Accurate reporting of HER2 (ERBB2) gene copy number status in newly diagnosed breast and gastric cancers is critical for selecting patients predicted to respond to anti-HER2 therapy. Reading the story of how targeted HER2 therapies were developed and how they positively impact patients with breast cancer brings home the importance of this testing. In current clinical practice, tumors are evaluated for HER2 positivity by protein-based immunohistochemistry (IHC) and/or chromosome 17-based fluorescence in situ hybridization (FISH). In the majority of cases, these testing modalities provide a clearly actionable “positive” or “negative” answer. However, in an estimated 10- to 20% of breast and gastric cancers, both IHC and FISH tests are reported as “equivocal” providing the clinician with no guidance as to the potential effectiveness of targeted anti-HER2 therapy for the patient.
The Hi-Res HER2 array-based comparative genomic hybridization (aCGH) microarray provides an alternative molecular testing method for determining HER2 status in breast cancer and resolution of these tough double equivocal specimens. This DNA-based technology uses fluorescently labeled test and reference DNA probes hybridized to a DNA microarray to produce a high-resolution view of the HER2 amplicon in context of the entirety of chromosome 17. The p arm, q arm, and centromere region are subjectively and objectively visualized by CGH revealing, in many cases, complex chromosome 17 rearrangements such as centromere amplification, p arm loss, and additional amplified loci.
PacificDx is pleased to offer HI-RES HER2 microarray testing as a tech-only service to the greater clinical community. Please Contact Us for referral information.