title: Effects of pneumoperitoneum on tumor implantation with decreasing tumor inoculum.
abstract: BACKGROUND
  The aim of this study was to determine the effect of pneumoperitoneum on the rate of trocar-site implantation with decreasing inoculum of cancer cells.
  
  
  METHODS
  A total of 0.5 ml of GW-39 human colon cancer cell suspensions at 1 percent (approximately 3.2 x 10(5) cells) and at 0.5 percent (approximately 1.6 x 10(5) cells; v/v) were injected into the abdomen of hamsters through a midline incision. Animals in each group were randomized to receive either pneumoperitoneum (1 percent = 33; 0.5 percent = 43) or not (1 percent = 32; 0.5 percent = 39). Gross and microscopic tumor implants were documented seven weeks later at four trocar sites.
  
  
  RESULTS
  In the 1 percent group, pneumoperitoneum significantly increased trocar-site tumor implants from 50 to 71 percent (P < 0.001). Pneumoperitoneum also resulted in the following: 1) more frequent involvement of all four concurrent sites (38 vs. 10 percent; P < 0.02); 2) more frequent palpable tumors (13 vs. 5 percent; P < 0.01); 3) larger tumor mass (2.1 +/- 0.6 g vs. 0.2 +/- 0.1 g; P < 0.02). In the 0.5 percent group, pneumoperitoneum did not significantly increase trocar-site tumor implants, and it did not result in a larger tumor mass. The percent increase in trocar-site implants owing to pneumoperitoneum was influenced by the amount of tumor inoculum (21 percent in the 1 percent group; 10 percent in the 0.5 percent group). The mass of palpable tumor implants after pneumoperitoneum decreased with decreased inoculum: 1 percent = 2.1 +/- 0.6 g; 0.5 percent = 0.3 +/- 0.1 g (P < 0.0001).
  
  
  CONCLUSIONS
  Pneumoperitoneum significantly increased both tumor implantation rate and mass when approximately 3.2 x 10(5) colon cancer cells were injected into the peritoneal cavity. These effects of pneumoperitoneum diminished with one-half as many tumor cells injected in the peritoneal cavity.
authors.affiliation: Department of Surgery, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Wu
authors.forename: D B
authors.initials: DB
authors.lastname: Jones
authors.forename: L W
authors.initials: LW
authors.lastname: Guo
authors.forename: E B
authors.initials: EB
authors.lastname: Brasfield
authors.forename: M B
authors.initials: MB
authors.lastname: Ruiz
authors.forename: J M
authors.initials: JM
authors.lastname: Connett
authors.forename: J W
authors.initials: JW
authors.lastname: Fleshman
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000473:pathology; D003110:Colonic Neoplasms / Q000473:pathology; D006224:Cricetinae; D006801:Humans; D010535:Laparoscopy / Q000009:adverse effects; D008297:Male; D008647:Mesocricetus; D009366:Neoplasm Seeding; D009368:Neoplasm Transplantation / Q000379:methods; D010529:Peritoneal Cavity; D011028:Pneumoperitoneum, Artificial / Q000009:adverse effects*