Abnormal oxidative metabolism of estradiol in women with breast cancer.

The three dominant oxidative biotransformations of estradiol were examined in 10 normal women and 33 females with breast cancer by using a recently devised radiometric method. Estradiol tracers, labeled with 3H specifically in the 17 alpha, C-2, or 16 alpha position, were used to measure both the rate and extent of 17 beta-ol oxidation (the initial metabolic step) and the subsequent 2- and 16 alpha-oxidative reactions. The mean +/- SEM values for the extent of extradiol metabolism at these three specific sites for the extent of estradiol metabolism at these three specific sites were 76.9 +/- 5.3%, 31.1 +/- 4.0%, and 9.3 +/- 0.8%, respectively in normal subjects. Corresponding data in patients with breast cancer--i.e., 73.0 +/- 4.2%, 32.7 +/- 2.7%, and 14.9 +/- 1.5%--revealed a significantly greater extent of 16 alpha-hydroxylation in the latter population. Because the 16 alpha-hydroxylated compounds (including estriol) are themselves potent estrogens, these changes may have important hyperestrogenic consequences that could have a bearing on the etiology of the disease.