The following is a summary of “Use of a dosimetry-based RAI protocol for treatment of benign hyperthyroidism optimises response while minimising exposure to ionising radiation,” published in the April 2024 issue of Endocrinology by Miller, et al.

Determining the optimal treatment strategy for radioiodine (RAI) protocols in benign hyperthyroidism remained challenging. While European Law advocated individualized activities, many centers persist with fixed dosages. In 2016, the institution transitioned from fixed dosing to a dosimetry protocol, allowing for personalized activities based on thyroid volume and radioiodine uptake.

For a retrospective study, researchers sought to compare success rates between a dosimetry protocol targeting an absorbed dose of 150 Gy for Graves’ disease (GD) and 125 Gy for Toxic Multinodular Goiter (TMNG) with fixed dosing (200MBq for GD and 400MBq for TMNG) among 204 patients with hyperthyroid. Success was defined as achieving a non-hyperthyroid state at 1 year for both disease states. Results were analyzed for disease-specific or patient-specific response modifiers.

The study included 204 patients; 74% (n = 151) received fixed activities, while 26% (n = 53) received dosimetry-calculated activities. A dosimetry-based protocol achieved success in 80.5% of patients with GD and 100% of patients with TMNG. Differences in success rates and median activity administered between the fixed (204Mbq) and dosimetry (246MBq) cohorts were not statistically significant (P = .64). However, 44% of patients with GD and 70% of patients with TMNG received lower activities with dosimetry. Dosimetry led to successful treatment and reduced RAI exposure for 36% of patients with GD, 70% of patients with TMNG, and 44% of patients overall.

The study demonstrated that a dosimetry-based protocol for TMNG and GD achieved comparable success rates to fixed protocols while reducing RAI exposure for over a third of patients with GD and most patients with TMNG. It also suggested that RAI can effectively treat hyperthyroidism with activities lower than common clinical practice. Although no specific response modifiers were identified, the data supported the need for future prospective trials to investigate further individual patient factors influencing RAI treatment response.

Reference: onlinelibrary.wiley.com/doi/10.1111/cen.15054