64Cu- DOTA,1-Nal(3)]-octreotide (DOTANOC) PET/CT in Neuroendocrine Tumors: Initial Experience in Single Centre in Mexico.

Introduction: The use of molecular imaging using radiolabeled somatostatin analogs has revolutionized the management of Neuroendocrine tumors (NETs). Recently 64 Copper (⁶⁴Cu) has been used as an alternative to 68 Gallium (⁶⁸Ga) in peptide labeling, ⁶⁴Cu has certain advantages such as long half-life and a decay profile that can be used for positron emission tomography imaging and radionuclide therapy. (T1 / 2 = 12.7 hours; β +: 19%, β−: 38%). Materials and Methods: From March 2019 to December 2019; seventeen patients (10 men and 7 woman, aged 42 to 69 (mean age 65.5 +/- 10.1 years) with histopathological and immunohistochemical diagnosis of neuroendocrine tumor (12 well differentiated and 5 moderately differentiated) were scanned for staging (n=15) and re staging (n=2). All patients underwent whole-body PET / CT scans 60 - 70 min after the intravenous injection of 185 - 259 Mbq of ⁶⁴Cu-DOTA,1-Nal(3)]-octreotide (⁶⁴Cu-DOTANOC). PET / CT images were analyzed semi-quantitatively using SUVmax. ⁶⁴Cu was produced in a IBA twin 18 MeV Cyclotron with the irradiation of natNi in a Nirta solid target and DOTANOC was radiolabeled by incubation in acid medium and purified in solid phase reaching a yield higher than 95%.

Results: ⁶⁴Cu-DOTANOC was well tolerated in all patients and none adverse effects were noticed. ⁶⁴Cu-DOTANOC was positive in 16 of 18 patients and found 57 lesions (21 in liver, 18 bone lesions, 12 in lymph nodes, 3 lung, 3 peritoneal nodules). The patients with negative scan were studied for restaging after surgical intervention with curative intention. The SUV_max of tumoral lesions ranged between 8.73 to 50.42 (mean 18.5 +/- 16.24), SUV_max [mean ± SD] in normal organs of biodistribution like hypophysis, thyroid, liver, spleen, kidney, adrenal, and uncinate process were 5.68 +/- 2.3, 2.6 +/- 1.8, 10.29 +/- 5.9, 25.1 +/- 15.35, 14.6 +/-8.9, 13.9 +/- 7.4, 10.5 +/- 6.5 respectively. One week after 5 patients were scanned complementary with 68Ga-DOTATOC. ⁶⁴Cu-DOTANOC found 4 lymph nodes and 1 peritoneal nodule that was not seen with ⁶⁸Ga-DOTATOC, this findings did not had clinical impact. SUV_max between both radiopharmaceuticals in tumoral lesions no shows significant differences (⁶⁴Cu DOTANOC 14.2 +/- 5.4 vs ⁶⁸Ga-DOTATOC 13.1 +/- 3.5) p=0.51.

Conclusions: ⁶⁴Cu-DOTANOC is a highly effective radiopharmaceutical in the detection of neuroendocrine tumors, shows a biodistribution and sensitivity similar to ⁶⁸Ga-DOTATOC, probably with greater detection capacity due to the affinity to a greater number of somatostatin receptors (SSTR2, SSTR3, SSTR5), additionally its physical characteristics give it a potential theragnostic use, and its long live could be used to acquire late images to improve accuracy or to increase the accessibility to this type of molecular imaging in centers that do not have a ⁶⁸Ge/68Ga generator.

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