In vitro inhibition of tumour growth in a helium-rich environment:: Implications for laparoscopic surgery

Background: The recent results of several experimental studies have suggested that tumour implantation after laparoscopic surgery for intra-abdominal malignancy may be partly related to the chemical composition of the insufflation gas used during surgery. These studies have demonstrated that the use of helium as a laparoscopic insufflation agent for cancer surgery results in less tumour implantation and growth at port sites. To further investigate these findings, the present study was performed to compare the growth of cultured tumour cells after exposure to simulated laparoscopic environments, rich in helium, carbon dioxide (CO2), or air. Methods: A rat mammary adenocarcinoma cell suspension was exposed to a simulated laparoscopic environment for 40 min in one of the following groups: (i) control (atmospheric air. equivalent to a 'gasless' laparoscopic environment): (ii) a CO2-rich environment; and (iii) a helium-rich environment. Cells were then cultured for 18 h and optical density readings wore used to assess the number of viable tumour cells at the end of this period. The experiment was performed twice using an identical protocol to ensure consistency in the results. In a further study, pH was continuously measured using an antimony probe during a 40 min insufflation period and for 10 min after insufflation. Results: Cell growth was significantly lower after incubation in the helium-rich environment compared to both the CO2 and control groups (P < 0.001). There was a significant decrease in pH in the CO2 group which was not observed during exposure to either air or helium. Conclusions: The inhibition of tumour growth in a helium-rich environment demonstrated by this study, and the reduced incidence of port-site metastases seen in other experimental studies. suggests that the clinical use of helium as an insufflation gas may have important advantages ol er CO2.