I also had anal cancer in April 2014. I understand what you are going thru. It is awful. I can relate as I recently had an embarrassing accident. Thank God it was only my family that had to endure it. I thought if I didn't eat anything before the gathering it would be better, but when I did eat everything came...well you know.. There is absolutely no way to control it.
I am now on Colestipol. It is a prescription that is used for high cholesterol but binds to the intestines. I cut mine in half as it seems to be constipating but better than the "other way".