Lu-PRRT Used More Intensively on Advanced Gastro-Entero-Pancreatic and Lung Neuroendocrine Neoplasms: Preliminary Results on Toxicity from a Randomized Study.

Introduction: Lu-PRRT in neuroendocrine tumors is usually delivered with a total cumulative activity (TCA) of 29.6 GBq, divided into 4 cycles and with fixed interval between cycles (IBCs) of 8 weeks. Based on previous radiobiological studies, reducing IBC could improve efficacy without increasing toxicity. The purpose of this study was to evaluate safety of Lu-PRRT with two different IBC: intensive (every 5 weeks) or standard (every 8-10 weeks).

Methods: From May 2016 to July 2018, patients with advanced and progressive GEP and bronchial NENs were enrolled in a prospective randomized phase II study. Patients with risk factors for toxicity (RF) were planned for a TCA of 18.5 GBq, patients without RF of 27.8 GBq, divided into 5 cycles. Patients were then randomly assigned to be treated according to the intensive or to the standard IBC. Toxicity was monitored according to CTCAE.

Results: One hundred and twenty patients (61 in the intensive group and 59 in the standard one) were evaluable for overall toxicity. Five patients (4.1%) had major (G3) hematological toxicity, 2 in the intensive group and 3 in the standard one. Other G3 toxicities related to creatinine, alanine aminotransferase, nausea, and asthenia were observed in the intensive group. 112 patients (54 in the intensive group and 58 in the standard one) performed at least 2 cycles and were also evaluable for cycle-by-cycle toxicity, resulting similar between the two groups.

Conclusion: According to our preliminary results, Lu-PRRT administered intensively could be considered as safe as the standard schedule, when TCA is chosen according to the RF. Further data are needed to confirm these results.