Surveillance of patients to detect recurrent thyroid carcinoma

BACKGROUND The purpose of this study was to evaluate the utility of surveillance with annual whole‐body iodine‐131 ( 131 I) 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 postoperative 131 I therapy, and had at least 1 negative whole‐body 131 I scintigraphy 1 year after 131 I therapy. There were 59 females and 17 males (age range, 12–74 years). Surgery consisted of a total thyroidectomy for 84% of patients and a subtotal thyroidectomy for 16%. 131 I was administered within 1 month of thyroidectomy and annually thereafter until complete ablation of remaining thyroid tissue occurred. Annual follow‐up diagnostic whole‐body 131 I scintigraphy was performed at Years 1 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 131 I (median, 1). The administered activity per treatment was 30–211 mCi, and the total activity administered that was necessary to achieve complete ablation of functioning thyroid tissue ranged from 30 to 514 mCi (median, 100 mCi). The relapse free survival at both 5 and 10 years was 88%. By definition, all of these patients had a negative 131 I scintigraphy at 1 year after their last therapeutic 131 I administration. Seven patients had a positive 131 I scintigraphy 1 year after the first negative scintigraphy. Two other patients had positive 131 I images after 2 consecutive negative annual 131 I scintigraphic studies. The predictive value for relapse free survival of 1 negative diagnostic 131 I study of these patients was 91% (± 0.02), and for 2 consecutive annual negative 131 I studies the value was 97% (± 0.02); these results were significantly different ( P = 0.0197). A stepwise logistic regression analysis was performed in an effort to identify risk factors for disease recurrence after complete ablation. None of the variables assessed—age, gender, tumor histology, tumor size, vascular invasion, capsular invasion, surgical margin status, or lymph node status—was predictive of recurrence after complete ablation. CONCLUSIONS A single negative 131 I scintigraphic study after complete ablation has a lower predictive value for relapse free survival than do two consecutive annual negative studies. Annual 131 I imaging is recommended for surveillance until 2 consecutive annual negative studies are obtained, after which repeat imaging at 3–5 years appears to be satisfactory. Cancer 1999;85:945–51. © 1999 American Cancer Society.