Dr. Fernandez on the Need to Refine Immunohistochemistry Testing in HER2+ Breast Cancer

Aileen I. Fernandez, PhD, postdoctoral fellow, Yale School of Medicine, discusses the need to refine immunohistochemistry (IHC) testing in HER2-positive breast cancer.

Findings from a study evaluating low HER2 expression in patients with breast cancer underscored a discrepancy between the frequency clinicians agreed upon immunohistochemistry (IHC) results of 0 vs 1+ or 2+ vs 3+. Clinicians were more likely to agree upon diagnoses of IHC 2+ or 3+ compared with 0 or 1+.

These findings indicate that IHC testing results should be analyzed carefully, Fernandez explains. Historically, IHC 2+ or 3+ results were focused on because they informed treatment selection with trastuzumab (Herceptin). However, as scoring accuracy is imperfect, misassignment remains a risk, Fernandez explain.

Developing a new test, answering preanalytical questions, and standardizing testing across the board would be helpful, Fernandez says. Moreover, in reading IHC test results, differences with the machines and the clinicians interpreting the results may provide insight as to why there remains disagreement in IHC analysis.

Moreover, as the field of breast cancer continues to evolve, other therapies targeted toward biomarkers beyond HER2 will emerge, further underscoring the need for improved testing, concludes Fernandez.