title: 18-Fluorine fluorodeoxyglucose positron emission tomography in the pretreatment evaluation of thymic epithelial neoplasms: a metabolic biopsy confirmed by Ki-67 expression.
abstract: OBJECTIVE
  To investigate the usefulness of 18-fluorine fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET-CT) in the pretreatment evaluation of thymic epithelial neoplasms (TENs). We previously demonstrated that the ratio between standardized uptake value of the tumour and aortic arch (SUV T/M) correlates with World Health Organization (WHO) classification. We now focused our evaluation on thymomas only, excluding carcinomas. We also searched for the expression of a pathological biomarker, Ki-67, that gained both diagnostic and prognostic relevance for various solid tumours. Its correlation with SUV T/M and WHO classification was evaluated.
  
  
  METHODS
  We performed a retrospective dynamic cohort study of data from January 2006 to December 2012, on 23 consecutive patients with pathologically proven TEN, excluding thymic carcinomas, evaluated with PET-CT. For each patient, SUV T/M was calculated. The patients were then categorized, according to WHO classification, into two groups (low-risk: 3 A, 9 AB, 5 B1; high-risk: 5 B2, 1 B3) and Ki-67 labelling index (LI) was defined. We employed the Spearman rank non-linear correlation coefficient (ρ) to estimate the correlations between variables.
  
  
  RESULTS
  SUV T/M proved to be significantly higher for high-positive Ki-67 samples, indicating a strong correlation between SUV T/M and Ki-67 LI (ρ = 0.8). Furthermore, high Ki-67 LI samples correlate with the higher-risk WHO subgroup (ρ = 0.9).
  
  
  CONCLUSIONS
  FDG PET-CT can provide a useful tool in the preoperative work-up of TEN, reflecting its proliferation capacity, as described also by the Ki-67 expression. In particular, SUV T/M could provide a 'metabolic biopsy' to divide TEN into high-risk and low-risk neoplasms.
authors.affiliation: Thoracic Surgery Unit, Santa Croce e Carle Hospital, Cuneo, Italy vitimassa@hotmail.it.
authors.forename: Andrea
authors.initials: A
authors.lastname: Viti
authors.affiliation: Thoracic Surgery Unit, Santa Croce e Carle Hospital, Cuneo, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Bertolaccini
authors.affiliation: Thoracic Surgery Unit, Santa Croce e Carle Hospital, Cuneo, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cavallo
authors.affiliation: Pathology Service, Santa Croce e Carle Hospital, Cuneo, Italy.
authors.forename: Mirella
authors.initials: M
authors.lastname: Fortunato
authors.affiliation: Nuclear Medicine Service, Santa Croce e Carle Hospital, Cuneo, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bianchi
authors.affiliation: Thoracic Surgery Unit, Santa Croce e Carle Hospital, Cuneo, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Terzi
mesh_terms: D000328:Adult; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis / Q000096:biosynthesis*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods; D009375:Neoplasms, Glandular and Epithelial / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D013953:Thymus Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology*; D014057:Tomography, X-Ray Computed
chemical_list: D019394:Ki-67 Antigen; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Ki-67; PET–CT; Thymoma