title: Is radioactive iodine- 131 treatment related to the occurrence of non-synchronous second primary malignancy in patients with differentiated thyroid cancer?
abstract: OBJECTIVE
  Much controversy relates to the risk of non-synchronous second primary malignancies (NSSPM) after radioactive iodine treatment (RAI-131) in differentiated thyroid cancer (DTC) patients. This study evaluated the relationship between RAI-131 and NSSPM in DTC survivors with long-term follow-up.
  
  
  METHODS
  Retrospective analysis of 413 DTC cases was performed; 252 received RAI-131 and 161 were treated with thyroidectomy alone. Exclusion criteria were: prior or synchronous non-thyroidal malignancies (within the first year), familial syndromes associated to multiple neoplasms, ionizing radiation exposure or second tumors with unknown histopathology.
  
  
  RESULTS
  During a mean follow-up of 11.0 ± 7.5 years, 17 (4.1%) patients developed solid NSSPM. Patients with NSSPM were older than those without (p = 0.02). RAI-131 and I-131 cumulative activity were similar in patients with and without NSSPM (p = 0.18 and p = 0.78, respectively). Incidence of NSSPM was 5.2% in patients with RAI-131 treatment and 2.5% in those without RAI-131 (p = 0.18). Using multivariate analysis, RAI-131 was not significantly associated with NSSPM occurrence (p = 0.35); age was the only independent predictor (p = 0.04). Under log rank statistical analysis, after 10 years of follow-up, it was observed a tendency of lower NSSPM-free survival among patients that received RAI-131 treatment (0.96 vs . 0.87; p = 0.06), what was not affected by age at DTC diagnosis.
  
  
  CONCLUSIONS
  In our cohort of DTC survivors, with a long-term follow-up period, RAI-131 treatment and I-131 cumulative dose were not significantly associated with NSSPM occurrence. A tendency of premature NSSPM occurrence among patients treated with RAI-131 was observed, suggesting an anticipating oncogenic effect by interaction with other risk factors.
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Marcelo Cruzick de
authors.initials: MC
authors.lastname: Souza
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Denise P
authors.initials: DP
authors.lastname: Momesso
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Vaisman
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Vieira Neto
authors.affiliation: Research Divison, Hospital Universitário Clementino Fraga Filho, Rio de Janeiro, RJ, Brazil.
authors.forename: Rosangela Aparecida Gomes
authors.initials: RA
authors.lastname: Martins
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Rossana
authors.initials: R
authors.lastname: Corbo
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Mario
authors.initials: M
authors.lastname: Vaisman
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D018572:Disease-Free Survival; D023381:Endpoint Determination; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007457:Iodine Radioisotopes / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D060787:Neoplasm Grading; D009381:Neoplasms, Radiation-Induced; D016609:Neoplasms, Second Primary / Q000453:epidemiology / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D013965:Thyroidectomy
chemical_list: D007457:Iodine Radioisotopes