Materials and Methods
This study included 194 patients (35 males, 159 females) diagnosed consecutively between 1987 and 1998 with differentiated thyroid cancer and treated by total thyroidectomy and remnant ablation with 100150 mCi of 131I, following the protocol established by the Thyroid Unit of the Servicio Navarro de Salud.
All patients underwent 131I-WBS between 6 and 9 months after ablative doses, and Tg serum levels were also determined coinciding with the scans.
Forty-nine patients (20.1%) with positive anti-TgAb and/or distant metastasis at diagnosis were excluded.
The mean age was 43.7 ± 14.1 years. Histologic types were distributed as follows: 124 (63.9%) papillary carcinomas, 53 (27.3%) follicular, and 17 (8.8%) Hürtle cell type. According to the classification of De Groot et al., 149 patients (76.8%) presented with grade 1 or locally limited tumor, 26 patients (13.4%) were grade 2, and 19 (9.8%) were grade 3.
During the follow-up period, a clinical examination and neck ultrasound were carried out at least annually. During the first 3 years of follow up, diagnostic 131I-WBS and measurement of Tg levels off levothyroxine were carried out every year. Afterwards, these determinations were done at longer intervals. When Tg levels off levothyroxine were detected, other radiologic methods such as computed tomography (CT) scan, magnetic resonance imaging (MRI), and positron emission tomography (PET) were used to determine the localization of tumor. Mean follow-up was 7.7 ± 3.5 years.
Tg level measurement was carried out using a commercial immunoradiometric assay (IRMA Pasteur, E.R.I.A., Paris, France) with a functional sensitivity of 0.5 ng/mL. Patients were screened for serum anti-Tg Ab (IRMA, Sorin Biomedica Diagnostics, Saluggia, Italy) at the same time.
Radioiodine whole body scans (131I-WBS) were carried out after withdrawal of levothyroxine for at least 1 month and after confirmation of TSH levels of greater than 30 mUI/mL. Patients were advised to adopt a low dietary intake of iodine 15 days before the scan. Scans were carried out with a General Electric (Milwaukee, WI) gamma camera, using a high-energy collimator, 4872 hours after tracer doses of 10 mCi 131I were administered. Anterior and posterior images were obtained and each projection took at least 30 minutes.
Persistence or recurrence of the disease was defined either as a level of plasma Tg higher than 2 ng/mL off levothyroxine or a positive uptake outside the thyroid bed after 131I-WBS or the presence of disease demonstrated by other image methods.
Thyroid. 2004;14(4) © 2004 Mary Ann Liebert, Inc.
Cite this: Prognostic Value of Thyroglobulin Serum Levels and 131I Whole-Body Scan after Initial Treatment of Low-Risk Differentiated Thyroid Cancer - Medscape - Apr 01, 2004.