1438 Objectives: Neuroendocrine tumors (NET) are a heterogenous group of tumors, once thought rare, but now show a rising incidence. The tumor often times is indolent, thus leading to a late diagnosis at an advanced metastatic stage. Peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogue has emerged as a new encouraging systemic treatment modality, especially for unresectable metastasized NETs. PRRT is not only known to reduce tumor burden but also NET-related symptoms, thus increasing quality of life. We present here our initial experience with lutetium-177 (177Lu) labeled Dotatate since FDA approval in January 2018 in patients with NET and other somatostatin receptor (SSTR) positive tumors.
Methods: Sixty-three patients (33 males and 30 females; 37 - 81-year-old, mean ± SD: 62.1 ± 10.4 years) were treated with PRRT at our institution. Thereof 58 had progressing NETs (32 of the pancreas, 18 of the small intestine, 1 of the coecum, 1 of the appendix, 1 of the stomach and 5 of unknown primary), 3 had a paraganglioma, and 2 had a pheochromocytoma. Treatment was scheduled every 8 weeks for a total of 4 cycles. 68Ga-Dotatate PET/CT was performed at baseline, interim after 2 cycles, and following completion of PRRT. RECIST and SSTR density based on change of SUVmax were used to evaluate response to therapy. We assessed progression-free survival (PFS), objective response rate (ORR) and, considering the short follow-up time, an interim overall survival (OS).
Results: 36/63 (57.1%) patients completed all 4 cycles of PRRT, receiving a full dose of 7400MBq each. 10/63 (15.9%) patients had to discontinue treatment (4 after 1st cycle, 3 after 2nd cycle, and 3 after 3rd cycle) due to co-morbidities. 17/63 (27%) patients are still scheduled to receive additional cycles. The 11-month PFS rate was 57% and the 14-month PFS rate was 62%. The ORR was 26%. In the interim OS analysis, 8 deaths occurred from co-morbidities.
Conclusions: In our heterogenous and heavily pretreated patient cohort, the preliminary data show overall good results of PRRT with a high ORR.
623 Background: Neuroendocrine tumors (NETs) are rare but increasing in incidence. The only curative treatment is surgery, which in many cases is not an option due to metastatic disease at diagnosis. The NETTER-1 study showed high efficacy and low toxicity of peptide receptor radionuclide therapy (PRRT) for midgut NETs. Here, we present our initial experience with PRRT in the treatment of patients with NET. Methods: Fifty-two patients (27 males and 25 females; 37 - 81 yo, mean ± SD: 61.8 ± 10.6 years) with documented progressive NET (25 pancreas, 17 small intestine, 1 coecum, 4 unknown primary, 3 paragangliomas, and 2 pheochromocytomas) were referred to undergo PRRT at our institution from July 2018 to September 2019. Laboratory tests were obtained at baseline, 1 week before each cycle and every 3 months following treatment. Progression-free survival (PFS), objective response rate (ORR) and toxicity were assessed. An interim overall survival (OS) analysis was performed. Results, when possible, were compared with the NETTER-1 trial. Lines of therapy were documented. Results: 22/52 (42%) patients completed all 4 cycles of PRRT. 18/52 (34%) patients are currently being treated. 12/52 (23%) patients had to discontinue treatment. Hematotoxicity was the only side effect which can be related to PRRT. The 6-month and 9-month PFS rate was 82.4% and 66.8% respectively vs. 89% and 84% in the NETTER-1 trial. The ORR was 36% vs. 18% in the NETTER-1 trial. In the interim OS analysis, 6 deaths occurred. In contrast to the NETTER-1 study, PRRT in our patient cohort was performed later in the course of treatment (median lines of therapy before PRRT = 4 ±1.3 (range 1-6)). Conclusions: Our preliminary data show overall good results of PRRT in patients with NETs. However, compared to the NETTER-1 trial, PFS is shorter which is most likely due to the extensive pretreatment, but ORR was higher. [Table: see text]
