As your Dr. will tell you before you start treatment, you cannot take herbal supplements during treatment.
What you do pre tx and post tx is one thing, but it is extremely important not to take any supplements during treatment. Please talk to your medical team about it for more info. Vitamins are generally okay, but I advise you to please run it by the doc first.
You are about to start an important and difficult course and no herbal supplement will help you through it, in fact it is possible that some herbs will interfere with treatment. Don't take my word for it-ask the med. professionals.
I was thinking this was posted earlier myself Hrsepwr!