Pete
I doubt that antioxidants promote cancer growth at least not directly. (please send me the link to the article)

What is likely the issue here is this. Large amounts of antioxidants interfere with treatment (radiation/chemo). The idea with some chemo and radiation is to damage the crap out of your DNA and if the cells are replicating rapidly they cannot keep up with the repair and decide to die. Antioxidants protect cellular components. The concern is that large amounts of antioxidants may also protect cancer cells from damage. Therefore you do not use AO during therapy but you can (should) take them afterwards.

M