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Oncologists praise gene expression profiling tests as a decision-making tool for women with early-stage breast cancer but also have significant reservations

Toronto, March 6, 2015

By Leslie Shepherd

Dr. Yvonne Bombard
Dr. Yvonne Bombard

Oncologists welcome gene expression profiling tests as an added tool in deciding whether women with early-stage breast cancer should have chemotherapy, a new study has found. But they have significant reservations about the cost of the test and whether it is being overused and used for the right patients.

Oncologists also acknowledged in the study by Dr. Yvonne Bombard, a genomics health services researcher in the Li Ka Shing Knowledge Institute of St. Michael’s Hospital, that they may not be explaining the test in a way that patients understand what it does.

Her paper was published online today in the journal The Oncologist.

Current guidelines for treating early-stage breast cancer—cancer that has not spread to nearby lymph nodes or other parts of the body—result in thousands of women receiving chemotherapy without benefitting from it.

Gene expression profiling tests such as Oncotype Dx can help differentiate women who might benefit from chemotherapy versus those that might not. The test analyzes the patterns of 21 different genes within the cancer cells to help predict how likely it is that a women’s cancer will recur within 10 years after initial treatment and how beneficial chemotherapy will be to her.

Fourteen oncologists were interviewed at teaching and community hospitals in Toronto. Most said the tests enhanced their confidence in deciding whether to recommend chemotherapy in cases where the best course of action was unclear to both the physician and the patient – especially when they were truly undecided. While most said the test supported their assessment rather than altering their practice, one oncologist described the test as a “tie-breaker.”

But they raised concerns about overuse and inappropriate use of the test; over-reliance on the test relative to other, more established pathological indicators; the fact that testing takes places in only one lab in California; aggressive marketing of the test and its high cost, about $4,000.

Dr. Bombard said these reservations were consistent with general concerns about overuse of laboratory testing, which has increased rapidly, contributing to the financial strain on health care systems. Estimates suggest that 10 to 50 per cent of lab tests in Canada might be unnecessary and one-third of U.S. health-care spending results from overuse or misuse of tests, procedures and therapies.

In addition, while many oncologists said it was simple to explain the test to patients, they remained uncertain about patients’ understanding of the test results and their treatment implications.

This study received funding from Cancer Care Ontario, the Ontario Institute for Cancer Research and the Canadian Centre for Applied Research in Cancer Control.

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

Media contacts

For more information, or to arrange an interview with Dr. Bombard, please contact:

Leslie Shepherd
Manager, Media Strategy, St. Michael's Hospital
416-864-6094
shepherdl@smh.ca