An experimental postoperative metastasis system using Yoshida sarcoma inoculated subcutaneously into footpad.

When Yoshida sarcoma cells were inoculated subcutaneously into the left footpad of Donryu rats, the weight of the left lumbar lymph nodes increased proportionally to the number of the inoculated cells. Resection of primary implants the day after the inoculation of 5 x 10(6) cells failed to rescue the host rats and they died of metastases within 12 days. There was no significant difference in mean survival days between the rats (8.9 days) whose primary implants were resected on the 5th day after inoculation and the control rats (8.6 days) bearing the primary implants. Mitomycin-C, a highly effective drug against Yoshida sarcoma cells, produced many long survivors (over 30 days) in the treated rats whose primary implants were resected the day after inoculation, but failed to do so when resected 5 days after inoculation. All of them died of metastases within 20 days. Based on these results, this present system is discussed for its usefulness as a screening and evaluation model for antitumor agents.