In a new study, researchers say it might be possible to detect some types of cancers through blood tests, offering hope for reducing cancer mortality by early detection.
The study called the Taizhou Longitudinal Study (TZL) recruited 123,115 subjects aged between 25-90 years who provided their plasma samples that were stored from 2007-2014 and monitored for cancer occurrence.
Using PanSeer, a non-invasive blood test that is based on circulating tumor DNA methylation, researchers report that by the end of 2017, a total of 575 initially healthy samples who presented as asymptomatic were diagnosed with one of the five most common cancer types (stomach, esophagus, colorectum, lung or liver) within four years of blood draw.
PanSeer was able to detect five common types of cancers in 95 percent of asymptomatic individuals who were later diagnosed with cancer, demonstrating that cancer can be detected by non-invasive methods up to four years before symptom onset.
The PanSeer test is most likely to identify cancer in those individuals that already have cancerous growths but are asymptomatic to other diagnostic tests and screening methods.
It cannot predict a patient who will develop cancer at a later stage if that individual does not already have a cancerous growth.
The PanSeer test is also a first-line screening method, a patient who tests positive on it will have to subsequently undergo a reflex blood test or follow-up imaging so that their tissue of origin can be mapped, followed by a pathological examination to confirm the presence of cancer. Importantly, the test cannot detect the type of cancer.
Researchers noted that all tumors, no matter the size, maintain a connection with the bloodstream since tumors pull out nutrients from the blood.
This means, sometimes, proteins and genetic material spill out from the tumor into the bloodstream, making it possible to detect their presence through certain types of blood tests, also referred to as “liquid biopsies”.
A test done on a sample of blood to look for cancer cells from a tumor that are circulating in the blood or for pieces of DNA from tumor cells that are in the blood.
Typically, cancers are detected when individuals present themselves with certain symptoms, post which a number of tests are used for diagnosis such as laboratory tests, tumor biopsies, and diagnostic imaging among others.