A Quantitative Evaluation of Hepatic Uptake on I-131 Whole-Body Scintigraphy for Postablative Therapy of Thyroid Carcinoma

摘要

This study aimed to determine clinical association between quantitative hepatic uptake on postablative whole-body scan (WBS) with differentiated thyroid cancer (DTC) prognosis.We analyzed 541 scans of 216 DTC patients who were divided into 3 groups based on radioactive iodine (I-131) WBS uptake and clinical follow-up: group 1 (completion of ablation), group 2 (abnormal uptake in the cervical region), and group 3 (abnormal uptake with distant metastases). For each group, we calculated the ratio of I-131 WBS hepatic uptake (H) to cranial uptake as background (B); this ratio was defined as H/B. Furthermore, we made a distinction between group 1, as having completed radioactive iodine therapy (RIT) (CR), and group 2 and 3, as requiring subsequent RIT (RR).The average H/B scores were 1.34 (median, 1.36; range 1.00-2.1) for group1; 1.89 (median, 1.75; range 1.41-4.20) for group 2; and 2.09 (median, 1.90; range 1.50-4.32) for group 3. Bonferroni multiple comparisons revealed significant differences in H/B among these groups. The H/B of group 1 was significantly smaller than that of other 2 groups (P<0.0001). The precise cutoff value of H/B for therapeutic effect was 1.5. Moreover, 159 of 160 scans in the CR and 375 of 381 patients in the RR were correctly diagnosed using this cutoff value in the final outcome of RIT, yielding a sensitivity, specificity, positive predictive value, and negative predictive value of 99.4%, 98.4%, 99.7%, and 96.3%, respectively.Increased hepatic uptake of I-131 on WBS may predict disease-related progression.