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Thursday, April 22, 1999Research on cancer finds differences between sexes
OTTAWA - Canadian researchers have found remarkable differences in the way lung cancers develop in men and women.
The finding may shed light on why women are more sensitive to carcinogens in tobacco than men, regardless of body size, smoking history, or how much they smoke.
It could also lead to improved detection of lung cancer, expected to kill 17,400 Canadians this year.
"I think we need to use a different screening strategy," said Dr. Stephen Lam, a University of British Columbia professor of pulmonary medicine.
Dr. Lam and a team of researchers from the B.C. Cancer Agency found male smokers have a higher rate of pre-cancerous damage to their large central airways. About 50% of lung cancer occurs in former smokers.
By contrast, female smokers tend to suffer damage to the smaller, peripheral airways where a bronchoscope -- used to detect lesions -- cannot reach.
"The lung is just like a tree branching into smaller and smaller tubes," said Dr. Lam.
"There are probably about 15 generations of the tree, and a bronchoscope can only reach about five."
The study, published today in the Journal of the National Cancer Institute, says better screening tests are needed to detect cancer in women. For example, since they do not suffer damage to their central airways like men, a test of airflow obstruction -- commonly used to detect those at risk of cancer -- does not work particularly well in women.
Dr. Lam said if Canadian hospitals used computed tomography (CT) chest scans, which are far more sensitive than the chest X-rays currently being used, many lung cancers could be caught at an early, treatable stage.
"A CT scan would also pick up these lesions better than a conventional sputum [test]," he said.
"Actually it has been done in Japan for a few years now. They are quite advanced in this area. We are just starting to do the same thing now in North America."
Dr. Lam is trying to convince the B.C. government to conduct a pilot study looking at efficacy.
When lung cancer cells are detected in sputum, the cure rate ranges from 90% to 100%. If nodules have already formed, the cure rate is 70% to 80%.
"In Japan, because they've been doing this kind of [CT] screening, if they find cancer at one centimetre, the cure rate so far is close to 100%."
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Canadian Cancer Statistics 1999
Read the study on the Canadian Cancer Society site in English or French.
Canadian Cancer Society
A large and helpful site.
Based in the National Institute of Health. Prize features are links and access to a cancer database.
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