Simple blood tests could be the future of cancer diagnosis

A newly approved test called Shield can detect colon cancer from a blood sample.

Shield is only a blood drop in an ocean of emerging "liquid biopsies" These tests often detect a lower fraction of cancer cases than gold-standard screening tools like colonoscopies.

They will likely supplement, rather than replace, traditional screening methods, experts say.

The Shield test is approved for use every three years , but it could be more accurate if it were done every year or two .

Pancreatic cancer is the third -most-common cause of cancer death in the U.S. There is no broad-based screening program for people at average risk of pancreatic cancer.

By the time most people notice symptoms, the disease is already very advanced.

There is no good treatment for early cancers, so catching them ahead doesn't necessarily lead to improved outcomes.

After taking an MCD test, patients may wait up to six months to know one way or the other.

There are no evidence-based clinical guidelines that tell doctors the best way to follow up on positive results from MCD tests.