Removing oxygen-derived free radicals delays hepatic metastases and prolongs survival in colonic cancer. A study in the rat.

This study examined the influence of the oxygen-derived free radical removing agents allopurinol and dimethyl sulphoxide (DMSO) on the occurrence of hepatic metastases and on the survival rate in the rat with 1,2-dimethylhydrazine (DMH)-induced colonic tumours. At 10 weeks of age, rats were subcutaneously injected every week with 10 mg per kg body weight of DMH for 28 weeks. This produced colonic carcinoma in 80% of animals. The rats that were at this stage continued on their drinking water developed multiple hepatic metastases within 3 months and died at the age of 14.9 +/- 0.3 months (mean +/- SEM). Administration of 1,2 or 5% allopurinol or DMSO for drinking after production of the colonic tumours prevented the development of hepatic metastases 3 months later and significantly (p less than 0.01) extended survival to at least 22.1 +/- 0.1 months of age (mean +/- SEM). The results suggest that in the rat with colonic carcinoma, removing oxyradicals impairs the development of hepatic metastases and prolongs survival.