Does hepatic visualisation show residual/metastatic thyroid tissue in differentiated thyroid cancer?

Abstract

Aim: Diffuse homogen hepatic uptake in whole-body scan (WBS) after radioiodine remnant ablation (RRA) suggests that there is occult or visible remnant thyroid tissue and/or tumor tissue. It is thought that the reason is hepatic metabolization of radioiodine (1311) marked thyroglobulin fragments which are secreted by remnant/tumor tissue. The aims of this study were to investigate whether the hepatic visualisation after radioiodine remnant ablation showed the presence of metastatic or residual disease in patients with differentiated thyroid cancer and also to investigate whether early or late WBS after RRA (RxWBS) had an effect on the physiological hepatic uptake. Material and Method: 201 DTC patients were evaluated (F/M: 152/49; mean age: 49.61 +/- 13 years (range: 18-85 years)) who referred for RRA. The therapeutic 1311 dose ranged from 100mCi to 200mCi. RxWBS was performed earlier (in 1-4th-day after RRA) in 106 patients (Group 1) and was performed later (in 5-9th-day after RRA) in 95 patients (Group 2). Results: Diffuse hepatic uptake were seen only in three patients (2.8%) and was not seen in 103 patients (97.2%) in Group 1. However, in Group 2 diffuse hepatic uptake was seen in 93 patients (97.9%) (p<0.05) and not seen only in 2 patients (2.1%). There is not a statistically significant relationship between the hepatic uptake and serum Tg. LT4 and TSH level. There is a statistically significant relationship between anti-Tg level and hepatic uptake. Discussion: Physiological diffuse hepatic uptake of radioiodine in WBS after RRA may not be seen during the early WBS. Thus, metastatic foci may be missed with early scanning. We conclude that RxWBS after RRA should be done in late period.