New diagnostic blood tests are rapidly changing cancer treatment. They are called liquid biopsies. They are eliminating needle or surgical biopsies for some patients.
Rather than capturing cells from the tumor itself, the process is to take a blood sample and capture cancer cells or the DNA from cancer cells in the sample. It is not clear how these tests will be used and how much of a change they will make in medicine, but a number of doctors see it as leading to a major change that will allow for an increase in personalized medicine.
More frequent timely testing
It makes it possibly to repeatedly sample what a cancer is doing in a noninvasive manner. This has several important implications. It hasn’t been easy to sample cancer on a repeated basis in the past and never non-invasively. This allows not only profiling the cancer’s genes, but it also makes it possible to track mutations and to target drugs to them. Plus, you can get faster feedback and therefore tell whether a protocol is working and how it might need to be changed over time.
The technology is improving rapidly, as is its use. It was only used in research two years ago. There are now several available on the market and more than ten in development. Some doctors are starting to use them on a regular basis, and more are beginning to try them.
Examples of usefulness
One example of their benefit is in breast cancer recurrences where the recurrence can be found far sooner than it normally would be, which can give an edge in treatment.
University of Texas MD Anderson Cancer Center now uses liquid biopsies on about 10 percent of its metastatic colon cancer patients. It is also useful in place of, or to support lung biopsies, which can be difficult to do.
Treatment effectiveness
Some doctors are quite excited because most cancer drugs are quite toxic and many times are not effective. This will allow doctors to determine the effectiveness more quickly and save the cost of the drugs and the damage and suffering that the patient goes through.
Currently, doctors are using them when they don’t know where the cancer is, or when it is difficult to get to it for a regular biopsy. It is also useful when the patient’s current drug no longer works and it is necessary to figure out what direction to take treatment going forward.
The problem at present though is that studies of the process haven’t caught up to the liquid biopsy process. It is clear that there is great potential, but there are no studies proving that they are beneficial or if they are accurate and what their specificity is.
Dr. M. Cristofanilli of Thomas Jefferson University in Philadelphia points out several features of liquid biopsies and cancer that make them useful. When you do a tissue biopsy, in most cases a sample is taken from only one spot in the tumor. But, different regions of the tumor can vary dramatically, having different genes and/or hormones active.
Two other items make liquid biopsies useful. When tumors metastasize, just as with different regions within the tumor, they can vary quite a bit in the different locations that they spread to. On top of that, they change again due to the treatment drugs and radiation.
For most tissue biopsies, you don’t or can’t do them on a regular basis. That means you are frequently working with outdated information. Considering the speed with which cancer can change, this is a problem.
The first liquid biopsy tests looked for entire cancer cells in the blood stream that had been shed by the tumor. Now they are targeting DNA from the tumor that is circulating in the blood stream.
Cost effective?
One more question about them is cost. At present, they aren’t cheap, so they are not something you are going to do on a daily basis. The price may come down, but you also need to look at how much they cost versus the entire cost of treating a patient for cancer. If liquid biopsies can dramatically decrease the overall cost of treatment and improve outcome, they will be widely used in short order. But the data isn’t yet in.