Fecal DNA tests

As a follow-up to my post on the updated USPSTF guidelines on colon cancer screening, a reader asks me to comment on fecal DNA tests, which along with virtual colonoscopy, was given an “I” recommendation meaning there was not enough data to provide guidance:

I would be very interested to hear your thoughts about their omission of a less well-known new option, stool DNA (SDNA).

The task force opined that SDNA (which just recently became available as the Colosure test from Labcorp) was pricey and insufficiently studied. I think their timing was unfortunate and they based that on old information, as three major publications were just announced (on Sept 22 (October American Journal of Gastroenterology), Oct 6 (November Annals of Internal Medicine) also August Gastroenterology), and the new version (Colosure, launched in July and not yet marketed much) has a list price of only $200 while outperforming the previous generation costing $495.

My investigation has made me a fan of SDNA. It was recently added to the American Cancer Society (ACS) and US Multi-Society Task Force guidelines. It is currently available only as Colosure from Labcorp, suggested for people over 50 every 3-5 years. I think SDNA is currently the best option (preferably in combination with colonoscopy).

Colorectal cancers shed DNA in the stool which then can be collected and screened for.

The sensitivity ranges from 52 to 91 percent, and specificity ranges from 93 to 97 percent.

An entire bowel movement needs to be collected, and it’s shipped to the lab in ice.

It’s a better test than fecal occult cards, but not as accurate as a colonoscopy. In addition, studies show it is not cost-effective compared to more established methods. There is also no data giving guidance for re-screening intervals, or what to do in cases with a positive stool DNA and negative colonoscopy.

Like virtual colonoscopy, I think that a stool DNA is promising alternative for non-invasive screening for colon cancer. The sensitivity and specificity beats fecal occult cards.

Questions remain regarding cost-effectiveness, whether there is a mortality benefit, and patient compliance given it’s a more cumbersome collection process. Apparently the second generation stool DNA tests have an improved sensitivity and a lower cost, but further study needs to be done.

I agree with the current “I” recommendation, but especially with the second generation stool DNA tests, I can see this getting approved in future versions of the USPSTF recommendations.

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