Validity of thyroglobulin mRNA assay in peripheral blood of postoperative thyroid carcinoma patients in predicting tumor recurrences varies according to the histologic type

Abstract

BACKGROUND The objective of the current study was to evaluate the ability of serum thyroglobulin mRNA assay in detecting local and distant recurrences in patients who underwent surgery for thyroid carcinoma. METHODS Sixty‐six consecutive patients were studied. One year after surgery, all patients underwent clinical examination and radioiodine scan, and a blood sample was taken for serum thyroglobulin (Tg) immunoassay and for Tg mRNA assay by reverse transcription–polymerase chain reaction (RT‐PCR). RNA was extracted from cells pellet and analyzed by RT‐PCR using specific primers for Tg. RESULTS Thyroglobulin mRNA was detected in 14 (21.2%) patients. Seven of 16 patients with elevated serum thyroglobulin had detectable Tg mRNA. Six of 30 (20%) patients with absent or minimal thyroid bed radioiodine uptake and 7 of 36 (19.4%) patients with significant thyroid bed uptake had detectable Tg mRNA. Among 5 patients with metastases, only 1 (20%) showed circulating Tg mRNA. Overall, the sensitivity, specificity, and accuracy of Tg mRNA assay in predicting the results of the ¹³¹I whole‐body scans was 25%, 80%, 25%, respectively. Fourteen of 53 (26.4%) patients with papillary thyroid carcinoma had detectable thyroglobulin mRNA whereas none of the patients with other histologic types did. The sensitivity, specificity, and accuracy of Tg mRNA assay in predicting the results of the ¹³¹I whole‐body scans in patients with papillary thyroid carcinoma was 100%, 75%, and 100%, respectively. Of note, the percentage of cases with detectable Tg mRNA was similar among patients who did not receive postoperative ¹³¹I and those who had postoperative radioiodine treatment. CONCLUSIONS The current study suggests that the validity of the Tg mRNA assay varies according to the histologic type of thyroid carcinoma and that this assay may play a role in the identification of metastatic disease in the subgroup of patients affected by papillary thyroid carcinoma but does not appear to be sensitive or active enough to direct clinical management. Cancer 2001;92:2273–9. © 2001 American Cancer Society.