title: Prognostic value of preoperative 18F-FDG PET/CT in papillary thyroid cancer patients with a high metastatic lymph node ratio: a multicenter retrospective cohort study.
abstract: OBJECTIVE
  Metastatic lymph node ratio (MLNR) is a known significant predictor of disease-free survival in differentiated thyroid cancer. The authors investigated the ability of preoperative fluorine-18 fluorodeoxyglucose (F-FDG) PET/CT to predict recurrence after surgery with radioactive iodine therapy considering MLNR.
  
  
  METHODS
  A total of 274 patients who underwent preoperative PET/CT and surgery with radioactive iodine therapy were enrolled. The tumor-to-liver uptake ratio on PET/CT was calculated by dividing the maximum standardized uptake value of a primary lesion by the mean standardized uptake value of the normal liver. High F-FDG uptake was defined as tumor-to-liver uptake ratio more than the median cutoff value (2.1). MLNR was calculated by dividing the number of metastatic lymph nodes (LNs) by the number of cervical LNs removed. A high MLNR was also defined as one more than a threshold value (0.4), identified by plotting Kaplan-Meier survival curves and comparing them using the log-rank test. The prognostic significances of clinicopathologic variables were analyzed.
  
  
  RESULTS
  Fifteen (5.5%) patients developed recurrence in the thyroid bed or in cervical LNs. Cox regression analysis showed that a high MLNR was significantly associated with a worse disease-free survival (odds ratio 6.95; 95% confidence interval: 2.36-20.47; P<0.001). A subgroup analysis of 70 patients with a high MLNR showed that only high F-FDG uptake was significantly associated with a worse disease-free survival (odds ratio 5.77; 95% confidence interval: 1.22-27.16; P=0.027).
  
  
  CONCLUSIONS
  High F-FDG uptake of primary lesion on preoperative PET/CT has selective prognostic value according to the extent of metastatic LNs (MLNR>0.4).
authors.affiliation: aDepartment of Nuclear Medicine, Chonnam National University Hwasun Hospital bDepartment of Radiology, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea cDepartment of Nuclear Medicine, Yeungnam University Medical School and Hospital dDepartment of Nuclear Medicine, Chosun University Hospital eDepartment of Nuclear Medicine, Chonnam National University Hospital fDepartment of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea.
authors.forename: Seong Young
authors.initials: SY
authors.lastname: Kwon
authors.forename: Eun Kyoung
authors.initials: EK
authors.lastname: Choi
authors.forename: Eun Jung
authors.initials: EJ
authors.lastname: Kong
authors.forename: Ari
authors.initials: A
authors.lastname: Chong
authors.forename: Jung-Min
authors.initials: JM
authors.lastname: Ha
authors.forename: Kyung Ah
authors.initials: KA
authors.lastname: Chun
authors.forename: Ihn Ho
authors.initials: IH
authors.lastname: Cho
authors.forename: Hee-Seung
authors.initials: HS
authors.lastname: Bom
authors.forename: Jung-Joon
authors.initials: JJ
authors.lastname: Min
authors.forename: Jahae
authors.initials: J
authors.lastname: Kim
authors.forename: Ho-Chun
authors.initials: HC
authors.lastname: Song
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: O
authors.forename: Sung Hoon
authors.initials: SH
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001692:Biological Transport; D002277:Carcinoma / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology*; D002291:Carcinoma, Papillary; D015331:Cohort Studies; D018572:Disease-Free Survival; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography; D012189:Retrospective Studies; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology*; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18