Neoadjuvant Intraperitoneal Chemotherapy in Patients with Pseudomyxoma Peritonei-A Novel Treatment Approach

Neoadjuvant intravenous chemotherapy in patients with pseudomyxoma peritonei (PMP) has not shown convincing results. The effectiveness of neoadjuvant intraperitoneal (IP) chemotherapy has never been reported. This prospective, non-randomized phase II study included patients with PMP treated between May 2017 and December 2018, who were not considered suitable for primary cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). The majority of patients were treated with laparoscopic HIPEC (oxaliplatin 200 mg/m², 60 min, 43 °C). IP chemotherapy was started 2 weeks after docetaxel 40 mg/m² + cisplatin 40 mg/m², accompanied by oral S1 (tegafur, gimeracil, and oteracil) (50 mg/m²) for 14 days, followed by one week rest. Clinical parameters and complications were recorded. In total, 22/27 patients qualified for CRS and HIPEC after neoadjuvant treatment. A complete cytoreduction (Completeness of cytoreduction Score 0/1) could be achieved in 54.5%. The postoperative morbidity rate was 13.6% and mortality was rate 4.5%. In total, 20/22 patients had major pathological tumor responses. The mean drop in CEA was 28.2% and in the peritoneal carcinomatosis index (PCI) was 2.6. Positive or suspicious cytology turned negative in 69.2% of patients. Thus, for PMP patients who were not amenable for primary surgery, the majority received complete cytoreduction after treatment with neoadjuvant IP chemotherapy, with satisfying tumor regression and with low complication rates. The oncological benefit in terms of survival with this new treatment regimen needs to be proven.