Estrogen

Although most people think of estrogen as a single entity, these hormones are actually three biochemically distinct molecules the body produces naturally—estrone (E1), estradiol (E2), and estriol (E3). These three estrogen molecules have different activities that make them more or less "estrogenic." The estrogenic activity often determines the mutagenic or carcinogenic potential of an estrogen.

Another nutrition site: http://www.chiro.org/nutrition/FULL/Estrogens_Two-Way_Street.shtml

More from this site, though, because it seems sort of informative:

These estrogens break down or are detoxified into estrogen metabolites—daughter compounds—called 2-hydroxyestrone, 4-hydroxyestrone, and 16-hydroxyestrone.

In premenopausal women, the ovaries produce the estrogen estradiol (E2), which converts into estrone (E1), both of which must eventually be broken down and excreted from the body. This breakdown occurs primarily in the liver, and the excreted metabolites flow out in the bile or urine.

Studies show that when 2-hydroxylation increases, the body resists cancer, and that when 2-hydroxylation decreases, cancer risk increases.

But, all of this is for postmenopausal women and it is about risk, not actual cancer.

Oh no, now it is starting in on epidemiology. 'Nother backbone post needed.

But one thing is: risk of developing a certain cancer is different from risk of developing any cancer is different from risk of cancer recurring in the same person is different from the risk of *that particular cancer" recurring.