A clinical score (CS) for patients with well-differentiated neuroendocrine tumors (WD NETs) under consideration for peptide receptor radionuclide therapy (PRRT) with Lu 177-dotatate.

Abstract

363 Background: Despite the benefit of PRRT for patients with WD NETs, questions remain regarding sequencing and optimal patient selection for the treatment. We developed a CS at Vanderbilt Ingram Cancer Center (VICC) that we hoped would predict outcomes for patients with WD NETs receiving PRRT. Methods: Patients with progressive WD NETs (N = 146) under consideration for PRRT with Lu 177-dotatate between 3/1/2016-3/17/2020 at VICC (N = 122) and Rush Medical Center (RMC) (N = 24) were scored. The CS included 5 categories: available non-PRRT treatments for tumor type, prior systemic treatments, patient symptoms, tumor burden in critical organs and peritoneal carcinomatosis presence. All categories were scored from 0-2 except the peritoneal carcinomatosis category which was scored from 0-1; scoring criteria were determined by the VICC NET tumor board. All patients at VICC were prospectively scored, while patients from RMC were scored retrospectively with the investigator blinded to patient outcomes. The primary outcome, progression-free survival (PFS) was estimated by the Kaplan‐Meier method; a Cox proportional‐hazards model adjusting primary tumor site, tumor grade and number of PRRT doses administered (none, 1-2 doses or 3-4 doses) was used to analyze effect of CS. Results: Median patient age was 62.7 while median CS was 5 (range 1-8); the most common primary tumor sites were small intestinal (N = 81) and pancreatic (N = 37). A total of 101 patients and 31 patients received 3-4 doses and no doses of PRRT, respectively. On multivariable analysis, in patients treated with 3-4 doses of PRRT, for each 2-point increase in CS, the estimated hazard ratio (HR) for PFS was 3.26 (95% confidence interval (CI) 2.05-5.19). On multivariable analysis, in patients who received no doses of PRRT, for each 2-point increase in CS, the estimated HR for PFS was 1.37 (95% CI .78-2.41). Conclusions: Among patients treated with 3-4 doses PRRT, those with lower CS had better PFS with the treatment compared to patients with higher CS. This PFS difference, based upon CS, was not observed in patients who did not receive PRRT, suggesting the predictive utility of the CS for patients with WD NETs receiving PRRT with Lu 177-dotatate. Though the CS needs to be validated, it is the first of its kind reported.