Banner by Meghan Carlton and Deirdre Nuebl
Targeting Eight Types of Cancer with a Single Blood Test
by Reyna Jones
Early detection of cancer is critical in increasing the probability of long-term survival and treatment success. However, many cancer types do not currently have non-invasive screening tests to detect malignancy. Johns Hopkins Kimmel Cancer Center recognized this urgent need for screening tests to detect cancer prior to symptom presentation and metastasis of disease; they developed CancerSEEK, a blood test that screens for eight different cancers: breast, colorectum, esophagus, liver, lung, ovary, pancreas, and stomach. These particular cancers were chosen because they make up over 60 percent of cancer-related deaths in America. Notably, five of these cancers (esophagus, liver, ovary, pancreas, and stomach) do not currently have screenings for early disease detection. According to Dr. Bert Vogelstein co-director of the Ludwig Center at Johns Hopkins, “This test represents the next step in changing the focus of cancer research from late-stage disease to early disease, which I believe will be critical to reducing cancer deaths in the long term.”
During tumor development, cancer cells can break away from the tumor’s core or release DNA into the bloodstream when the lifespan of the cell is complete. Although the mechanism behind the release of this DNA is currently unknown, scientists believe that apoptosis and necrosis (forms of cell death in which cellular components such as DNA fragments are released) may be responsible. Scientists call this released genetic material circulating tumor DNA (ctDNA). CancerSEEK functions, in part, by identifying mutations in the ctDNA taken from a patient blood sample. Multiple factors make this test unique. The first is that it can detect both DNA and protein using a small, yet effective mutation panel that focuses on 16 genes and eight proteins, allowing for screening of various types of tumors with increased specificity. The second is that this blood test can pinpoint the physical location of cancerous cells. CancerSEEK uses artificial intelligence algorithms to essentially combine the probability of identifying different DNA mutations with the levels of the eight proteins to detect and identify cancer.
Exactly how accurate is CancerSEEK in detecting the different forms of cancer? Researchers found that the sensitivity of the test varied depending on both the stage and type of cancer. Researchers tested the functionality and accuracy of CancerSEEK in 1,005 patients with stage I to III nonmetastatic cancers, cancers that have not spread from the original site. The cancers are assigned stage classifications based on numerous factors such as cell type, tumor type, and tumor size. Researchers determined that the CancerSEEK test has a higher sensitivity for more advanced disease; it detected 73 to 78 percent of stage II and III cancers, but only 43 percent of stage I cancers. According to Mangesh Thorat, the Deputy Director of Barts Clinical Trials Unit in the United Kingdom, “Stage one, when we want to diagnose these cancers, the sensitivity is quite low…That is something that might hold this test back when we try to think about implementing it.” The ability of CancerSEEK to correctly identify specific types of cancer ranged from 33 to 98 percent. Breast cancer had the lowest sensitivity, as it was detected only 33 percent of the time. Ovarian cancer had the highest sensitivity and was detected in 98 percent of cases. The blood test accurately detected 69 to 98% of cancer types that do not currently have screenings available, a huge step toward effective cancer diagnosis and subsequent development of treatment strategies.
False positive results are always a concern for any test or screen. False positives can often lead to additional and unnecessary invasive tests and procedures with a very large price tag. In testing the specificity of the blood test, researchers recruited 812 healthy, cancer-free patients to act as a control. CancerSEEK was found to have > 99 percent specificity for detecting different cancer types as only seven of the 812 healthy individuals received a false positive result for cancer.
The development of a single blood test that can screen patients for cancer is undoubtedly exciting. However, many may wonder about the cost and availability of CancerSEEK. Researchers realize that a preventative screening for cancer will only be effective if it is affordable. Therefore, they designed the test to be cost-effective for patients by utilizing a small mutation panel. The researchers believe that CancerSEEK may eventually cost less than $500. Although CancerSEEK continues through additional developmental stages, it is the investigators’ goal to mainstream CancerSEEK so that it can be conveniently available to patients through their primary care physician. According to Nickolas Papadopoulos, senior author and professor of oncology and pathology, “We believe that having a screening test to detect cancer in individuals that still feel healthy - they have no symptoms, and hopefully the cancer is in very early stages - will be easier to treat and simple to treat and save their lives compared to just extending their lives.”