Adapted from Dr. Peter Lin's evaluation of the CancerSeek® Test, a blood test measuring the levels of circulating proteins and mutations in cell-free DNA.
Cancer cells are dying all the time, and some of their DNA will end up in the bloodstream. This CancerSeek® test looks for 16 of these cancer genes. Also, cancers make certain proteins, and so eight such proteins are also included in the test. The detection of these genes or proteins will tell us that there is a cancer; but where is it? With some sophisticated software to look at the patterns of which genes and which proteins, the type of cancer can be determined. For example, ovarian cancer will have different genes and proteins that light up compared with liver cancer. Therefore, this test can not only detect cancer, but also help identify which tissue is involved.
To test the “test,” researchers looked at 1005 patients who had known cancers between stage I and III; non- metastasized. The patients were chosen who had one of the eight most common cancers, which included cancers in the ovary, liver, stomach, pancreas, esophagus, colorectum, lung, and breast. The researchers stated that these eight cancers account for 60% of cancer deaths in the US in 2017.
Overall, the test was able to detect 70% of these eight cancers. However, there were differences in the detection rates for the different cancers. Ovarian and liver cancers were the best at 98%. Breast cancer was the lowest at 33%. This basically means that the researchers need to find a better gene or protein that can be used to identify that cancer.
Stage I cancers were detected at 43%, stage II cancers at 73%, and stage III cancers at 78%. Of the stage I cancers, liver cancer was detected at 100%, whereas esophageal cancer was the lowest, at 20%. This concept will change the face of cancer detection and management. The early detection will mean earlier treatment on smaller lesions or perhaps even on lesions that we could not even see on imaging. The most exciting aspect, though, is that this test could allow treaters to rapidly decide if a therapy is working or not. Imagine that a patient has the test and then a particular therapy is given. If it is working, the mutated genes should increase as the cancer cells are killed followed by a drop and then no more mutated DNA in the blood because the cancer has been eradicated. So, within weeks Oncologists would know if the treatment is successful or not. If the DNA does not drop, then the therapy is not working and a switch to another therapy can be made quickly. This is dramatically different from the current method, which is to give the therapy, wait 3 months to do imaging to see if the lesion has reduced in size, and then decide if a change is needed. Valuable time is often wasted, and patients may have had to endure side effects without any benefit. So, a blood test will be revolutionary for the treatment of patients with cancer.