Philadelphia Inquirer examines efficacy of genetic testing to determine risk of breast cancer relapse

The Philadelphia Inquirer on Sunday examined the efficacy of Genomic Health's Oncotype DX test and Amsterdam, Netherlands-based Agendia's MammaPrint, both of which measure a woman's odds of breast cancer relapse by testing her removed tumor for genes that can predict the likelihood of her cancer returning (McCullough, Philadelphia Inquirer, 4/1).

Oncotype DX is one new tool that examines the DNA of a woman's tumor cells for mutations in 16 genes linked to breast cancer development.

The test can predict the likelihood that breast cancer will recur and can improve the chances of survival. According to Genomic Health, the process has been performed on about 17,000 women (Kaiser Daily Women's Health Policy Report, 11/7/06).

MammaPrint, which FDA approved in February, measures the activity of 70 genes in tissue taken from a surgically removed breast tumor to determine the risk of recurrence in women under age 61 after five- and 10-year periods (Kaiser Daily Women's Health Policy Report, 2/7).

According to the Inquirer, both tests can predict to a certain degree if women at high risk of relapse would benefit from chemotherapy and if low-risk women would not.

However, "neither test has enough data to predict whether chemo definitely benefits women at medium risk," the Inquirer reports.

To clarify what women who have a medium risk of recurrence should do, a federally funded clinical trial of Oncotype DX is under way, and a trial of MammaPrint is scheduled to begin in Europe, the Inquirer reports.

For now, many questions remain about "how to validate, regulate and pay for such tests -- and about how useful they really are," according to the Inquirer (Philadelphia Inquirer, 4/1).