The findings, published in this month's edition of the international scientific journal Cancer Research, come after scientists at Princess Margaret Hospital's research arm, Ontario Cancer Institute (OCI), examined over 19,000 genes in a group of 39 lung cancer patients. The scientists discovered unique genetic differences between lung cancer patients that had high likelihood of failing standard treatment compared to those with a better prognosis. Generally, about 50-60 per cent of lung cancer patients treated by surgery will have their cancer reoccur.

"This genetic fingerprint is actually a pattern of genes in the lung tumor that correlated with dramatically different chances of cancer relapse," said Dr. Ming Tsao, leader of the study, a pathologist with Princess Margaret Hospital and Professor of Laboratory Medicine and Pathobiology at the University of Toronto. "In the future, this may allow us to be much more precise in assessing risk and determining whether to be more aggressive in our treatment for some patients."

Dr. Dennis Wigle, lead author and Director of Cancer Genomics for the Lung Cancer site group at University Health Network, said: "This is an exciting finding, not just for the results, but also in the way we approached the research."

Rather than examining genes individually in hope of discovering a single one responsible for lung cancer, the researchers started with over 19,000 genes that were narrowed to the 3,000 which seemed most likely to be important. Using microarrays produced at the University Health Network's Clinical Genomics Centre and the latest computer software, the researchers further narrowed the search to a cluster of 22 genes. These genes were expressed differently in patients whose lung cancer reappeared after treatment compared to those whose cancer did not reoccur within two years.

The discovery is not based on a single abnormality in any particular gene, but rather the recognition that it is the pattern of many interconnected genes that appears to be controlled differently in lung cancer. This ability to measure the levels of thousands of genes all at once provides unprecedented insight into the inner workings of individual lung tumors.

"The goal is to further refine the fingerprint and eventually produce a lung cancer-specific microarray for testing in clinical trials," said Dr. Frances Shepherd, the Head of the Lung Cancer site group at University Health Network, and the Chair of the National Cancer Institute of Canada Clinical Trials Group Lung Cancer Committee.

The study was supported by grants from the National Cancer Institute of Canada, the National Science and Engineering research Council of Canada, the Physicians' Services Inc. Foundation and the Princess Margaret Hospital Microarray Clinical Research Program.

Lung cancer remains by the far the number one cancer killer. Last year alone, an estimated 18,000 Canadians died from lung cancer, while another 21,200 were diagnosed with the disease.

Princess Margaret Hospital and its research arm, Ontario Cancer Institute, have achieved an international reputation as global leaders in the fight against cancer. Princess Margaret Hospital is a member of the University Health Network, which also includes Toronto General Hospital and Toronto Western Hospital. All three are teaching hospitals affiliated with the University of Toronto.

Note: If no author is given, the source is cited instead.

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