Rectal cancer measurement discrepancies



I’m about 6 weeks out from diagnosis with stage 3 rectal cancer.  Mayo has classified my cancer as T3N1M0 (Per imaging done on 1/30).  My tumor is about 7.5cm from the anal verge.  I’ve gotten opinions from 4 institutions so far and one of the things that concerns me most is the variability in measurements from the anal verge.  The 7.5 is the average of my measurements and is from the institution I’m most seriously considering for treatment.  However, two other institutions have measured 6.5 and 8.5. My undersanding is that bowel function quality of life is very correlated with amount of rectum left.  The two lower numbers were measured with a flexible sigmoid scope, whereas the highest was with a straight/fixed sigmoid scope. The surgeon using the latter believed straight/fixed was the only way to ensure an accurate measurement.  I know the surgeons will do their best once underway, but I also know they have to remove 5cm safety margin below the tumor, so each centimeter seems to matter.


Welcome insights from others, thanks!