Surveillance of patients to detect recurrent thyroid carcinoma

BACKGROUND. The purpose of this study was to evaluate the utility of survei llance with annual whole-body iodine-131 (I-131) scintigraphy for patients with recurrent thyroid carcinoma. METHODS. The records of patients with thyroid carcinoma were reviewed. The 76 patients included in this study had undergone thyroidectomy and postoper ative I-131 therapy, and had at least 1 negative whole-body I-131 scintigra phy 1 year after I-131 therapy. There were 59 females and 17 males (age ran ge, 12-74 years). Surgery consisted of a total thyroidectomy for 84% of pat ients and a subtotal thyroidectomy for 16%. 131I was administered within 1 month of thyroidectomy and annually thereafter until complete ablation of r emaining thyroid tissue occurred. Annual follow-up diagnostic whole-body I- 131 scintigraphy was performed at Years I and 2, and then every 3-5 years. Some patients also had scintigraphy performed in Years 3, 4, and 5. RESULTS. Patients received 1-4 annual administrations of I-131 (median, 1). The administered activity per treatment was 30-211 mCi, and the total acti vity administered that was necessary to achieve complete ablation of functi oning thyroid tissue ranged from 30 to 514 mCi (median, 100 mCi). The relap se free survival at both 5 and IO years was 88%. By definition, all of thes e patients had a negative I-131 scintigraphy at 1 year after their last the rapeutic I-131 administration. Seven patients had a positive 131I scintigra phy 1 year after the first negative scintigraphy. Two other patients had po sitive I-131 images after 2 consecutive negative annual I-131 scintigraphic studies. The predictive value for relapse free survival of 1 negative diag nostic I-131 study Of these patients was 91% (+/- 0.02), and for 2 consecut ive annual negative I-131 studies the Value was 97% (+/- 0.02); these resul ts were significantly different (P = 0.0197). A stepwise logistic regressio n analysis was performed in an effort to identify risk factors for disease recurrence after complete ablation. None of the variables assessed-age, gen der, tumor histology, tumor size, Vascular invasion, capsular invasion, sur gical margin status, or lymph node status-was predictive of recurrence afte r complete ablation. CONCLUSIONS. A single negative I-131 scintigraphic study after complete abl ation has a lower predictive value for relapse free survival than do two co nsecutive annual negative studies. Annual I-131 imaging is recommended for surveillance until 2 consecutive annual negative studies are obtained, afte r which repeat imaging at 3-5 years appears to be satisfactory. (C) 1999 Am erican Cancer Society.