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[Relationship between thyroglobulin and reliability of thallium 201 scintigraphy in differentiated thyroid cancer]
K Brandt-Mainz1, S P Müller, C Reiners
1Klinik und Poliklinik für Nuklearmedizin, Universitätskliniken Essen, Deutschland.
Aim:
Tumor scintigraphy with 201-TlCl is an established diagnostic method in the follow-up of differentiated thyroid cancer. We investigated the relationship between thyroglobulin (Tg) level and tumor detectability.
Subject And Methods:
We analyzed the scans of 122 patients (66 patients with proven tumor). The patient population was divided into groups with Tg above (N = 33) and below (N = 33) 5 ng/ml under TSH suppression or above (N = 33) and below (N = 33) 50 ng/ml under TSH stimulation. Tumor detectability was compared by ROC-analysis (True-Positive-Fraction test, specificity 90%).
Results:
There was no significant difference (sensitivity 75% versus 64%; p = 0.55) for patients above and below 5 ng/ml under TSH suppression and a just significant difference (sensitivity 80% versus 58%; p = 0.04) for patients above and below 50 ng/ml under TSH stimulation. In 18 patients from our sample with tumor, Tg under TSH suppression was negative, but 201-TlCl-scan was able to detect tumor in 12 patients.
Conclusion:
Our results demonstrate only a moderate dependence of tumor detectability on Tg level, probably without significant clinical relevance. Even in patients with slight Tg elevation 201-TlCl scintigraphy is justified.