I have to agree with Meesh. There is a slight increase in UCers risk of colon cancer - however, we're more likely to have regular c-scopes to check for such things. So, if by chance a UCer would develop colon cancer, it would be caught early, which is easier to treat.
I suggest a frank discussion with your GI if you are still feeling concerned.
Pan-colitis and GERD diagnosed May 2003
Osteopenia diagnosed Feb 2006
Asacol 12 per day, Azathioprine 75mg, Aciphex, Effexor XR, Forvia and a Probiotic