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Medicine Science

A Blood Test That Screens For Cancer 71

Posted by samzenpus
from the it's-in-the-blood dept.
sciencehabit writes "People usually find out that they have cancer after developing symptoms or through a screening test such as a mammogram—signs that may appear only after the cancer has grown or spread so much that it can't be cured. But what if you could find out from a simple, highly accurate blood test that you had an incipient tumor? 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."
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A Blood Test That Screens For Cancer

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  • It may not help (Score:4, Informative)

    by sirwired (27582) on Friday November 30, 2012 @06:15AM (#42140105)

    Some screening tests for cancer byproducts already exist, like the PSA test for prostate cancer. Other early-detection tests abound, such as Mammograms and Colonoscopies. While some of the screening tests, such as the Pap Smear, have shown to dramatically reduce cancer deaths, others, such as the PSA and Mammogram have detected a lot of cancers, but done absolutely bupkis to reduce death rates when given to populations not otherwise at high risk. Colonoscopies work, but are extremely expensive vs. the benefit they provide. (As in, it'd be a lot more efficient to spend healthcare dollars elsewhere, and there are other screening tests nearly as effective that are much cheaper.) Apparently they don't do a good job detecting aggressive cancers in those populations early enough to make a difference. With how fast some aggressive cancers work, the tests might have to be administered several times a year (at the cost of countless billions) to make any difference.

    In addition, the PSA and Mammogram HAVE caused billions to be spent on procedures with quite severe side effects to further diagnose, and treat, problems that almost certainly would not have killed their "victims." Most Prostate tumors grow slowly enough that you could leave it alone for the rest of your life, and die of something else instead; meanwhile, prostate cancer treatment almost always causes problems with incontinence and impotence; two major quality of life issues. Most "breast cancers" detected by mammograms are Ductal Carcinoma In Situ, another type of cancer that is unlikely to kill you any time soon.

    We need to think VERY carefully before rolling out any MORE widespread cancer screening tests, since many of the ones we have now simply don't work.

  • by clickclickdrone (964164) on Friday November 30, 2012 @07:03AM (#42140301)

    may just end up detecting many small cancers

    Exactly. ISTR reading that at any one time, most people have dozens of small 'cancers' but in most cases, the body destroys them before they get a hold. It's only when our own defences fail that the cancer goes on to become a 'proper' one and become a health hazard.

  • Re:Nobel prize (Score:4, Informative)

    by bluefoxlucid (723572) on Friday November 30, 2012 @08:31AM (#42140687) Journal

    Even better, the false positive rate is important. Regular testing for ovarian cancer in women is something you simply should not do; an ovarian cancer test should only be done if your doctor thinks you have ovarian cancer. Because of the rate of false positives, the rate of false positives in follow-up tests, the rate of complications, and the rate of death in complications, it turns out that roughly 1 in 1000 women who don't get regular testing would die of ovarian cancer, whereas if every woman over age 50 got regular ovarian cancer testing once a year we'd see a death rate of 3 in 1000 due to complications from unnecessary surgery to treat the non-existent cancer in false-positive cases.

    If this leads to people looking for cancer that doesn't exist or isn't important, a lot of false positives will start occurring. Even if it's highly accurate at detecting cancer, it won't tell you anything about the cancer. Now you have to look for it. So many cancer tests, so much false positive... you might find several cancers that don't actually exist, because the tests raise false positives occasionally and you're running tests for everything. False positives lead to unnecessary treatment, which is expensive and harmful. You're better off playing cancer roulette.

I've never been canoeing before, but I imagine there must be just a few simple heuristics you have to remember... Yes, don't fall out, and don't hit rocks.

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