Oncologists see gene expression profiling tests as helpful but have concerns

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 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 surveyed 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.