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This Article Figures Only Full Text Full Text (PDF) Supplemental Data All Versions of this Article: jnumed.108.053421v1 50/9/1427    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JNM Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Gabriel, M. Articles by Virgolini, I. J. PubMed PubMed Citation Articles by Gabriel, M. Articles by Virgolini, I. J.

⁶⁸Ga-DOTA-Tyr³-Octreotide PET for Assessing Response to Somatostatin-Receptor–Mediated Radionuclide Therapy

¹ Department of Nuclear Medicine, Innsbruck Medical University, Innsbruck, Austria; and ² Department of Radiology, Innsbruck Medical University, Innsbruck, Austria

Correspondence: For correspondence or reprints contact: Michael Gabriel, Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, 6020 Innsbruck, Austria. E-mail: michael.gabriel{at}i-med.ac.at

⁶⁸Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-D-Phe¹-Tyr³-octreotide (DOTA-TOC) PET has proven its usefulness in the diagnosis of patients with neuroendocrine tumors. Radionuclide therapy (⁹⁰Y-DOTA-TOC or ¹⁷⁷Lu-DOTA-octreotate) is a choice of treatment that also requires an accurate diagnostic modality for early evaluation of treatment response. Our study compared ⁶⁸Ga-DOTA-TOC PET with CT or MRI using the Response Evaluation Criteria in Solid Tumors. Furthermore, standardized uptake values (SUVs) were calculated and compared with treatment outcome. Methods: Forty-six patients (29 men, 17 women; age range, 34–84 y) with advanced neuroendocrine tumors were investigated before and after 2–7 cycles of radionuclide therapy. Long-acting somatostatin analogs were not applied for at least 6 wk preceding the follow-up. Data were acquired with a dedicated PET scanner. Emission image sets were acquired at 90–100 min after injection. ⁶⁸Ga-DOTA-TOC PET images were visually interpreted by 2 experienced nuclear medicine physicians. For comparison, multislice helical CT scans and 1.5-T MRI scans were obtained. Attenuation-corrected PET images were used to determine SUVs. Repeated CT evaluation and other imaging modalities, for example, ¹⁸F-FDG, were used as the reference standard. Results: According to the reference standard, ⁶⁸Ga-DOTA-TOC PET and CT showed a concordant result in 32 patients (70%). In the remaining 14 patients (30%), discrepancies were observed, with a final outcome of progressive disease in 9 patients and remission in 5 patients. ⁶⁸Ga-DOTA-TOC PET was correct in 10 patients (21.7%), including 5 patients with progressive disease. In these patients, metastatic spread was detected with the follow-up whole-body PET but was missed when concomitant CT was used. On the other hand, CT confirmed small pulmonary metastases not detected on ⁶⁸Ga-DOTA-TOC in 1 patient and progressive liver disease not detected on ⁶⁸Ga-DOTA-TOC in 3 patients. Quantitative SUV analysis of individual tumor lesions showed a large range of variability. Conclusion: ⁶⁸Ga-DOTA-TOC PET shows no advantage over conventional anatomic imaging for assessing response to therapy when all CT information obtained during follow-up is compared. Only the development of new metastases during therapy was detected earlier in some cases when whole-body PET was used. SUV analysis of individual lesions is of no additional value in predicting individual responses to therapy.

Key Words: PET • radionuclide therapy • neuroendocrine • gallium-68 • neuroendocrine tumors • peptide-related radionuclide therapy

COPYRIGHT © 2009 by the Society of Nuclear Medicine, Inc.

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JNM 2009 50: 11A-12A. [Full Text]