Association between residual thyroid carcinoma and diffuse hepatic uptake of I-131 following radioiodine ablation in postoperative total thyroidectomy patients

In patients with differentiated thyroid cancer (DTC) total or near-total th yroidectomy, postoperative I-131 ablation, and thyroid suppression therapy are reported to be associated with fewer recurrences than other treatments. Many patients with DTC after total thyroidectomy and radioablation therapy have diffuse hepatic uptake of radioiodine, and its clinical importance is debated. Some investigators report that diffuse liver uptake correlates wi th uptake in the thyroid bed or the presence of metastatic thyroid cancer s omewhere in the body, whereas others note no such correlation. The purpose of this research was to determine the clinical importance of diffuse hepati c uptake of radioiodine after I-131 ablative therapy in patients with DTC, We retrospectively reviewed 141 posttherapy scans done in 118 patients with DTC. Patients had had total thyroidectomy and were hypothyroid when serum thyroglobulin (Tg) levels were obtained, and they were treated with 30 to 2 00 mCi of I-131. Scans were performed 3 to 21 days after radioablation ther apy. Information was collected regarding the patients' age and gender, the interval between the ablation therapy and scan, uptake of radioiodine, seru m thyroglobulin level, thyroid-stimulating hormone (TSH) level, thyroglobul in antibodies, TNM classification, mortality, and recurrence. Diffuse liver uptake was classified from 0 to 4 depending on hepatic brightness. Radioio dine scans were done to determine whether there was uptake in the thyroid b ed or elsewhere. Statistical analyses included analysis of variance and Kap lan-Meier survival analysis. Diffuse hepatic uptake was observed (grades 1- 4) in 96.4% of the patients; thus 3.6% had no hepatic uptake. There was no significant association between liver uptake and the uptake in the thyroid bed, the dose of I-131 administered for ablation therapy, thyroglobulin lev els, age, stage of the disease, presence of local or distant metastases, re currence, or survival. Diffuse hepatic uptake was therefore not associated with residual normal thyroid or metastases as suggested by some but not all previous investigators.