PJ's right about the mixed messages, which is why it's probably best to see what your doctor's thoughts are about it.
I just know from my own personal experience with half a dozen oncologists that have told me to avoid soy and herbal products as if they were the plauge. Not sure why there is so many mixed messages on this subject, but with time all things pertaining to cancer changes as new studies and reports come out. Some doctors are old school, and some very up to the minute on research,
For me, I just find it easier avoiding all of it, that way I have no worries and no lectures from the doc = )