Salivary gland side effects commonly develop several weeks after initial radioactive iodine ablation

Area of Science:

• Endocrinology
• Oncology
• Nuclear Medicine

Background:

• Salivary gland side effects (SSEs) are a significant morbidity for thyroid cancer patients undergoing radioactive iodine (RAI) treatment.
• The incidence, timing, and resolution of SSEs after RAI for remnant ablation are not well-defined.

Purpose of the Study:

• To determine the incidence and time course of SSEs within the first year after RAI remnant ablation (RRA).
• To investigate the dose-response relationship between RAI activity and SSEs.
• To compare SSEs based on preparation methods: recombinant human thyroid-stimulating hormone (rhTSH) versus thyroid hormone withdrawal (THW).

Main Methods:

• Retrospective review of clinical records of 262 patients undergoing RRA.
• Analysis of SSE incidence within one year of RRA.
• Dose-response analysis for RAI activity and SSEs.
• Comparison of SSEs between rhTSH and THW preparation methods.

Main Results:

• SSEs occurred in 39% of patients within the first year; persistent SSEs were <5% at 7-year follow-up.
• A significant dose-response was observed between RAI activity and salivary gland swelling (P=0.001), but not dry mouth, altered taste, or pain.
• Thyroid hormone withdrawal (THW) was associated with lower salivary gland swelling (20%) compared to rhTSH (10%) despite higher RAI doses (P=0.017).

Conclusions:

• While SSEs are common after RRA, most are transient, with a low overall incidence of persistent effects.
• Careful patient selection for RRA and using the minimum effective RAI dose are crucial to balance treatment benefits and minimize adverse events.