THE EFFECT OF LAPAROTOMY AND LAPAROSCOPY ON THE ESTABLISHMENT OF SPONTANEOUS TUMOR-METASTASES

Background. Surgical extirpation of solid tumors may not be entirely p ossible, and the consequence of surgical excision is invariably the re lease of tumor cells into the systemic circulation. The aim of this st udy was to determine whether laparotomy affects the establishment of s pontaneous pulmonary metastases after excision of the primary tumor in a murine flank tumor model and to determine possible underlying immun e abnormalities. Methods. An initial experiment was carried out to com pare the development of gross spontaneous pulmonary metastases in the presence of a primary flank tumor and after excision of the tumor in C 57/BL6 female mice. Another group of mice had flank tumors excised and were simultaneously randomized to undergo anesthetic only (control), laparoscopy, or laparotomy, after which the subsequent development of pulmonary metastases was determined. Finally, a third experiment entai led determination of natural killer cell (NK) cytotoxicity and the eff ect of splenic macrophages on NK cytotoxicity at days 1, 7, and 14 aft er tumor excision. Results, Excision of the primary tumor resulted in a significant increase in the number of pulmonary metastases in mice c ompared with mice that did not have tumors excised (P =.01). Both lapa rotomy and laparoscopy significantly increased the number of spontaneo us pulmonary metastases after tumor excision compared with controls (P less than or equal to .01) and there was also a significant differenc e between laparotomy and laparoscopy groups (P =.00). NK cytotoxicity was significantly suppressed at all time points after operation in the laparotomy group compared with both the laparoscopy group and the con trols (P less than or equal to.01). Suppression occurred after laparos copy at 24 hours after the procedure compared with controls (P = .00); by day 7 this difference was not significant, but at day 14 there was again a significant suppression (P less than or equal to .03). Spleni c macrophages appeared to be a suppressor to natural killer cell cytot oxicity (NKCC) in the corresponding groups and at the corresponding ti me points. Conclusions. The differential establishment of spontaneous metastases after tumor excision and laparotomy and, to a lesser extent laparoscopy results in lowered host antitumor surveillance and may be mediated at least in part by the generation of splenic suppressor cel ls in the early postoperative period causing a more marked and prolong ed effect after laparotomy, than after laparoscopy.