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(2006) Phase II study on stereotactic body radiotherapy of colorectal metastases, Acta Oncologica, 45:7,[823][824][825][826][827][828][829][830]

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None of the modalities can yet replace surgical staging. However, they all contributed to important knowledge and were, furthermore, able to upstage low-risk patients who would not have been recommended lymph node resection based on histology and grade alone.

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Somatostatin receptor imaging is a valuable tool in the diagnosis, follow-up, and treatment planning of neuroendocrine tumor (NET). PET-based tracers using 68 Ga as the radioisotope have in most centers replaced SPECT-based tracers as the gold standard. 64 Cu-DOTATATE is a new PET tracer that has been shown to be far superior to the SPECT tracer 111 In-diethylenetriaminepentaacetic acid-octreotide. Because of the advantages of 64 Cu over 68 Ga, we hypothesized that the tracer has a higher sensitivity than 68 Ga-based tracers. To test this hypothesis, we compared on a head-to-head basis the diagnostic performance of 64 Cu-DOTATATE with that of 68 Ga-DOTATOC in NET patients. Methods: Fifty-nine NET patients were scanned with both 64 Cu-DOTATATE and 68 Ga-DOTATOC PET/CT and compared on a head-to-head basis. Discordant lesions were verified during at least 30 mo of follow-up. Results: A total of 701 lesions were concordantly detected on both 64 Cu-DOTATATE and 68 Ga-DOTATOC PET/CT scans, whereas an additional 68 lesions were found by only one of the scans. 64 Cu-DOTATATE showed 42 lesions not found on 68 Ga-DOTATOC, of which 33 were found to be true-positive on follow-up. 68 Ga-DOTATOC showed 26 lesions not found on 64 Cu-DOTATATE, of which 7 were found to be true-positive on follow-up. False-positives were mainly lymph node lesions. Accordingly, 83% of the additional true lesions found on only one of the scans were found by 64 Cu-DOTATATE. On a patient-basis, additional true lesions were found by 64 Cu-DOTATATE and 68 Ga-DOTATOC in 13 and 3 patients, respectively. All patients with additional lesions also had concordant lesions found by both scans. Conclusion: 64 Cu-DOTATATE has advantages over 68 Ga-DOTATOC in the detection of lesions in NET patients. Although patient-based sensitivity was the same for 64 Cu-DOTATATE and 68 Ga-DOTATOC in this cohort, significantly more lesions were detected by 64 Cu-DOTATATE. Furthermore, the shelf life of more than 24 h and the scanning window of at least 3 h make 64 Cu-DOTATATE favorable and easy to use in the clinical setting.

The use of positron emitter-labeled compounds for somatostatin receptor imaging (SRI) has become attractive because of the prospect of improved spatial resolution, accelerated imaging procedures, and the ability to quantify tissue radioactivity concentrations. This paper provides results from first-in-humans use of 64 Cu-DOTATATE, an avidly binding somatostatin receptor ligand linked to a radioisotope with intermediate half-life and favorable positron energy (half-life, 12.7 h; maximum positron energy, 0.653 MeV). Methods: In a prospective setup, 14 patients with a history of neuroendocrine tumors underwent both PET/CT with 64 Cu-DOTATATE and SPECT/CT with our current routine imaging agent 111 In-diethylenetriaminepentaacetic acid-octreotide. After intravenous injection of 193-232 MBq of 64 Cu-DOTATATE, whole-body PET scans were acquired at 1 h (n 5 14), 3 h (n 5 12), and 24 h (n 5 5) after administration. Tissue radioactivity concentrations for normal organs and lesions were quantified, and standardized uptake values were calculated for the early (1 h) and delayed (3 h) scans. Using the data for 5 patients, we assessed the radiation dose with OLINDA/EXM software. Furthermore, the clinical performance of 64 Cu-DOTATATE with respect to lesion detection was compared with conventional SRI. Results: SRI with 64 Cu-DOTATATE produced images of excellent quality and high spatial resolution. Images were characterized by high and stable tumor-to-background ratios over an imaging time window of at least 3 h. Compared with conventional scintigraphy, 64 Cu-DOTATATE PET identified additional lesions in 6 of 14 patients (43%). In 5 patients, lesions were localized in organs and organ systems not previously known as metastatic sites, including the early-stage detection of a secondary neuroendocrine tumor in a patient with a known mutation in the multiple endocrine neoplasia type I gene. All major additional findings seen only on PET could be confirmed on the basis of a clinical follow-up interval of 18 mo. Calculated radiation dose estimates yielded an effective dose of 6.3 mSv for an injected activity of 200 MBq of 64 Cu-DOTATATE, with the liver being the organ with the highest absorbed radiation dose (0.16 mGy/MBq).Conclusion: This first-in-humans study supports the clinical use of 64 Cu-DOTATATE for SRI with excellent imaging quality, reduced radiation burden, and increased lesion detection rate when compared with 111 In-diethylenetriaminepentaacetic acid-octreotide.