title: Prognostic implication of thyroglobulin and quantified whole body scan after initial radioiodine therapy on early prediction of ablation and clinical response for the patients with differentiated thyroid cancer.
abstract: OBJECTIVE
  To investigate predictors for successful ablation and disease-free status after high-dose radioiodine therapy in patients with differentiated thyroid cancer.
  
  
  METHODS
  We enrolled 173 consecutive patients with differentiated thyroid cancer between November 2001 and December 2004 retrospectively (female 145, 46 ± 12 years). All patients underwent total thyroidectomy and I-131 ablative therapy (IAT) (3.7-5.4 GBq). The success or failure of ablation was assessed 6-9 months after the IAT with reference to undetectable thyroglobulin (Tg) and negative I-131 whole body scan (WBS). Afterward, the decision for disease-free status was evaluated using Tg and WBS (follow-up period after 1st IAT 7-81 months, median 43 months, criteria of disease-free: less than 10 ng/ml TSH-stimulated Tg or less than 2 ng/ml TSH-unstimulated Tg and/or negative WBS). Clinical and tumoral factors such as sex, age, pathologic type, the size of tumor, quantified cervical uptake in WBS1, pattern in WBS1, ablative therapy dose, AJCC stage, lymph node (LN) stage, Tg just before IAT (Tg1), and ablation status were assessed using logistic regression analyses.
  
  
  RESULTS
  There were 93 successful ablations (54 %). Significant predictors for the ablation failure were Tg1 (OR = 8.42; 95 % CI = 2.76-25.69; p < 0.0001), LN metastasis (OR = 3.05; 95 % CI = 1.11-8.37; p = 0.031), and quantified cervical uptake in WBS1 (OR = 4.95; 95 % CI = 1.07-22.88; p = 0.041). One hundred fifty-five patients were determined as disease-free after follow-up. All the eighteen patients with persistent disease were identified as ablation failure after first IAT. Significant predictors for the disease-free status were Tg1 (OR = 0.98; 95 % CI = 0.97-0.99; p = 0.028), tumor size (OR = 0.53; 95 % CI = 0.28-0.96; p = 0.044), and quantified cervical uptake in WBS1 (OR = 0.87; 95 % CI = 0.76-0.98; p = 0.024).
  
  
  CONCLUSIONS
  The thyroglobulin and quantified cervical uptake in whole body scan are significant predictors for the successful ablation and disease-free status after follow-up.
authors.affiliation: Department of Nuclear Medicine, Korea Cancer Center Hospital, Seoul, Korea.
authors.forename: Ilhan
authors.initials: I
authors.lastname: Lim
authors.forename: Seok-Ki
authors.initials: SK
authors.lastname: Kim
authors.forename: Seung-Sik
authors.initials: SS
authors.lastname: Hwang
authors.forename: Sun Wook
authors.initials: SW
authors.lastname: Kim
authors.forename: Ki Wook
authors.initials: KW
authors.lastname: Chung
authors.forename: Han Sung
authors.initials: HS
authors.lastname: Kang
authors.forename: Eun Sook
authors.initials: ES
authors.lastname: Lee
mesh_terms: D055011:Ablation Techniques; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012737:Sex Factors; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000473:pathology / Q000532:radiotherapy*; D016896:Treatment Outcome; D047368:Tumor Burden; D051598:Whole Body Imaging; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D013954:Thyroglobulin