Abstract
Gallium-68 DOTATATE provides physiologic imaging and assists in disease localization for somatostatin receptor (SSTR) positive neuroendocrine tumor (NET) patients. However, questions regarding usefulness of gallium- 68 DOTATATE imaging in identifying the primary site in neuroendocrine tumors (NETS) of unknown primary, correlation of NET grade with median Standardized Uptake Value (SUV) and effects of long acting somatostatin analog on gallium-68 DOTATATE imaging quality needs to be evaluated.A single institution retrospective review of the first 200 NET patients with gallium-68 DOTATATE imaging from Dec 2016 to Dec 2017 was conducted. Questions related to NETs of unknown primary, correlation of Standardized Uptake Value (SUV) to Ki-67 (which signifies proliferation rate), the effects of long-acting systemic somatostatin analog (SSA) on SUV were part of our data analysis.From these 200 patients, 59.5% (119) were females, 40.5% (81) were males; the median age was 62 years. The following primary tumor sites were identified: small bowel-37.5%; pancreas-18.5%; bronchial-14%; colon-3.5%; rectum-2%; appendix-1.5%; adrenal-0.5%; prostate-0.5%; others-3% and unknown primary-19%. Mean hepatic SUV of the lesion with the greatest radiolabeled uptake in 96 patients was similar irrespective to exposure to long acting SSA. Patients exposed to long acting SSA had mean SUV of 31.3 vs 27.8 for SSA naïve patients. The difference was not statistically significant.Gallium-68 DOTATATE imaging seems to distinguished G3 NET from G1/G2 based on mean SUV, and also identified the primary tumor site in 17 of 38 (45%) patients with unknown primary. Systemic exposure to long acting SSA does not appear to influence mean SUV of gallium-68 DOTATATE scan.
Highlights
Neuroendocrine tumors (NETs) are unique neoplasms that are known for their phenotypic as well as molecular heterogeneity [1]
NETs can be characterized as high grade, intermediate grade or low grade based on proliferative activity according to Ki 67 index
We investigated the correlation between somatostatin receptor avidity with the gallium-68 DOTATATE scan and the Ki 67 index as noted on histopathology
Summary
Neuroendocrine tumors (NETs) are unique neoplasms that are known for their phenotypic as well as molecular heterogeneity [1]. NETs can be characterized as high grade, intermediate grade or low grade based on proliferative activity according to Ki 67 index. Low and intermediate grade well differentiated NETs (Ki 67 ≤ 20%) tend to overexpress somatostatin receptors (SSTRs) and have the potential to secrete various peptide hormones in about 20–40% cases [3]. High grade neuroendocrine neoplasms are characterized by Ki 67 index of > 20% and are subdivided into well differentiated and poorly differentiated subtypes [3]. This distinction, based on morphology (well differentiated vs poorly differentiated), is fairly new and strategies regarding distinct managements are currently being explored. In general grade 3 neuroendocrine neoplasms are fast growing, not somatostatin receptor dense, and rarely produce functional hormones
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