Abstract
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Objectives Somatostatin analogues target five different somatostatin receptors (SSR) expressed on neuroendocrine tumors (NET). Octreoscan is currently the standard of care and only FDA approved and commercially available diagnostic test for well-differentiated NET. 111In-Octreotide has high affinity for SSR2, and Octreoscan has lower image resolution than PET resulting in high detection failure of 20-50% of NET. In comparison, 68Ga-DOTATATE has a higher affinity for SSR2, and PET/CT has 2-3 fold higher spatial resolution than gamma camera imaging. The purpose of the study is to compare the sensitivity of 68Ga-DOTATATE PET/CT (Ga) to 111In-Octreotide SPECT (Octreoscan) in NET patients.
Methods Thirty-seven patients underwent 1 Octreoscan on the ECAM Siemens dual detector gamma camera or equivalent camera and 1 Ga on the Biograph 16 Siemens PET/CT scanner. The Ga was performed within 28 days after the Octreoscan. Areas of abnormal uptake were compared with CT or MRI to confirm presence of lesions. The Octreoscan was read by a Nuclear Medicine physician (NM) blinded to the Ga results, and the Ga scan read by another NM blinded to the Octreoscan results. A consensus read was then performed. Lesions quantified were in organs, lymph nodes, and bones.
Results Paired t-test analysis was performed. Ga shows significantly higher detection rate versus Octreoscan for organs (p-value of 0.0049), bones (p-value of 0.0106), and combined organ, lymph node, and bone lesions (p-value of 0.0002). There is no statistically significant difference between the two scans in detection of lymph nodes (p-value of 0.2933).
Conclusions Ga PET/CT is more accurate for staging and superior to Octreoscan SPECT in the detection of overall number of lesions in the body as well as organs and bones. Ga PET/CT also allows for calculation of standardized uptake value, has less whole body radiation, and is performed in less time versus Octreoscan.
Research Support RITA Foundation, Houston, TX, United States