I was in a similar situation (sort of) in that I had surgery first, then 4 rounds of FOLFOX, then 5FU continuously for 6 weeks while I went through 30 radiation treatments; then finished my 8 rounds of FOLFOX (last 2 w/o the oxi). Anyway - radiation. It's my understanding that radiation only addresses a LOCAL recurrence - so it doesn't do a thing for any cancer cells that may be floating around in your body and just haven't grown large enough to show up on a scan. Also my understanding that with rectal cancer, because there are so many lymph nodes in that area, treatment protocal for rectal cancer is you do radiation to prevent a local recurrence - or at least that's the hope. Again, my understanding - that colons are not radiated because they are moving around more in your body - harder to actually target an area safely with the colon vs. the rectum.
All that said, honestly, radiation was pure hell for me. But I had a temporary ileostomy when I went through it, so at least I was spared the butt burn. I think I was about 10 rounds in before I started to experience side effects. My side effects started as crazy itching - but turned into pain - a lot of it internally. It was awful. It would burn like hell when I peed. If I drank more water, it diluted the burn a little, but I had to pee more frequently - so it was a trade off. I'm not trying to scare you or discourage you - but no one warned me just how bad it would be. Still, I made it through 30 rounds. I've never had a local recurrence, but I did have spread (lungs/lymph nodes in my chest); so was it worth it? Who knows.
Have you discussed your desire to stop treatments (and why) with your radiation oncologist? I know when I've had trouble with chemo regimens, we've tweaked the doses, frequency, etc. until we can find something I can tolerate. I don't know if those options are available for radiation treatments or not. Make sure you have all the facts about why you should complete radiation (from your doctor); weigh them against what you feel you can physically tolerate - consider the "what ifs" and what you can and can't live with later - and make the decision that is best for you. These decisions aren't easy. So much of a cancer is a roll of the dice. It's so frustrating. Best of luck with your decision.
Belle - "Don't Retreat - Reload"DX 10/07 Stage III Rectal
Surgery 11/07; 27 of 38 nodes
Perm Colostomy 8/11
12/10 recurrence lungs & LN's
VATS Jan 2011
Radiation Oct 2013
Chemo for Life
2012 Colondar Model