(PM P15) Prognostic Factors And Outcomes Of Non-Invasive Mucinous Appendiceal Neoplasms With And Without Peritoneal Spread

Background: Patients treated surgically for limited non-invasive mucinous neoplasm may recur with development of peritoneal carcinomatosis (PC). This study analyzes the risk of recurrence. Materials and methods: Patients with low- and high-grade mucinous neoplasm of the appendix (LAMN/HAMN), with or without mucinous carcinoma peritonei (LGMCP/HGMCP) at presentation were included. Patients with limited disease underwent surgical resection only. Patients with peritoneal dissemination underwent cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC). Patients without PC (group 1) were compared to those presented with PC (group 2).

Results: Thirty-nine patients were included, 25 in group 1 and 14 in group 2. The majority was female: 60% in group 1 and 71% in group 2. Median age in both groups was 61 years. LAMN was diagnosed in 96% and 92% patients in groups 1 and 2, respectively. Mucin outside the appendix was acellular in 83% in group 1. Two (8%) patients in group 1 progressed to PC with PCI of 9 and 22 compared to a median PCI of 23.5 in group 2. Recurrence rate after CRS/HIPEC was 36% in group 1 compared to 8% in those who developed PC during follow-up.

Conclusions: The incidence of progression to PC among patients presented initially with only primary appendiceal neoplasm was 8%. Patients who present with initial PC arising from a LAMN/HAMN have a higher recurrence rate after CRS and HIPEC compared to patients who developed PC during follow-up after initial limited LAMN/HAMN. There may be genomic or molecular differences between these groups that require investigation.