Treatment of peritoneal disease arising from mucinous vs. non-mucinous appendiceal neoplasms with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

Objectives: Non-mucinous appendiceal neoplasms (NMAN) are rare. The role of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) in treating peritoneal dissemination from NMAN is poorly defined. We hypothesise that histology impacts survival and compared the disease characteristics and short- and long-term outcomes of mucinous and non-mucinous appendiceal neoplasms treated with CRS/HIPEC. Methods: We retrospectively reviewed a prospective database of 228 patients with peritoneal disease from appendiceal primaries proceeding to CRS/HIPEC from 01/01/2008 to 30/06/2022 at a tertiary referral centre in New Zealand. Results: There were 209 mucinous appendiceal neoplasms (MANs) and 19 NMANs. NMANs were more likely to metastasise to lymph nodes (p<0.001) and be treated with systemic chemotherapy (p<0.001) than MANs. Surgery for NMAN was more likely to involve small bowel resection (p<0.001) and less likely to achieve complete cytoreduction (p<0.001). Short-term outcomes were similar between MAN and NMAN. CRS/HIPEC for NMAN had a major complication rate of 15.3 % and no perioperative mortality. Extraperitoneal recurrence, including pleural and systemic recurrence, was more likely to occur in NMAN than all grades of MAN. The median overall survival was not reached in MAN and 16.0 months in NMAN. High PCI, ECOG, and tumour grade were associated with poor survival in NMAN. Conclusions: The prognosis following CRS/HIPEC for NMAN is poor. Patients with NMAN need to be judiciously selected for CRS/HIPEC.