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Blood test could benefit women with advanced breast cancer

Mount Sinai Hospital is home to Canada’s first circulating tumour (CTC) test used in a clinical setting – a simple blood test that is poised to become an important tool in deciding how best to treat women with breast cancer that has advanced beyond the early stages. 

“This test was developed over 10 years ago, but this is the first time it has been used in a clinical setting in Canada,” explains Dr. Martin Chang, a pathologist at Mount Sinai. “It has enormous diagnostic potential for metastatic breast, prostate or colon cancers. It is basically the first step – the Model T – in developing a blood test for advanced cancer.”

Cancer spreads in part because cancer cells can leave the primary tumour and enter the bloodstream. While circulating throughout the body these cells can potentially seed new tumours in the liver, bone, brain or other organs, in the process known as metastasis. The CTC test counts cancer cells in a small blood sample, and the number provides insights into the patient’s prognosis and how treatment is working. “We know that if a person’s CTC count is five or more [within a 7.5 cc tube of blood], that their prognosis is less favourable,” explains Dr. Chang. “This helps us recognize that their current treatment may not be having the desired effect and that a change is needed.”

Mount Sinai has been able to acquire the high-end CTC technology as a direct result of donor Andrew Hoffman and his Hold ‘em for Life Charity Challenge events, which have raised millions of dollars to fund cancer research and other initiatives at Mount Sinai and other hospitals.

The CTC test also holds significant research potential. “When cancer cells break away from the original tumour and end up somewhere else in the body, they change,” says Dr. Chang. “So when breast cancer spreads to the liver, we can’t necessarily keep treating it as the same breast cancer.” This test can help scientists study the characteristics of metastatic cells in the bloodstream, characteristics that may be different for each person.

“The hope is that these blood tests will eventually be treated as ‘liquid biopsies’, which is a much less invasive procedure than a tissue biopsy, guiding treatment of metastatic cancer as the tumour changes over time and in response to treatment,” says Dr. Pamela Goodwin, Marvelle Koffler Chair in Breast Research and Director of the Marvelle Koffler Breast Centre at Mount Sinai. This holds potential for a personalized approach for treating breast cancer – helping clinicians tailor treatment to each person.