Prognostic role of undetectable ablation thyroglobulin and follow-up thyroglobulin in patients with thyroid cancer.

摘要

BackgroundThyroid epithelial cells are the sole source of thyroglobulin (Tg). Detection of Tg after thyroid ablation is, therefore, indicative of recurrent or persistent disease in patients with differentiated thyroid carcinoma (DTC).ObjectiveTo evaluate the prognostic role of serum Tg levels during follow-up of patients who were considered Tg-negative at the time of thyroid ablation.Design and InterventionThis was a retrospective study of consecutive patients with DTC who were treated at a single center in the Netherlands between 1989 and 2006. All participants were considered Tg-negative (< 1.5 mug/l) in the presence of TSH levels > 30mIU/l at the time of ablation. Patients underwent near-total thyroidectomy, followed by a diagnostic whole-body scan and radioablation with a 1.85-5.55 GBq dose of ~(131)I 4-6 weeks later. A post-ablation whole-body scan was performed after 10 days. The levels of serum Tg were assessed at ablation and during follow-up under conditions of endogenous TSH stimulation (i.e.hypothyroidism) and exogenous TSH suppression (i.e. after administration of levothyroxine). Serum Tg levels were measured by radioimmunoassay until March 2004, and with an immunochemiluminometric assay thereafter. Serum Tg-specific antibody (TgAb) is known to interfere with the Tg test. The presence of TgAb in Tg-negative serum sampleswas, therefore, determined with a standard Tg recovery test. After March 2004, however, serum TgAb levels were measured with an immunochemiluminometric assay.Outcome MeasuresThe main Outcome Measures included serum Tg levels, TgAb, tumor recurrence or persistence, and standardized survival rates.ResultsOnly 94 of the 346 patients assessed by the investigators met the inclusion criteria. The study cohort was predominantly female (84%), the age range was 16-89 years, the median duration of follow-up was 8 years, and the most common tumor type was papillary thyroid carcinoma (64 cases). A total of 64 patients were classified as high risk (age >= 40 years and with nodal or distant metastases). Persistent or recurrent disease was detected in eight high-risk patients during follow-up, three of whom became TgAb-positive and two of whom became Tg-positive during follow-up. The overall standardized survival rate of the study cohort was comparable to that of the original group of 346 patients (P = 0.91). Combined Tg-negativity and TgAb-negativity at the time of ablation was not a predictive factor for future recurrence. By contrast, patients who developed Tg-positivity or TgAb-positivity during follow-up had a reduced disease-free survival rate when compared with their Tg-negative and TgAb-negative peers (standardized survival 0.62 versus 0.93, P = 0.006). Histology and immunohistochemical staining for Tg were unable to predict disease recurrence.ConclusionMeasurement of serum Tg and TgAb levels during follow-up of patients considered Tg-negative at ablation might aid diagnosis of recurrent or persistent DTC.