Endocrine Abstracts

JOINT2481

Background: PRRT with ¹⁷⁷Lu-DOTATATE is approved for the treatment of metastatic or unresectable, progressive, well-differentiated, SSTR-positive gastroenteropancreatic neuroendocrine tumors (NETs). Although controlled randomized trials are lacking, several studies have shown that PRRT is also effective for SSTR-positive lung NETs. Our study aimed to evaluate the efficacy and safety of ¹⁷⁷Lu-DOTATATE PRRT in patients with lung NETs.

Materials and Methods: We retrospectively selected patients with metastatic and/or unresectable lung NET who completed treatment with ¹⁷⁷Lu-DOTATATE PRRT at a tertiary oncology center, between 2011 and 2023. Response rates, progression-free survival (PFS), overall survival (OS), and toxicity were assessed.

Results: Twenty-two patients were identified (mean age 63. 1±11. 4 years; 18, 82% men): 12 (55%) with atypical carcinoids, 9 (41%) with typical carcinoids, and 1 (4%) unclassified. Eighteen (82%) patients had hepatic metastasis, 15 (68%), bone metastasis, 9 (41%), lymph node metastasis, and 7 (32%), other. Fourteen patients (64%) were symptomatic, 5 (36%) of whom had carcinoid syndrome. Most patients were previously treated with somatostatin analogs (17; 77%) and chemotherapy (12; 55%). All patients were treated due to disease progression: 19 patients received 3 cycles of ¹⁷⁷Lu-DOTATATE and 4, 4 cycles, with a median cumulative activity of 19. 7 GBq (range, 14. 4-29. 6). Median follow-up time after the first cycle was 45 months (range: 7-147), with 16 (73%) deaths recorded. Median PFS was 19 months (95%CI 10-28) and median OS was 46 months (95%CI 38-53). Objective response rate was 32% (7 patients), with all responses documented as partial. Stable disease was described in 7 (32%) patients, yielding a disease control rate of 64%. Of the 14 symptomatic patients, 5 (36%) showed improvement after PRRT, 3 (21%) experienced worsening symptoms, and 6 (43%), no change. There were no cases of clinically significant (grade 3/4) hematologic, hepatic, or renal toxicity. Previous treatment with somatostatin analogs was associated with longer PFS and the presence of respiratory symptoms, with shorter PFS.

Conclusions: ¹⁷⁷Lu-DOTATATE PRRT seems to be a valuable treatment option for advanced progressive lung NET, with a minimal risk of toxicity. Randomized prospective studies are needed to validate these findings.