Influence of different gases used for laparoscopy (helium, carbon dioxide, room air, xenon) on tumor volume, proliferation, and apoptosis

Background: Previous reports suggest that helium pneumoperitoneum used for laparoscopic surgery suppresses postoperative tumor growth. The present study was designed to determine the effects of gases used in laparoscopy on tumor volume, proliferation, and apoptosis in rats with implanted malignoma. Methods: In 36 rats Morris hepatoma 3294A cells were implanted intrahepatically. Then, after 5 days, they underwent laparoscopy using helium (n = 7), CO₂ (n = 7), room air (n = 7), or xenon (n = 8). One group received anesthesia only (n = 7). Rats were killed 10 days after implantation to assess tumor volume, proliferation, and apoptosis. Results: Helium pneumoperitoneum caused a significant smaller tumor volume compared to other groups (Kruskal-Wallis test: p = 0.001; median tumor volume: control: 44 mm³; helium: 19 mm³). There was no significant difference in tumor cell proliferation (PCNA) and apoptosis (TUNEL reaction) between the groups. Conclusions: There was a significant decrease of tumor volume using helium pneumoperitoneum compared to the other gases, but no decreased tumor cell proliferation or increased tumor cell apoptosis.