Treatment with octreotide does not reduce tumor uptake of (68)Ga-DOTATATE as measured by PET/CT in patients with neuroendocrine tumors.

Abstract

We hypothesized that (68)Ga-DOTATATE uptake of neuroendocrine tumors is sensitive to therapy with a nonradioactive somatostatin analog. (68)Ga-DOTATATE PET/CT was used to examine 105 patients, 35 of whom had been pretreated with long-acting octreotide. The maximum standardized uptake value (SUV(max)) of target tissues, as well as metastases, was compared between the groups of patients with (group 1) and without (group 2) octreotide treatment. The SUV(max) of the spleen and liver was significantly lower in group 1 than in group 2 (both P < 0.001). There were no significant group differences in SUV(max) for primary tumors (28.6 ± 6.8 vs. 32.9 ± 31.5) or metastases in the liver (27.2 ± 14.8 vs. 25.7 ± 10.7), lymph nodes (41.4 ± 19.5 vs. 25.0 ± 6.3), or skeleton (39.5 ± 22.0 vs. 15.4 ± 7.8). In 9 patients available for intraindividual comparison, tumor uptake was unaffected by treatment with somatostatin analogs (21.7 vs. 20.6; P = 0.93). Treatment with a long-acting somatostatin analog did not significantly reduce (68)Ga-DOTATATE binding in neuroendocrine tumors but tended to improve the tumor-to-background ratio.