title: Evidence for higher success rates and successful treatment earlier in Graves' disease with higher radioactive iodine doses.
abstract: BACKGROUND
  Graves' disease is commonly treated with curative intent using radioactive iodine (RAI). While higher doses have been shown to increase success rates, more evidence is needed. Further, very few studies assess the time to treatment success without the need for antithyroid drugs after a single dose of RAI within the first year post-dose, despite earlier success being an important treatment objective. We aimed to evaluate the outcome of different RAI doses in terms of success rates and time to achieve this success (eu- or hypothyroidism). We hypothesized that higher doses would not only increase success rates, but bring about successful treatment earlier.
  
  
  METHODS
  We retrospectively analyzed the medical records of all patients diagnosed with Graves' disease between 1994 and 2009. Details of RAI treatment and outcomes thereof were documented. In our analysis, we divided the patients who received RAI treatment into three groups according to the dose received: I (≤15 mCi); II (16-20 mCi); III (≥21 mCi).
  
  
  RESULTS
  There were 498 patients diagnosed with Graves' disease. However, 105 were either lost to follow-up or still undergoing treatment. Of the remaining 393, there were 258 who received RAI treatment. The average initial dose was 21.42±6.5 mCi and overall success rate was 86%. Success rates were 74%, 85%, and 89% (p<0.05), while average time to successful treatment was 8.1, 4.6, and 2.9 months, respectively (p<0.001), for groups I, II, and III. When 20 mCi was given empirically, 85% obtained successful treatment; most of these within 3 months (mean 3.9; mode and median 3 months).
  
  
  CONCLUSIONS
  This study provides additional evidence that success post-treatment correlates with administered dose and shows clearly, for the first time, that successful treatment is achieved earlier with higher doses. This knowledge is relevant to all clinicians managing Graves' disease as it can be taken into consideration when discussing treatment plans with patients.
authors.affiliation: SEMPR, Endocrinology and Metabolism Service, Clinics Hospital, Federal University of Paraná, Curitiba, Brazil.
authors.forename: Shoshana
authors.initials: S
authors.lastname: Sztal-Mazer
authors.forename: Viviane Yumi
authors.initials: VY
authors.lastname: Nakatani
authors.forename: Luis Gustavo
authors.initials: LG
authors.lastname: Bortolini
authors.forename: Cesar Luiz
authors.initials: CL
authors.lastname: Boguszewski
authors.forename: Hans
authors.initials: H
authors.lastname: Graf
authors.forename: Gisah Amaral
authors.initials: GA
authors.lastname: de Carvalho
mesh_terms: D000328:Adult; D013956:Antithyroid Agents / Q000627:therapeutic use; D005260:Female; D006111:Graves Disease / Q000188:drug therapy / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage* / Q000627:therapeutic use; D008297:Male; D012189:Retrospective Studies; D061665:Time-to-Treatment; D016896:Treatment Outcome
chemical_list: D013956:Antithyroid Agents; D007457:Iodine Radioisotopes