Researchers have developed a challenging process that has been known for several years that can detect the presence of eight cancers by a simple blood test. This blood test is known as Cancer SEEK, this test sometimes also refers to as liquid biopsies that can detect cancers earlier, before the symptoms appear. This test can indicate the presence of eight cancers: breasts, liver, esophagus, lung, colorectal, ovary, pancreas and stomach. There is no blood test yet that can detect cancer in one clinical use. The researchers used the known biomarkers that can detect signs of solid tumors in the blood before they spread to other parts of the body. They searched the effective combination of known mutations to identify cancers using ctDNA (circulating tumor DNA) to confirm the cancer diagnosis. These circulating tumors DNA travel in the bloodstreams that are released from cancer cells. The test, called CancerSEEK, evaluates the presence of 2,001 genetic mutations and levels of eight proteins. The researchers tested CancerSEEK in 1,005 patients who had been diagnosed with cancer but whose cancers hadn’t yet spread at the time of enrollment. They tested 812 healthy controls for comparison. Overall, Cancer SEEK detected 70% of the cancers. Sensitivity ranged from 98% for ovarian cancers to 33% for breast cancers. Sensitivity varied by cancer stage: 78% for Stage III cancers; 73% for Stage II cancers; and 43% for Stage I cancers. Only 7 of the 812 people without known cancers scored positive (>99% specificity).
Classical methods can’t assess the tumor’s genomic status for monitoring cancer dynamics, such as tumor markers and scans to estimate tumor size status. Genetic analyses of a sample of the tumor also referred to as a biopsy, are becoming standard care in pathology departments. However, a biopsy only provides a snapshot of genomic changes on that particular piece of tumor. A biopsy also commonly requires an invasive surgical procedure, so cannot be performed frequently. So if changes are occurring over time, decisions based on old results will be outdated.
One of the most advanced examples of liquid biopsy application in cancer care is in the treatment of lung cancer. Researchers examined lung cancers treated with a drug to target something called the epidermal growth factor receptor (EGFR) on cancer cells, become resistant to therapy. Then they found the culprit responsible for the resistance: a small change in the EGFR gene, known as T790M mutation. Scientists were then able to devise a new drug to target T790M. So when patients develop resistance to the first therapy, they could be treated with this new drug.
In parallel, the development to detect this mutation in blood plasma or even urine ctDNA allows for patients to be monitored and timely change of treatment to occur when resistance starts to show.
Our recent study showed that response to treatment can be tracked by measuring ctDNA in the blood of melanoma patients. A decrease in the amount of ctDNA accurately faced the decline of cancer. But more importantly, increases in ctDNA indicated that the cancer was coming back. This is important as it can expedite treatment change when the cancer is still under control and the patient’s health hasn’t been compromised.