Combined Therapy Shows Promising 70% Response Rate in NET Trials

Michael Soulen, MD, spoke to Targeted Oncology about the safety and efficacy regarding the novel combined treatment for neuroendocrine tumors (NETs) that utilizes both systemic chemotherapy and peptide receptor radionuclide therapy (PRRT), specifically Lutetium-177 dotatate, at the 2025 North American Neuroendocrine Tumor Society (NANETS) Symposium.

Soulen described a 21-patient phase 1 study successfully conducted several years ago to assess the combination's tolerability. The primary concern was potential synergistic toxicity, which could render the treatment intolerable for patients. However, the study demonstrated that the combined approach was feasible and safe, provided the treatment cycle was slightly adjusted from the initial 28-day model. The key adjustment was extending the interval between treatments to allow for proper bone marrow recovery.

Regarding efficacy, the phase 1 trial showed impressive objective response rates (ORR), approaching 70%. Typical PRRT alone yields ORRs closer to 20-30%. The initial results also indicated a progression-free survival (PFS) rate of around 70% at 1 year.

A subsequent phase 2 trial is now underway and is currently 90% accrued, with 45 of 50 patients enrolled. While phase 1 results are often highly optimistic, the early data from phase 2 suggests that the strong response rates are holding up well. The final follow-up for the phase 2 trial is set for 2 years per patient, promising detailed long-term data on this powerful treatment combination.