Prognostic value of recombinant TSH-stimulated thyroglobulin determination in follow-up of differentiated thyroid cancer
Javier Santamaria, Maria Dolores Moure, Teresa Ruiz-Azua, Maria Angeles Aniel-Quiroga & Maria Sonia Gaztambide
Introduction: There is no known reliability about an undetectable recombinant human TSH (rhTSH) stimulated serum thyroglobulin (Tg) concentrations, predicts no long-term relapse, or the threshold of it. An rhTSH-stimulated serum Tg determination was made to all patients with DTC that maintained undetectable baseline Tg and negative imaging tests. We correlate their findings with their long-term evolution.
Methods: We collected 91 patients with DTC, 73 women and 18 men, 75 papillar, 16 follicular. All had a total thyroidectomy and I-131ablation before performing the test (mean 79.6±82.9, median 40 months). All cases had a successful treatment: negative imaging tests, undetectable rhTSH-stimulated serum Tg, and negative anti-Tg-Abs. We correlated these results with clinical outcome. Follow-up time until the last query or to the detection of recurrence was 31.1±19.9, median: 30 months.
Results: At the end of follow-up period recurrence was detected in 4 cases. Another 8 cases had Tg> 2 ng/ml but without either imaging or pathologic testing of tumor recurrence.
Conclusions: The measured of stimulated serum thyroglogulin is imperative, 9% of our cases with undetectable basal Tg shows a positive stimulation. Although detection of recurrence is more frequent with increasing the stimulated Tg level, there is no value that ensures the absence of recurrence, so these patients should be monitored indefinitely. The presence of lymphadenopathy at the time of diagnosis is the major predictor of recurrence in this group of patient.