title: Is there a role for PET/CT parameters to differentiate thyroid cartilage invasion from penetration?
abstract: BACKGROUND
  Assessment of thyroid cartilage invasion (tumor extension through inner cortex) and thyroid cartilage penetration (tumor involving both the inner and outer cortices of thyroid cartilage) may be challenging with CT (Computed Tomography) and MR imaging (Magnetic Resonance Imaging). Positron Emission Tomography/Computed Tomography (PET/CT) is a non invasive imaging modality that provides both anatomic and metabolic information. Quantitative data obtained from PET/CT, also known as PET/CT parameters, include maximum, mean or peak standardized uptake values (SUVmax, SUVmean, SUVpeak), metabolic tumor volume (MTV), total lesion glycolysis (TLG), standardized added metabolic activity (SAM) and normalized standardized added metabolic activity (NSAM). Our aim was to examine if FDG PET/CT parameters could differentiate thyroid cartilage invasion from penetration.
  
  
  METHODS
  50 patients who underwent PET/CT before laryngectomy for squamous cell carcinoma of the larynx, had SUVmax, SUVmean, SUVpeak, TLG, MTV, SAM and NSAM calculated on a dedicated workstation. Univariate and multivariate analysis was performed. ROC analysis was used to determine the ability of PET/CT parameters to predict pathologically proven thyroid cartilage invasion or penetration.
  
  
  RESULTS
  Of the 50 patients, 50% (25/50 patients) had history of prior radiation therapy. Among the previously irradiated group, 24% had thyroid cartilage invasion and penetration. 8% of the patients in this group had thyroid cartilage invasion only. Among the non-irradiated group, 76% had thyroid cartilage invasion and penetration, 8% had thyroid cartilage invasion without penetration. ROC analysis revealed that none of the PET/CT parameters had enough power to predict thyroid cartilage penetration, but TLG, MTV and SAM had enough power to predict thyroid cartilage invasion in non-irradiated patients. TLG, MTV, SAM and NSAM had enough power to predict thyroid cartilage invasion and penetration in irradiated group.
  
  
  CONCLUSIONS
  TLG, MTV and SAM have enough power to predict thyroid cartilage invasion and penetration in irradiated patients. PET/CT parameters do not have enough potential to differentiate thyroid cartilage invasion from penetration.
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States. Electronic address: ayse.kendi@emory.edu.
authors.forename: A Tuba
authors.initials: AT
authors.lastname: Kendi
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States.
authors.forename: Amanda
authors.initials: A
authors.lastname: Corey
authors.affiliation: Pathology, Emory University, Atlanta, GA, United States.
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Magliocca
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States.
authors.forename: James R
authors.initials: JR
authors.lastname: Galt
authors.affiliation: Department of Biostatistics & Bioinformatics, Emory University, Atlanta, GA, United States.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Biostatistics & Bioinformatics, Emory University, Atlanta, GA, United States.
authors.forename: Zhengjia
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Radiation Oncology, Emory University, Atlanta, GA, United States.
authors.forename: Kristin
authors.initials: K
authors.lastname: Higgins
authors.affiliation: Radiation Oncology, Emory University, Atlanta, GA, United States.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Beitler
authors.affiliation: Otolaryngology, Head and Neck Surgery, Emory University, Atlanta, GA, United States.
authors.forename: J Trad
authors.initials: JT
authors.lastname: Wadsworth
authors.affiliation: Otolaryngology, Head and Neck Surgery, Emory University, Atlanta, GA, United States.
authors.forename: Mark W
authors.initials: MW
authors.lastname: El-Deiry
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States.
authors.forename: David M
authors.initials: DM
authors.lastname: Schuster
authors.affiliation: Hematology Oncology, Winship Cancer Institute of Emory University, Atlanta, GA, United States.
authors.forename: Nabil F
authors.initials: NF
authors.lastname: Saba
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Hudgins
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D009361:Neoplasm Invasiveness; D049268:Positron-Emission Tomography / Q000379:methods*; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013957:Thyroid Cartilage / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Head and neck squamous cell carcinoma; Larynx; Positron emission tomography; Thyroid cartilage