While the study comes hedged about with "more research needed" and "consult your physician", the bottom line is this:

Women who reported taking black cohosh (5 percent of blacks and 2 percent of whites) were at 61 percent lower risk of breast cancer, the researchers found.

Also, those who took an herbal preparation derived from black cohosh called Remifemin had a 53 percent lower risk of the disease.

That is a truly hefty protective finding.  Many breast cancers are detected in the post-menopausal years, the risk rising as we age.  Unless the use of Black Cohosh is contra-indicated for you in some way, I would call this a valuable line of defense.

Study: Black Cohosh may halve breast cancer risk

Enzymatic Therapy's REMIFEMIN

Solaray's Black Cohosh Extract