Relationship between thyroglobulin and reliability of thallium 201 scintigraphy in differentiated thyroid cancer
Brandt-Mainz, K.; Müller, S.P.; Reiners, C.; Bockisch, A.
Nuklearmedizin. Nuclear Medicine 39(1): 20-25
2000
ISSN/ISBN: 0029-5566 PMID: 10726253 Document Number: 525317
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. 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%). 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. 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.