Clinical and in vivo response following surgery or surgery plus adjuvant chemotherapy or immunotherapy for colorectal carcinoma in a rat model.

Two cohorts of rats, 240 with colon cancer and 150 controls, were assessed clinically and immunologically for their response to tumour and its management which was either by surgical excision alone or by surgical excision combined with either adjuvant chemotherapy or immunotherapy. The histology and invasion characteristics were observed for similarity with those of human lesions. Metastases were found in liver, lymph nodes, the peritoneum or lungs in 27% of animals during follow up. Significantly fewer adjuvant-treated rats had metastases than those receiving surgery alone (P less than 0.05), and less total tumour weight was found in the adjuvant-treated rats at four (P less than 0.03) and six (P less than 0.001) weeks postoperatively. Animals in the adjuvant immunotherapy group survived longer than in either other group (P less than 0.001). The crude parameters of host response to tumour, body, spleen and mesenteric lymph node weight were recorded and the latter two indexed to body weight. The body weight of tumour and control rats increased significantly with time (P less than 0.04). The spleen and mesenteric node indices were significantly (P less than 0.04) greater in tumour than control rats and were varied by recurrent tumour growth and by the adjuvant treatment administered postoperatively.