Secondary cytoreduction and perioperative intraperitoneal chemotherapy after initial debulking of pseudomyxoma peritonei: a study of timing and the impact of malignant dedifferentiation.

BACKGROUND: 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.

STUDY DESIGN: 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.

RESULTS: 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).

CONCLUSIONS: 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.