Blood test developed by Hong Kong researchers can detect nasopharyngeal cancer risk in asymptomatic patients, Chinese University says

Study participants with persistently positive test results are 17 times more likely to get disease later in life, researchers say
Findings show false positives subsequently diagnosed with cancer years later, they add

Hong Kong healthcare and hospitals

Emily Hung

Published: 8:12pm, 11 Jul 2023

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Chinese University has said a blood test created by its researchers in Hong Kong has been proven to be effective in detecting early nasopharyngeal cancer risk in asymptomatic patients, with those showing persistently positive test results 17 times more likely to get the disease later in life.

The university’s research team on Tuesday also said its findings revealed that some of the “false positives” – those who showed positive results in an initial screening but did not have cancer – were subsequently diagnosed with it years later.

Professor Dennis Lo Yuk-Ming, director of the Li Ka Shing Institute of Health Sciences at the university, said there were two possibilities behind this result.

Chinese University researchers say their blood test is effective in detecting early nasopharyngeal cancer risk in asymptomatic patients. Photo: May Tse

“It was possible that the false positive people were carrying the cancer virus, which gradually developed into cancer years later, or they were already at an extremely early stage of cancer which was not yet detectable by endoscopic examination or MRI,” he said.

“If those people did not have cancer at that stage, but the virus was active in their bodies. Could we do something, say prescribe medicine to suppress the virus activity? That’s one of the questions we need to work on.”

The plasma screening test can detect the Epstein-Barr virus in the blood, which is closely associated with nasopharyngeal cancer, one of the most common cancers in the city, with about 700 new cases recorded every year.

The risk of developing the disease is three times higher for men, with the peak incidence age being about 50 to 60.

Only 20 per cent of cases are detected early when the five-year survival rate is about 90 per cent. Most are discovered at a later stage when the chances of survival for the same time period drop below 70 per cent.

Antibody screening for the disease only has a positive predictive value of 5 per cent, while the university’s blood test has an accuracy rate of about 19 per cent.

As part of the study, the research team tested more than 20,000 asymptomatic middle-aged men from 2013 to 2016.

Among them, 309 received persistently positive results in the initial and follow-up tests, with 34 later diagnosed in endoscopic and MRI exams, out of which 70 per cent were in the early cancer stage.

Between 2017 and 2021, the team launched a second round of screening for 17,000 of the initial participants, among which 677 and 237 had transient and persistent positive results in the first stage, respectively, but were not diagnosed with cancer in endoscopic and MRI exams.

Twenty-four participants were diagnosed with cancer, out of which three displayed transient positive results in the first round, and four showed persistent positive results.

Professor Allen Chan Kwan-chee, from the university’s Chemical Pathology department, said the findings suggested a correlation between positive results and the risk of developing nasopharyngeal cancer later in life.

He said that participants with transient positive results were 4.4 times more likely to develop the disease, while those with persistent positive results were 17 times more likely to get cancer.

“The findings tell us that even if you get a positive result, but are not diagnosed with cancer immediately, you should not ignore the risk,” he said.

“We recommend them to conduct a cancer screening every one or two years, to facilitate early detection and increase the survival rate.”

Researchers would continue to monitor the 20,000 cases, he added.

Discussions were under way with the Hospital Authority to make the first generation of the plasma screening technology, which is a real-time polymerase chain reaction test, available at public hospitals, Chan revealed.

But he said that the latest version of the screening was more costly and would only be available at private institutions for HK$2,000 (US$255).

As plasma-DNA-based tests are becoming increasingly common in detecting various kinds of cancer, Professor Lo said he believed a similar phenomenon involving false positives could be affecting other cancers as well, adding that more studies were needed.

The findings have been published in NEJM Evidence, a publication under the New England Journal of Medicine Group.

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