Prognostic Utility of Total 68 Ga-DOTATATE-Avid Tumor Volume in Patients With Neuroendocrine Tumors.

BACKGROUND & AIMS: Survival times vary among patients with neuroendocrine tumors (NETs) - even among those with the same site, stage, and grade of primary tumor. This makes it difficult to select treatment for patients with unresectable NETs because some patients can survive decades without treatment. 68 Gallium-DOTATATE positron emission tomography with computed tomography (68 Ga-DOTATATE PET/CT) is a sensitive imaging technique for detection of NETs. We investigated the prognostic accuracy of 68 Ga-DOTATATE PET/CT-based analysis of tumor volume in patients with NETs.

METHODS: We performed a prospective study of 184 patients with NETs (128 [69.6%] with metastases and 11 patients [6.0%] with locally advanced disease) at the National Institutes of Health Clinical Center (Bethesda, MD) from 2013 through 2017. All patients underwent 68 Ga-DOTATATE PET/CT image analysis and total 68 Ga-DOTATATE-Avid tumor volume (68 Ga-DOTATATE TV) was determined. We also measured fasting serum chromogranin A, neuron-specific enolase, gastrin, glucagon, vasoactive intestinal peptide, pancreatic polypeptide, and 24-hour urinary 5-hydroxyindoleacetic acid levels in all patients. Disease progression was defined as a new lesion or a growth of a known lesion during the interval between baseline 68 Ga-DOTATATE PET/CT scan and follow-up imaging (14.0 ± 6.1 months; range, 1-35 months). The primary outcomes were progression-free survival (PFS) and disease-specific mortality during a median follow-up time of 18 months (range, 4-35 months).

RESULTS: We found an inverse correlation between quartiles of 68 Ga-DOTATATE TV and PFS (P = .001) and disease-specific survival (P = .002). A 68 Ga-DOTATATE TV of 7.0 mL or more was associated with higher odds of disease progression (hazard ratio, 3.0; P = .04). A 68 Ga-DOTATATE TV of 35.8 mL or more was associated with increased risk of disease-specific death (hazard ratio, 10.6) in multivariable analysis (P = .01), as well as in subgroup analysis of patients with pancreatic NETs.

CONCLUSIONS: In a prospective study, we demonstrated the prognostic utility of 68 Ga-DOTATATE TV in a large cohort of patients with NETs, in terms of PFS and disease-specific mortality.