title: Long-term survival in differentiated thyroid cancer is worse after low-activity initial post-surgical 131I therapy in both high- and low-risk patients.
abstract: BACKGROUND
  Recent trial results have revived interest in low-activity initial (131)I therapy (RIT) of differentiated thyroid cancer (DTC).
  
  
  OBJECTIVE
  This study sought to compare different initial (131)I activities for outcome.
  
  
  METHODS
  A database study was performed in a University hospital.
  
  
  METHODS
  1298 DTC patients were included (698 low risk, 434 high risk M0, and 136 M1), grouped according to ablation activity (I, ≤ 2000 MBq [54 mCi]; II, 2000-3000 MBq [54-81 mCi]; and III, >3000 MBq [81 mCi]), subdivided by age (<45 and ≥ 45 y at diagnosis).
  
  
  METHODS
  Complete remission (CR, defined as thyroglobulin [Tg] below functional sensitivity combined with visually negative (131)I diagnostic whole-body scintigraphy), recurrence, DTC-specific mortality, and relative survival rates were studied.
  
  
  RESULTS
  Low-risk patients: In patients <45 years, a lower median cumulative activity was required to achieve CR in group III (3590 MBq) than in groups I (8050 MBq) and II (6300 MBq). In patients at least 45 years of age, DTC-specific mortality was significantly higher in group I than in groups II and III (15-y: 16.1 ± 7.7%, 0.8 ± 0.8%, and 7.2 ± 5.5%, respectively; P = .004). High-risk M0 patients: In patients at least 45 years of age, the recurrence rate (15-y: 44.4 ± 16.6%, 24.1 ± 7.6%, and 8.6 ± 3.9%; P = .001) and DTC-specific mortality (15-y: 51.8 ± 15.8%, 13.2 ± 4.4%, and 9.5 ± 3.7%; P = .004) were significantly higher in group I than in groups II and III. M1 patients: There were no significant differences in survival results between different activity groups in either age category.
  
  
  CONCLUSIONS
  Before adopting low initial activity RIT for, especially older, low-risk patients, results of long-term followup should be regarded critically. Low-activity RIT in older, high-risk patients is not to be recommended.
authors.affiliation: Department of Nuclear Medicine (F.A.V., C.R., H.H.), and Comprehensive Cancer Center Mainfranken (U.M.), University of Wuerzburg, 97080 Wuerzburg, Germany; and Department of Nuclear Medicine (F.A.V.), RWTH University Hospital Aachen, 52074 Aachen, Germany.
authors.forename: Frederik A
authors.initials: FA
authors.lastname: Verburg
authors.forename: Uwe
authors.initials: U
authors.lastname: Mäder
authors.forename: Christoph
authors.initials: C
authors.lastname: Reiners
authors.forename: Heribert
authors.initials: H
authors.lastname: Hänscheid
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008017:Life Expectancy; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D012306:Risk; D016019:Survival Analysis; D013964:Thyroid Neoplasms / Q000401:mortality* / Q000532:radiotherapy / Q000601:surgery; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes