Impact of Cellularity on Oncologic Outcomes Following Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemoperfusion for Pseudomyxoma Peritonei.

Abstract

The Peritoneal Surface Oncology Group International (PSOGI) recommends pathologic reporting of tumor cellularity in patients with pseudomyxoma peritonei (PMP) undergoing cytoreductive surgery and hyperthermic intraperitoneal chemoperfusion (CRS-HIPEC). We investigated the prognostic significance of PMP cellularity, or lack thereof (acellular mucin), following CRS-HIPEC. We reviewed clinical data for 310 CRS-HIPEC procedures in low-grade (American Joint Committee on Cancer grade G1) PMP with acellular mucin (n=19), scant cellularity (n=30), or moderate cellularity (n=242). Kaplan-Meier survival curves and multivariate Cox regression models identified prognostic factors affecting oncologic outcomes. Compared with patients with acellular mucin, those with scant and moderate cellularity had higher PCI and less-frequent complete macroscopic resection. After an estimated median follow-up of 49months, 4 patients (14%) with scant cellularity and 127 patients (56%) with moderate cellularity progressed, while none of the patients with acellular mucin progressed. While the median progression-free survival (PFS) was not reached for patients with acellular mucin or scant cellularity (estimated 5-year PFS probability of 100 and 83%, respectively), patients with moderate cellularity demonstrated a median PFS of 32months (estimated 5-year PFS probability of 27%). In a multivariate model, degree of disease cellularity, or lack thereof (acellular mucin), was an independent predictor of PFS but not overall survival. Early disease progression is unlikely in patients with acellular mucin undergoing CRS-HIPEC, as opposed to a 14% recurrence rate with scant cellularity. Thorough pathologic assessment for cellularity, or lack thereof (acellular mucin), is vital for accurate prognostication of disease progression for patients with low-grade PMP undergoing CRS-HIPEC.