did it say that glutamine was in some way linked to having cancer, or just that cancer cells use glutamine?
If it doesn't raise your risk then I don't see a reason to avoid it.
Personally, glutamine is an absolute godsend for me in terms of intestinal inflammation. Nothing else even comes close. I'm pretty sure that having constant inflammation issues in my GI tract is more likely to give me cancer than 20g of glutamine every morning.