Do operations facilitate tumor growth? An experimental model in rats.

Enhancement of tumor growth by operation is a concern often expressed by surgeons and patients anticipating cancer surgery. Two series of experiments were performed in which Fischer 344 rats and a carcinogen-induced transplantable rat colon cancer were used to test whether anesthesia and operation facilitate tumor implantation and growth. In the first experiments two groups of rats were given intraperitoneal tumor cells. One group underwent sham laparotomy; the second did not undergo surgery. In the second set of experiments rats were injected subcutaneously with tumor cells and then divided into four groups. The first group did not undergo laparotomy. The second underwent laparotomy on day 1, the third on day 15, and the fourth on days 15 and 29 after tumor implantation. Animals were followed for the incidence and growth rate of tumors that developed. The initial experiments demonstrated that 89% of the operated versus 49% of the nonoperated animals developed a tumor (p less than 0.001). The second experiment demonstrated that: animals undergoing multiple operations have a higher incidence of subcutaneous tumor nodules than nonoperated animals (p less than 0.05); animals undergoing multiple operations have a higher incidence of subcutaneous tumor nodules than animals undergoing a single operation (p less than 0.05); animals undergoing multiple operations had larger size tumor masses than the nonoperated animals (p less than 0.05) and than animals undergoing only one operation (p less than 0.04). This study supports the hypothesis that multiple operations and anesthesia may enhance tumor implantation and growth of metastases. This should be considered when designing therapy for patients with cancer.