People undergoing treatment for cancer know that an important part of their care is monitoring for the improvement, progression, or recurrence of their disease. Investigators are now studying and making good progress with a new technique that may be a more accurate, sensitive, and convenient way to monitor cancerous tumors than traditional methods.
The new technique is based on the principle that all growing cells shed DNA. DNA is the genetic material contained within the nucleus of cells. It was discovered that developing fetuses shed pieces of cell-free DNA into their mother's blood. That finding has already led to tests that can analyze a pregnant woman's blood for DNA from her developing baby to screen for conditions such as Down syndrome. (See our article on Cell-Free Fetal DNA test.)
Scientists have also been exploring ways to use the new technique in cancer care. As tumor cells grow, they shed pieces of distinct DNA into the person's blood. Researchers have found that they can use a patient's blood sample to look for snippets of DNA that have been shed from tumors. The technique is often referred to as a "liquid biopsy" because instead of having to perform a traditional biopsy—a surgical procedure to remove a sample of tissue to look for cancer cells—it uses blood to look for circulating pieces DNA from the tumor. By analyzing a cancer patient's blood for distinct tumor DNA, researchers have been able to monitor treatment of the tumor and even change treatments if one does not seem to be working, as well as more easily monitor for recurrence of the cancer.
Liquid biopsies have many advantages over traditional testing such as tissue biopsies or CT scans. Tissue biopsies pose a risk for some patients because of exposure to anesthesia or complications of surgery and cannot always be done if they are in hard to reach spots, such as the brain. CT and other types of scans are expensive and pose a radiation risk for patients. In addition, there can be inconclusive findings or spots on scans that don't clearly show improvement or worsening, while DNA analysis can be much more sensitive.
While the technology for liquid biopsies has been known for a while, use is speeding up as the blood tests to detect the DNA snippets improve. Several companies are now making the DNA tests and some insurers cover some of the tests. Significant for patients, liquid biopsies require a simple blood draw from the arm and therefore can be done far more frequently, if needed, than biopsies or scans.
In a recent article in the New York Times, Dr. José Baselga, physician in chief and chief medical officer at Memorial Sloan Kettering Cancer Center said "this could change forever the way we follow up not only response to treatments but also the emergence of resistance, and down the line could even be used for really early diagnosis."
So far, the technique has only been studied in lung, colon and blood cancers. However, a National Cancer Institute study of 126 patients published earlier this year in The Lancet Oncology found that the liquid biopsy test predicted recurrences of the most common form of lymphoma more than three months before they were able to be seen on a CT scan. It also identified patients who were not likely to have a successful response to the proposed treatment—giving physicians a chance to change drugs, if an alternative is available, to try to reach a better outcome.
Other similar studies are planned to evaluate the new technique. Scientists caution that more studies are needed to assess the accuracy and reliability of the test for various cancers and to determine how it might be applied in clinical practice.