Abstract / Summary
Abstract Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE is an established treatment for advanced somatostatin receptor-positive neuroendocrine tumors (NETs), yet a subset of patients derives limited benefit. Reliable biomarkers to predict response are lacking. While interim functional imaging has shown promise in predicting outcomes, data on interim anatomic imaging remain limited. We retrospectively analyzed patients with well-differentiated NETs who received ≥ 3 cycles of 177Lu-DOTATATE and underwent interim anatomic imaging (computed tomography or magnetic resonance imaging). Radiographic responses on interim and post-PRRT imaging were categorized as partial response (PR), stable disease (SD), progressive disease (PD), or mixed. Logistic regression models assessed predictors of posttreatment outcomes. Kaplan–Meier analyses estimated progression-free survival (PFS). Among 37 patients (median age 65.1 years), most had small bowel (51%) or pancreatic (40%) NETs. Interim imaging showed PR in 43.2%, SD in 32.4%, PD in 13.5%, and mixed responses in 10.8%. Interim PR and SD were highly predictive of respective outcomes on post-PRRT imaging (odds ratio [OR] 49.3, p = 0.004; OR 62.1, p = 0.002). Median PFS trended longer in patients with interim SD versus PR (34.5 vs. 17.7 months; p = 0.07). Pseudo-progression was rare and identified in two patients. Interim PD was associated with poor outcomes (median PFS 8.6 months). PR or SD on interim scans correlate strongly with posttreatment response, while interim PD may warrant therapeutic reassessment among patients receiving 177Lu-DOTATATE. Prospective validation is needed to refine imaging-based treatment adaptation strategies.