Background: Cytology of ascites or peritoneal washing is a routine part of intraoperative staging of peritoneal metastases. The aim of this study was to determine the value of cytology in patients undergoing PIPAC.
Methods: A retrospective cohort study was performed in patients having undergone PIPAC treatment in Lausanne (Switzerland) between January 2015 and January 2020 for peritoneal carcinomatosis of various origin (colorectal, gastric, ovarian, hepatobiliary and mesothelioma). Data on demographics, clinical characteristics, surgical treatment and evolution of cytology between PIPAC 1 and 3 was collected. Results: In the study period, 75 patients underwent a total of 144 PIPAC procedures. The median age was 63 years (IQR 51-70) and 67% of patients were female (n= 50). Patients with negative and positive cytology only differed in terms of symptoms of ascites (16% vs 39% respectively, p=0.04), median ascites volume (100 mL vs 0 mL, p=0.01) and median PCI (9 vs 19, p < 0.01). Number of PIPAC treatments per patient did not differ (p=0.23). Among 20 patients who completed 3 PIPACs (as per local protocol), one with initially positive cytology became negative. The opposite happened in 2 patients.
Conclusion: The number of PIPAC treatments did not differ between patients with negative and positive cytology. Minimal conversion happened between procedures. No treatment alterations were made based on cytology in our cohort.