A systematic review of absorbed doses and response in patients treated with radioiodine for differentiated thyroid cancer

Background: Treatment of patients with thyroid cancer with Na[131I]I is routinely performed with empirical activity levels. Treatment success may be expected to correlate with the absorbed doses delivered to targets (thyroid remnants or metastatic lesions), but no systematic review or meta-analysis of absorbed dose-effect relationships has yet been performed.

Methods: A systematic review and meta-analysis of reports published before August 22, 2025, was performed using PubMed, Web of Science, and OVID MEDLINE. Studies were included if they reported the proportion of patients achieving successful outcome as defined in individual publications and the absorbed doses delivered to targets. The study is registered with PROSPERO (CRD42024554956).

Results: In total, 3723 studies were identified of which 18 were eligible for analysis. Number of patients in the included studies ranged from 4 to 509. For patients treated with Na[131I]I for thyroid remnant ablation, the reported success rates ranged from 60% to 100%, while lower success rates of 43-58% were found for patients with metastatic lesions. Success rates for patients with a thyroid remnant absorbed dose of 300 Gy or more ranged from 78% to 96%, while patients with metastatic lesions receiving at least 80 Gy had success rates ranging from 46% to 98%.

Conclusions: While individual studies have demonstrated the importance of absorbed doses from Na[131I]I for differentiated thyroid cancer, no conclusive absorbed dose-effect relationship has been established in this review. A lack of standardization of dosimetry methodologies and follow-up criteria in the studies obscures the relationship. Large-scale observational prospective studies are required to determine the absorbed doses required for successful personalized treatments of patients with thyroid cancer with Na[131I]I.