What if a Blood Test Could Detect Breast Cancer?
David Walt, PhD, of the Department of Pathology at Brigham and Women’s Hospital has developed an innovative blood biomarker test for breast cancer. When integrated with mammography, this test may help patients avoid follow-up breast cancer diagnostic procedures like biopsies, CTs, ultrasounds, and MRIs, as well as the delays in needed treatment that may follow.
Can a new blood test detect breast cancer?
Dr. Walt: Blood tests for cancer are not new; in fact, there are lots of blood tests for cancer. They typically look at DNA coming from cancer cells—called cell-free DNA. Most of the tests can detect a variety of cancers but with differing levels of sensitivity and specificity. Breast cancer, in particular, has not had good sensitivity with these tests to date and it’s unclear exactly why. It could be that there aren’t good markers for breast cancer using these methods or that the markers are not present in high enough concentrations.
How is this test different?
Dr. Walt: Physicians need to know the subtype of the cancer to provide the most effective treatment. Breast cancer is classified into subtypes based on the receptors on the surface of the cancer cells, including estrogen receptors, progesterone receptors, and HER2 receptors. Different subtypes require different treatments. Typically, subtyping involves taking a biopsy of the tumor, which is then sent to a pathology lab, where it is stained and analyzed to identify which receptors are present.
Our test aims to detect both breast cancer and its subtype without a biopsy. We use individual protein assays that are 1,000 times more sensitive than those in other tests. Most protein assays are based on a BULK measurement in which all the protein molecules are detected and give a single signal. Our method enables us to literally count individual molecules—a digital readout—that allows us to achieve ultrasensitive levels of detection.
Why did you choose to focus on breast cancer?
Dr. Walt: There is a lot of room for improvement in both the diagnosis of breast cancer and the patient experience. Currently, breast cancer diagnosis relies on imaging techniques like mammograms and, if necessary, biopsies to confirm cancer. Typically, if a scan shows something that needs follow-up, a patient would be brought back for an ultrasound or a follow-up imaging procedure, such as a higher resolution version of a mammogram. If the ultrasound or additional imaging shows something of concern, this blood test can be used to determine the need for biopsies which are painful, invasive, and according to the National Breast Cancer Foundation, 80% negative for breast cancer. Additionally, current screening methods have a high false negative rate, missing cancers that require treatment in one out of eight cases.
A blood test could reduce false positives and provide a less stressful, cost-effective way for providers to diagnose breast cancer earlier, without the need for biopsies. Finding cancers sooner and with greater accuracy, especially aggressive cancers, leads to earlier treatments and better outcomes for patients.
What’s the future of this test becoming clinically available?
Dr. Walt: Cancer biomarker detection is a burgeoning area of research and is still a young field. It’s exciting to see the early success, but there is more work to be done. We need to continue to improve our test’s sensitivity and specificity so that we have a more accurate test that provides the best possible diagnosis to both individuals with breast cancer and healthy people. Achieving this goal will require us to find additional biomarkers. Once we’ve settled on a final biomarker panel, we need to validate the test at different clinical sites and with diverse populations to ensure that our test doesn’t just work here but everywhere and for everyone.
