The antitumor activity and immunosuppressive effects of 5-fluorouracil suppositories in rectal cancer patients.

The antitumor activity and immunological effects of the local administration of 5FU were investigated by determining the tissue concentration of 5FU, histological appearance of the primary tumor, and lymphocyte subsets of the regional lymph nodes in 23 rectal cancer patients. Twelve patients were treated with 5FU suppositories preoperatively, being the 5FU group, while 11 patients were given no preoperative treatment, being the control group. The 5FU concentrations in the primary tumors were higher than those in the regional lymph nodes and appeared to remain high for an extended period. No histological changes peculiar to the 5FU group were observed in the primary tumors. An analysis of the lymphocyte subsets in the pararectal nodes revealed that Leu2a+15- cells, or cytotoxic T lymphocytes, were significantly decreased in numbers in the 5FU group compared to the control group. These results suggest that the local use of 5FU may not only exert an antitumor effect against rectal cancer, but can also cause the suppression of antitumor immunity in the regional lymph nodes.