Physiological and tumoral uptake of ⁶⁸Ga-DOTATATE: standardized uptake values and challenges in interpretation

The objective of this study is to determine the range of SUV_max of 68Ga-DOTATATE in normal organs and tumoral lesions and establish uptake unrelated to NET.

One hundred and twenty patients (57 men, 63 women), who underwent ⁶⁸Ga-DOTATATE PET/CT imaging in our institution were analyzed. Patients were indicated for ⁶⁸Ga-DOTATATE PET/CT imaging to detect primary tumor or metastasis of suspected or previously known NET, to determine SSTR positivity and to detect occult source of ectopic Cushing syndrome. Normal range of uptake was calculated for the organs that were proven to have no pathology by either conventional radiological imaging or clinical follow-up, using SUV_max as a semiquantitative measure. Uptake and tumor to background (T/B) ratios of tumoral lesions in liver, pancreas, bone, brain and lymph nodes were calculated. Uptakes due to lesions unrelated to NET were also documented.

Significant uptake was found in spleen, kidneys, adrenal glands, liver and pituitary gland with mean SUV_max of 24.67, 14.30, 13.73, 9.12 and 9.74 respectively. Uptake was measured separately for the pancreatic head and body separately, however, besides a slightly heterogeneous uptake; the difference was not statistically significant. Uptake in the tumoral lesions had high (T/B) ratios with mean SUV_max of 28.72, 25.21, 18.28, 34.73 and 12.59 for liver, pancreas, bone, brain and lymph nodes, respectively. Incidental benign tumoral lesions were detected in 3 patients (2.5 %) which were meningioma and fibrous dysplasia demonstrating significant and breast fibroadenoma demonstrating mild ⁶⁸Ga-DOTATATE uptake. Non-neoplastic processes were detected in 4 patients (14.1 %), including postsurgical inflammation, reactive lymph nodes, arthritis and demonstrated faint to mild ⁶⁸Ga-DOTATATE uptake, with the exception of significant uptake in accessory spleen.

⁶⁸Ga-DOTATATE has high T/B ratio with physiological biodistribution comparable to its counterparts. However, the presence of SSTRs in benign and malignant lesions unrelated to NET may be challenging in interpretation particularly where the physiological uptake is variable.