title: Difficulties in deciding whether to ablate patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma: do guidelines mainly apply in the centres that produce them? Results of a retrospective, two-centre quality assurance study.
abstract: OBJECTIVE
  We determined the reasons for radioiodine thyroid remnant ablation, and the procedure's necessity based on postsurgical remnant size, in patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma (DTC). We identified key clinicopathological, treatment and remnant characteristics, and factors associated with remnant size in 336 patients with pT1/2, M0 DTC ablated during the period September 2010 to October 2013 at one Cypriot or one Greek referral centre.
  
  
  METHODS
  Clinicopathological/treatment characteristics were compiled from charts. Experienced nuclear medicine physicians rated the numbers/intensities of uptake foci in the thyroid bed on postablation planar scintigrams using scales of 0-4 points and 0-3 points, respectively. The product of these scores was taken as the "remnant score" that ranged from 0 (no remnant) to 12 (multiple remnants, intense uptake).
  
  
  RESULTS
  DTC was predominantly papillary. The median [25th-75th percentile] longest primary tumour diameter was 1.0 cm [0.7-1.5 cm]. Despite favourable histotypes and primary tumour classifications, patients often had preablation characteristics suggesting elevated or uncertain risk: 31.0% of patients (104 of 336) had primary tumour multifocality, 22.0% (74) had confirmed cervical lymph node metastases, 37.2% (125) had unknown nodal status, and 38.1% (128) had antithyroglobulin antibody seropositivity. The median [25th-75th percentile] remnant score was 4 [2-6]; 39.9% of patients (134 of 336) had scores ≥6. For the entire cohort, T or N stages (r ≤ 0.174, P ≤ 0.05) correlated positively with the remnant score in a univariate Spearman analysis. The numbers of patients referred by the surgeon, cervical lymph nodes excised and metastatic nodes excised correlated negatively (r ≤ 0.243, P ≤ 0.038) with the remnant score, and the first two factors independently predicted the remnant score (P ≤ 0.037) in a multivariate analysis.
  
  
  CONCLUSIONS
  Patients with putatively "low-intermediate-risk" DTC frequently had disease characteristics denoting high or uncertain risk, suggesting that "selective" radioiodine ablation in such patients may seldom be applicable outside international centres of excellence. Proxies for surgeon experience and surgical completeness correlated with remnant number/uptake intensity and may aid ablation-related decision-making.
authors.affiliation: Department of Nuclear Medicine, Bank of Cyprus Oncology Centre, 32 Acropoleos Avenue, Strovolos, Nicosia, 2006, Cyprus. savvas.frangos@gmail.com.
authors.forename: Savvas
authors.initials: S
authors.lastname: Frangos
authors.affiliation: Department of Nuclear Medicine, Aristotle University, Papageorgiou Hospital, 56403, Thessaloniki, Greece.
authors.forename: Ioannis P
authors.initials: IP
authors.lastname: Iakovou
authors.affiliation: Spencer-Fontayne Corporation, 33 Bentley Avenue, Jersey City, NJ, 07304-1901, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Marlowe
authors.affiliation: Department of Nuclear Medicine, Bank of Cyprus Oncology Centre, 32 Acropoleos Avenue, Strovolos, Nicosia, 2006, Cyprus.
authors.forename: Nicolaos
authors.initials: N
authors.lastname: Eftychiou
authors.affiliation: Department of Nuclear Medicine, Bank of Cyprus Oncology Centre, 32 Acropoleos Avenue, Strovolos, Nicosia, 2006, Cyprus.
authors.forename: Loukia
authors.initials: L
authors.lastname: Patsali
authors.affiliation: Department of Nuclear Medicine, Bank of Cyprus Oncology Centre, 32 Acropoleos Avenue, Strovolos, Nicosia, 2006, Cyprus.
authors.forename: Anna
authors.initials: A
authors.lastname: Vanezi
authors.affiliation: Department of Nuclear Medicine, Bank of Cyprus Oncology Centre, 32 Acropoleos Avenue, Strovolos, Nicosia, 2006, Cyprus.
authors.forename: Androulla
authors.initials: A
authors.lastname: Savva
authors.affiliation: Department of Nuclear Medicine, Aristotle University, Papageorgiou Hospital, 56403, Thessaloniki, Greece.
authors.forename: Vassilis
authors.initials: V
authors.lastname: Mpalaris
authors.affiliation: Department of Nuclear Medicine, Aristotle University, Papageorgiou Hospital, 56403, Thessaloniki, Greece.
authors.forename: Evanthia I
authors.initials: EI
authors.lastname: Giannoula
mesh_terms: D055011:Ablation Techniques / Q000009:adverse effects; D000328:Adult; D003657:Decision Making; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D007457:Iodine Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D011785:Quality Assurance, Health Care; D019275:Radiopharmaceuticals / Q000009:adverse effects / Q000627:therapeutic use*; D013964:Thyroid Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals
keywords: Clinicopathological; Guidelines; Low-risk DTC; Surgeon experience; Thyroid remnant ablation; Thyroid remnant size