title: Patients with high-risk differentiated thyroid cancer have a lower I-131 ablation success rate than low-risk ones in spite of a high ablation activity.
abstract: OBJECTIVE
  To examine success rates in strictly defined high-risk differentiated thyroid cancer (DTC) patients who received a high-activity (≥5550 MBq) adjuvant postoperative I-131 therapy and compare these to the rates found in highest risk and low-risk patients.
  
  
  METHODS
  Retrospective database study.
  
  
  METHODS
  We examined 377 patients with DTC who received I-131 ablation. Patients with distant metastases were classified as very high risk. Patients with primary tumours >4 cm, extensive extrathyroidal invasion (pT4a or pT4b in accordance with the 7th edition of the TNM system), and patients with ≥5 lymph node metastases or any lateral compartment lymph node metastases were considered high risk. All other patients were considered low risk.
  
  
  METHODS
  Ablation success rate at first TSH-stimulated follow-up.
  
  
  RESULTS
  The ablation success rate was 72·6% in low-risk patients, 51·7% in high-risk patients and 13·8% in highest risk patients (all differences P < 0·001). In none of the groups, a significant difference in the initial I-131 activity was found between patients with successful and unsuccessful ablation (low risk: P = 0·16, high risk: P = 0·91 and highest risk: P = 0·48). Furthermore, there was no difference in ablation success between patients who received <5550 MBq and those who received ≥5550 Mbq (low risk: P = 0·31, high risk: P = 0·69 and highest risk: P = 0·22).
  
  
  CONCLUSIONS
  Patients with high-risk DTC have a significantly reduced I-131 ablation success rate compared to low-risk ones in spite of high initial I-131 activities. As successful ablation is prognostically important, efforts should be made to improve outcome in these patients.
authors.affiliation: Department of Nuclear Medicine, Aachen, RWTH University Hospital Aachen, Aachen, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Winter
authors.affiliation: Department of Nuclear Medicine, Aachen, RWTH University Hospital Aachen, Aachen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Winter
authors.affiliation: Department of Nuclear Medicine, Aachen, RWTH University Hospital Aachen, Aachen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Krohn
authors.affiliation: Department of Nuclear Medicine, Aachen, RWTH University Hospital Aachen, Aachen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Heinzel
authors.affiliation: Department of Nuclear Medicine, Aachen, RWTH University Hospital Aachen, Aachen, Germany.
authors.forename: F F
authors.initials: FF
authors.lastname: Behrendt
authors.affiliation: Endocrinology Service, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Tuttle
authors.affiliation: Department of Nuclear Medicine, Aachen, RWTH University Hospital Aachen, Aachen, Germany.|Department of Nuclear Medicine, Maastricht UMC, Maastricht, The Netherlands.
authors.forename: F M
authors.initials: FM
authors.lastname: Mottaghy
authors.affiliation: Department of Nuclear Medicine, Aachen, RWTH University Hospital Aachen, Aachen, Germany.|Department of Nuclear Medicine, Maastricht UMC, Maastricht, The Netherlands.
authors.forename: F A
authors.initials: FA
authors.lastname: Verburg
mesh_terms: D055011:Ablation Techniques / Q000379:methods*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008207:Lymphatic Metastasis / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D018570:Risk Assessment; D013964:Thyroid Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes