New tests detect early cancer signs
Local firm creates simpler procedure
Lung, colon, breast tumours targetted
PRITHI YELAJA
STAFF REPORTER
A Toronto company has come up with simple tests to detect disease early in the three biggest cancer killers — lung, colorectal and breast — and potentially save lives.
Preliminary results show the tests are able to detect early stage disease, which has the greatest potential for cure, in 54 per cent of patients with colon cancer and 57 per cent of patients with lung cancer.
The test is particularly promising in the case of lung cancer, which up until now has had no tool for early detection. It is less advanced for breast cancer, but early results are encouraging, said Dr. Mike Evelegh, principal scientist with International Medical Innovations (IMI), a small biotechnology start-up.
"The nice thing about our technology is these are simple easy to do tests. The mucous or fluid samples that are taken are completely non-invasive and can be done as part of an annual physical exam in the family doctor's office," he said.
"Using the same technology we've been able to differentiate cancer from non-cancer in three very different types of samples, so that helps to validate the methodology we're working with."
IMI was to present its clinical results at the American Association for Cancer Research meeting in Toronto this weekend, but the conference was abruptly cancelled due to fears of SARS.
Having the results accepted for presentation at the association meeting was a coup, said Evelegh, adding the association will publish the results in its journal.
Ranging in price from $10 to $40, IMI's tests are cheaper than currently available screening tests and could serve as important mass screening tools for cancer, benefiting not only patients, but also saving the cash-strapped health system money, said Dr. Brent Norton, founder and president of IMI.
When cancer is forming in an organ, the rapid metabolism of the tumour robs the tissues around it of some nutrients and in essence they starve and secrete aberrant sugars. The tests work by detecting these abnormal sugars in samples of mucous or fluid, which are directly associated with the early formation of tumours.
The samples are smeared on a special card and treated with an enzyme that exposes the sugars. A developer chemical is added which turns a magenta colour in the presence of cancer. The greater the colour intensity, the greater the likelihood of cancer.
In the case of colorectal cancer — the number two cancer killer, striking 17,600 Canadians a year and claiming 6,600 lives — the physician takes a mucous sample during a routine digital rectal exam.
In a study involving 1,787 patients at St. Michael's Hospital in Toronto, the test detected early stage cancer in 54 per cent of patients. Moreover, the test was 85 per cent accurate for those who didn't have cancer.
Patients who have a positive result on the test would then go on to have a colonoscopy, a much more expensive (about $700) and intrusive diagnostic test for colorectal cancer in which the patient is mildly sedated, so the doctor can snake a flexible tube up into the colon through the rectum.
"We can't just go right to colonoscopy for everyone because it just isn't practical, so we need a test to help identify those people who don't have symptoms but have early disease," said Evelegh.
The fecal occult blood test, the screening tool currently used to detect colorectal cancer, picks up about 35 per cent of early disease. But people typically don't want to take the test, which involves collecting stool samples to check for blood, an early cancer warning. Dr. John Miller, a chest surgeon at St. Joseph's Hospital in Hamilton who led clinical trials of IMI's test for lung cancer, knows the anguish of patients whose disease was found too late for treatment. Lung cancer is the deadliest of all the cancers, striking 20,800 Canadians a year, killing 18,400. Eighty-five per cent of lung cancer patients are current or former smokers.
There is some debate around whether early detection makes any difference in survival rates for lung cancer, but Miller says there was no clear answer largely because there was no test available. He is convinced early detection saves lives.
In patients in the study whose lung cancer was caught early, at stage 1, the chance of survival jumps to 80 per cent, he noted.
A total of 500 patients are involved in the ongoing clinical trial of IMI's test for lung cancer — 100 cancer patients, 200 healthy smokers with no obvious disease and 200 others with benign lung disease such as asthma. The researchers didn't know to which group patients belonged.
Samples were taken by having patients spit sputum in a cup, which was analyzed for presence of aberrant sugars. Based on preliminary results from 81 patients, the test was able to detect 57 per cent of early stage and 65 per cent of late stage cancer with a specificity of 90 per cent, so only 10 per cent of people without disease were falsely positive.
IMI's test for early breast cancer detection is in the very preliminary stages but has shown promise. The clinical trial involved 16 women with stage 1 breast cancer. When fluid was taken from both breasts, the one with cancer and one without, the test was able to differentiate between the two. The next step is to do a much larger study of healthy women suspected of having cancer to determine whether the test can detect those who do.
"Certainly it's an exciting, innovative new technology that warrants further exploration," said Dr. Anees Chagpar, a breast surgeon at MD Anderson Cancer Center in Houston that led the study.
The tests require clearance from health regulators before they come on the market.
The colorectal and lung tests are expected to be on the market in Canada and Europe by the end of next year; the breast cancer test may be ready in two years.
Using the same technology, IMI plans to develop tests for cervical and prostate cancer.
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