Effect of estrogen and antiestrogen therapy in rats bearing mesenchymal tumors.

We applied both hormonal and antiestrogen treatment in female Wistar rats to analyze the estrogen dependence of the growth of sarcomas induced with 9,10-dimethyl-1,2-benzanthracene. Animals bearing tumors of 10 mm in diameter were divided at random into five groups and submitted to different treatments during 24 weeks. The treatment with ovariectomy and tamoxifen in tumor-bearing animals resulted in tumor growth suppression and prolonged survival by a protection against the lethal tumor. On the other hand, the estrogen treatment exerted an adverse effect showing a faster growth of the tumors and a great decrease in survival. In summary, the antiestrogen treatment can have an antitumor effect in mesenchymal tumors, possibly by modifying the immunological status of the host.