Viral DNA test successfully screened those at high risk of nasopharyngeal cancer

Cancer of the nasopharynx (that part of the throat between the back of the nose and the back of the mouth) is uncommon in the UK but is prevalent in Southeast Asia. Those at most risk are middle-aged men of Chinese descent, particularly smokers with a family history of the condition. Symptoms include a stuffy nose, nose bleeds, deafness or tinnitus (hissing) in one ear and a lump in the neck, but often do not appear until the cancer has spread. If diagnosed in its earliest stage it is potentially curable with a five-year survival rate as high as 95%, so a screening test is needed before symptoms develop in those at risk.

Blood plasma tests for antibodies to the Epstein-Barr virus (EBV), a common virus that causes glandular fever, and for DNA fragments of the EBV virus are often positive in patients with symptoms of nasopharyngeal cancer. The difficulty with the use of plasma EBV DNA as a screening test in those without symptoms has been that many healthy people carry the virus.

Professors Dennis Lo and Allen Chan of the Chinese University of Hong Kong were the principal authors of a large screening study published in The New England Journal of Medicine on 10 August 2017. They had shown in an earlier study that repeating positive EBV DNA tests after some weeks differentiated those with nasopharyngeal cancer, who had persistently positive results, from carriers who usually had transient results (test results are sometimes negative and sometimes positive). The authors’ new study recruited 20,174 high risk men of Chinese descent aged 40 to 62 living in Hong Kong who had no relevant symptoms. Persistent plasma EBV DNA fragments were detected in 309 men, who were then offered examination of their nasopharynx with an endoscope and by MRI scanning. Of the 300 men examined, 34 (11%) were found to have nasopharyngeal cancer, and it was at an early and potentially curable stage in 16 of them. Most were detected by simple endoscopy rather than by a more costly MRI scan. The authors of the study concluded that analysis of EBV DNA in plasma was useful for screening an at-risk population for nasopharyngeal cancer.

In an accompanying editorial, Dr Richard Ambinder of the Johns Hopkins School of Medicine, Baltimore commented that, because early-stage nasopharyngeal cancer is generally curable with local radiation therapy, the findings are clinically important and the data presented suggest that lives have been saved. "Like cervical cytologic testing or testing for human papillomavirus in the cervix for early detection of cervical cancer, plasma EBV DNA screening may profoundly change the natural history of nasopharyngeal carcinoma".

The senior author of the study, Professor Dennis Lo, said “I hope the number of people dying of nasopharyngeal carcinoma in China will drop significantly after the screening is widely available and ultimately make it a rare case to die of this cancer”.

For more information about the benefits and harms of health screening programmes see the Sense about Science booklet ‘Making Sense of Screening'.