I mentioned recently that I had been to my gastroenterologist’s office for a follow up appointment. Among other things, I asked his opinion about the advisability of having colonoscopy after age 75. I’ve had four colonoscopies, the last being in 2016. The last thing I want is to find I have colorectal cancer, a perfectly preventable disorder, because I neglected preventive surveillance. Just because a person turns 75 years old, It doesn’t mean his life is irrelevant. It doesn’t mean if he was found to have cancer it should be ignored. On the contrary; it’s the time to pull out all the stops and treat him within limits set by his age.
He explained my need for a colonoscopy in the following way: 1. I have had four negative colonoscopies in the past. 2. In none of those colonoscopies were any polyps found. 3. I have no first degree relatives who have been diagnosed with polyps or cancer. Those three criteria place me in the average risk category for acquiring CRC after my 75th birthday. So he felt that ruled out the need for a colonoscopy.
I then asked about Cologard screening. It was his feeling that since I had long-standing hemorrhoids, that despite having a hemorrhoidectomy, the Cologard test would probably be positive, so he didn’t recommend that, either.
Then came the news that a third option existed. That new choice was an FDA approved blood test for colorectal cancer. It was not the Galleri test that allegedly is sensitive enough to detect 50 different cancers, nor was it the carcinoembryonic antigen, the CEA, a decades-old test used to follow known cases or CRC. No, this is a blood test intended purely for screening, and it called The Shield test. It was developed by a company called Guardant Health. This is a new test that detects alterations in colorectal cancer DNA that is i in the patient’s blood stream. It is to be used in high risk individuals, but it is not sensitive enough to detect stage I cancers reliably. It will detect Stage I CRC only 55%-65% of the time. It is better, however, at detecting Stages II, III, and IV CRC’s.
The Shield test is indicated for screening only and not for patients with a personal history of CRC, adenoma, or polyps. Chances of false positive tests are increased if the patient has ulcerative colitis, inflammatory bowel disease, or Crohn’s disease. A negative result does not guarantee the absence of CRC or advanced adenoma. My doctor’s response to me was the the Shield was “not ready for prime time,” meaning the test’s limitations were of enough concern that he recommended I not have it done.
So being in the “average risk” group of patients (it seems like it should be the low risk group) the plan is to practice “watchful waiting” and just keep an eye out for any symptoms. Whether or not the Shield test will be a valuable cancer screening tool later remains to be seen.
References: www.Google.com/view-article/shield-blood-test
