title: Positive predictive value of serum thyroglobulin levels, measured during the first year of follow-up after thyroid hormone withdrawal, in thyroid cancer patients.
abstract: The follow-up of patients with papillary and follicular thyroid carcinoma after thyroidectomy and radioiodine ablation is mainly based on serum thyroglobulin (Tg) level deter-mination. The positive predictive value (PPV) of serum Tg level after thyroid hormone withdrawal, measured during the first 6-12 months of follow-up (initial off L-T(4) Tg), was studied in 256 consecutive differentiated thyroid cancer patients. All underwent a total thyroidectomy and 3.7 GBq (131)I ablation; 37 patients had an elevated initial off L-T(4) Tg level. This study focuses on these 37 patients, 9 of whom had a clinical recurrence. The present data confirm that in this selected cohort of patients, 74-185 MBq (131)I-total body scan (TBS) has no clinical interest in the initial work-up and during the subsequent follow-up because it was negative in all patients, except in one with recurrent disease. The PPV of initial serum off L-T(4) Tg level above 5 ng/ml and 10 ng/ml was 42% and 53%, respectively; this PPV was only 50% at the time of recurrence or subsequent control. This relatively low PPV is related to the low recurrence rate in this series of patients, despite a prolonged follow-up, and to the subsequent decrease of serum Tg level in 14 of 37 (38%) patients in the absence of any further treatment. In contrast, the PPV of the increasing slope of serum Tg levels obtained after thyroid hormone withdrawal (83%) was excellent. In conclusion, we confirm that (131)I-TBS has a limited interest for the follow-up of thyroid cancer patients. Follow-up should rely on serum Tg level and prognostic parameters; however, initial serum Tg may be produced by thyroid tissues of various significance, an increase at two consecutive determinations indicating disease progression and a decrease being related to late effects of therapy. The best PPV is brought by the slope of serum Tg levels.
authors.affiliation: Department of Nuclear Medicine and Endocrine Tumors, Institut Gustave Roussy, Villejuif, France 94805.
authors.forename: E
authors.initials: E
authors.lastname: Baudin
authors.forename: C
authors.initials: C
authors.lastname: Do Cao
authors.forename: A F
authors.initials: AF
authors.lastname: Cailleux
authors.forename: S
authors.initials: S
authors.lastname: Leboulleux
authors.forename: J P
authors.initials: JP
authors.lastname: Travagli
authors.forename: M
authors.initials: M
authors.lastname: Schlumberger
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000097:blood* / Q000628:therapy; D000293:Adolescent; D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000097:blood* / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D013954:Thyroglobulin / Q000097:blood*; D013963:Thyroid Hormones / Q000627:therapeutic use*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000628:therapy
chemical_list: D007457:Iodine Radioisotopes; D013963:Thyroid Hormones; D013954:Thyroglobulin