68Ga-DOTA-Tyr3-octreotide PET for assessing response to somatostatin-receptor-mediated radionuclide therapy.

Abstract

UNLABELLED:

(68)Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide (DOTA-TOC) PET has proven its usefulness in the diagnosis of patients with neuroendocrine tumors. Radionuclide therapy ((90)Y-DOTA-TOC or (177)Lu-DOTA-octreotate) is a choice of treatment that also requires an accurate diagnostic modality for early evaluation of treatment response. Our study compared (68)Ga-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. (68)Ga-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, (18)F-FDG, were used as the reference standard.

RESULTS:

According to the reference standard, (68)Ga-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. (68)Ga-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 (68)Ga-DOTA-TOC in 1 patient and progressive liver disease not detected on (68)Ga-DOTA-TOC in 3 patients. Quantitative SUV analysis of individual tumor lesions showed a large range of variability.

CONCLUSION:

(68)Ga-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.

• Authors: Michael Gabriel, Andreas Oberauer, Georg Dobrozemsky, Clemens Decristoforo, Daniel Putzer, Dorota Kendler, Christian Uprimny, Peter Kovacs, Reto Bale, Irene J Virgolini
• Journal: Journal of nuclear medicine : official publication, Society of Nuclear Medicine (J Nucl Med) Vol. 50 Issue 9 Pg. 1427-34 (Sep 2009) ISSN: 0161-5505 [Print] United States
• PMID: 19690033 (Publication Type: Comparative Study, Evaluation Study, Journal Article)

Chemical References

• Organometallic Compounds
• Radiopharmaceuticals
• Receptors, Somatostatin
• gallium Ga 68 dotatate
• 90Y-octreotide, DOTA-Tyr(3)-
• lutetium Lu 177 dotatate
• Octreotide

Topics

• Adult
• Aged
• Aged, 80 and over
• Female
• Humans
• Magnetic Resonance Imaging
• Male
• Middle Aged
• Neuroendocrine Tumors (diagnostic imaging, metabolism, radiotherapy)
• Octreotide (analogs & derivatives, pharmacokinetics, therapeutic use)
• Organometallic Compounds (pharmacokinetics, therapeutic use)
• Positron-Emission Tomography (methods)
• Prognosis
• Radiopharmaceuticals (pharmacokinetics, therapeutic use)
• Receptors, Somatostatin (metabolism)
• Reproducibility of Results
• Sensitivity and Specificity
• Tomography, X-Ray Computed
• Treatment Outcome