MammaPrint analyzes the activity level of 70 different genes found in fresh tumor tissue removed from women experiencing early stage (1 or 2), lymph node-negative breast cancer. That analysis leads to a numerical ranking that assigns women to one of two groups: high risk for recurrence or low risk.
Women in the high-risk group have twice the chance of breast cancer recurrence within 10 years as women in the low-risk group.
Chemotherapy Prescribed Twice as often as Needed
So, if the test says a woman is low-risk, what does that mean? Much less reason for an often debilitating series of injections of powerful chemotherapy drugs. While chemo is commonly recommended as a safeguard for many women with early-stage breast cancer, studies show that itâ€™s prescribed an estimated twice as often as it needs to be.
Twenty percent of women under age 51 with node-negative breast cancer eventually develop distant metastases; but 45 percent are treated initially with chemotherapy. Dr. Joyce Oâ€™Shaughnessy, writing last summer in the New England Journal of Medicine, says that eventually an estimated 30 to 50 percent fewer women will receive chemo, due to individualized data gathered from MammaPrint and similar gene analysis tests.
MammaPrint's Prediction Accuracy Varies
It appears MammaPrint is much more accurate at predicting that a woman wonâ€™t have a recurrence, rather than that she will. Ninety percent of the women assigned to the low-risk recurrence group did NOT have a recurrence; on the other hand, just 23% of the women assigned to the high-risk group saw their breast cancer return.
The test isnâ€™t perfect; in fact, on the high-risk end, itâ€™s far from it. Doctors stress that gene analysis will be just one weapon in their arsenal of predictive tools, which currently rely mainly on tumor size and type. But according to Dr. Steven Gutman, head of the FDAâ€™s office of In Vitro Diagnostic Device Evaluation and Safety, â€śI think itâ€™s better than having no information at all. It does provide a risk profile for patients.â€ť
Other FDA officials stressed that women should assess further informationâ€“their personal and family medical history, for instanceâ€“in deciding whether or not to receive chemotherapy.
While Agendiaâ€™s version of MammaPrint is the first formally approved by the FDA, MammaPrint has actually been in use in the United States since 2005, when MPI, Inc., a Phoenix gene diagnostics company, licensed it from Agendia and introduced it as the first commercially available individualized gene diagnostic test for women with breast cancer.
The MPI test costs about $3,200, and is covered by most insurance companies. The difference is, Agendia spokesmen asked for approval from the FDA for their test, and received it on Tuesday.