Active surveillance strategy for low-grade appendiceal mucinous neoplasm (LAMN): 5-year results

Objectives Low-grade appendiceal mucinous neoplasms (LAMNs) are rare tumors with potential progression to pseudomyxoma peritonei (PMP). The optimal management of patients without macroscopic peritoneal disease remains debated. We previously reported 3-year outcomes of an active surveillance (AS) strategy. This study evaluates the 5-year results of the same cohort. Methods This prospective observational study was conducted at a tertiary referral center. Patients with histologically confirmed LAMN, normal postoperative MRI and tumor markers, and limited or no extra-appendiceal mucin were enrolled in an AS protocol. Surveillance included clinical examination, serum tumor markers, and abdominopelvic MRI at 6 months and annually thereafter. Disease progression was defined as histologically proven PMP. Results Among the 30 patients initially included, 25 completed a mean 5-year follow-up and 5 were excluded after exceeding 75 years of age. No new PMP cases occurred among patients disease-free at 3 years. All four patients previously suspected of radiologic progression underwent cytoreduction and HIPEC; only two (8 %) had histologically confirmed low-grade PMP and achieved remission after complete cytoreduction. Two cases were false-positive imaging findings. Conclusions After 5 years, active surveillance remains a safe and effective long-term strategy for selected patients with LAMN, supporting conservative MRI-based follow-up and avoiding unnecessary aggressive surgery.