Objective  To analyze diagnosis and treatment status, natural history, and prognostic factors of patients with pseudomyxoma peritonei (PMP) based on real-world data.

  Methods  Real-world data of patients with PMP with a complete natural history, including clinicopathological characteristics, non-standardized treatment (time of misdiagnosis, time of mistreatment, previous anti-tumor treatment), cytoreductive surgery + hyperthermic intraperitoneal chemotherapy (CRS+HIPEC) treatment operation time, intraoperative blood transfusion, peritoneal cancer index (PCI) score, completeness of cytoreduction (CC) score, number of organs removed, number of peritoneal resection areas, serious adverse events (SAEs), and follow-up until patient death, were retrospectively analyzed at Beijing Shijitan Hospital, Capital Medical University, from February 2009 to July 2020. The Kaplan-Meier method was used to draw survival curves, and the Log-rank test was used to compare between groups. Prognostic factors affecting survival were analyzed using univariate and multivariate analyses with a Cox proportional hazards regression model.

  Results  : Overall, 94 patients were included, among whom 57 (60.6%) were male and 37(39.4%) were female; the median age of the patients was 54 (24–76) years. Fifty-nine (62.8%) patients previously received antitumor therapy. The median misdiagnosis time was 0.8 (0–62.5) months, and the median time of mistreatment was 15.3 (0–214.8) months. All patients received CRS+HIPEC treatment. The median operation time was 10.1 (4.8–16.5) hours, the mean number of organ resection was 2 (0–8), and the number of median peritonectomy was 5 (0–9). The PCI score was 32 (3–39) points, the CC score was 2–3 in 80.9% (76/94) of patients, and the SAE incidence rate was 35.1% (33/94). The median overall survival of 94 patients was 30.8 (2.4–218.4) months, and the 1-, 2-, 3-, and 5-year survival rates were 96.8%, 63.8%, 44.7%, and 23.4%, respectively. Stratified analysis showed that the median survival time of patients with previous intraperitoneal chemotherapy (46.5 months vs. 26.3 months), PSS 1–3 points (39.0 months vs. 21.9 months), low-/high-grade pathology (41.5/40.9 months vs. 20.1 months), KPS ≥80 (41.5 months vs. 23.9 months), no lymph node metastasis (35.5 months vs. 17.1 months), or Ki-67<50% (46.4 months vs. 20.8 months) was prolonged (P<0.05). Univariate analysis showed that the following five factors were related to 5-year survival rates: PSS score (P=0.021), previous intraperitoneal chemotherapy (P=0.008), pathological type (P=0.004), lymph node metastasis (P=0.008), and Ki-67 expression (P=0.003). Multivariate analysis revealed that the following three independent prognostic factors affected 5-year survival rates: previous intraperitoneal chemotherapy (HR=0.458, 95%CI: 0.253–0.827, P=0.010), lymph node metastasis (HR=2.879, 95%CI: 1.345–6.163, P=0.006), and Ki-67≥50% (HR=2.502, 95%CI: 1.418–4.417, P=0.002).

  Conclusions  : Non-standardized treatment of PMP is common and long-standing in the real world. However, preoperative intraperitoneal infusion chemotherapy may provide a new treatment direction for PMP.