By Dr. Anthony Policastro

People are interested in early detection of things like cancer. That is why we currently do screening tests for a number of them.

There are colonoscopy screens. There is now Cologuard. There are mammograms. There are annual dermatological exams. There are prose-specific antigen (PSA) tests. All of these are aimed at the detection of something already present.

There are also whole-body CT scans. The idea is to do a scan of the entire body to look for hidden processes. This technique has not been shown to be very effective in healthy individuals. As a matter of fact, it often finds things that are normal variations. The result is that the patient gets more tests done. The tests might produce their own complications for someone who has nothing wrong.

There is something new on the horizon that takes testing a step further. Its name is Multicancer Early Detection Tests (MECD).

The logic is that we all have old cells that die every day. The level of DNA in those cells tends to be steady. Cancer cells are faster growing and therefore have more dead cells as well. The result is that there is more DNA than expected in that group of cells.

In addition, cancer cells produce certain substances that normal cells do not. An elevation in the level of these substances suggests that cancer cells are present. A third aspect is that tumor cells produce a type of DNA not consistent with what is found in other cells. All of these things allow for an early detection of cancer cells.

The technology for this is only 10 years old. To this point, the only real study utilizing it was done in sick patients. That study showed that it picked up cancer cells in 75.5 percent of patients with cancer. It also was negative 97.6 percent of the time when patients did not have cancer. Because it is not 100 percent even in sick patients, it is not a test to substitute for other methods.

The tests can be done on blood or urine. They can be done on other fluids like saliva.

There has not yet been a good study on healthy patients. What we do know is that current screening methods like those mentioned above are clearly more reliable than this theoretical model.

Given the current state of the research, it looks like it will take about another 10 years before we have enough information for MECD tests to be clinically useful. That means I get to wait until I am 87 years old to take advantage of them.