Comparison of 68Ga-DOTATOC biodistribution in patients with and without spleenectomy

Ga-68 labeled somatostatin analogues such as 68Ga-DOTA0-Phe1-Tyr3-octrotide (DOTATOC) as PET tracers, have significantly improved the imaging of somatostatin receptors (SSTRs) expressing tumors. Due to unspecific parenchymal binding and the expression of SSTRs on leukocytes in the spleen this is the organ with the highest non-tumor uptake of DOTATOC. Therefore, we investigated the potential changes of normal tissue distribution and tumor concentration in patients with neuroendocrine tumors (NETs) with or without spleenectomy.

Out of 420 patients with pancreatic NET undergoing 68GA-DOTATOC PET/CT eleven patients with and eleven patients without spleenectomy were derived and matched in regard to tumor histology, tumor load, age and gender. The SUV(max) of liver metastases as well as of the following normal tissues was determined: pituitary gland, thyroid gland, liver parenchyma, kidneys and suprarenal glands.

SUV(max) values with and without spleenectomy were: in the liver metastasis (19.17 ± 6.05 versus 37.67 ± 16.31), in the thyroid gland (2.56 ± 1.33 versus 2.66 ± 0.94), in the pituitary gland (4.08 ± 1.79 versus 4.92 ± 1.93) in suprarenal glands (7.18 ± 3.33 versus 9.73 ± 3.46 on the left side and 7.32 ± 3.03 versus 11.19 ± 5.72 on the right side), in the kidneys (8.1 3 ± 4.26 on the left side and 8.11 ± 4.16 on the right side versus 8.62 ± 2.17 on the left side and 9.79 ± 2.18 on the right side) and in normal liver tissue (5.74 ± 1.55 versus 6.22 ± 1.95). The difference was statistically significant (Wilcoxon test P<0.05) in tumor lesions, adrenal and kidney tissue.

Spleenectomy must be considered as a relevant factor when reporting the outcome of SSTR targeted diagnostics and therapies.