title: Evaluating the prognostic factors associated with cancer-specific survival of differentiated thyroid carcinoma presenting with distant metastasis.
abstract: BACKGROUND
  Because patients with differentiated thyroid carcinoma (DTC) presenting with distant metastasis (DM) have a particularly poor prognosis, examining the prognostic factors in this group is essential. We aimed to evaluate the prognostic factors affecting cancer-specific survival (CSS) in DTC patients presenting with DM.
  
  
  METHODS
  Of the 1227 DTC patients, 51 (4.2 %) presented with DM at diagnosis. All patients underwent a total thyroidectomy, followed by radioiodine (RAI) ablation and postablation whole body scan (WBS). Patients were considered to have an osseous metastasis if one of the metastatic sites involved a bone, while RAI avidity was determined by any visual uptake in a known metastatic site on the first WBS. Factors predictive of CSS were determined by univariate and multivariate analyses by the Cox proportional hazard model.
  
  
  RESULTS
  In univariate analysis, older age (relative risk [RR] 1.050, 95 % confidence interval [CI] 1.010-1.091, P = 0.014), DM discovered before WBS (RR 3.401, 95 % CI 1.127-10.309, P = 0.030), follicular thyroid carcinoma (RR 3.095, 95 % CI 1.168-8.205, P = 0.025), osseous metastasis (RR 4.695, 95 % CI 1.379-15.873, P = 0.013), non-RAI avidity (RR 3.355, 95 % CI 1.280-8.772, P = 0.014), and external beam radiotherapy to DM (RR 3.241, 95 % CI 1.093-9.614, P = 0.034) were significant poor prognostic factors for CSS. In the multivariate analysis, after adjusting for other factors, osseous metastasis (RR 6.849, 95 % CI 1.495-31.250, P = 0.013) and non-RAI avidity (RR 7.752, 95 % CI 2.198-27.027, P = 0.001) were the two independent poor prognostic factors for CSS. Older age almost reached statistically significance (RR 1.055, 95 % CI 0.996-1.117, P = 0.068).
  
  
  CONCLUSIONS
  DTC patients presenting with DM accounted for 4.2 % of all patients. Because osseous metastasis and RAI avidity were independent prognostic factors, future therapy should be directed at improving the treatment efficacy of osseous and/or non-RAI-avid metastases.
authors.affiliation: Department of Surgery, The University of Hong Kong, Hong Kong SAR, China. blang@hku.hk
authors.forename: Brian Hung-Hin
authors.initials: BH
authors.lastname: Lang
authors.forename: Kai Pun
authors.initials: KP
authors.lastname: Wong
authors.forename: Chung Yeung
authors.initials: CY
authors.lastname: Cheung
authors.forename: Koon Yat
authors.initials: KY
authors.lastname: Wan
authors.forename: Chung-Yau
authors.initials: CY
authors.lastname: Lo
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000401:mortality* / Q000556:secondary / Q000628:therapy; D000293:Adolescent; D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000401:mortality* / Q000556:secondary / Q000628:therapy; D002291:Carcinoma, Papillary / Q000401:mortality* / Q000556:secondary / Q000628:therapy; D017115:Catheter Ablation; D002648:Child; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000401:mortality / Q000556:secondary / Q000628:therapy; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D011446:Prospective Studies; D015996:Survival Rate; D013964:Thyroid Neoplasms / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D013965:Thyroidectomy / Q000401:mortality*; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes