PT - JOURNAL ARTICLE AU - Poeppel, Thorsten D. AU - Binse, Ina AU - Petersenn, Stephan AU - Lahner, Harald AU - Schott, Matthias AU - Antoch, Gerald AU - Brandau, Wolfgang AU - Bockisch, Andreas AU - Boy, Christian TI - <sup>68</sup>Ga-DOTATOC Versus <sup>68</sup>Ga-DOTATATE PET/CT in Functional Imaging of Neuroendocrine Tumors AID - 10.2967/jnumed.111.091165 DP - 2011 Dec 01 TA - Journal of Nuclear Medicine PG - 1864--1870 VI - 52 IP - 12 4099 - http://jnm.snmjournals.org/content/52/12/1864.short 4100 - http://jnm.snmjournals.org/content/52/12/1864.full SO - J Nucl Med2011 Dec 01; 52 AB - Radiolabeled somatostatin analogs represent valuable tools for both in vivo diagnosis and therapy of neuroendocrine tumors (NETs) because of the frequent tumoral overexpression of somatostatin receptors (sst). The 2 compounds most often used in functional imaging with PET are 68Ga-DOTATATE and 68Ga-DOTATOC. Both ligands share a quite similar sst binding profile. However, the in vitro affinity of 68Ga-DOTATATE in binding the sst subtype 2 (sst2) is approximately 10-fold higher than that of 68Ga-DOTATOC. This difference may affect their efficiency in the detection of NET lesions because it is the sst2 that is predominantly overexpressed in NET. We thus compared the diagnostic value of PET/CT with both radiolabeled somatostatin analogs (68Ga-DOTATATE and 68Ga-DOTATOC) in the same NET patients. Methods: Forty patients with metastatic NETs underwent 68Ga-DOTATOC and 68Ga-DOTATATE PET/CT as part of the work-up before prospective peptide receptor radionuclide therapy. The performance of both imaging methods was analyzed and compared for the detection of individual lesions per patient and for 8 defined body regions. A region was regarded positive if at least 1 lesion was detected in that region. In addition, radiopeptide uptake in terms of the maximal standardized uptake value (SUVmax) was compared for concordant lesions and renal parenchyma. Results: Seventy-eight regions were found positive with 68Ga-DOTATATE versus 79 regions with 68Ga-DOTATOC (not significant). Overall, however, significantly fewer lesions were detected with 68Ga-DOTATATE than with 68Ga-DOTATOC (254 vs. 262, P &lt; 0.05). Mean 68Ga-DOTATATE SUVmax across all lesions was significantly lower than 68Ga-DOTATOC (16.0 ± 10.8 vs. 20.4 ± 14.7, P &lt; 0.01). Mean SUVmax for renal parenchyma was not significantly different between 68Ga-DOTATATE and 68Ga-DOTATOC (12.7 ± 3.0 vs. 13.2 ± 3.3). Conclusion: 68Ga-DOTATOC and 68Ga-DOTATATE possess a comparable diagnostic accuracy for the detection of NET lesions, with 68Ga-DOTATOC having a potential advantage. The approximately 10-fold higher affinity for the sst2 of 68Ga-DOTATATE does not prove to be clinically relevant. Quite unexpectedly, SUVmax of 68Ga-DOTATOC scans tended to be higher than their 68Ga-DOTATATE counterparts.