Monday, November 3, 2014

New Colon Cancer Screening Test May Be Over-Hyped

Let's admit that most cancer screening tests are no fun. Whether it's women submitting to mammography and having their breasts squeezed into the shape of donuts, or men getting PSA tests with the further possibility- if the PSA is too high -  of tearing out up to 16 sections of gland in prostate biopsy (the pain of which puts more than 40 percent off from ever having it again) or having a colonoscopy with all that implies, including having to sit on the 'throne' for hours before to empty one's bowel contents.

Many current stool tests look for blood that could suggest a tumor. Cologuard does this too but the key additional benefit is that it detects DNA that could be a sign of cancer or precancerous growths called polyps. People send a stool sample to a lab, where it is tested. If the test is positive, the next step is a diagnostic colonoscopy. A relatively thin, flexible tube equipped with a tiny camera is passed through the large intestine for an examination that takes from 20-30 minutes. Those who reject the sedation, as I usually do, can observe the entire procedure on a TV screen.

If polyps or other growths are visible they can be removed and checked for cancer via biopsy. When this is done for cancer-screening purposes and precancerous polyps are removed, colonoscopy actually prevents cancer, it doesn't just detect it. But it requires drinking laxatives the day before to clean out the bowel and this is one of the parts most people hate.

So it has been welcome news for many facing the latter screening to learn that from today a new colon cancer screening test is available.  The test, approved by the FDA and nicknamed "Cologuard"   is the first to look for cancer-related DNA in stool (something similar to the earlier blood in stool tests) and is expected to  entice millions of people who've avoided colon cancer screening to get this new home test that's noninvasive (and also doesn't require the nasty preparation demanded by colonoscopy, sigmoidoscopy or barium enema.)

Then there are the ads touting "the breakthrough test ... that's as easy as going to the bathroom". Well, maybe not that easy - as I discovered on weighing the possible benefits in order to dodge another colonoscopy, especially after having had high dose rate brachytherapy radiation for carcinoma of the prostate.

Let's note that the best measure of a screening test's worth is whether it lowers the risk of cancer. But Cologuard has not been directly tested against colonoscopy for screening efficacy though it is being marketed as an alternative. A large study compared Cologuard to one of the older stool blood tests and found it detected 92 percent of colorectal cancers and 42 percent of advanced precancerous growths, compared with 74 percent of cancers and 24 percent of growths for the older test.

Cologuard's main downside is more false alarms or false positives. Also, it's correctly ruled out colon cancer only 87 percent of the time versus 95 percent for the standard colonoscopy. More disturbing, it leads 13 percent to have follow-up colonoscopies they really didn't need — because they didn't have cancer. Yet if the alternative was to screen everyone with a colonoscopy in the first place, Cologuard could avoid 87 percent of them.

The cost is another factor that might have many opting for Cologuard which goes for  $599 compared to $1,900 for a colonoscopy.  If you have the Cologuard DNA test every three years, it would be $1,800 — about the cost of a colonoscopy, which is good for 10 years unless polyps are found- then it's performed every three years. Medicare covers the new test (good if I decide to opt for it)  but private insurers aren't covering it yet.

Let's now put this in perspective in terms of colon cancer incidence: Colorectal cancer is the second-leading cause of cancer deaths in the United States and the fourth worldwide. More than 143,000 new cases and 52,000 deaths from the disease are expected this year but only about 60 percent of at-risk people get screened currently.

Given this, it may well be that - in the words of one oncologist, the best colon cancer screening test is the one that people are willing to get.

If that happens to be Cologuard, then we shouldn't dismiss it, but rather be aware of its limitations. As observed by Dr. Kenneth Lin, a Georgetown University family physician and former staff doctor for the preventive services task force:

"You'd rather have more options than not, but I don't think there's enough data to declare this test superior to any other test because of the false positives and lack of proof that it will save lives"

Still, it's far better than no test!

No comments: