Clinical significance of diffuse hepatic uptake on post-therapeutic early and delayed 131I scan in differentiated thyroid cancer: a preliminary report

The purpose of this study was to investigate the clinical significance of diffuse hepatic uptake on post-therapeutic early and delayed I-131 scan in patients with differentiated thyroid cancer (DTC). We retrospectively analyzed 219 DTC patients who underwent high-dose I-131 treatment and subsequent post-therapeutic dual I-131 scan. Both early (third day after I-131 treatment) and delayed (5-6th day after I-131 treatment) I-131 scan images were visually assessed and diffuse hepatic uptake was scored using a 4-point grading system depending on intensity. On early I-131 scan, 73 patients (33.4 %) showed diffuse hepatic uptake, while 191 patients (87.2 %) patients showed diffuse hepatic uptake on delayed scan (p < 0.0001). The serum levels of ALT in patients with diffuse hepatic uptake on early scan were higher than those without diffuse hepatic uptake on early scan (p = 0.03 for ALT and p = 0.08 for AST). The serum levels of ALT and AST trended with the grade of hepatic uptake on delayed scan (p = 0.03 for ALT and p = 0.05 for AST). Diffuse hepatic uptake on early or delayed scan showed no significant relationship in the presence of thyroid remnants, metastatic DTC lesions, tumor recurrence during follow-up, and the serum thyroglobulin level (p > 0.05). On logistic regression analysis, both serum ALT (p = 0.01) and AST (p = 0.04) levels were significant predictive factors for diffuse hepatic uptake on early scan, while only serum ALT (p = 0.01) level was significant predictive factor for diffuse hepatic uptake on delayed scan. The frequency of diffuse hepatic uptake on the delayed scan was significantly higher than the early scan. Diffuse hepatic uptake on early post-therapeutic scan and the intensity of diffuse hepatic uptake on delayed scan showed significant correlation with the serum levels of hepatic enzymes, but no significant association in the presence of thyroid remnants, metastatic DTC lesions, and tumor recurrence during follow-up. The timing and intensity of diffuse hepatic uptake on post-therapeutic scan may be related with factors such as hepatic function other than the thyroid tissue or DTC.