Adjuvant therapy with somatostatin analogs for recurrent gastric neuroendocrine tumors type 1.

665 Background: Neuroendocrine gastric tumors (gNETs) type 1 are associated with chronic autoimmune atrophic gastritis, hypergastrinemia and usually have multifocal lesions and high frequency of recurrence (up to 70% for 2 years). Somatostatin analogs (SA) showed promising data in neoadjuvant setting with 84% of complete responses in a small retrospective trial. The aim of this study was to evaluate the efficacy of adjuvant treatment with SA for recurrent gNETs type 1. Methods: This retrospective, single-center study included patients (pts) with recurrent gNETs who received adjuvant treatment with SA. Recruitment of pts was carried out from 2012 to February 2024. Results: The study included 35 pts, 33 females and 2 males. Endoscopic mucosal resection (EMR) was performed in 34 cases (97.1%), gastric resection in 1 (2.9%). The median of previous EMR was 2 (1-6) procedures. Most of the pts have multifocal lesions – 28 (80%), the median of lesions is 5. The median tumor size – 6 mm, tumor size >10 mm was observed in 2 cases (5.7%), one of them had N+. The median of ki67 was 3,5% (1-10%), grade 1 (G) - 14 (40%) and G2 - 21 (60%). All pts received adjuvant therapy with SA, 33 (94.3%)long-active releasing octreotide30 mg and 2 (5.7%) lanreotide 120 mg every 4 weeks. The time of SA therapy was <12 months in 23 cases (65.7%) and ≥12 months in 12 (34.3%). The median of follow-up was 30.5 months. The median disease-free survival (DFS) was not reached (95% CI, 67-NR). We compared median DFS after previous EMR (DFS1) without adjuvant SA and DFS after EMR with adjuvant SA (DFS2). The DFS2 was significantly higher – median of DFS1 was 8.8 months (95% CI, 2.7-14.9) not reached (95% CI, 67-NR, p<0.01) . Adjuvant treatment with SA ≥12 months was associated with improved DFS compared to <12 months – not reached (95% CI, 58.1-NR) versus 61 months (95% CI, 26.2-96.2, p=0.05). Adjuvant SA reduced gastrin levels after a year of therapy by ≥50% from baseline in 13 cases (37.1%). Conclusions: Adjuvant treatment with SA significantly improved DFS and should be considered for recurrent and multifocal gNETs type 1. Duration of therapy ≥12 months was significantly associated with improvement in DFS compared with shorter duration of therapy.