So sorry for the cancer diagnosis of your husband, @lindadob.
I agre with what @paul28 has written.

I had a transanal resection for a polyp that the first biopsy (taken at a colonoscopy) said was pre-cancerous. Second biopsy (post-surgical) revealed positive margins. Surgeon said, no new surgery because she could see nothing more and because polyp was too close to the sphincter, and she didn't want to put the sphincter at risk. She sent me to an oncologist. He said the same: no surgery so as not to put the sphincter at risk, better radiotherapy. Now I have a rare, very low rectovaginal fistula because of the radiotherapy.

I consulted the same surgeon about fixing the fistula. She offered a flap with a temporary colostomy with a fairly high chance of recurrence of a fistula. Went for a second opinion. Surgeon #2 said: they should have operated again after the biopsy indicating the positive margin and wait & see before doing radiotherapy. A third opinion from an investigator and surgeon oncologist said the same thing.

A more recent colonoscopy revealed a new polyp facing the fistula, so now, on Jan. 26, I'm having a resection of the rectum, mesorectum and sigmoid with a coloanal anastomosis, to avoid a colostomy, to reduce the risk of a new fistula, of a new polyp, and of cancer.