title: Diagnostic value of metabolic heterogeneity as a reliable parameter for differentiating malignant parotid gland tumors.
abstract: OBJECTIVE
  Exact classifying between malignant and benign tumors in the parotid gland is important because the cancer has relatively poor prognosis. There have been several studies that F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) can differentiate between malignant and benign parotid gland tumors. However, the role of FDG PET is still controversial because many benign parotid gland tumors, such as Warthin's tumor and pleomorphic adenoma, show high FDG uptake. We hypothesized that metabolic heterogeneity would differentiate malignant parotid tumors because tumoral heterogeneity is an important characteristic in the malignancies.
  
  
  METHODS
  From January 2010 to April 2015, we retrospectively reviewed the 46 patients who showed FDG uptake at the parotid gland. To differentiate malignant parotid gland tumors, we obtained maximum SUV and mean SUV. Metabolic tumor volume and total lesion glycolysis were measured as metabolic volumetric parameters. We also included heterogeneity parameters of FDG PET such as heterogeneity factor (HF) and the coefficient of variation for all patients.
  
  
  RESULTS
  There was significant difference of HF between malignant (-0.30 ± 0.25; range -0.937 to -0.084) and benign parotid gland tumors (-0.06 ± 0.05; range -0.291 to -0.012; p < 0.0001). In receiver operating characteristic analysis, when ≤-0.084 was used as the cut-off value for HF, the sensitivity and specificity were 100 % (95 % CI 81.5-100) and 89.2 % (95 % CI 71.8-97.7), respectively. HF showed the highest area under the curve of 0.947 among the parameters. In logistic regression analysis, the HF was the most powerful factor for differentiation of the parotid gland tumors (p = 0.002).
  
  
  CONCLUSIONS
  Our results suggest that HF can be utilized as a reliable and non-invasive method for differentiation of malignant and benign parotid gland tumors.
authors.affiliation: Department of Nuclear Medicine, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan, 602-739, Republic of Korea.|Biomedical Research Institute, Pusan National University Hospital, Busan, Republic of Korea.
authors.forename: Bum Soo
authors.initials: BS
authors.lastname: Kim
authors.affiliation: Department of Nuclear Medicine, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan, 602-739, Republic of Korea. growthkim@daum.net.|Biomedical Research Institute, Pusan National University Hospital, Busan, Republic of Korea. growthkim@daum.net.
authors.forename: Seong-Jang
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Nuclear Medicine, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan, 602-739, Republic of Korea.|Biomedical Research Institute, Pusan National University Hospital, Busan, Republic of Korea.
authors.forename: Kyoungjune
authors.initials: K
authors.lastname: Pak
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D010307:Parotid Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D000072078:Positron Emission Tomography Computed Tomography; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D019788:Fluorodeoxyglucose F18
keywords: FDG PET; Heterogeneity; Parotid gland tumor