, P = 0.070, 0.009). No significant difference was found in treatment times , Pathologic type, Operative type, interval between two RIA sessions (all P> 0.05).

Conclusions: Post-RIA changes on follow-up ultrasonography increased with the number of follow-ups and then stabilized at follow-up approximately 33 months. changes after radioiodine retreatment is related to the dose, age, gender, ATA risk stratification , but which was not found to be related to and the number of RIA sessions.