Thyroid echogenicity predicts outcome of radioiodine therapy in patients with Graves' disease

J Clin Endocrinol Metab. 2007 Sep;92(9):3547-52. doi: 10.1210/jc.2007-0879. Epub 2007 Jul 3.

Abstract

Context: Despite accounting for variations in gland size and iodine kinetics, the success of radioiodine therapy in patients with Graves' disease remains moderately common and unpredictable.

Objectives: We hypothesized that hypoechogenic glands, with large, densely packed cells, are more radiosensitive than normoechogenic glands, in which much radiation is wasted on more abundant colloid. We evaluated this hypothesis in a cohort of patients with Graves' disease.

Design: This was a prospective trial of patients recruited during 4 yr and followed up 1 yr after radioiodine therapy.

Setting: This trial was held in a university hospital-outpatient clinic.

Patients: A total of 177 consecutive patients with first presentation of Graves' disease (28 males), 23-76 yr old, who relapsed after antithyroid therapy were included in the study.

Intervention: The patients were assigned to an ablative target-absorbed dose of 200 Gy (n = 78) or randomly to 100 or 120 Gy of nonablative dose (n = 99).

Main outcome measures: The measures were incidences of hyperthyroidism, euthyroidism, and hypothyroidism at 12-month follow-up.

Results: At follow-up there were 25 hyperthyroid, 44 euthyroid, and 108 hypothyroid patients. Compared with 96 patients with a hypoechogenic gland, in 81 patients with a normoechogenic gland, there were more hyperthyroid (22 vs. 7%) and euthyroid (41 vs. 11%), but less hypothyroid outcomes (37 vs. 81%; P < 0.0001). The other independent predictor of increased radioresistance was the large gland volume.

Conclusion: In patients with Graves' disease, normoechogenic and large glands are associated with increased radioresistance.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Female
  • Follow-Up Studies
  • Graves Disease / diagnosis*
  • Graves Disease / radiotherapy*
  • Humans
  • Iodine Radioisotopes / therapeutic use*
  • Male
  • Middle Aged
  • Organ Size / radiation effects
  • Prognosis
  • Radiotherapy Dosage
  • Salvage Therapy
  • Thyroid Gland / diagnostic imaging*
  • Thyroid Gland / pathology*
  • Treatment Outcome
  • Ultrasonography

Substances

  • Iodine Radioisotopes