Objective To observe the effect of Xiaoyan Decoction （antitumor decoction） on cachexia in mice with lung cancer and its antitumor mechanism.Methods Forty mice were randomized into the healthy group

lung cancer group

Xiaoyan De-coction group and megestrol acetate group

with 10in each.The leptin content and the expressions of p53and C-myc protein were observed after 12days of continuous treatment.Results Comparing with the lung cancer group

the reaction

body hair and food intake improved significantly in the Xiaoyan Decoction group and megestrol acetate group （P<0.01）

especially the food intake in the Xiaoyan Decoction group （P<0.01）.The situation of reaction and body hair was the worst in the lung cancer group.The mice were sacrificed after treatment.Comparing with the healthy group

the bodyweights in the lung cancer group

Xiaoyan Decoction group and megestrol acetate group were significantly decreased （P<0.05or P<0.01）

especially in the lung cancer group （P<0.01）

especially in the Xiaoyan Decoction group （P<0.01）.Comparing with the lung cancer group

the tumor weight was significantly decreased in the Xiaoyan Decoction group and megestrol acetate group on the 12th day of treatment（P<0.01）

especially in the Xiaoyan Decoction group （P<0.01）.Comparing with the healthy group

the leptin levels in the lung cancer group

Xiaoyan Decoction group and megestrol acetate group were decreased

especially in the lung cancer group and megestrol acetate group （P<0.05）.Comparing with the lung cancer group

the expressions of p53were sig-nificantly increased in the Xiaoyan Decoction group and megestrol acetate group （P<0.01）

especially in the Xiaoyan Decoction group （P<0.01）.Comparing with the lung cancer group

the expressions of C-myc were significantly decreased in the Xiaoyan Decoction group and megestrol acetate group （P<0.01）

especially in the Xiaoyan Decoction group （P<0.01）.Conclusion Xiaoyan Decoction can improve appetite

body function and immune function

increase bodyweight and leptin level

promote p53expression and inhibit C-myc expression and tumor growth in mice with lung cancer.