Tumor-to-Blood Ratio for Assessment of Somatostatin Receptor Density in Neuroendocrine Tumors Using 68Ga-DOTATOC and 68Ga-DOTATATE

J Nucl Med. 2020 Feb;61(2):217-221. doi: 10.2967/jnumed.119.228072. Epub 2019 Jul 13.

Abstract

PET/CT with 68Ga-DOTA-somatostatin analogs has been tested for therapy monitoring in patients with neuroendocrine tumors (NETs). However, SUVs in tumors do not correlate with the net influx rate (Ki), as a representation of the somatostatin receptor expression. In this study, tumor-to-blood ratio (TBR) was evaluated as an alternative tool for semiquantitative assessment of 68Ga-DOTATOC and 68Ga-DOTATATE tumor uptake and as a therapy monitoring tool for patients with NETs. Methods: Twenty-two NET patients underwent a 45-min dynamic PET/CT scan after injection of 68Ga-DOTATOC or 68Ga-DOTATATE. Ki was determined using the Patlak method, and TBR was calculated for the 40- to 45-min interval. Results: A linear relation was found between Ki and TBR, with a square of Pearson correlation of 0.98 and 0.93 for 68Ga-DOTATOC and 68Ga-DOTATATE, respectively. Conclusion: A high correlation was found between Ki and TBR. Hence, TBR reflects somatostatin receptor density more accurately than SUV and is suggested as the preferred metric for semiquantitative assessment of 68Ga-DOTATOC and 68Ga-DOTATATE tumor uptake.

Keywords: 68Ga-DOTATATE; 68Ga-DOTATOC; SUV; net influx rate; neuroendocrine tumors, tumor-to-blood ratio.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neuroendocrine Tumors / blood
  • Neuroendocrine Tumors / diagnostic imaging*
  • Neuroendocrine Tumors / metabolism*
  • Octreotide / analogs & derivatives*
  • Organometallic Compounds*
  • Positron Emission Tomography Computed Tomography*
  • Receptors, Somatostatin / blood*
  • Receptors, Somatostatin / metabolism*

Substances

  • Ga(III)-DOTATOC
  • Organometallic Compounds
  • Receptors, Somatostatin
  • gallium Ga 68 dotatate
  • Octreotide