A California-based company called Pathway Genomics is aiming to shake up this way of thinking about cancer detection. In September, Pathway announced that it would be offering an "early warning" test that it says can detect snippets of abnormal DNA -- for a whole group of major cancers, including breast, ovarian, lung, thyroid and prostate -- in otherwise healthy people from a single vial of blood.
Pathway's test, which will start at cost $299 per test and is recommended to be taken every three months, looks at 96 genetic markers associated a number of different cancers. You can ask your doctor to order it for you, or you can order it yourself through the company's Web site (Pathway will submit your information to one of its own physicians for review first).
The concept is elegant, but many cancer specialists have cautioned that the tests may not be as useful as you might think.
J. Leonard Lichtenfeld, deputy chief medical officer for the American Cancer Society, is among those who believes in the huge promise of blood-based biopsies -- but he is just as sure that they are not ready for prime time just yet.
Below are Lichtenfeld's thoughts on the new liquid biopsy screening tools.
This interview has been edited for length and clarity.
Q: What will this new era of early detection of cancer mean for consumers? What are some of the potential benefits?
Lichtenfeld: When I started my practice in the 1970s we wanted to believe that finding every cancer early through screening was going to save every life. That's what we thought. Here we are four decades later and there's no question that we've saved a lot of lives, but all the expectations were not met.
Today we are very much in the same area. Although the science is moving forward rapidly, we are still far from understanding what it means....
We are going to run head on to the situation where we come to understand that cancer cells occur in our bodies much more frequently than most people appreciate. The general public equates cancer with a palpable cancer that too often become more serious and lead to death. But there are many scientists and oncologists that know that as we move our detection capabilities further downstream we are going to find a lot of cancers that are not going to make a difference. If they were left alone the patient will die with that cancer but not from that cancer. The best example is prostate cancer but there are many others.
Q: What are the risks of the new blood tests?
Lichtenfeld: I am very concerned about promoting such a test as a cancer early detection test. We have learned from history that we have had expectations of these tests -- particularly with prostate cancer tests but also to some extent with mammograms -- that exceeded what the science has eventually taught us. The risks in a test like this are several-fold. Number one, we could find a clue that there's a cancer but never find the cancer. Number two, we could potentially find a DNA signature from a cancer that may never cause a person a harm. Number three, we may find cancers but we don't know whether it's going to be a problem. We don't have the tests available to determine that.
And then finally we don't know what action to take. If we can't find the cancer but we find the signature do we give the patient chemotherapy or some other form of therapy? We just don't know. So having that information doesn't help us.
Q: What do we know about the accuracy of these tests? Pathway has said it has begun clinical trials involving patients but has yet to publish any results.
Lichtenfeld: If someone has a cancer, will this in fact pick it up? We don't know. You may have a cancer but you may not have a fragment in the blood and have a false sense of security. There are a lot of unanswered scientific questions. How often does this test find a cancer that is present? And when it's abnormal does this mean a cancer is really present? Without adequate study we are treading in dangerous territory.
I don't know of any reputable organization or authority that would be able to provide guidance on this test, how to use this test, how to interpret it, and how to use the results. There's one side of the argument that says patients should be able to get whatever information they want, but what to do with that information is absolutely a blank slate for cancer specialists and primary care providers. We just would not know how to properly advise patients.
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