Treatment of iodine-negative thyroglobulin-positive thyroid cancer: differences in outcome in patients with macrometastases and patients with micrometastases.

PURPOSE: During the follow-up of patients with well-differentiated thyroid carcinoma, some patients have elevated serum thyroglobulin (Tg) levels without any evidence of radioiodine accumulation on diagnostic whole-body scan (d-WBS). The treatment strategy in these patients is considered a clinical dilemma, with some groups recommending blind use of high-dose radioiodine therapy. The aim of this study was to evaluate whether or not high doses of radioiodine have beneficial effects in these patients.

METHODS: Twenty-seven patients were included in the study. All patients had negative d-WBS and elevated levels of Tg. All received high doses of radioiodine. The mean follow-up period was 6.3+/-5.8 years. There were 11 patients with macrometastases and 16 with micrometastases.

RESULTS: Post-treatment WBS revealed radioiodine accumulation in 19 of 24 (79%) patients. Serum Tg levels were decreased in 8 of 16 (50%) patients. Among patients with micrometastases, five out of seven (71%) demonstrated a decrease in serum Tg levels. Among patients with macrometastases, three out of nine (33%) demonstrated a decrease in Tg values and three (33%) have died due to metastatic thyroid cancer.

CONCLUSION: Radioiodine treatment may have a beneficial therapeutic effect in patients who have elevated levels of serum Tg and negative d-WBS. This is especially true in those patients with micrometastases; in patients with macrometastases, a beneficial effect of this approach may be observed less frequently.