68Ga-EDTA PET/CT imaging and plasma clearance for glomerular filtration rate quantification: comparison to conventional 51Cr-EDTA.

UNLABELLED: Glomerular filtration rate (GFR) can accurately be determined using (51)Cr-ethylenediaminetetraacetic acid (EDTA) plasma clearance counting but is time-consuming and requires technical skills and equipment not always available in imaging departments. (68)Ga-EDTA can be readily available using an onsite generator, and PET/CT enables both imaging of renal function and accurate camera-based quantitation of clearance of activity from blood and its appearance in the urine. This study aimed to assess agreement between (68)Ga-EDTA GFR ((68)Ga-GFR) and (51)Cr-EDTA GFR ((51)Cr-GFR), using serial plasma sampling and PET imaging. METHODS: (68)Ga-EDTA and (51)Cr-EDTA were injected concurrently in 31 patients. Dynamic PET/CT encompassing the kidneys was acquired for 10 min followed by 3 sequential 3-min multibed step acquisitions from kidneys to bladder. PET quantification was performed using renal activity at 1-2 min (PETinitial), renal excretion at 2-10 min (PETearly), and, subsequently, urinary excretion into the collecting system and bladder (PETlate). Plasma sampling at 2, 3, and 4 h was performed, with (68)Ga followed by (51)Cr counting after positron decay. The level of agreement for GFR determination was calculated using a Bland-Altman plot and Pearson correlation coefficient (PCC). RESULTS: (51)Cr-GFR ranged from 10 to 220 mL/min (mean, 85 mL/min). There was good agreement between (68)Ga-GFR and (51)Cr-GFR using serial plasma sampling, with a Bland-Altman bias of -14 ± 20 mL/min and a PCC of 0.94 (95% confidence interval, 0.88-0.97). Of the 3 methods used for camera-based quantification, the strongest correlation was for plasma sampling-derived GFR with PETlate (PCC of 0.90; 95% confidence interval, 0.80-0.95). CONCLUSION: (68)Ga-GFR agreed well with (51)Cr-GFR for estimation of GFR using serial plasma counting. PET dynamic imaging provides a method to estimate GFR without plasma sampling, with the additional advantage of enabling renal imaging in a single study. Additional validation in a larger cohort is warranted to further assess utility.

High-administered activity In-111 octreotide therapy with concomitant radiosensitizing 5FU chemotherapy for treatment of neuroendocrine tumors: preliminary experience.

INTRODUCTION: High-administered activity In-111 octreotide (HA-Oc) therapy has been used for patients with disseminated neuroendocrine tumors (NET) with high somatostatin receptor (SSR) expression. Combining HA-Oc with radiosensitizing 5-fluorouracil (5FU) chemotherapy could enhance efficacy. Our other aim was to assess whether concomitant 5FU would contribute to significant additional toxicity. METHODS: Fifteen (15) consecutive patients who received 3 cycles of HA-Oc+5FU were evaluated. Symptomatic, octreoscan, computed tomography (CT), hormonal responses, and toxicity were reviewed at 3 months post-last treatment. Long-term follow-up was performed to death or April 2008 to assess late toxicity and time to progression requiring retreatment. RESULTS: At 3 months post-treatment, 67% of patients had symptomatic improvement, with 20% experiencing a complete resolution of symptoms. Overall, 90% achieved stabilization or a decrease in hormone levels. Octreoscan improvement/stabilization occurred in 95% and CT stabilization in 80% of patients with previously progressive disease, but no partial or complete regression by Response Evaluation Criteria in Solid Tumors criteria. Transient lymphopenia and nausea were the most common side-effects, and there was no significant renal or grade 4 hematologic toxicity. Subacute side-effects included a peripherally inserted central catheter line thrombosis (1 patient), discomfort/pain associated with lesion necrosis, and 1 lymph node swelling. Median time to retreatment was 23 months (range, 6-34) for 10 patients. Six (6) patients deceased (no deaths directly related to 5FU); 9 patients (60%) are alive at 36-139 months. CONCLUSIONS: HA-Oc+5FU achieve a high rate of symptomatic response associated with stabilization/improvement in hormonal and functional scan abnormalities. Combination treatment achieved disease stabilization in the majority of patients with previously progressive disease. There was no significant observed increase in toxicity with additional 5FU, making it a promising adjunct to radiopeptide receptor therapy for progressive NET.