Hyperthermia and Fibrinolytic Therapy Do Not Improve the Beneficial Effect of Radioimmunotherapy Following Cytoreductive Surgery in Rats with Peritoneal Carcinomatosis of Colorectal Origin

Animal models of colorectal peritoneal metastasis

Colorectal cancer remains an important cause of mortality worldwide. The presence of peritoneal carcinomatosis (PC) causes significant symptoms and is notoriously difficult to treat. Therefore, informative preclinical research into the mechanisms and possible novel treatment options of colorectal PC is essential in order to improve the prognostic outlook in these patients. Several syngeneic and xenograft animal models of colorectal PC were established, studying a wide range of experimental procedures and substances. Regrettably, more sophisticated models such as those giving rise to spontaneous PC or involving genetically engineered mice are lacking. Here, we provide an overview of all reported colorectal PC animal models and briefly discuss their use, strengths, and limitations.

The benefit of intraperitoneal chemotherapy for the treatment of colorectal carcinomatosis

The clinical practice of hyperthermic intraperitoneal chemoperfusion (HIPEC) for carcinomatosis has lacked preclinical justification. A standardized mouse model was created to evaluate the independent effects of intraperitoneal chemotherapy. Diffuse colorectal carcinomatosis was generated in mice prior to intraperitoneal lavage with mitomycin C (MMC) at clinically comparable dosing for variable lengths of time. Tumor volumes, MMC tissue concentrations and survival were measured in comparison to saline lavage and intravenous MMC. Magnetic resonance imaging revealed a direct correlation between tumor volume, MMC dose and exposure time and survival. Intravenous MMC demonstrated a rapid clearance from the blood, lower peritoneal tissue concentrations, less tumor growth inhibition and decreased survival compared to intraperitoneal administration. Intraperitoneal chemotherapy inhibited tumor growth independent of cytoreduction or hyperthermia, demonstrated improved peritoneal tissue concentration and was associated with increased survival. These data support the clinical utility of the intraperitoneal chemotherapy component of HIPEC.

Whole-body hyperthermia combined with hyperthermic intraperitoneal chemotherapy for the treatment of stage IV advanced gastric cancer

BACKGROUND

Currently known as a metastatic disease, stage IV gastric cancer cannot be cured by surgery, but treatments are recommended to relieve symptoms such as pain and to prolong survival.

METHODS

With better access to metastases and certain large or inoperable tumours, we applied two treatment sessions of combined therapy of whole-body hyperthermia and hyperthermic intraperitoneal chemo-perfusion in the treatment group, while patients in the control group were treated with oxaliplatin combined with 5-fluorouracil chemotherapy or Xeloda. We used the RECIST criteria for outcome evaluation.

RESULTS

With the combined treatment, we found the complete and partial remission rate of patients to be 61.5%, and the rate of stable disease was 19.2%. Symptoms such as pain and a large volume of ascites were alleviated, and the quality of life was correspondingly improved. In addition, the combined treatment had a significant therapeutic benefit against the primary tumour and the metastases to the lymph nodes and liver. Survival time was also significantly prolonged (the 1-year survival rate was 38.5% compared to the control group rate of 19%).

CONCLUSIONS

These results suggest that whole-body hyperthermia combined with hyperthermic intraperitoneal chemotherapy is an effective treatment for patients with advanced gastric malignancies.

Establishment and identification of a rabbit model of peritoneal carcinomatosis from gastric cancer

BACKGROUND

Gastric cancer peritoneal carcinomatosis is a common clinical problem, but there are no suitable large animal models to study this problem. This study was to establish a stable rabbit peritoneal carcinomatosis model of gastric cancer using VX2 tumor, and analyze the clinico-pathological features.

METHODS

VX2 tumor was implanted into 36 New Zealand rabbits by 3 methods: laparotomic orthotopic injection of cancer cells into the submucosal layer of the stomach (Group A), laparotomic implantation of tumor tissue into the greater omentum immediately beneath the gastric antrum (Group B), and percutaneous injection of tumor cells directly into the peritoneal cavity (Group C), 12 rabbits in each group. The animals were closely observed and detailed clinico-pathological studies were conducted.

RESULTS

The success rates of peritoneal carcinomatosis formation were 100% (12/12), 91.7% (11/12) and 58.3% (7/12), respectively, for Groups A, B and C (P = 0.019, A versus C; P = 0.077, B versus C; P = 0.500, A versus B, Fisher's exact test). Two weeks after submucosal cancer cells injection in Group A, ulcerative gastric cancer with peritoneal carcinomatosis showed typical VX2 tumor pathology, with widespread intraperitoneal metastatic nodules, bloody ascites and perspicuous pulmonary metastases. The clinico-pathological progression pattern was very similar to patients of advanced gastric cancer with peritoneal carcinomatosis. Groups B and C showed similar pattern of cancer progression, but less aggressive.

CONCLUSIONS

First large animal model of peritoneal carcinomatosis from gastric cancer has been established by laparotomic orthotopic injection of VX2 cancer cells into the submucosal layer of the stomach, providing a more suitable model for surgical interventional studies. The clinico-pathological features of this model resemble human peritoneal carcinomatosis.