CO2 pneumoperitoneum does not enhance tumor growth and metastasis: study of a rat cecal wall inoculation model

Although many studies have evaluated the effects of carbon dioxide pneumoperitoneum on port site recurrence, little is known about its outcome on tumor growth and metastasis. The effect of pneumoperitoneum with carbon dioxide on cecal tumor growth and metastasis was compared with laparotomy using a rat colon cancer cell line.

Time Course Study: Fifty WF/BN F1 hybrid rats were inoculated with 2,000,000 WB2054M5 tumor cells into the cecal wall and explored two to ten weeks after injection. Main Study: 152 rats were randomly assigned either to 6-mmHg CO2 pneumoperitoneum (30 minutes) or 4-cm laparotomy (30 minutes) two weeks after tumor inoculation and were explored four weeks after treatment.

Time Course Study: Thirty-seven (95 percent) of the surviving rats developed a cecal wall tumor, and there was progressive tumor growth and metastasis over the ten-week period. At six weeks, metastasis occurred to the liver in 25 percent, to the lung in 38 percent, and to the lymph node in 63 percent, and peritoneal seeding occurred in 38 percent; this time period was chosen for the main study. Main Study: At the time of treatment (2 weeks), 124 rats were eligible for randomization. One hundred two rats survived the six-week period (50 pneumoperitoneum, 52 laparotomy) and were killed. There were no differences between the CO2 pneumoperitoneum and laparotomy groups regarding cecal tumor growth (1.043 vs. 0.894 g) and metastases to the liver (32 vs. 37 percent), lung (34 vs. 17 percent), lymph node (84 vs. 77 percent), and wound or port (20 vs. 23 percent).

A cecal wall inoculation model mimics the natural cascade of colon cancer growth and metastasis. CO2 pneumoperitoneum did not affect the tumor growth and metastasis to the liver and other organs when compared with laparotomy in this model.