Bill,
You are getting "standard of care" treatment for Stage 3 colon cancer. I'm not sure on the stats, but I would guess that your odds are slightly better of not having a recurrence on Folfox than if you just took 5-FU and Leucovorin, and your odds are slightly better on 5-FU and Leucovorin than if you didn't do chemo. The choice to do chemo is always yours. I did the full 12 treatments because I had 14 positive lymph nodes out of 36, but Folfox has left me with numb hands and feet and my cancer recurred anyway.
If you are thinking of giving up the chemo because of side effects, consider a couple of things first. 1. can you adjust your pre-meds or pills post chemo to reduce the side effects. 2 Ask the doctor about reducing the dosage. I found a 10% reduction did wonders for reducing my side effects. 3. Consider dropping Oxaliplatin and continuing on 5-FU and Leucovorin or moving to Xeloda.
I would recommend staying on some kind of chemo and the easiest way to do that is not having to deal with bad side effects.
Jack