Peptide receptor radionuclide therapy (Lu-177 PRRT) in neuroendocrine tumors (NET) over 16 years: Single institution experience.

628 Background: Peptide receptor radionuclide therapy (PRRT) is one of the standard treatments for unresectable or metastatic neuroendocrine tumors (NETs). Treatment with Lu177-Dotatate PRRT therapy resulted in markedly longer progression-free survival and a significantly higher response rate than high-dose octreotide LAR among patients with advanced neuroendocrine tumors. Recently, an overall survival benefit has been announced in survival analysis. This study aims to report the efficacy of PRRT in NET cases treated at King Faisal Specialist Hospital and Research Center (KFSHRC) in Saudi Arabia. Methods: Patients with unresectable, well-differentiated NET who received PRRT from 2008 to 2024 were included. Data on primary sites, WHO grade, Ki67%, ECOG PS, and many other characteristics were collected. Outcomes, including ORR, OS, and PFS, were estimated according to different variables. Results: 79 patients treated with Lu-177 PRRT from 2008 to 2024 (16.5 years). Age at diagnosis: 18-87 (M: 45). 20 patients (25.3%) had WHO G1, 49 (62%) had G2 and 10 had G3. The primary site was small intestine (SI) in 28 (35.4%), pancreatic in 27 (34.2%) and 24 had other sites. 32 tumors (40.5%) were functional. 33 patients (41.8%) achieved PR, 29 (36.7%) had SD, whereas 15 (20%) had disease progression on PRRT. ORR data was not available in two patients. At median FU of 35.7 months, 23 patients (29.1%) were dead and 23 patients (29.1%) were alive with no disease progression. 5-year OS: 63%, MS: 76.1 mo, and 5-year PFS: 15.2%, mPFS: 18.4 mo. mPFS was different among many variables as follows: For WHO grades, mPFS: 13.7 months for G1, 24.6 months for G2 and 11.1 months for G3. (P value: <0.001). For primary sites, mPFS: 27.1 months in small intestine, 18.4 months for pancreatic tumors, 15.3 months for other primary sites. (P value: <0.001). For Ki67, mPFS: 22.4 months for Ki67<10% and 15.8 months for Ki67≥10%. (P value: 0.146). Conclusions: PRRT appeared to be effective across all well differentiated NETs regardless of WHO grade, Ki67 rate or primary sites. Results of this small retrospective study from single institution in Saudi Arabia are comparable with the international results.