Clinical Surveillance After Macroscopically Complete Surgery for Low-Grade Appendiceal Mucinous Neoplasms (LAMN) with or Without Limited Peritoneal Spread: Long-Term Results in a Prospective Series

Background: Low-grade appendiceal mucinous neoplasm (LAMN) is the most common primary lesion of pseudomyxoma peritonei, a disease whose standard treatment is cytoreduction and hyperthermic intraperitoneal chemotherapy. The optimal management of LAMN is not well defined. This study prospectively assessed a clinical surveillance strategy for LAMN with or without limited peritoneal spread. Methods: During 2003–2017, the study prospectively enrolled 41 patients treated by macroscopically complete surgery for LAMN with or without limited peritoneal spread (pelvis and right lower quadrant). Follow-up assessment included thoracic-abdomino-pelvic computed tomography scan and serum tumor markers scheduled after surgery, then every 6 months for 5 years, and yearly thereafter. All specimens were reviewed by a dedicated pathologist. Results: Appendectomy and five right colectomies were performed for 36 patients. Nine patients also underwent macroscopically complete cytoreduction of mucinous peritoneal disease, and four patients had hysterectomy plus bilateral salphingo-oophorectomy. Appendiceal rupture was evaluable in 38 of the 41 patients, being present in 21 patients (51.2%). Mucin, cells, or both outside the appendix were observed in 24 patients (58.5%). The median follow-up period was 58 months (range 9.3–162 months). The 5-year recurrence-free survival rate was 95.1%. Only two patients experienced peritoneal recurrences (4.9%), respectively 18 and 22 months after appendectomy. Their primary lesions were LAMNs with and without appendix wall rupture or extra-appendiceal mucin, respectively. No death occurred. Conclusion: These findings strongly suggest that radically resected LAMN, even with limited peritoneal spread, carries a low recurrence risk. Furthermore, appendix wall perforation and the presence of mucin, cells, or both outside the appendix were not associated with a higher risk of metachronous peritoneal dissemination. In this setting, clinical and radiologic surveillance is a viable choice.