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McGill researchers find link to genes

By AARON DERFEL, The Gazette January 29, 2011

A group of Montreal researchers and their U.S. colleagues have discovered a new, highly accurate genetic test that can predict whether some women with breast cancer will suffer a relapse.

The test is reported to be superior than an existing test, and has the potential to spare women at a very low risk of relapse of breast cancer from undergoing toxic chemotherapy.

Increasingly, oncologists are zeroing in on the genetic underpinnings of cancer. For breast cancer, that means testing for things like the HER2/ neu gene, and consequently tailoring a drug therapy like Herception for that type of disease.

Almost half of all breast cancer patients belong to a group that is considered at low risk of a relapse. These patients are deemed to be estrogen receptor-positive and lymph node-negative. In their case, the cancer has not spread to the lymph nodes.

The problem is that 10 to 15 per cent of patients in this group go on to suffer a relapse of breast cancer after surgery. Until now, the only solution was to follow up with aggressive chemotherapy even though most in that group didn’t need it.

That’s where the new genetic expression test comes in, developed by scientists at the Research Institute of the McGill University Health Centre, along with colleagues from the Dana Farber Cancer Institute and Harvard Medical School.

The test analyzes two sets of 29 genes from tumour samples. One set of genes is responsible for uncontrolled cell growth -the very essence of cancer -and the second set involve genetic instability.

Thus, if the test results show high expressions of both sets of these genes, the patient would be at a high risk of a relapse.

“The added information provided by our test would enable oncologists to identify those at very low risk of relapse, for whom the risk-benefit ratio would be in favour of withholding chemotherapy, and to identify patients in this low-risk group who would benefit from more aggressive treatments,” said Alain Nepveu, an MUHC molecular biologist.

Some of these aggressive treatments can cause premature menopause as well as secondary cancers, so it’s important for doctors to have a very good idea of who could benefit from continued therapy, Nepveu said.

A test is already available in the U.S. to determine who among the low-risk patients will relapse, but it does have a high false positive rate of more than 18 per cent.

“I think our test is superior because we analyze the two sets of genes, while the other one focuses only on just cell proliferation,” Nepveu.

The findings of the research were published in the Proceedings of the National Academy of Sciences. The next step will be to study the test in a clinical setting. If it proves accurate as expected, the test could be commercialized within five years, he Nepveu said.

In Quebec, 6,100 women are expected to learn they have breast cancer this year, and of that number, 1,400 will die from the disease, according to the Quebec Breast Cancer Foundation.

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