Prognostic value of somatostatin receptor expressing tumor volume calculated from ⁶⁸Ga-DOTATATE PET/CT in patients with well-differentiated neuroendocrine tumors

To evaluate the prognostic value of volumetric parameters calculated from ⁶⁸Ga-1,4,7,10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-Thr³-octreotate (⁶⁸Ga-DOTATATE) positron emission tomography/computed tomography (PET/CT) in patients with well-differentiated neuroendocrine tumor (WD-NET).

Ninety-two patients (44 men and 48 women, mean age of 59.5-year-old) with pathologically confirmed WD-NET (grades 1 or 2) were enrolled in a prospective expanded access protocol. Selected data was analyzed retrospectively for this project. Maximum standardized uptake value (SUV_max) in the lesion with the highest ⁶⁸Ga-DOTATATE uptake was measured and recorded for each patient. In addition, two volumetric parameters, namely, somatostatin receptor expressing tumor volume (SRETV) and total lesion somatostatin receptor expression (TLSRE), were calculated in each ⁶⁸Ga-DOTATATE-avid lesion. SRETV was defined as tumor volume with higher ⁶⁸Ga-DOTATATE uptake than the 50% of SUV_max within the volume of interest (VOI) for each lesion. TLSRE was calculated by multiplying SRETV and mean SUV within the same VOI. Thereafter, the sum of SRETV (ΣSRETV) and TLSRE (ΣTLSRE) for all detected lesions per patient were calculated. Progression-free survival (PFS) was set as primary endpoint. Kaplan-Meier survival analysis, log-rank test, and Cox’s proportional hazard model were used for statistical analysis.

Univariate analyses revealed significant difference of PFS for WHO tumor grade and ΣSRETV (P < 0.05), while there were no significant differences in age, sex, SUV_max, and ΣTLSRE (P > 0.05). Multivariate analysis identified WHO tumor grade and ΣSRETV as independent predictors of PFS.

ΣSRETV calculated from ⁶⁸Ga-DOTATATE PET/CT may have prognostic value of PFS in WD-NET patients.