The indolent nature of type 1 gastric neuroendocrine tumors under 1 cm

Background: Type 1 gastric neuroendocrine tumors (T1-gNETs) are typically indolent. Current guidelines suggest endoscopic surveillance for lesions ≤10 mm, mainly based on expert consensus. Aim: To evaluate outcomes in patients with T1-gNETs ≤10 mm managed by endoscopic surveillance. Methods: This dual-center retrospective study (2000-2023) included patients from two Western ENETS Centers of Excellence with T1-gNETs ≤10 mm under surveillance. Primary endpoints were disease progression rate and progression-free survival (PFS); p < 0.05 was considered significant. Results: A total of 125 patients (66.4 % female; median age 59.5 years) with a median tumor size of 3 mm were analyzed. Most tumors were G1 (92.8 %), and 75.2 % had ≤5 lesions. Over a median follow-up of 72 months, progression occurred in 5 patients (4 %), with no metastases. Low-grade dysplasia was found in 2.4 % and early gastric cancer in 1.6 %. Eleven patients (8.8 %) died, none from tumor-related causes. Restricted mean survival time was 266.5 months. The 5-year PFS rate was 97.8 %. Having ≤5 lesions was significantly associated with lower progression risk (HR = 0.14, 95 % CI: 0.014-0.76, p = 0.022). Conclusions: T1-gNETs ≤10 mm show low progression risk and can be safely managed with lifelong surveillance. In patients with solitary or few lesions, extended intervals may be appropriate.