Adjuvant chemotherapy in a new metastasizing caecum tumor model.

A metastasizing tumour model in which a non-immunogenic tumor (Lewis lung carcinoma) is implanted in the caecum of syngeneic mice, is described. The most interesting property of this model is the formation of spontaneous hepatic and transperitoneal metastases. Resection of the caecum tumor 14 days after implantation leaves micrometastases in liver, peritoneum and lungs. This gives the opportunity for the study of adjuvant therapy. Adjuvant chemotherapy with cyclophosphamide cured a significant percentage of animals with micrometastases in liver and peritoneum. Cyclophosphamide therapy had no effect on micrometastases in liver and peritoneum when the primary tumor was left in place. This finding underlines the importance of aggressive treatment of the primary tumor before adjuvant chemotherapy can be effective in colorectal cancer.