Dr. Keith Roach
October 29, 2026, 5:08 a.m. ET
Dear Dr. Roach: I am an 85 year old woman. I took the Cologuard test a month ago and it came back positive. My GI doctor told me that at my age he wouldn’t perform a colonoscopy. I asked for other alternatives and he said there was a virtual CT colonoscopy. I had soft tissue sarcoma a year ago and had CT scans of my pelvic area and chest. My blood tests are good as well as my analyses. How do you feel during the colon scan? -MK
Dear MK: I understand why you are worried. When a test like Cologuard is positive, there is a significant risk of colon cancer. The best estimate of your risk of having an advanced polyp is currently around 38%, and the chance that you will have true colon cancer is around 4%.
I understand why your gastroenterologist is worried about a colonoscopy. The risk of adverse events in people aged 80 is significantly higher. The sarcoma and radiation therapy you received may increase your specific risk even more than in other people. I will tell my other readers (especially my clinician readers) that the person ordering Cologuard should have thought carefully about what to do in the event of a positive result before ordering it.
If you’re willing to live with a 4% risk of colon cancer, you can stop there. Since you’ve had numerous CT scans (called virtual colonograms) of your abdomen, including at least one recently, it’s reassuring to know that you probably don’t have advanced colon cancer. Blood tests also give some reassurance but are not definitive.
I recommend caution with a virtual scanner as it is uncomfortable for many people. Plus, if the result is positive, you still don’t know what to do. I would ask the gastroenterologist if he would perform a colonoscopy if the virtual colonogram showed a significant problem.
If the answer is still “no”, you should, again, not consider any further assessment; however, if he said he would do the colonoscopy with a positive scan, then you might decide to do it. But it must be recognized that this decision exposes you to a risk of complications, which is approximately 1%.
The most common complication is colon perforation, which requires hospitalization. A 4% risk of cancer remains higher than a 1% risk of perforation. A colonoscopy remains the best way to evaluate cancer and obtain a biopsy of any suspicious masses or polyps.
It’s also worth considering whether you would agree to surgery if necessary. If you are in no way considering surgery to remove colon cancer, it may not make sense to pursue further investigation. However, I have seen people with very advanced, surgically incurable cancer recommended palliative surgery, because acute obstruction of the intestine by cancer is a terrible outcome.
If you are at an impasse with your current gastroenterologist, i.e. you want to proceed with a colonoscopy and he refuses, you have the right to seek a second opinion.Readers can email questions to ToYourGoodHealth@med.cornell.edu.
Gn Health
