Radioiodine ablation in thyroid cancer patients: renal function and external radiation dose rate at discharge according to patient preparation.

BACKGROUND: An elevated thyroid stimulating hormone (TSH) level is essential for the uptake of radioiodine into thyroid remnants and residual thyroid cancer in patients undergoing high-dose radioiodine therapy (HD-RIT). Recently, the use of recombinant human thyroid stimulating hormone (rh-TSH) has increased in preference over the conventional method of thyroid hormone withdrawal (THW). However, the clinical influences of the two methods, aside from the therapeutic effects, have not been widely evaluated. The aim of this work was to investigate the influences of the two methods, particularly on the renal function and external radiation dose rate (EDR) from patients undergoing HD-RIT. METHODS: From February 2012 to November 2016, 667 patients (M:F=138:529, mean age: 47.7±11.8 years), who underwent first HD-RIT (120, 150, or 180 mCi, 1 mCi=37 MBq) for ablation of remnant thyroid tissue or residual thyroid cancer, were enrolled. Patients who were proven to have distant metastasis to lung or bone were excluded. Low- to high-risk patients based on 2015 American thyroid association management guidelines who underwent first HD-RIT in our department were included. The period from total thyroidectomy to HD-RIT was limited within 12 months. The following parameters were collected and evaluated: age, gender, histology type and TNM stage of thyroid cancer, glomerular filtration rate on the admission day for total thyroidectomy (baseline GFR), GFR on the day of HD-RIT (follow-up GFR), thyroglobulin (Tg) and TSH levels on the day of HD-RIT, and EDR on the discharge day after HD-RIT. RESULTS: There were 386 patients using the THW method and 281 patients choosing the rh-TSH method. The baseline GFR of the THW group (106±16 mL/min/1.73 m2) and that of the rh-TSH group (104±17 mL/min/1.73 m2) were within normal limits and there was no significant difference. However, follow-up GFR of the THW group (84±17 mL/min/1.73 m2) was much lower than that of the rh-TSH group (104±16 mL/min/1.73 m2) (P=0.000). In the THW group, the follow-up GFR decreased significantly (P=0.000), yet the follow-up GFR of the rh-TSH group was not statistically different when compared with its baseline GFR (P=0.142). EDRs were lower in all rh-TSH subgroups compared to those of THW subgroups with statistical significance. Tg and TSH levels were not different between the two groups, excluding a few small-sized subgroups analyses. CONCLUSIONS: In this retrospective analysis of renal function and EDR, the use of rh-TSH appears to help maintain renal function and finally decrease EDR in contrast to the THW method when undergoing HD-RIT.

Clinical value of intratumoral metabolic heterogeneity in [18F]FDG PET/CT for prediction of recurrence in patients with locally advanced colorectal cancer.

BACKGROUND: The aim of this study was to find a reliable predictor of recurrence in patients with locally advanced colorectal cancer. METHODS: We enrolled 96 patients for this retrospective study. We investigated metabolic (SUVmax, metabolic tumor volume, total lesion glycolysis, and heterogeneity), clinical (age, sex, stage, and CEA level) and pathologic (Ki-67, p53, CD31, COX-2, E-cadherin and EGFR) parameters. The coefficient of variation (COV) was chosen to assess heterogeneity of [18F]FDG uptake by dividing the standard deviation of the SUV by SUVmean. Recurrence-free survival was compared with each metabolic, clinical and pathologic parameters by using univariate and multivariate survival analysis. RESULTS: Among 96 patients, 19 patients (19.8%) showed disease recurrence. In the ROC analysis, the optimal cutoff values of SUVmax, metabolic tumor volume (cm3), total lesion glycolysis (cm3), and metabolic heterogeneity were determined as 17.6, 10.05, 232.46, and 0.48, respectively. In univariate analysis, probability of recurrence was statistically increased in those with metabolic tumor volume >10.05 (P=0.045), and those with metabolic heterogeneity >0.48 (P=0.031). In multivariate analysis, metabolic heterogeneity was the only independent prognostic factor (HR 4.56, 95% CI 1.57-13.23, P=0.006). CONCLUSIONS: Intratumoral metabolic heterogeneity assessed by COV is a reliable predictive factor for disease recurrence in patients with locally advanced colorectal cancer. Therefore, its application could be an important step for personalized management of colorectal cancer.

Imatinib analogs as potential agents for PET imaging of Bcr-Abl and c-KIT expression at a kinase level.

We synthesized two series of imatinib mesylate (STI-571) analogs to develop a Bcr-Abl and c-KIT receptor-specific labeling agent for positron emission tomography (PET) imaging to measure Bcr-Abl and c-KIT expression levels in a mouse model. The methods of molecular modeling, synthesis of STI-571 and its analogs, in vitro kinase assays, and radiolabeling are described. Molecular modeling revealed that these analogs bind the same Bcr-Abl and c-KIT binding sites as those bound by STI-571. The analogs potently inhibit the tyrosine kinase activity of Bcr-Abl and c-KIT, similarly to STI-571. [(18)F]-labeled STI-571 was prepared with high specific activity (75 GBq/µmol) by nucleophilic displacement and an average radiochemical yield of 12%. [(131)I]-labeled STI-571 was prepared with high purity (>95%) and an average radiochemical yield of 23%. The uptake rates of [(18)F]-STI-571 in K562 cells expressing Abl and in U87WT cells overexpressing c-KIT were significantly higher than those in the U87 cell and could be inhibited by STI-71 (confirming the specificity of uptake). PET scans of K562 and U87WT tumor-bearing mice with [(18)F]-STI-571 as a contrast agent showed visible tumor uptake and tumor-to-non-target contrast.