Influence of pneumoperitoneum on tumor growth and pattern of intra-abdominal tumor spreading: In vivo study of a murine model

Background/Aims: The employment of laparoscopy in the treatment of locally advanced colorectal cancer is still questioned by many surgeons, mainly due to the fear of spreading tumors by the laparoscopic procedure. However, it is still unknown whether laparoscopy is actually associated with increased tumor dissemination, especially for those with tumor invasion through the serosa. The main purpose of this study is to investigate the effect of pneumoperitoneum on the intra-abdominal tumor growth and spreading of colon cancer cells by an animal study of murine model. Methodology: Under anesthesia, 10⁶ tumor cells (CT26) were inoculated into the lower abdominal cavity of BALB/c mice by a mini-laparotomy. The mice were randomized to undergo pneumoperitoneum with CO₂ (n=10), helium (n=10), or to act as controls (n=10). Pneumoperitoneum was established over 20 min at a pressure of 10cm H ₂O. The distribution pattern and the weight of peritoneal tumor growth of each mouse were recorded and analyzed at 15 days after surgery. Results: The mean ratios of the tumor mass over the total body weight of the mice were 0.77±1.13% (control group), 4.30±0.$6% (CO ₂ pneumoperitoneum), and 2.17±0.88% (helium pneumoperitoneum). The mean tumdr weight ratio (3.23±1.38%) of the pneumoperitoneal group was 4 times larger than that of the control group (p<0.001). Regarding the use of different insufflation gases over tumor growth, CO₂ accelerates tumor growth more significantly than helium (p<0.001). Intraabdominal distribution (p=0.047) and diaphragm spreading (p<0.001) were significantly greater in the pneumoperitoneum group than the control group. Conclusions: The results of this animal study imply that presence of a pneumoperitoneum enhances the implantation and growth of free intraperitoneal malignant colon cancer cells in this in vivo mouse model. The results of the current study suggest that insufflation during pneumoperitoneum may play an important role in the development of peritoneal dissemination when there are free tumor cells in the intra-abdominal cavity, and the effect of using CO ₂ might be greater than that of using helium.