Long-acting octreotide treatment has no impact on tumor uptake of 99mTc-HYNIC-TOC in patients with neuroendocrine tumors

Objective Our purpose is to investigate whether the tumor uptake of Tc-99m-HYNIC-TOC in patients with neuroendocrine tumor would be influenced when the patients were treated with long-acting octreotide. Methods Sixty G2 neuroendocrine tumor patients who underwent Tc-99m-HYNIC-TOC single-photon emission computed tomography/computed tomography imaging were retrospectively analyzed. The ratios of target/muscle of normal organs and tumors were compared between the patients with (n = 30) and without octreotide treatment (n = 30). In addition, the octreotide treatment group was divided into two subgroups based on whether the time intervals were more than 14 days between the last time of octreotide administration and the day of imaging. Results There was no statistical significance in target/muscle of primary tumors (23.86 +/- 4.49 vs. 20.72 +/- 5.37, P = 0.070), metastases in the liver (20.74 +/- 6.14 vs. 19.72 +/- 6.54, P = 0.211), lymph nodes (16.29 +/- 9.45 vs. 15.52 +/- 7.67, P = 0.867), bone (9.18 +/- 3.83 vs. 9.07 +/- 3.61, P = 0.989) and lung (16.99 +/- 6.06 vs. 12.40 +/- 5.97, P = 0.133) between octreotide treated and untreated group. However, target/muscle of normal liver and bone were lower in the octreotide treated group than in untreated group (P = 0.003, and 0.0001, respectively). There was also no significant difference in target/muscle of normal organs, primary tumors and metastases between the two subgroups. Conclusion Octreotide treatment had no impact on the results of Tc-99m-HYNIC-TOC single-photon emission computed tomography/computed tomography to detect tumors and metastasis in patients with neuroendocrine tumor. However, the uptake in normal liver and bone can be reduced, which might increase the detection rate of lesions in corresponding organs.