A blood test that screens for multiple cancers at once promises to boost early detection

Detecting cancer early before it spreads throughout the body can be lifesaving. This is why doctors recommend regular screening for several common cancer types, using a variety of methods. Colonoscopies, for example, screen for colon cancer, while mammograms screen for breast cancer.

While important, getting all these tests done can be logistically challenging, expensive and sometimes uncomfortable for patients. But what if a single blood test could screen for most common cancer types all at once?

This is the promise of multicancer early detection tests, or MCEDs. This year, President Joe Biden identified developing MCED tests as a priority for the Cancer Moonshot, a US$1.8 billion federal effort to reduce the cancer death rate and improve the quality of life of cancer survivors and those living with cancer.

As a laboratory medicine physician and researcher who develops molecular tests for cancer, I believe MCED tests are likely to transform cancer screening in the near future, particularly if they receive strong federal support to enable rapid innovation.

How MCED tests work

All cells in the body, including tumor cells, shed DNA into the bloodstream when they die. MCED tests look for the trace amounts of tumor DNA in the bloodstream. This circulating “cell-free” DNA contains information about what type of tissue it came from and whether it is normal or cancerous.

Testing to look for circulating tumor DNA in the blood is not new. These liquid biopsies – a fancy way of saying blood tests – are already widely used for patients with advanced-stage cancer. Doctors use these blood tests to look for mutations in the tumor DNA that help guide treatment. Because patients with late-stage cancer tend to have a large amount of tumor DNA circulating in the blood, it’s relatively easy to detect the presence of these genetic changes.