Prognostic value of volumetric parameters calculated from 68Ga-DOTATATE PET/CT in patients with well-differentiated neuroendocrine tumors

Objectives: To evaluate prognostic value of volumetric parameters calculated from 68Ga-DOTATATE PET/CT in patients with well-differentiated neuroendocrine tumor (WD-NET). Methods: Ninety-two patients with pathologically diagnosed WD-NET (grade 1 or 2) were enrolled in this retrospective study. There were 44 men and 48 women, with a mean age of 59.5 years. Maximum standardized uptake value (SUVmax) in the lesion with the highest 68Ga-DOTATATE uptake was measured in each patient. In addition, two volumetric parameters, named somatostatin receptor expressing tumor volume (SRETV) and total lesion somatostatin receptor expression (TLSRE), were calculated in the 68Ga-DOTATATE-avid lesions. SRETV was defined as tumor volume with higher 68Ga-DOTATATE uptake than the 50% of SUVmax within the region of interest (ROI) for each lesion. TLSRE was calculated by multiplying SRETV and mean SUV within the same ROI. Thereafter, the sum of SRETV (ΣSRETV) and TLSRE (ΣTLSRE) for six lesions with the largest values per patient were calculated. Progression-free survival (PFS) was set as primary endpoint. Kaplan-Meier method, log-rank test and Cox's proportional hazard model were used for statistical analysis. Results: Univariate analyses revealed significant difference of PFS for tumor grade (P: 0.006), ΣSRETV (P: 0.006), and ΣTLSRE (P: 0.035), while there were no significant differences in age, sex and SUVmax (P > 0.05). Multivariate analysis showed that WHO tumor grade (P: 0.007) and ΣSRETV (P: 0.043) were independent predictors of PFS. Conclusions: Volumetric parameters calculated from 68Ga-DOTATATE PET/CT have prognostic value of PFS in WD-NET patients, that is, larger amount of volumetric parameters may correlate with shorter PFS.