Pilot Study on the Growth Inhibition by Estramustine Phosphate (Estracyt®) of Rat Mammary Tumours Sensitive and Insensitive to Oestrogen

Abstract

Rat mammary tumors induced by 7,12-dimethylbenz(a)anthracene had a higher concentration of 3H and 14C than muscle after injection of estramustine phosphate labeled with 3H in the estrogen moiety and 14C in the alkylating moiety. TLC showed that dephosphorylated estramustine phosphate was present in the tumors but no free estradiol-17.beta.. The uptake of the drug in the tumors was paralleled by a dose dependent retardation of tumor growth and a prevention of tumor number increase. Estramustine phosphate also retarded growth of mammary tumors resistant to treatment with estradiol-17.beta.. Estramustine phosphate probably has a greater effect on tumor growth than estrogen.