Efficacy of adjuvant therapy with somatostatin analogues in recurrent type I gastric neuroendocrine tumors

Introduction. Neuroendocrine gastric tumor (gNETs) type 1 associated with chronic autoimmune atrophic gastritis, hypergastrinemia and usually have multifocal lesions and high frequency of local recurrence (~70 % for 2 year). Somatostatin analogs (SA) showed promised data in neoadjuvant setting with 84 % of complete response in meta-analysis. The aim of this study was to evaluate efficacy 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 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). The most of pts have multifocal lesions – 28 (80 %), the median of lesions is 5. Tumor size >10 mm was observed at 2 cases (5.7 %), the median size – 6 mm. One pts had N+. The median of Ki67 was 3,5 % (1–10 %), 21 (60 %) pts have G2 tumors and 14 (40 %) – G1. All pts received adjuvant therapy with SA, 33 (94.3 %) long-active octreotide 30 mg and 2 (5.7 %) lanreotide 120 mg. The time of SA therapy was <12 months in 23 cases (65.7 %) and ≥ 12 months at 12 (34.3 %). With a median follow-up of 30.5 months, median DFS was not reached (NR) [95 % CI 67-NR]. Adjuvant SA reduced gastrin levels after a year of therapy by ≥50 % from baseline in 13 cases (37.1 %). We compared DFI after previous EMR (DFS 1) and DFS after EMR with adjuvant SA (DFS 2), DFS 2 was significantly higher – not reached (95 % CI, 67 – NR) versus 8.8 months (95 % CI 2.7–14.9, p<0.01). Adjuvant treatment with SA ≥ 12 months was associated with improve DFS – 61 months (95 % CI 26.2–96.2) versus not reached (95 % CI 58.1 – NR, p = 0.05). No cases of death due to disease progression were observed. Conclusions. Adjuvant therapy with somatostatin analogs significantly reduced gastrin levels and improved disease-free survival, demonstrating their antiproliferative effect in type 1 gastric neuroendocrine tumors. However, given the favorable prognosis and low risk of regional or distant metastases, the role of these agents in the treatment of gastric NETs requires further clarification in prospective studies.