This is not just about cancers that affect the blood. From the article:

    By sequencing the abnormal DNA that a tumor releases into a person’s
    bloodstream, researchers are now one step closer to a universal cancer
    test. Although the technique is now only sensitive enough to detect
    advanced cancers, that may be a matter of money: As sequencing costs
    decrease, the developers of the method say, the test could eventually
    pick up early tumors as well.