Hi Mike,
OSM and WSM have given you really good information. As my situation was very similar to yours I thought I would tell you about my experience.
I had an adenoma detected during a colonoscopy. At first biopsy it was thought to be benign but as it was very flat I was referred to a specialist in endoscopic mucosal resection (EMR) to have it removed. The short story is that when it was removed it turned out to be malignant (very low in the rectum, at a T2 level, moderately differentiated, no evidence of vascular or lymphatic invasion). I was referred to a colorectal surgeon. I had an MRI which suggested that there was no lymph node involvement (bearing in mind that MRI is only 85% accurate). My surgeon said this:
"If you were an otherwise fit 45 year old (I was 56) then I would strongly recommend an ultra low anterior resection (ULAR); if you were a 75 year old with other health issues I would strongly recommend watch and wait; you are in the middle so it's a decision you will have to make. It depends on how much of a gambler you are, but I would err on the side of having the ULAR". He then went on to explain that he thought he could do SSO so that I wouldn't need to have a permanent colostomy, but that he would only be able to make an accurate assessment when he had my rectum in his sights. He explained that there was a trade-off, that I may go on to have LARS (as Mia explained). He explained that without the ULAR there was no definitive way to rule out lymph node involvement. He said that post ULAR with no LN involvement I had only a 3% chance of recurrence. He suggested that if I chose watch and wait and there really was undetected LN involvement then by the time this was detected "salvage" surgery would only be curative in 50% of cases. I have however seen better statistics for watch and wait, but they generally relate to those who had pre-adjuvant chemo/radiation. As a Stage 1 at no time was I offered pre-adjuvant chemo/radiation. Chemo/radiation is no walk in the park either, as many people are left with significant side effects that impact their quality of life.
This was probably the hardest decision I have ever had to make.
I chose to have the ULAR. I had it in March 2015, with a temporary ileostomy. I was lucky and really had very few problems with Susie stoma. I had my reversal in May 2015 and that was when the fun really began. I won't sugarcoat it; I had urgency, frequency, clustering, spasming, pain, and lots of blubbering and feeling depressed. However I was lucky in that I always had pretty good control. It was really only at the 6 month mark that I saw significant improvement. I'm now 8 months out from reversal and things are much better.
When I was having a rough time after reversal I often wished I'd opted for the watch and wait. After all, my surgeon has me on the same surveillance schedule that I would have had if I'd chosen watch and wait, so I still experience scanxiety on a regular basis.
I have read recent research which suggests that selected Stage 1 rectal patients (well differentiated, no lymph or vascular involvement, T1 depth) will do well after local excision. I agree with both Jaynee and Mia that this newer approach may be a really good option as long as you fit the criteria, are prepared to adhere strictly to the surveilance regimen, and have a disposition which allows you to tolerate a significant level of uncertainty.
Wishing you all the best for the future, whichever way you decide.
Jan