Based on recent statistics, cancer remains the second most common cause of death, immediately behind heart disease. In fact, the chance of developing cancer in one’s lifetime is one in five. These statistics persist despite all the recent advances in cancer treatment and care. And therefore, efforts to try and prevent cancer from the start or detect it early remain important pursuits. Unfortunately, screening individuals for cancer is still a challenging endeavor. Many are expensive, and some are invasive, making their feasibility questionable. It’s for these reasons that scientists are hoping that testing blood for cancer might offer better results. Also known as a liquid biopsy, many companies are developing blood tests that could screen for a variety of malignancies.
When it comes to cancer screening tests, the vast majority evaluate patients for one type or another. But imagine if a single sample of blood might provide early detection of several different types at once? The potential for such testing blood for cancer lies within this question. But simply because a liquid biopsy suggests a cancer may be lurking about, it doesn’t mean it should be used. There are many caveats to consider before administering such a test to the masses. First, such a test must be accurate and specific. But it also must improve the risk for illness and death as well. These are the areas where science is still struggling when it comes to creating a comprehensive liquid biopsy for cancers.
(Read up on cancer screening via breathalyzer tests in this Bold story!)
“We screen for four or five cancers in this country, but (many) cancer deaths are coming from cancers that we’re not looking for at all.” – Dr. Joshua Ofman, President and Chief Medical Officer, Grail, Inc.
Liquid Biopsy Studies
Testing blood for cancer is not something new. Various serum samples have been collected for decades looking for specific cancer markers. In addition, many cancer patients who have received treatment routinely have such cancer markers followed. This can help determine remission or reoccurrence. But modern tests are more refined, testing for tiny DNA fragments known to be associated with various cancer cells. This is why a single liquid biopsy or collection of blood might screen for several different types of malignancies. Notably, several companies are exploring these types of tests aggressively.
One of these companies is Thrive Earlier Detection (acquired by Exact Sciences), which was created by a group of doctors at Johns Hopkins. They have launched large studies involving more than 10,000 women to determine detection rates of cancer using their test. The initial results demonstrated that a quarter of the cancer detected resulted from their liquid biopsy test, which is noteworthy. Another company, Grail, Inc., is currently enrolling 140,000 patients in their study in the United Kingdom. They similar hope that testing blood for cancer using their approach will also greatly increase detection rates. But thus far, study of these screening strategies has a long way to go before a definitive answer is known.
“[Testing blood for cancer] is not at the place where it could be used today. It will need many more studies to demonstrate value.” – Dr. Len Lichtenfeld, Deputy Chief Medical Officer, American Cancer Society
Questions to Be Answered
While the promising results at Thrive are exciting, other studies have not offered similar findings. A 16-year UK study involving over 200,000 women found that early ovarian cancer detection failed to provide better results. Another in Japan also found that mass screening children for cancer failed to change outcomes. Because of this, many scientists are leery of testing blood for cancer in large populations. Indeed, a liquid biopsy might detect a cancer early. But that doesn’t mean such a cancer requires treatment or may respond better to care. In addition, all screening tests have false positives, which can lead to anxiety as well as unnecessary therapies. Unless these issues are better defined, it’s hard to know if these tests are worthwhile.
Interestingly, the FDA does not require approval before screening tests like a liquid biopsy is performed. Health insurance companies will not typically cover such tests. That means testing blood for cancer is an out-of-pocket expense. For example, those who wish to have Grail’s liquid biopsy test, they pay just under $1,000 for the results. But despite the lack of approval and cost, some 2,000 doctors already routinely encourage patients to get these tests. There’s little doubt that blood tests for cancer have great potential for better managing cancer. But between the costs and the risks, most medical experts aren’t yet ready to move ahead.
“For a drug, the FDA demands that there is a substantial high likelihood that the benefits not only are proven, but they outweigh the harms. That’s not the case for devices like blood tests.” – Dr. Barry Kramer of the Lisa Schwartz Foundation for Truth in Medicine
Future Potential for Cancer Screening
This past year, the White House established a goal to reduce cancer rates in half within 25 years. Notably, innovative cancer treatments will play a role in realizing this goal. But generally speaking, cancer treatments work better when given in the early stages of a malignancy. This is why the potential for testing blood for cancer is significant. If a simple blood sample could detect multiple cancers earlier, then more cures may be possible. Unfortunately, whether this is actually true or not is not yet known. So many are holding judgment on a liquid biopsy approach until more information is available.
In any case, a liquid biopsy is much safer and less complicated that other screening tests. Tissue biopsies are more invasive with most having possible side effects. Others involve elaborate imaging studies that are often expensive and uncomfortable. Therefore, even if testing blood for cancer proves to be feasible in only a few scenarios, it still offers advantages. The issue right now is simply trying to determine the types of situations where these screening methods make sense. Given that many startups are pursuing additional studies aggressively, that answer will likely be sooner rather than later. And fingers are crossed hoping liquid biopsies can make a significant impact on cancer care.