Effects of Laparoscopy on Tumor Growth

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.

Differences in tumour growth, tumour cell proliferation and immune function after laparoscopy and laparotomy in an animal model

BACKGROUND

Clinical and experimental studies have shown that laparoscopy preserves the immune response and can give better clinical results than laparotomy. However, the use of laparoscopy for the treatment of cancer patients is still controversial due to the risk of port-site and haematogenous metastases and increased tumour growth. The purpose of this experimental study was to assess tumour growth and the mechanism of differential tumour behaviour after laparoscopy and laparotomy.

METHODS

Seventy-five young, male Wistar rats were randomly assigned to one of two experiments. Experiment 1: 45 animals were inoculated subcutaneously with Walker carcinosarcoma 256 cells and were subdivided into three groups of 15 rats. Control group la was submitted to anaesthesia only, group 1b received carbon dioxide (CO(2)) pneumoperitoneum,while group 1c received a laparotomy. Animals were sacrificed on postoperative day (POD) 7; tumours were excised and weighed to evaluate tumour growth. Nucleolar organiser regions identified by silver staining (AgNORs) were analysed to evaluate cell proliferation. Experiment 2: 30 rats were submitted to the same procedures as before, with ten animals in each group (2a, 2b, 2c), and a delayed-type hypersensitivity response (DTH) was used to evaluate the immune function.

RESULTS

The average tumour mass was 1.76 g in group 1a, 2.81 g in group 1b and 4.21 g in group 1c (p < 0.05). The AgNOR expression results were similar in the three groups. The immune function was better preserved in the control group (2a: average inflammatory area on POD1 = 106 mm(2) and on POD2 = 128.18 mm(2)), than in the pneumoperitoneum group (2b: average inflammatory area on POD1 = 79.75 mm(2) and on POD2 = 126.93 mm(2)); the worst results were in the laparotomy group (2c: average inflammatory area on POD1 = 33.33 mm(2) and on POD2 = 61.32 mm(2)).There were significant differences between groups 2a and 2c and between 2b and 2c.

CONCLUSION

Laparotomy stimulates a greater tumour growth than CO(2) pneumoperitoneum, but there is no difference in tumour cell proliferation. The cellular immune function is better preserved in animals submitted to CO pneumoperitoneum than in the laparotomized animals. These results suggest a relationship between a weaker immune response and a greater tumour growth.