Molecular Assays Reclassify Early Breast Cancer Type

February 2013, Vol 4, No 2

San Antonio, TX—Molecular subtyping of early breast cancers using Mamma­Print and BluePrint assays allows the precise and accurate prediction of the molecular phenotype of the disease, which has the potential to guide the selection of personalized therapy if the tests are used prospectively.

“The use of MammaPrint and BluePrint should be implemented in the management of primary breast cancer for the selection of adjuvant therapy in the era of personalized care,” said lead investigator Massimo Cristofanilli, MD, FACP, Chair, De­partment of Medical Oncology, Fox Chase Cancer Center, Philadelphia, PA, at the 2012 San Antonio Breast Cancer Symposium.

A retrospective study of 208 tumor samples found that molecular subtyping with these 2 assays led to reclassification of 25% of the tumors, which would have been treated differently if the tests were applied prospectively.

The study used frozen tumor samples from 208 patients. Of the patients, 59% were hormone receptor positive (estrogen receptor [ER]/progesterone receptor [PR]+), 20% were HER2 positive, and 24% were triple negative by locally assessed immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). All patients under­went lumpectomy or mastectomy with axillary staging.

The microarray-based assays included BluePrint and MammaPrint. BluePrint is an 80-gene assay that discriminates between luminal-type, basal-type, and HER2-type breast cancer. MammaPrint is a 70-gene assay that substratifies luminal-type breast cancer into low-risk luminal A and high-risk luminal B breast cancers.

Breaking down the results of molecular subtyping showed that 13 of 188 (11%) tumors that were ER+, PR+, or HER2 negative are not classified as luminal type by BluePrint; 24 of 41 (61%) clinically HER2-positive patients are not classified as HER2 type by BluePrint; and 10 of 49 (20%) triple-negative tumors are not classified as basal type by BluePrint.

Of the total patients, 51 were reclassified as a result of molecular subtyping. Of these, 28 patients were reassessed centrally for ER, PR, and HER2 status by IHC and FISH.

The patients with luminal-type early breast cancer that was identified by BluePrint have excellent relapse-free survival rates of 97% for patients with luminal A cancer and 98% for patients with luminal B cancer.

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