rinaina,
I think you will have to make up your own mind (or rely on your onc) because even the experts can't agree on all facets of antioxidant activities in cancer.
One area where there seems to be agreement is in the field of prevention.
Antioxidants by suppressing free radicals which may be cancer causing are reducing the risk of initiating a cancerous tumour.
However once the disease is in progress the use of antioxidants is still debated as you will be aware after reading about the controversy between Dr
Gabriella D’Andrea who published a paper in 2005 (after several more by other researchers, against the use of antioxidants while undergoing cytotoxic treatments such as chemo drugs generating free radicals to kill cancer cells), & Ralph Moss Phd who published an essay of counter arguments.
However when the cancer treatment does not involve an oxidative process it could be that
antioxidants may still play a usefull role. But I am not an expert on the subject to make a recommandation.
Ref.
http://www.annieappleseedproject.org/annieappleseedproject/ptsunchemanr.html
http://www.cancerdecisions.com/112005_page.html