Is It Appropriate To Offer The Public “Liquid Biopsies” For the Early Detection Of Cancer?

The recent announcement by a California company offering DNA blood tests (also known as “liquid biopsies”) for the early detection of cancer takes us to a place most of us expected we would get to, but much earlier than we are prepared for. Simply stated, our technology and rush to get new tests to market-even before we have a basic understanding of how to use those tests to improve the health of consumers–has outstripped our scientific understanding, and we ignore the implications at our own peril. [more]

First, some history:

The concept of having a blood test to diagnose cancer early is not new. In fact, I recall an international meeting about a decade ago where a lecturer predicted the diagnosis of cancer through a simple finger stick that would be sent to a lab for analysis.

Fast forward to June of 2009 when I was a guest on the Today Show and was asked to offer a closing thought telling viewers something they didn’t know about cancer. My comment was to the effect that one day in the not too distant future we would be able to find cancer cells circulating in the blood in people who didn’t know they had cancer, essentially an early detection test at the earliest moment possible.

Another person on the panel-my colleague and fellow advocate Dr. Susan Love-reacted in appropriate mock horror, stating that we were about to make everyone in the country a cancer survivor. Six years later, I understand full well what Dr. Love meant. She was right, and I recently had the opportunity to share that observation with her personally.

This company’s recent announcement now puts the issue of very early cancer detection squarely on the table. And it raises many more questions than it answers.

And it comes at a time when our ability to find previously undetectable cancers with a test from an easily obtained blood sample is becoming more than a scene from Star Trek. Recent reports have described the unexpected discovery of cancer in pregnant women whose prenatal genomic blood tests found abnormalities. Normally, this finding would mean that the baby had a genetic abnormality. However in a small number of circumstances it was found that it wasn’t the baby who had the problem, it was the mother-where the test predicted a soon to be discovered cancer.

Another report showed the value of measuring the amount of circulating tumor DNA in the blood of patients with certain types of cancer. Elegant research, a small number of patients, but a proof of concept paper that showed the test could predict when a cancer was going to recur.

Yet another research paper showed that by carefully examining changes in breast cancer tissue a test could be developed that would show whether primary treatment was successful, predict a recurrence, and even show when the breast cancer changed its genetic code-a not uncommon finding in cancer when it relapses and/or spreads to other part s of the body.

Then comes this week’s news: a company that is advertising a cancer “early detection” test (they go so far as to call it a “cancer stethoscope”) directly to consumers for $699, or $299 if the consumer gets the test done routinely every 3 months-sort of along the model advocated recently by entrepreneur Mark Cuban, and criticized by me and others in recent blog posts. The test in question is only done by this one company, measuring over 90 genetic abnormalities in the blood sample. And, since this is a proprietary laboratory test it can be offered directly to the public and the company can make whatever claims it chooses to consumers and health professionals–who may not even be aware there is no oversight by the Food and Drug Administration to verify the claims made for the test. (The Centers for Medicare and Medicaid services oversees the general quality of the laboratories offering these tests, but does not do specific review of a test in these situations).

So why the concern about this announcement? Well, there are several issues that need to be addressed.

First and foremost, although our technology in understanding the genetics of cancer and our ability to detect these small fragments in the blood is advancing rapidly, we have no clue what it means when someone who has no clinical or visible evidence of cancer has these cell fragments found on a “routine” test. It’s the health equivalent of AOL’s “You’ve got mail!” The test is essentially telling you “You’ve got cancer!” But because the particular abnormalities detected by this test can be found in several different types of cancer, it can’t be linked to a particular site in the body or how problematic the cancer may be now or in the future.

Our bodies are constantly giving birth to cells that could grow into cancer. Nearly all of the time, our own systems kill off the abnormal cells before that happens.  We also know that many small cancers can exist in our bodies but never grow, or if they grow will never cause any difficulty.  Think of prostate cancer as an example: almost every man who lives long enough will have prostate cancer cells present-but not every man is harmed by prostate cancer. Thus, the questions about how much value the PSA test brings to the care of our male patients.

Another question is what we do if we found DNA fragments in someone who had no clinical evidence of cancer? What if we do additional scans and blood tests and don’t find a cancer? Depending on the findings, DNA mutations in cancer aren’t necessarily specific to one organ or tissue. Or if it is relatively specific, what if we do a test such as a colonoscopy on suspicion of colon cancer and don’t find anything? How many scans, how many colonoscopies, how often do we follow-up? Who knows? I certainly don’t and neither does anyone else. And in the process, aside from doing all these studies, what if we cause an adverse event and cause harm?

Then there is the other side of the question: what if someone actually has cancer, gets the blood test, and it doesn’t show up? That is not such a far-fetched scenario-especially when one examines the data offered on the company’s website.

The company freely admits they have not done the research to demonstrate how the technology fits into the care of real patients without cancer who may get the test and get an abnormal result.  According to news reports, that research is pending-but far from completed.

I have voiced my concerns that we should expect the evidence and the science to be our guide when it comes to the advice and treatment we offer our patients. Yes, there is a substantial art to the practice of medicine, but without science we are really babes lost in the woods. Take an abnormal result from this test to your doctor and the real possibility exists they will have no clue what to do with it.

Oh, without doubt there will be testimonials that this test saved someone’s life. But if we have learned nothing else from the past four decades of cancer screening it should be that just because we wish it so doesn’t make it so. And this entire discussion begs the question of what you tell a life or disability insurance company if you have received an abnormal test result saying you have cancer and you don’t disclose it on an application.

As I wrote above, our science is advancing at an incredibly rapid rate. Having such a test available was not only predictable, it was expected. But before we embrace this as a simple blood test such as a cholesterol or blood count, there is so much more we need to know and understand.

It will be interesting to see how the regulatory agencies and the insurers approach this brave new world. However, in the meantime I suspect there are a number of knowledgeable experts who consider this a step too far and would agree with me that this test is simply not ready for prime time.

Caveat emptor is clearly the message of the day.

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