Treatment with Octreotide Does Not Reduce Tumor Uptake of 68Ga-DOTATATE as Measured by PET/CT in Patients with Neuroendocrine Tumors

We hypothesized that Ga-68-DOTATATE uptake of neuroendocrine tumors is sensitive to therapy with a nonradioactive somatostatin analog. Methods: Ga-68-DOTATATE PET/CT was used to examine 105 patients, 35 of whom had been pretreated with long-acting octreotide. The maximum standardized uptake value (SUVmax) of target tissues, as well as metastases, was compared between the groups of patients with (group 1) and without (group 2) octreotide treatment. Results: The SUVmax 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 SUVmax 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). Conclusion: Treatment with a long-acting somatostatin analog did not significantly reduce Ga-68-DOTATATE binding in neuroendocrine tumors but tended to improve the tumor-to-background ratio.