Brad,
That's a tough situation. In particular, with a cancer history, a lot of the typical Crohn's medications are a much riskier deal for you. I would suggest asking your doctor about the possibility of doing a course of enteral nutrition (special liquid-formula diet) to induce remission, and then using it as a supplement to help maintain remission. This is a dietary treatment that has been around for 40 years and has been tested in randomized, published, clinical studies in patients with Crohn's disease. It remains a standard treatment for Crohn's in Europe, Canada, and the Far East, but is rarely mentioned as a treatment possibility to patients in the US. The remission rates are very good, but doctors in the US tend to think it's too difficult to ask patients to stick with a liquid diet for several weeks. It might be something to discuss with your GI.