title: Clinical and Dosimetric Variables Related to Outcome After Treatment of Graves' Disease With 550 and 1110 MBq of 131I: Results of a Prospective Randomized Trial.
abstract: : Therapy of Graves' hyperthyroidism (HTG) with I is still mostly performed on an empirical basis. The present study was carried out to evaluate clinical and dosimetric variables associated with outcome in HTG therapy, which could contribute to planning and defining the most appropriate activity to be administered.
  
  
  METHODS
  Patients with HTG were randomly assigned to therapy with 555 MBq (15mci) or 1110 MBq (30 mCi) of I. Estimation of thyroid radiation absorbed dose was made according to MIRD methodology. Success was defined as clinical/laboratory euthyroidism or hypothyroidism one year after therapy. The association between clinical, laboratory, and dosimetric variables with 1-year outcome was measured using bivariate analysis, followed by logistic regression.
  
  
  RESULTS
  Ninety-one patients included completed the follow-up. Therapeutic success was observed in 77 (84.6%) of them, in a greater proportion when 1110 MBq of I was administered as compared with 550 MBq (94.8% vs 77.4%, P = 0.02). Besides administered activity, multivariate analysis indicated that outcome was related to patient age and gland mass. A higher therapeutic success rate was achieved with doses greater than 300 Gy as compared with doses less than 300 Gy (89% vs 60%, P = 0.01).
  
  
  CONCLUSIONS
  Administered activity, age, and gland mass were related to the outcome. Radiation absorbed dose, although not significant according to multivariate analysis, may be used as a quantitative parameter in therapy planning, with a target dose of 300 Gy. In cases where a rapid and efficient response to radioiodine treatment is required, adoption of a simplified protocol employing high activities is justified.
authors.affiliation: From the Sao Paulo University Medical School, Sao Paulo, Brazil.
authors.forename: Marcelo Tatit
authors.initials: MT
authors.lastname: Sapienza
authors.forename: George Barberio
authors.initials: GB
authors.lastname: Coura-Filho
authors.forename: José
authors.initials: J
authors.lastname: Willegaignon
authors.forename: Tomoco
authors.initials: T
authors.lastname: Watanabe
authors.forename: Paulo Schiavom
authors.initials: PS
authors.lastname: Duarte
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Buchpiguel
mesh_terms: D000328:Adult; D005260:Female; D006111:Graves Disease / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D011879:Radiotherapy Dosage
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals