Scientists use the term liquid biopsy to describe testing blood or other body fluids for signs of cancer. Liquid biopsies are still in the early stages of development, but researchers are excited about their potential as a simple way to detect cancer, particularly for cancers that are not easily diagnosed by other methods.
One such cancer is nasopharyngeal cancer, which starts at the top of the throat, behind the nose. When it is detected early, treatment is less aggressive and usually more successful than if it is detected at a later stage.
Researchers in Hong Kong recently published the results of a clinical trial that tested whether liquid biopsies could be used to screen for nasopharyngeal cancer in men who had no symptoms of the disease. Their results provide evidence that liquid biopsies could detect this cancer at a very early stage, improving survival.
Epstein-Barr virus is associated with nasopharyngeal cancer
The researchers collected blood samples from more than 20,000 middle-aged Chinese men, a population at particularly high risk of developing nasopharyngeal cancer. They tested the samples to look for DNA from the Epstein-Barr virus, a common virus that infects more than 90% of people in the world before age 20.
This virus is commonly associated with nasopharyngeal cancer, and researchers were interested in whether finding it in a blood sample was a reliable indication that cancer is present. Men who had 2 positive results for virus DNA underwent further testing to look for cancer.
Virus DNA was reliable indicator of cancer
The researchers found that only a small percentage of the men (1.5%) had 2 positive results for viral DNA in their blood and were referred for further testing. But more than 10% of the men who had further testing were diagnosed with nasopharyngeal cancer.
Importantly, many of these men (71%) were diagnosed at an early stage where the tumour was small and had not spread. Only 20% of men would have historically been diagnosed at this stage without screening. As a result, the men in the study also had much higher survival than men who were diagnosed without screening.
When the researchers followed up with the participants, they found that only one who did not have virus DNA in their blood sample had been diagnosed with nasopharyngeal cancer within a year of the test. This finding supports that the test was highly sensitive.
Clinical trial provides proof-of-concept for liquid biopsy
Screening tests for cancer need to be sensitive (to catch as many cases as possible) and specific (to prevent misdiagnosis in people who don’t actually have the disease). This trial shows that this form of liquid biopsy gives excellent results on both fronts, in this particular high-risk group.
Nasopharyngeal cancer is not a very common cancer in North America, and it is unlikely that a screening program for it would be introduced in Canada. However, this research is important, not just because it shows that screening for nasopharyngeal cancer with liquid biopsy can improve survival. The results can be interpreted more broadly.
The study provides strong evidence that the concept of using liquid biopsy for as a screening tool to detect cancer even when there are no symptoms is sound. Now further studies can apply the same concept to other forms of the disease.
Eileen Hoftyzer, BSc, and Carolyn Goard, PhD