Liquid biopsy test rapidly monitors disease load in patients with advanced breast cancer
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Researchers at Johns Hopkins Sidney Kimmel Cancer Center have developed an automated liquid biopsy test that can detect cancer DNA in the blood of patients with metastatic breast cancer within 5 hours.
Liquid Biopsy for Breast Cancer Methylation (LBx-BCM) works with a currently available molecular testing platform, GeneXpert (Cepheid), and can detect methylation in one or more of nine genes modified in breast cancer in 4.5 hours.
“Patients who are undergoing chemotherapy or other therapies for metastatic breast cancer really want to know as soon as possible how they are doing,” Saraswati Sukumar, PhD, professor of oncology and pathology at Johns Hopkins University School of Medicine, said in an interview with Healio. “In current clinical practice, they undergo radiographic imaging 8 to 12 weeks after they begin the chemotherapy to find out if their tumors have shrunk or not.”
Sukumar spoke with Healio about the technology, plans for its future, and its value in sparing patients with advanced breast cancer an extended wait for imaging results.
Healio: What is Liquid Biopsy for Breast Cancer Methylation and what inspired you to develop it?
Sukumar: We wanted to give patients a much quicker snapshot of how their tumor is responding to the chemotherapy. This test is able to detect tumor DNA that is shed into the bloodstream and gauge whether the tumor burden is going up or down with a single blood test. It’s a test that can be read out within a few hours of getting the blood sample.
What is the test detecting? Over the years, we’ve spent a lot of time trying to find those red flags indicating that tumor-specific methylated DNA is present in the blood. The methylated DNA in the blood is shed by dead tumor cells. Cell division and death occur continuously in the tumor. So, when tumor cells respond to therapy, they start dying in large numbers. The responding smaller tumors shed tiny amounts of methylated DNA and the tumors that have completely regressed shed no tumor DNA. If we see that the methylated DNA load in the blood has dropped a lot from the start of treatment to within 3 to 4 weeks, we know that the patient is, in all likelihood, responding to therapy. Conversely, if the methylated DNA levels go up or stay steady, that tells us the tumor is not responding to therapy.
Healio: What is unique about this test compared with other tests that use methylation markers?
Sukumar: Many of the other methylated marker tests require a lot of lab expertise, or they have to be sent off to a centralized facility to get the results. This cartridge-based test is so simple to perform that any lab tech can do it. Imagine that a patient living in a remote area of the country needs the test. Blood doesn’t need to be sent all the way to a central location. The test can be done in any facility that has a decent laboratory equipped with a GeneXpert machine that can run the cartridges. Interestingly, these devices are already widely distributed in hospitals in low- and middle-income countries, where they are used for diagnosing infectious diseases. The speed at which results are obtained is also very valuable to the clinicians and patients alike to plan the next steps of treatment.
Healio: How effective is it?
Sukumar: This paper is on selecting genes that are best able to detect cancer in the blood using the automated cartridge system for the very first time — to find out whether a blood test can work in that cartridge. We’ve shown that it works in the cartridge and that we are able to get results within 5 hours. The test predicted correctly whether the tumor load is going up or down 85 percent of the time. Most other methylated gene tests have not attained this level of accuracy.
Healio: What is next for this test?
Sukumar: We will soon announce the results of a prospective clinical study designed to validate our current findings. When a test is this simple and can be done with just a blood draw, it may become useful in remote areas with limited CT or PET imaging facilities. In these cases, the cartridge-based blood test that we are developing to monitor response to therapy will be a godsend. A lot more testing needs to be done before the cartridge assay is used routinely in the clinic.
For more information:
Saraswati Sukumar, PhD, can be reached at Johns Hopkins University, Breast Cancer Program, 1650 Orleans St., Baltimore, MD 21231; email: saras@jhmi.edu.
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