http://journals.ons.org/xp6/ONS/Library.xm...xml
This fantastic essay by an oncology nurse, just released in the last few months, has a good rationale for which herbs and supplements might be beneficial in the cancer context. I think Eric might have posted it earlier. The second part (you can find it by searching the same site) is about potential dangers in herbs and supplements.
I was especially interested to see that milk thistle was listed as being at least mildly estrogenic, so it's worth thinking twice about taking if you are er+.
I've emailed with the author and she seems pleased that her work is reaching the people who need it most!
Best,
Jeff