FDA OK's genetic predictor of breast cancer relapse
Agency says test has flaws but can aid in treatment decisions
The Food and Drug Administration yesterday approved a genetic test that, when conducted soon after a woman learns she has breast cancer, can predict the odds of the disease returning and worsening.
The test, called MammaPrint, analyzes tissue from a breast tumor to gauge the activity of 70 key genes and determines the likelihood of the cancer's recurrence. It has been sold since 2005 in the Netherlands by Agendia , an Amsterdam company.
The FDA's Dr. Steven Gutman called MammaPrint a "fabulous tool" for doctors and patients.
"The doctor wants to know, the patient wants to know, whether they have a more aggressive or less aggressive tumor," Gutman said.
But he quickly acknowledged the major drawback of MammaPrint's computer analysis: It is less accurate when it predicts there is a high risk of cancer returning.
In studies, only about one-quarter to one-third of women given MammaPrint results that indicated they were highly likely to battle cancer again actually suffered a repeat bout within five to 10 years.
"The numbers speak for themselves. It's not a perfect test," Gutman said.
Because of that, the FDA cautioned that the test is not a substitute for the guidance of cancer specialists who weigh a woman's general health, age, tolerance for therapy, and other factors to best tailor her therapy.
Still, a Boston cancer expert sees the test's potential in helping to refine treatment decisions. "Some women get no benefit from chemotherapy and other women get a lot of benefit," said Dr. Harold Burstein , a Dana-Farber Cancer Institute breast oncologist . But those who get the least benefit from chemotherapy still endure hair loss , nausea, and other side effects, he said.
"It's just a drag," Burstein said. "We'd like to avoid it, if we don't need it."
This year, 178,480 American women will be diagnosed with breast cancer, and 40,000 are expected to die from it, according to the American Cancer Society .
While the MammaPrint test carries FDA approval, a spokesman said it is unclear how quickly it will be sold in the United States or how much it cost. For now, doctors will send breast tissue samples to the Netherlands for analysis and receive test results within a few days.
Doctors treating breast cancer now rely on Oncotype DX , which costs $3,464 and is made by Genomic Health Inc. The California company told investors yesterday that it delivered 14,500 copies of Oncotype DX to physicians in 2006 , compared with 7,000 in 2005 . Unlike MammaPrint, it is not approved by the FDA.
Doctors increasingly are relying on a small, but growing number of similar genetic tests to better match patients with treatments for such ailments like breast and bladder cancer. Many are known as "home brew" diagnostic tests -- developed in a single lab and, like Oncotype DX, are unregulated by the federal government.
MammaPrint's approval comes days before a public hearing on whether the FDA should more actively oversee "home brew" genetic tests.
Diedtra Henderson can be reached at dhenderson@globe.com. 
