Identifying Prognostic Factors in Japanese Women with Pseudomyxoma Peritonei: A Retrospective Clinico-Pathological Study of the Tohoku Gynecologic Cancer Unit

Pseudomyxoma peritonei (PMP) is a rare condition of mucinous ascites associated mainly with mucinous tumors of appendix or ovary. PMP often recurs after treatment and may eventually cause death by abdominal visceral dysfunction via compression with mucinous ascites. Although radical peritonectomy and hyperthermic intra-peritoneal chemotherapy are becoming popular globally, the optimal treatment of PMP has not been established in Japan. We conducted a retrospective multicenter study to clarify the optimal treatment and the prognostic factors of PMP. A total of 23 patients with PMP were analyzed in the Tohoku Gynecologic Cancer Unit (TGCU). Clinical and follow-up data were retrieved and a central pathology review was performed. The median follow-up period was 46 months. Eleven patients underwent complete resection. There were 7 deaths out of 13 recurrences/progressions in this period. All the recurrence/progression was confined to the abdomen. Unexpectedly, neither radical peritonectomy nor hyperthermic intra-peritoneal chemotherapy had been performed, indicating that both radical peritonectomy and hyperthermic intra-peritoneal chemotherapy are not yet popular in Japan. The medians of overall survival and disease-free period were 166 months and 30 months, respectively. Univariate and multivariate analyses revealed that the only prognostic factor was macroscopic residual tumor (P = 0.022). Although chemotherapy was not a prognostic factor (P = 0.16), those who received intra-peritoneal chemotherapy tended to have a better prognosis than those who received systemic or no chemotherapy (P = 0.064). In conclusion, the macroscopic residual tumor is an important prognostic factor in Japanese patients with PMP.