CO2 pneumoperitoneum increases systemic but not local tumor spread after intraperitoneal murine neuroblastoma spillage in mice

Abstract

Minimally invasive techniques are increasingly used for biopsy and resection of neuroblastoma, but the impact on the behavior of spilled tumor cells is unknown. We aimed to investigate whether CO(2) pneumoperitoneum can affect local or systemic tumor manifestation after spillage of neuroblastoma cells into the peritoneal cavity. Murine neuroblastoma cells (Neuro2a, 1x10(6)) were inoculated into the peritoneal cavity of 25 male A/J mice, which subsequently underwent CO(2) pneumoperitoneum (n = 12) or laparotomy (n = 13) for 1 h. At the 28th postoperative day, local (peritoneal and surface of the gut) and systemic (liver, lung, spine) tumor spread was graded in a blinded manner (1-4 point scale) and specimens were histologically examined for tumor manifestation (hematoxylin and eosin stain) and tumor cell proliferation rate (Ki-67-stain). In the case of no visible lesion, five random sections were histologically examined. Peritoneal carcinosis was graded macroscopically. Tumor manifestations were detected in 10 out of 12 (83%) animals after CO(2) pneumoperitoneum, and in 9 out of 13 (69%) after laparotomy (n.s.). Incidence of liver metastasis was higher after CO(2) pneumoperitoneum versus laparotomy (83% versus 31%; p < 0.05). Incidence and grading of peritoneal carcinosis was not significantly different between the groups (n.s.). Intrapulmonary metastasis was found in one mouse of each group, but no metastasis of the spine. However, the grading of liver metastasis was higher after CO(2) pneumoperitoneum compared to laparotomy (p < 0.05). Tumor cell proliferation (Ki-67 stain) in the liver did not differ between both groups. Moreover, proliferation always exceeded 50% of tumor cells, irrespective local or systemic tumor manifestation. CO(2) pneumoperitoneum increased intrahepatic metastasis, but not local peritoneal carcinosis in a murine neuroblastoma model. This suggests that laparoscopy could promote systemic dissemination of intraperitoneally spilled tumor cells when no chemotherapy is applied. It remains to be determined whether this is due to local immune suppression or direct modulation of tumor cell behavior.