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

J Nucl Med. 2009 Sep;50(9):1427-34. doi: 10.2967/jnumed.108.053421. Epub 2009 Aug 18.

Abstract

(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.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

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

Substances

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