It’s a simple fact. The earlier cancer is detected, the better the odds of successful treatment. However, under current testing standards, a cancer diagnosis usually happens after a patient has become symptomatic. And by the time a cancer is displaying symptoms, the disease progression can make successful cancer treatment either difficult or impossible.
Cancer is the number 2 cause of death in the United States. It claims nearly 600,000 lives annually, just behind heart disease, but still ahead of the newest competitor, coronavirus (Covid-19).
So it’s not surprising that intense and urgent efforts are ongoing to devise diagnostic tests that can identify cancer at an early stage, while the odds of successful treatment response are still good.
Dying cancer cells release their DNA
Cancer researchers have discovered that, when tumor cells die, microscopic fragments of their DNA are released into the host’s bloodstream as circulating tumor cells (CTCS). These biomarkers are called cell-free DNA, or more precisely, circulating tumor DNA (abbreviated as ctDNA).
What is a liquid biopsy?
Several competing organizations are in the process of developing what they call “liquid biopsies”. A liquid biopsy is a system of blood analysis designed to provide early detection of impending cancer. It is considerably less invasive than a standard tumor tissue biopsy.
Liquid biopsy companies are working to devise a blood test for cancer
At least two teams of bio-scientists are currently studying the ctDNA phenomenon, in hopes of devising a test that will detect cancers in real-time, while the potential patients are still asymptomatic.
What is CancerSEEK?
One of the liquid biopsy teams, working at Johns Hopkins University, has developed a testing protocol called CancerSEEK. The startup company that is attempting to commercialize CancerSEEK asserts that it is “designed to be integrated into your routine medical care, alongside other existing cancer screening tools.”
CancerSEEK is designed to detect the following types of cancer: breast cancer, lung cancer, colorectal cancer, prostate cancer, and ovarian cancer.
CancerSEEK employs machine learning (computer programming that teaches itself). This, it is hoped, will enable the diagnostic test to improve itself with every person that is screened.
Results were recently announced of a long-term test that used CancerSEEK to analyze over 10,000 asymptomatic women. During the test, 96 of the subjects became cancer patients.
- Of these 96, 26 previously unknown cancers were identified by CancerSEEK
- Another 24 were identified by standard screening, such as mammography and Pap smears
- The other 46 cancers were first detected by symptoms or other methods
12 of the 26 solid tumors detected by CancerSEEK were surgically removed, a result which does indicate significant potential clinical utility.
But even CancerSEEK’s developers are quick to concede that, at best, it is only a first step in a long process of future clinical trials. Some key questions remain unanswered, and much more research is necessary before CancerSEEK can become the “routine medical tool” that its proponents envision.
PanSeer is another cancer research product
Another leading liquid biopsy research team is based at the University of California San Diego. This group of scientists has developed a blood test for cancer they have dubbed PanSeer. They recently presented a paper detailing their progress to date.
The UCSD researchers gained access to samples from the Taizhou Longitudinal Study, a 10-year project launched in 2007 by Fudan University in central China.
Between 2007 and 2017, the Taizhou study enlisted over 120,000 individuals. Over the 10-year span of the study, each of those subjects regularly provided blood samples, and each of them underwent regular medical checkups. In all, over 1.6 million blood samples were collected.
As soon as anyone of the participants was diagnosed with cancer, the researchers had access to DNA fragments in blood samples taken from that person for one to four years prior to the time that the patient began to show the first symptoms of cancer.
The researchers were thus able to analyze blood samples taken long before the patient became symptomatic. They ultimately analyzed plasma samples taken from 605 asymptomatic individuals, 191 of whom were later diagnosed with cancer.
PanSeer shows impressive results detecting cancer
And when those samples were processed through the PanSeer test protocols, the results were impressive.
The test detected cancer in 91% of the subjects who had been asymptomatic when the blood draw was collected, and only developed cancer years after those samples were taken. The test also recognized cancer-free samples at a 95% accuracy rate.
“The ultimate goal would be performing blood tests like this routinely during annual health checkups,” said Kun Zhang, one of the study’s authors and a professor of bioengineering at UCSD.
While the PanSeer team is naturally pleased with their test’s preliminary results, they, just like the CancerSEEK group, caution that there is much work to be done before early detection of cancer in asymptomatic individuals, via liquid biopsy tests, is available for clinical application.
As noted by the National Cancer Institute, a significant flaw in current ctDNA testing is the number of false-positive results. The consequences of a false-positive test can include painful and expensive tissue biopsies, not to mention a great deal of unnecessary anxiety.
ctDNA testing is also likely to detect the existence of tiny early-stage tumors that will never grow into a threat to their hosts. Although literally accurate, these results are the functional equivalent of a false alarm.
The next generation of cancer care
Cancer research and precision medicine are moving at a rapid pace. We look forward to the day when these screening tests are a standard component of a routine health assessment.
About Dr. Thaïs Aliabadi
As one of the nation’s leading OB-GYNs, Dr. Thaïs Aliabadi offers the very best in gynecological and obstetric care. Together with her warm professional team, Dr. Aliabadi supports women through all phases of life. She fosters a special one-on-one relationship between patient and doctor.
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