Molecular subtyping classifies breast cancer tumors into one of four genetically distinct categories, or subtypes: Luminal A, Luminal B, Basal (a subset of triple negative), and HER2-type. Each subtype responds to certain kinds of treatments and not others. Some subtypes are also associated with a higher risk of disease recurrence, which can also affect treatment choices. In particular, women at high risk of recurrence are usually counseled to receive chemotherapy. Women at low risk can choose to forgo chemotherapy and its potentially damaging side effects and still expect a good outcome.

For the scientific poster, researchers examined tumor samples from a study population of 148 patients. The greatest discordance between MammaPrint and the 21-gene test about recurrence risk was found among 33% of the patients. Those patients were stratified by the latter test as being at low risk of recurrence, but MammaPrint identified them as being at a high risk of recurrence.


In an attempt to explain this discrepancy, BluePrint was used to determine the molecular subtype of the tumors with discordant results. The overwhelming number of patients, classified as low risk by the 21-gene assay but as high risk by MammaPrint, turned out to have the Luminal B subtype, which confers a high risk of recurrence.

"This new scientific poster has important implications for clinical practice," said Agendia's Chief Medical Officer, oncologist Neil Barth, M.D. "When breast cancer patients and their physicians are trying to decide whether chemotherapy would be beneficial, it is crucial that they know the molecular subtype of the cancer. The MammaPrint and BluePrint tests together provide this additional information about tumor biology, while the older, first-generation test does not, and may in fact supply inaccurate information about a patient's risk of recurrence."

The lunchtime symposium at the Miami conference was titled "Molecular Subtypes: Clinical Implications for Breast Cancer Patients in Your Practice." The featured speaker was Massimo Cristofanilli, M.D., a noted oncologist, who described recent research at his institution and several other noted cancer centers.

Researchers reported that molecular subtyping with MammaPrint and BluePrint was more effective than traditional, clinical pathology methods for identifying women who will not benefit from chemotherapy after breast cancer surgery. These women may therefore safely forego chemotherapy and its side effects.

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