Feasibility of Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) in a Rabbit Model of Peritoneal Metastases: PIPALIM Project

Abstract

Background: Animal models are essential for testing new pressurized intraperitoneal aerosol chemotherapy (PIPAC) protocols; however, no immunocompetent animal model of peritoneal surface malignancies (PSMs) treated with PIPAC has been established. This study evaluated the feasibility, safety, and oncological efficacy of PIPAC in a rabbit PSM model.

Methods: The study was conducted in two phases: (1) Feasibility Assessment: Three healthy rabbits underwent three consecutive PIPAC procedures (saline) at weekly intervals. The rabbits' well-being, morbidity, mortality, and histological changes were monitored. (2) Treatment Phase: Rabbits with PSM were treated with PIPAC using oxaliplatin, cisplatin-doxorubicin, or saline. Parameters such as animal well-being, ascites volume, morbidity, Peritoneal Cancer Index (PCI), histological response (Peritoneal Regression Grading Score [PRGS]), tumor cell proliferation/apoptosis, and circulating tumor DNA (ctDNA) levels were assessed.

Results: PIPAC was feasible and safe, with no increased morbidity or mortality. PIPAC demonstrated antitumor efficacy with lower PCI (control 21.6 vs. oxaliplatin 9.2 vs. cisplatin-doxorubicin 10.2; p < 0.001), improved histological response (PRGS: control 3.38 vs. oxaliplatin 1.95 vs. cisplatin-doxorubicin 1.85; p = 0.01), and reduced tumor cell proliferation (control 5.3% vs. oxaliplatin 0.82% vs. cisplatin-doxorubicin 0.62%; p < 0.0001). ctDNA levels showed promise for monitoring treatment response, warranting further investigation.

Conclusion: This study confirms the feasibility and effectiveness of PIPAC with oxaliplatin or cisplatin-doxorubicin in rabbits with PSM. The model provides a foundation for future research on PIPAC protocols and related treatments.

Keywords: Cancer; Intraperitoneal chemotherapy; PIPAC; Peritoneal metastases; Rabbit model.

Fig. 1

A HES staining and multiphoton imaging of rabbit visceral and parietal peritoneum with and without PIPAC. Scale bar in (a) = 50 µm. B Photographs of blue staining after PIPAC in intra-abdominal cavities illustrate the extent of nebulization diffusion (black arrowheads). M muscularis, PP parietal peritoneum, SHG second harmonic generation, StM striated muscle, SM submucosa, VP visceral peritoneum, SmM smooth muscle, Ve blood vessel, HES hematoxylin-eosin-saffron, PIPAC pressurized intraperitoneal aerosol chemotherapy

Fig. 2

A Impact of PIPAC-Oxa and PIPAC-CisP Doxo on rabbit well-being score versus control group. B Image of an abdominal CT scan at day 26 in a control rabbit revealed advanced peritoneal disease and bowel obstruction. C Mean score of the PCI in each treatment group. PIPAC pressurized intraperitoneal aerosol chemotherapy, CT computed tomography, PCI Peritoneal Cancer Index, Oxa oxaliplatin, CisP Doxo cisplatin-doxorubicin (mean ± standard deviation), * p < 0.05, ** p < 0.01, *** p < 0.001

Fig. 3

Histological analyses at D26 after the third PIPAC treatment. A HR was evaluated based on the PRGS. B Cell death by apoptosis was assessed using the TUNEL assay. C Cell proliferation was evaluated via anti-Ki67 immunostaining. Scale bars are in included in each image. PIPAC pressurized intraperitoneal aerosol chemotherapy, HR histological response, PRGS Peritoneal Regression Grading Score, HES hematoxylin-eosin-saffron staining, Oxa oxaliplatin, CisP Doxo cisplatin-doxorubicin (mean ± standard deviation), * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001

Fig. 4

ctDNA levels (mean ± standard deviation) in A plasma, B abdominal ascites supernatant, and C ascites cell pellet are higher but not statistically significant in the untreated rabbit group (control PIPAC) compared with the treated groups (PIPAC with oxaliplatin or cisplatin-doxorubicin). D The mean of the three previous parameters shows a similar trend, although the differences are still not statistically significant. CtDNA circulating tumor DNA, Oxa oxaliplatin, CisP Doxo cisplatin-doxorubicin, PIPAC pressurized intraperitoneal aerosol chemotherapy