Cancer Screening Achieves Frightening Sensitivity

Yale researchers have devised nano-sensors capable of detecting and measuring minute levels of cancer biomarkers in whole blood. Detection down to the concentration of picograms per milliliter -- with 10% "accuracy" -- are claimed. That is said to be equivalent to detecting a single grain of salt within a large swimming pool.

Their findings, which appear December 13 in the advanced online publication of Nature Nanotechnology, could dramatically simplify the way physicians test for biomarkers of cancer and other diseases.

The team—led by Mark Reed, Yale's Harold Hodgkinson Professor of Engineering & Applied Science, and Tarek Fahmy, an associate professor of biomedical and chemical engineering—used nanowire sensors to detect and measure concentrations of two specific biomarkers: one for prostate cancer and the other for breast cancer.

"Nanosensors have been around for the past decade, but they only worked in controlled, laboratory settings," Reed said. "This is the first time we've been able to use them with whole blood, which is a complicated solution containing proteins and ions and other things that affect detection."

To overcome the challenge of whole blood detection, the researchers developed a novel device that acts as a filter, catching the biomarkers—in this case, antigens specific to prostate and breast cancer—on a chip while washing away the rest of the blood. Creating a buildup of the antigens on the chip allows for detection down to extremely small concentrations, on the order of picograms per milliliter, with 10 percent accuracy. This is the equivalent of being able to detect the concentration of a single grain of salt dissolved in a large swimming pool. _Eurekalert

Now the question is: what do you do with someone when you detect a cancer biomarker at extreme low concentrations? Of course you can do other blood tests, multiple types of scans, xrays, biopsies, etc. to try to confirm and localise the malignancy. But at extreme low levels of biomarker there is a good chance that you will not be able to find any other evidence of disease. Then what?

Then you watch the patient more closely than you would have watched them otherwise. Serial biomarker testing using nano-sensors may prove to be the best way of following such "low-positive" patients. It will take time to incorporate such sensitive tests into clinical practise.

National Health Services may elect not to use such sensitive screening tests at all (or very selectively), due to the likely added expense of monitoring and confirming low-positive tests. Private insurance companies -- if any still exist in a few years -- will have no choice but to use whatever the standard of care is decided to be. Government run programs can do what they want, since a dead patient generates no further expenses ( so long as you cannot sue the government).

Once genetic screening tests are more readily available at the clinic level, along with nano-sensors for cancer, infectious agents, toxins, etc etc, the practise of primary care medicine is likely to change.