RT Journal Article
SR Electronic
T1 <sup>68</sup>Ga-DOTA-Tyr<sup>3</sup>-Octreotide PET for Assessing Response to Somatostatin-Receptor–Mediated Radionuclide Therapy
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1427
OP 1434
DO 10.2967/jnumed.108.053421
VO 50
IS 9
A1 Michael Gabriel
A1 Andreas Oberauer
A1 Georg Dobrozemsky
A1 Clemens Decristoforo
A1 Daniel Putzer
A1 Dorota Kendler
A1 Christian Uprimny
A1 Peter Kovacs
A1 Reto Bale
A1 Irene J. Virgolini
YR 2009
UL http://jnm.snmjournals.org/content/50/9/1427.abstract
AB 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.