Clinical outcomes after estimated versus calculated activity of radioiodine for the treatment of hyperthyroidism: systematic review and meta-analysis.
BACKGROUND
Despite the long experience with radioiodine for hyperthyroidism, controversy remains regarding the optimal method to determine the activity that is required to achieve long-term euthyroidism.


OBJECTIVE
To compare the effect of estimated versus calculated activity of radioiodine in hyperthyroidism. Design Systematic review and meta-analysis.


METHODS
We searched the databases Medline, EMBASE, Web of Science, and Cochrane Library for randomized and nonrandomized studies, comparing the effect of activity estimation methods with dosimetry for hyperthyroidism. The main outcome measure was the frequency of treatment success, defined as persistent euthyroidism after radioiodine treatment at the end of follow-up in the dose estimated and calculated dosimetry group. Furthermore, we assessed the cure rates of hyperthyroidism.


RESULTS
Three randomized and five nonrandomized studies, comparing the effect of estimated versus calculated activity of radioiodine on clinical outcomes for the treatment of hyperthyroidism, were included. The weighted mean relative frequency of successful treatment outcome (euthyroidism) was 1.03 (95% confidence interval (CI) 0.91-1.16) for estimated versus calculated activity; the weighted mean relative frequency of cure of hyperthyroidism (eu- or hypothyroidism) was 1.03 (95% CI 0.96-1.10). Subgroup analysis showed a relative frequency of euthyroidism of 1.03 (95% CI 0.84-1.26) for Graves' disease and of 1.05 (95% CI 0.91-1.19) for toxic multinodular goiter.


CONCLUSIONS
The two main methods used to determine the activity in the treatment of hyperthyroidism with radioiodine, estimated and calculated, resulted in an equally successful treatment outcome. However, the heterogeneity of the included studies is a strong limitation that prevents a definitive conclusion from this meta-analysis.
de Rooij
A
A
Departments of Clinical Epidemiology C7-R, Endocrinology and Metabolic Diseases Nuclear Medicine, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands.
Vandenbroucke
J P
JP
Smit
J W A
JW
Stokkel
M P M
MP
Dekkers
O M
OM
D004307:Dose-Response Relationship, Radiation; D006801:Humans; D006980:Hyperthyroidism / Q000532:radiotherapy*; D007457:Iodine Radioisotopes / Q000008:administration & dosage*; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
D007457:Iodine Radioisotopes