In a stunning new development Illumina, a silicon valley biotech company, is launching a new venture to perfect a blood test that will detect cancer earlier than anything now available. See this Wall St. Journal article for details. The theory behind the test is that cancers already shed tiny amounts of DNA into the bloodstream when they are too small to detect by other means. Cancers have unique, and often many, genetic mutations that convey the ability to grow fast, invade the bloodstream and spread to other organs. These mutations can be detected if the test used is sensitive enough. Presumably the concentration of these abnormal DNA fragments in blood will be very low — likely picograms per milliliter. But if the gain in the assay is set high enough and it is able to separate significant “driver” mutations from those with no adverse biologic activity (inactive or “passenger” mutations) the test will be fantastically useful. The company says it will need to “deep sequence” hundreds of thousands of tumors to develop a library of significant DNA mutations. If they can bring in the test at a price that the public (i.e., insurance carriers and Medicare) is willing to pay, this will be huge. Presumably in its early phase of roll-out sufficently neurrotic, wealthy people might be willing to spend substantial sums of their own mone — neurotic, because at first it won’t be clear whether the cancer fragments found in the blood will lead to meaningful very early detection — early enough to make a difference compared to what can be done with convention detection tools today. Dr. Stark says, “This could be the first step in developing the holy grail of cancer detection: a non-invasive test with high sensitivity and accuracy. Tumors previously thought highly lethal, such as liver cancer or cancer of the pancreas, might now be detectable when they are curable. This could turn out to be very big.”