Patterns and Predictors of Relapse Following Cytoreductive Surgery for Pseudomyxoma Peritonei

To evaluate the incidence, timing and anatomical pattern of relapse after cytoreductive surgery (CRS) for pseudomyxoma peritonei (PMP), and identify predictors of overall and early (within 12 months) relapse.

Retrospective cohort study of consecutive patients undergoing curative-intent CRS for appendiceal PMP at a single institution (2016-2025), recording the site of first relapse. Predictors of progression-free survival (PFS) and early relapse were evaluated using Cox and logistic regression.

Among 204 patients, CC-0/1 cytoreduction was achieved in 89% and HIPEC in 92%. At 37.1-month median follow-up, 89 patients (44%) relapsed; 3-year PFS and overall survival were 50.2% and 75.6%. Relapse was predominantly intraperitoneal, most often the pelvis and small bowel/mesentery (25% each). Histology and completeness of cytoreduction independently predicted PFS: low-grade (HR 2.18), high-grade (HR 2.79) and signet-ring PMP (HR 4.35) vs acellular mucin, CC-2/3 (HR 2.18), and male sex (HR 1.74). Early relapse occurred in 34 patients (17%), independently predicted by high-grade histology (OR 5.06) and CC-2/3 (OR 3.55).

Relapse after CRS for PMP is predominantly intraperitoneal, most often the small bowel/mesentery and pelvis. Histology and completeness of cytoreduction are the principal determinants of overall and early relapse, supporting risk-stratified surveillance and selective repeat cytoreduction.