Tumor implantation during laparoscopy using different insufflation gases - an experimental study using cultured cancer cells.

Recent work using an experimental model in our laboratory has shown that the likelihood of tumor implantation at laparoscopy port-sites following laparoscopy might be influenced by the specific gas used for insufflation. In particular helium insufflation was associated with less port site metastases. The model entailed an inbred rat strain and a tumor cell suspension of mixed heterogeneity, native to the rat strain. To determine whether our previous findings could be reproduced using a different model, we investigated the effect of insufflation with either helium or carbon dioxide gas on the implantation of a purified cell suspension of cultured cancer cells. Thirty-eight Dark Agouti rats were randomized to undergo a 40 minute period of laparoscopic insufflation with either helium or carbon dioxide (19 animals in each group/three different experiments). Three laparoscopy ports were placed and 2 x 10 5 cultured mammary adenocarcinoma cells were introduced into the abdominal cavity at the beginning of the period of insufflation. The rats were killed nine days after surgery and the port sites and abdominal cavity were examined for presence of tumor. Rats undergoing helium insufflation were equally likely to develop port-site metastases compared to rats undergoing carbon dioxide insufflation. There was, however, a predilection for port site metastases to develop at the port site used for camera placement in both groups. Because this port site accommodated a 2 mm laparoscope, it was associated with a larger wound than the other two port sites. Peritoneal tumor deposits elsewhere in the peritoneal cavity were more common following helium insufflation, compared to carbon dioxide. The outcome of this study is different to the results from previous studies using a heterogeneous tumor cell suspension in the same model in our laboratory, or elsewhere, with no advantages demonstrated for insufflation with helium gas. Purified cell suspensions could behave differently to a heterogeneous cell suspension of identical cancer cells in a port-site implantation model, and other cells present within heterogeneous tumor suspension might influence the likelihood of metastasis. As reported previously, tumor implantation is more likely in larger port site wounds and this is independent of the insufflation gas.