Regression induced by lentinan, of peritoneal carcinomatoses in a model of colon cancer in rat.

Lentinan has been tested in a model of colon cancer in rats. Peritoneal carcinomatoses were induced in BDIX rats by i.p. injections of syngeneic cells isolated from a colon carcinoma, and established in a permanent cell line. The treatment consisted of five i.p. injections, 2 days apart, of 2 mg lentinan/kg at a concentration of 200 micrograms/ml. This was started on day 14 after tumor cell injection, when the rats bore numerous nodules of 1-5 mm. Lentinan significantly inhibited the growth of carcinomatoses. Eleven out of the 20 rats treated with the best lentinan therapy were tumor free at autopsy on day 42. Lentinan significantly increased the life span of carcinomatous rats. The half life following tumor cell injection was 42 days in the control and 70 days in the treated group. Four out of 10 treated rats were still alive on day 210. They were tumor free at autopsy, whereas all the controls died between the 40th and the 70th day. The effectiveness of lentinan was dependent on the number and frequency of the injections. A dose effect was obtained and a strong influence of the concentration was shown.