Systemic chemotherapy in patients with unresectable pseudomyxoma peritonei from low-grade appendiceal mucinous neoplasms: a case series.

Background: Patients with unresectbale low-grade appendiceal mucinous neoplasms (LAMNs) with pseudomyxoma peritonei (PMP) have very few viable treatment options. While aggressive appendiceal pathologies benefit from systemic chemotherapy, it is not clear whether LAMNs do. This is partly due to the rarity of the disease and the heterogeneity in its classification and description in the literature. The purpose of this case series is to describe our institutional experience treating 5 patients with unresectable PMP secondary to LAMN with systemic chemotherapy. Case Description: A retrospective analysis was performed of all patients presenting to the University of Chicago Medical Center with PMP from LAMN between 2016-2020. Of 72 patients who underwent treatment for PMP from LAMN during this period, 5 patients with unresectable disease who had received systemic chemotherapy were included in analysis. Median age was 54 years and median peak peritoneal cancer index was 39. All patients received either folinic acid, fluorouracil, and oxaliplatin (FOLFOX) or folinic acid, fluorouracil, irinotecan, and oxaliplatin (FOLFIRINOX) as first line therapy, undergoing a median of 7 cycles of chemotherapy; 3 patients received anti-vascular endothelial growth factor (VEGF) therapy. Median progression-free survival (PFS) was 10.3 (range, 3.2-21.4) months with a median follow-up of 21.5 months. Although four patients with elevated carcinoembryonic antigen (CEA) at baseline showed a trend toward a CEA response after receiving chemotherapy, none demonstrated an imaging response to chemotherapy and none became resectable. Conclusions: Although our case series is small, it is the first to specifically describe the outcomes of patients with unresectable metastatic peritoneal disease from LAMNs treated with oxaliplatin-based systemic chemotherapy. PFS while on systemic chemotherapy for unresectable LAMN was consistent with previously described outcomes in heterogenous populations. Larger, prospective studies will be needed to define the exact benefit of chemotherapy in unresectable LAMNs.