[68Ga]Ga-DOTATATE-avid tumor volume, uptake and inflammation-based index correlate with survival in neuroendocrine tumor patients treated with [177Lu]Lu-DOTATATE PRRT.

To meet the increasing demand for PRRT in the treatment of patients with inoperable/disseminated well-differentiated neuroendocrine tumors (NETs) and to guide optimization strategies, adequate and accessible predictive tools that allow to stratify patients who will benefit from treatment from those who will not are becoming indispensable. Previously, we have investigated the role of baseline [⁶⁸Ga]Ga-DOTATOC PET tumor uptake and volumetric parameters and a blood-derived inflammatory biomarker, the inflammation-based index (IBI), for outcome prediction in NET patients treated with [⁹⁰Y]Y-DOTATOC. In this retrospective study in 83 NET patients treated with [¹⁷⁷Lu]Lu-DOTATATE in a routine clinical setting, we aimed to evaluate the generalizability of our previous findings to [¹⁷⁷Lu]Lu-DOTATATE treatment combined with a pre-therapeutic [⁶⁸Ga]Ga-DOTATATE PET. A semi-automatic customized SUV threshold-based approach was used for tumor delineation. The previously identified SUV_mean cut-off of 13.7 for better survival could not be applied to this patient cohort. Instead, a more optimal cut-off could be identified: an SUV_mean lower or equal than 11.2 was associated with worse overall survival (OS) (hazard ratio (HR) 2.28; P = 0.008). Also in line with our previous study, a [⁶⁸Ga]Ga-DOTATATE-avid tumor volume (TV) higher than 672 mL and an elevated baseline IBI were correlated with worse OS (HR 3.13 (P = 0.0001) and HR 2.00 (P = 0.034), respectively). Multivariate analysis confirmed independent associations between OS and baseline IBI (P = 0.032), SUV_mean (P = 0.027) and [⁶⁸Ga]Ga-DOTATATE-avid TV (P = 0.001). Taking baseline IBI, [⁶⁸Ga]Ga-DOTATATE-avid TV and [⁶⁸Ga]Ga-DOTATATE uptake into account may help guide PRRT treatment decisions.