Validity of thyroglobulin mRNA assay in peripheral blood of postoperative thyroid carcinoma patients in predicting tumor recurrences varies accordingto the histologic type - Results of a prospective study

BACKGROUND. The objective of the current study was to evaluate the ability of serum thyroglobulin mRNA assay in detecting local and distant recurrence s in patients who underwent surgery for thyroid carcinoma. METHODS. Sixty-six consecutive patients were studied. One year after surger y, 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 prim ers for Tg. RESULTS. Thyroglobulin mRNA was detected in 14 (21.2%) patients. Seven of 1 6 patients with elevated serum thyroglobulin had detectable Tg mRNA. Six of 30 (20%) patients with absent or minimal thyroid bed radioiodine uptake an d 7 of 36 (19.4%) patients with significant thyroid bed uptake had detectab le Tg mRNA. Among 5 patients with metastases, only 1 (20%) showed circulati ng Tg mRNA. Overall, the sensitivity, specificity, and accuracy of Tg mRNA assay in predicting the results of the I-131 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 wi th other histologic types did. The sensitivity, specificity, and accuracy o f Tg mRNA assay in predicting the results of the I-131 whole-body scans in patients with papillary thyroid carcinoma was 100%, 75%, and 100%, respecti vely. Of note, the percentage of cases with detectable Tg mRNA was similar among patients who did not receive postoperative I-131 and those who had po stoperative radioiodine treatment. CONCLUSIONS. The current study suggests that the validity of the Tg mRNA as say varies according to the histologic type of thyroid carcinoma and that t his assay may play a role in the identification of metastatic disease in th e subgroup of patients affected by papillary thyroid carcinoma but does not appear to be sensitive or active enough to direct clinical management. (C) 2001 American Cancer Society.