Dr. Susan Love Research Foundation | FDA Approves MammaPrint Prognostic Test

On February 6, 2007, the U.S. Food and Drug Administration (FDA) determined that a new genetic test designed to predict a woman's risk of having a distant breast cancer recurrence (metastasis) in five to 10 years could be marketed in the U.S.

Whether a cancer spreads depends in part on the activity of certain genes located in the tumor. The new test, called MammaPrint, uses a technology called microarray analysis that allows scientists to look at hundreds of genes simultaneously. The test is performed on a tumor sample after the tumor has been surgically removed.

By assessing the activity of 70 specific genes, MammaPrint produces a score that determines if the patient is at low or high risk of having the cancer spread from the breast to other areas of the body (metastasize). This information can then be used to guide treatment decisions.

MammaPrint was developed by Agendia, a laboratory located in Amsterdam, Netherlands, where it has been available since 2005. It is the first test that uses microarray analysis to be approved by the FDA.

The test can only be used to assess recurrence risk in patients who have a Stage I or Stage II breast cancer, negative nodes, and a tumor equal to or less than five centimeters in size. (More than half of all women diagnosed with breast cancer each year fit this description.

Because MammaPrint is so new, no one yet knows whether using the test results to help guide treatment decisions actually helps women at high risk for distant recurrence live longer.

Susan says:
Oncologists currently use a woman's age, tumor size, tumor grade, and estrogen receptor status to assess her risk for having her cancer recur. But it is still a "best guess" scenario. There's no perfect way of determining which women will develop a distant recurrence (metastasis). This means there is no way to accurately tell who will benefit from chemotherapy and who doesn't really need it. As a result, many women receive chemotherapy who probably don't need it, while others who could benefit don't get it.

As we learn more about breast cancer, we are also learning how to tailor treatments to the type of tumor a woman has. MammaPrint is a genetic test that may help some women make treatment choices. I say "may" because the test has not been widely used, and because it is far from perfect. MammaPrint does not and cannot precisely predict whether a woman will have a recurrence. It can only assess whether a woman is high risk or low risk—and even then, there are problems. According to the data submitted by Agendia to the FDA, MammaPrint accurately predicted which women were at low risk for having their cancer spread about 95percent of the time—which is pretty good. But it only accurately predicted which women were at high risk for distant recurrence 23 percent of the time. This means that 77 percent of the time it was wrong—which is clearly not good.

Any time a test is not 100 percent accurate, problems will ensue. In this case, if the test tells you that you are low risk it's probably right. But if it tells you that you are high risk, there is a good chance it's wrong. And I hate to think about women walking around worrying that they are at high risk for recurrence when they really aren't. For this reason, if you decide to have this test done (it needs to become available in the US first), it's very important that you don't perceive its findings as the end-all or be-all. It's really only just one more piece of information to use along with all of the other information you have about your tumor to help you and your physician choose the best breast cancer treatment for you.

The Oncotype DX Test is another genetic test that is similar to the MammaPrint test. It has been available in the US since 2004. This test assesses 21genes to predict recurrence risk. It is able to accurately divide women into three groups—low, medium, and high risk for recurrence. It can be used by women with node-negative, estrogen receptor (ER)-positive breast cancers. The Oncotype test is considered a "home-brew" test, which meant it could be marketed without FDA approval. This also means testing can only be done by the company that developed it, Genomic Health. But this is easy to do: your physician sends them a sample of your tumor tissue for analysis, and they send the results back. The test costs about $3000, and may—or may not—be covered by your insurance. Currently it is not known when MammaPrint will be available in the US, how much the test will cost, or whether insurance companies will cover it. Once the test is made available, any hospital laboratory will be able to use it.