Background: Laparoscopic resection for cancer is controversial and port-site metastases are not infrequent. The mechanisms of occurrence of port-site metastases remain unclear. Animal experiments have suggested a role for carbon dioxide (CO2), but port-site metastases also occur after thoracoscopy, where no CO2 is used. The aim of this study was to define the role of CO2 in the seeding of tumor cells in the human patient.
Methods: CO2, instruments, trocars, suction device, and peritoneal washing were examined during 12 staging laparoscopies for pancreatic cancer. The presence, viability, and biological significance of cells were investigated using conventional cytology, polymerase chain reaction (PCR), and restriction fragment length polymorphisms (RFLPs) to detect the presence of a mutant k-ras gene as a genetic marker of cancer cells.
Results: Cytology exam of peritoneal washing, instruments, the suction device, and trocars revealed many cells. Tumor cells were detected in 6/12 peritoneal, in 4/12 trocars and 4/11 instruments washings, but not in 12 CO2 samples. The DNA content of CO2 was very low-as assessed by PCR. Mutant DNA was detected by RFLP in four out of 12 aerosols. Six aerosols did not contain any DNA. Two aerosols were borderline.
Conclusions: During staging laparoscopy for pancreatic cancer in humans, CO2 contains only very low levels of free-floating tumor cells, even in the presence of massive peritoneal contamination. These results suggest that the incidence of port-site metastases might be reduced if mechanical contamination of the port sites with instruments or with the specimen can be avoided.