Prediction of [sup.177]Lu-DOTATATE Therapy Outcomes in Neuroendocrine Tumor Patients Using Semi-Automatic Tumor Delineation on [sup.68]Ga-DOTATATE PET/CT

[sup.177]Lu-DOTATATE is a radioactive drug that can treat advanced neuroendocrine tumors, a type of cancer. However, some patients do not benefit from [sup.177]Lu-DOTATATE treatment and there is an unmet need to identify such patients before they receive the treatment. Currently, each patient needs to have a positive result on a scan, such as [sup.68]Ga-DOTATATE PET/CT, prior to receiving [sup.177]Lu-DOTATATE treatment to verify that the drug can attack the patient’s cancer. This study used a semi-automatic analysis of [sup.68]Ga-DOTATATE PET/CT to predict the results of [sup.177]Lu-DOTATATE treatment. Having a large amount of cancer and/or a tumor with low signal on [sup.68]Ga-DOTATATE PET/CT predicted poor results of [sup.177]Lu-DOTATATE therapy. The semi-automatic nature of this method allows identification of patients at risk for treatment failure with little time and effort. Background: Treatment of metastatic neuroendocrine tumors (NET) with [sup.177]Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) results in favorable response only in a subset of patients. We investigated the prognostic value of quantitative pre-treatment semi-automatic [sup.68]Ga-DOTATATE PET/CT analysis in NET patients treated with PRRT. Methods: The medical records of 94 NET patients who received at least one cycle of PRRT at a single institution were retrospectively reviewed. On each pre-treatment [sup.68]Ga-DOTATATE PET/CT, the total tumor volume (TTV), maximum tumor standardized uptake value for the patient (SUVmax), and average uptake in the lesion with the lowest radiotracer uptake (SUVmin) were determined with a semi-automatic tumor delineation method. Progression-free survival (PFS) and overall survival (OS) among the patients were compared based on optimal cutoff values for the imaging parameters. Results: On Kaplan–Meier analysis and univariate Cox regression, significantly shorter PFS was observed in patients with lower SUVmax, lower SUVmin, and higher TTV. On multivariate Cox regression, lower SUVmin and higher TTV remained predictive of shorter PFS. Only higher TTV was found to be predictive of shorter OS on Kaplan–Meier and Cox regression analyses. In a post hoc Kaplan–Meier analysis, patients with at least one high-risk feature (low SUVmin or high TTV) showed shorter PFS and OS, which may be the most convenient parameter to measure in clinical practice. Conclusions: The tumor volume and lowest lesion uptake on [sup.68]Ga-DOTATATE PET/CT can predict disease p