To Perform, or Not to Perform Interim PET: Questioning the Impact of Midtherapy Evaluation During PRRT in GEP-NET Patients.

Purpose: This study aimed to analyze the impact of interim evaluation on the continuation of 177 Lu-based peptide receptor radionuclide therapy (PRRT) in gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and to survey its usage across German university hospitals.

Patients and methods: In 119 GEP-NET patients who underwent PRRT, we retrospectively assessed the results and therapeutic impact of restaging performed after 2 cycles using MRI/CT/somatostatin receptor imaging. Therapeutic decisions based on interim PET results were made in multidisciplinary tumor board meetings. Additionally, an online survey was conducted among 37 German university hospitals regarding their interim evaluation practices, focusing on the change in management.

Results: Of 119 patients, 83 completed 4 PRRT cycles; 36 stopped after 2: 27 showed PD, 3 had PR leading to surgery, 5 experienced toxicity, and 1 died. Those completing 4 cycles showed a median PFS of 38.0 months (95% confidence interval, 32.2-43.8). Seventeen of 37 surveyed hospitals routinely used interim evaluation. In a survey among 37 German university hospitals, 62% reported offering PRRT for GEP-NET patients, with 74% of these performing a routinely interim evaluation after 2 cycles of PRRT, primarily using PET/CT imaging techniques.

Conclusions: Interim PET after 2 PRRT cycles helps to identify early progression in GEP-NET patients. Standardizing interim evaluation practices could enhance the comparability of clinical outcomes and optimize patient management.