© 1999 Canadian Medical Association or its licensors
Accurate test for nasopharyngeal cancer developed by Canadian researchers
Saskatoon
Earlier diagnosis and treatment of a hard-to-detect type of cancer that is the leading cause of cancer deaths in Hong Kong, Southern China and many Mediterranean and Pacific Rim countries is a step closer to reality, thanks to a new test developed by Canadian researchers.
Dr. Michael Dosch, professor of immunology at the University of Toronto, has found that a modified version of the cytology brush is very accurate in diagnosing nasopharyngeal cancer. Cells are gently removed from the back of the nose, then subjected to DNA screening to confirm the presence of cancer.
In a study involving 178 patients with early- or late-stage tumours, Dosch and colleagues showed that the new procedure's sensitivity is more than 90% and specificity is around 98%. The findings, published in the Journal of the National Cancer Institute (1999;91[9]:796-800), are being heralded as a significant first step toward screening in high-risk populations - which in Canada includes people of Chinese, Jewish and Inuit descent.
Dosch feels the new technique has the potential to reduce mortality rates significantly. "Early detection is almost certain to improve the poor prognosis of nasopharyngeal cancer. To date, over two-thirds of patients are not diagnosed until the disease reaches a late or very late stage."
Worldwide, about a million new cases of nasopharyngeal cancer are detected annually. Because of their location deep in the nose, the tumours often grow undetected. As a result, prognosis is poor: 10-year survival rates run as low as 10% to 20%. Although the risk drops quickly when Chinese people immigrate to Canada, it is still 40 to 50 times higher than in Canadians of European descent.
Epstein-Barr virus (EBV), carried by almost all adults, is believed to be a central player in the development of nasopharyngeal tumours - EBV is present in all cells from them.
"With the ability to detect early [tumours] routinely, we [already are] considering new approaches to therapy that focus on the unique characteristics of this cancer, which is really an infectious disease quite distinct from other, non-EBV cancers," says Dosch.
Dosch and colleagues are currently planning a large, population-based clinical trial, "to help translate what we've done into practical medicine."-[copyright sign] Greg Basky, Saskatoon
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