Quantitative comparison of low dose and standard dose radioiodine therapy effectiveness in patients with low risk differentiated thyroid cancer.

BACKGROUND: The aim of this paper was to compare the results of postoperative I-131 remnant ablation therapy using a quantitative data in the low activity (1110 MBq) and standard dose (3700 MBq). METHODS: The study included two groups of patients with low risk differentiated thyroid cancer (DTC): Group L (low dose group) included 54 patients who were treated with 1110 MBq I-131 and Group S (standard dose group) included 61 patients treated with 3700 MBq. The postoperative thyroid remnants were assessed with the pretreatment thyroid uptake test (PTUT) and the whole body scans (WBS) were performed in the 7th day after the ablation treatment. We obtained the average count per pixel from the standard region of interest analysis of the thyroid bed (Tavc), liver (Lavc), thigh (Thavc) and whole body (WBkc). At the sixth month after the treatment, WBS were performed to 106 patients (45 patients from Group L and 61 patients from Group S) to evaluate the success of ablation treatment. RESULTS: A significant difference in PTUT and Tavc was not found between the two groups (P>0.05). However, Lavc, Thavc and WBkc were significantly higher in Group S compared with Group L (P<0.001). Although the percentage of ablation was higher in Group S (49 of 61 patients, 80.3% versus 34 of 45 patients, 75.6%), the statistical difference was not significant (P>0.05). CONCLUSIONS: In low risk DTC patients, low dose radioactive iodine can ablate thyroid remnants as effectively as a higher dose with less radiation exposure to other non-target organs and the whole body.

Combined imaging with 68Ga-DOTA-TATE and 18F-FDG PET/CT on the basis of volumetric parameters in neuroendocrine tumors.

AIM: To assess the additional contribution of the combined imaging approach with Ga-DOTA-TATE and fluorine-18 fluorodeoxyglucose (F-FDG) on the basis of volumetric parameters in neuroendocrine tumors (NETs). MATERIALS AND METHODS: Forty-one patients with NET (19 women, 22 men; age range: 30-79 years; mean age: 56.7±12.3 years) underwent Ga DOTA-TATE and F-FDG PET/computed tomography (CT) imaging. Within the drawn regions of interest, in addition to evaluating the maximum and mean standardized uptake values (SUVmax and SUVmean), the metabolic tumor volume (MTV) and total lesion glycolysis (TLG) in F-FDG PET/CT imaging, and the somatostatin receptor density and total lesion somatostatin receptor expression (TLSRE) in Ga somatostatin receptor imaging (SRI) were measured. The patients were graded on the basis of the proliferation index: well (G1; Ki-67 ≤2), moderately (G2; Ki-67=3-20), and poorly (G3; Ki-67>20) differentiated groups. RESULTS: Of the 41 NET patients, 22, 14, and five were in the G1 (53.7%), G2 (34.1%), and G3 (12.2%) groups, respectively. Liver metastases had significantly higher TLSRE values than the TLG values. Ki-67 levels showed a positive correlation with the primary tumor MTV and TLG values. Cg-A levels had a positive correlation with the volumetric parameters of the whole-body tumor burden (P<0.001). CONCLUSION: Ga SRI and F-FDG PET/CT provide complementary information on treatment protocol and response assessment. While assessing the prognosis and tumor aggressiveness, lesions and whole-body tumor burdens can be calculated on the basis of volumetric parameters by F-FDG PET/CT using MTV and TLG, and by Ga SRI using somatostatin receptor density and TLSRE.