Biodistribution of the Ga-68 labeled somatostatin analogue DOTA-NOC in patients with neuroendocrine tumors: characterization of uptake in normal organs and tumor lesions.

AIM: The aim of the study was 1) to determine the normal biodistribution of radiolabeled somatostatin analogue (68)Ga DOTA-NOC; 2) to establish the range of its uptake in liver, bone and lymph node metastases in patients with NET, 3) to establish the cut-off value for differentiating between physiological uptake and tumor related sstr expression in the processus uncinatus of pancreas.
METHODS: Maximum standardized uptake values (SUV(max)) of (68)Ga DOTA-NOC were determined in normal organs of 89 NET patients undergoing receptor PET/CT. In addition, SUV(max) of primary pancreatic neuroendocrine tumors (pNET), liver, bone and lymph node metastases were evaluated.
RESULTS: SUV(max) (mean + or - standard deviation) were determined in: pituitary gland 2.6 + or - 1.3, thyroid: 3.4 + or - 1.4, lung: 0.9 + or - 0.8, normal liver: 6.9 + or - 2 , spleen: 22.0 + or - 10.0, adrenal 6.0 + or - 2.5, kidney: 12.9 + or - 3.8, gastrointestinal tract 2.3 + or - 1.0, gluteal muscle:1.0 + or - 0.3, femur 0.8 + or - 0.3, blood pool 2.6 + or - 1.2 and processus uncinatus of pancreas 5.8 + or - 2.0. SUV(max) of (68)Ga DOTA-NOC was 19.6 + or - 13.4 (N.=200) in liver metastases, 12.5 + or - 10 (N.=67) in lymph nodes metastasis, 9.5 + or - 6.0 (N.=78) in bone lesions, and 20.8 + or - 10.8 (N.=26) in pancreatic neuroendocrine primary tumors. Target to non target (T/NT) ratios were 3.4 + or - 2.3 for liver metastases (with normal
CONCLUSIONS: There is a broad range of sstr expression in metastastic lesions and in pNET. The splenic uptake of (68)Ga DOTA-NOC is highly variable. (68)Ga DOTA-NOC is an excellent tracer for imaging somatostatin receptor positive tumors, which, due to the high target to non-target ratios, allows the detection of very small lesions, especially of lymph node and bone metastases.