Possible effect of pneumoperitoneum on the spreading of colon cancer tumor cells

PURPOSE: By using a murine hepatic metastatic model, we tried to investigate the possible influence of gas insufflation in colon cancer cells spreading from the portal system to the liver. METHODS: After transducing the human placental ALP gent into murine colon cancer cell line CT26, we successfully selected a clone of CT26/DAP that would yield a specific color following histochemical staining. Fifty mice were assigned into two groups, receiving either an intrasplenic injection of 10⁶ CT26/DAP cells alone or the cells followed by intra-abdominal helium insufflation with the pressure of 15 cm H₂O for ten minutes. Five mice in each group were used to observe their survival and the other mice were killed at four different time periods: 10 minutes, 24 hours, 48 hours, and 72 hours following cell injection. The livers and spleens were removed for histochemical staining. By counting the numbers of specific dark reddish spots of CT26/DAP cells, we could estimate the number of tumor cells on the hepatic surface. RESULTS: At the very beginning following tumor cell injection, we found a significantly greater number of tumor cells on the hepatic surface in mice with gas insufflation (6354 ± 1072 vs. 2133 ± 223, respectively; P = 0.012). But the difference of these two groups became smaller and smaller as time went by. The number of tumor cells on the hepatic surface would reach the lowest level at postoperative 48 hours, and the tumor foci then began to grow both in size and number. The above patterns of dynamic change in tumor cell distribution were similar in mice both with and without gas insufflation. Average survival was slightly shorter in mice with gas insufflation, but the difference was not statistically significant. CONCLUSION: Pneumoperitoneum caused by gas insufflation may increase tumor cell spread from the portal system to the liver at the very beginning stage; however, there was no significant difference in long-term survival between mice with and without gas insufflation in this murine animal model.