Secondary Cytoreduction and Perioperative Intraperitoneal Chemotherapy after Initial Debulking of Pseudomyxoma Peritonei: A Study of Timing and the Impact of Malignant Dedifferentiation

Abstract

Cytoreductive surgery and perioperative intraperitoneal chemotherapy (PIC) is recognized as an effective treatment modality for patients with pseudomyxoma peritonei. This study investigates its role as a secondary definitive treatment procedure after earlier primary treatments. Patients with pseudomyxoma peritonei undergoing secondary cytoreduction combined with PIC were identified from a prospective database. Retrospective analysis investigated the outcomes, prognostic factors, critical time points, and impact of malignant dedifferentiation. Survival analysis was performed via the Kaplan-Meier method and compared via the log-rank test. The median time to progression after secondary cytoreduction was 28 months (95% CI 14 to 41 months), median survival was 97 months (95% CI 82 to 113 months), and 10-year survival was 25%. Median overall survival from initial diagnosis was 17 years and 10-year survival rate was 75%. Forty-five patients remained disease free (63%). Requiring an urgent treatment (waiting time < 60 days) after disease progression (p = 0.045) and having moderate or severe symptoms (p = 0.033) were associated with a shorter time to progression. Improved survival was associated with patients who had low-grade tumors (p = 0.029), and those who required less urgent treatment (wait > 30 days) after disease progression (waiting up to 15 days, p = 0.010; waiting up to 30 days, p = 0.005). Malignant dedifferentiation appeared to affect survival from initial diagnosis (p = 0.062) and after secondary cytoreduction (p = 0.006). Secondary cytoreduction with PIC achieves long-term survival. Tumors that undergo malignant dedifferentiation appear to adversely affect survival, and this may support the rationale for early definitive treatment with cytoreduction and PIC.