Guide for HER2 Testing That's Not 'by Eye'

Nick Mulcahy

January 28, 2019

The digital revolution continues in pathology and a leading professional body is keeping up by issuing new guidance on an important diagnostic test for breast cancers. 

The College of American Pathologists (CAP) has published a new guideline on use of quantitative image analysis (QIA) of human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) for breast cancer.

HER2 testing is standard for all breast cancers and dictates subsequent treatment, but it has long been conducted using tests, such as fluorescence in situ hybridization (FISH), that require visual review by a pathologists, and so are interpreted "by eye."

QIA, on the other hand, electronically detects and tallies HER2 membranous immunohistochemical staining of invasive breast cancer cells and then provides a quantitative measure of that HER2 histologic feature.

Guideline lead author Marilyn Bui, MD, PhD, Moffitt Cancer Center, Tampa, Florida, explained the importance of the new automated technology. "QIA has been shown to improve consistency and accuracy of interpretation among pathologists," she said.

However, as the guideline authors point out, there are no recommendations to ensure QIA consistency and accuracy in American labs.

Meanwhile, QIA is out of the gate and in use in the United States. A 2016 survey of 826 laboratories enrolled in a CAP quality improvement program showed that 183 (22%) used QIA.

Into that information breach steps the new CAP guidance, published online January 15 in the Archives of Pathology & Laboratory Medicine. The guide mainly addresses "analytic" and "post-analytic" variables.

Analytic variables include items such as region of interest selection, and postanalytic variables include reporting preference.

This leaves out variables that occur earlier in the process such as tissue handling and slide preparation.

The QIA guideline is not 'extra work,' but rather it serves as a blueprint, a valuable tool.    Marilyn Bui, MD

The new guidance is not onerous for labs, suggested Bui.

"The QIA guideline is not 'extra work,' but rather it serves as a blueprint, a valuable tool, that is both evidence-based and practical. And it may save laboratories the extra work of developing quality processes on their own," she wrote in an email to Medscape Medical News.

Bui also noted that the standard of care in invasive breast cancer requires all patients be tested for HER2 status for prognostic and predictive purposes, as outlined in the American Society of Clinical Oncology (ASCO)/CAP HER2 testing in breast cancer guideline, which was updated in 2018.

Recommendations and Expert Opinions

The new CAP guidance for QIA of HER2 testing was authored by a panel comprised of nine practicing pathologists, one histotechnologist, one computer scientist researcher with expertise in computational imaging, and a research methodologist consultant to develop the guideline.

The expert panel members had an average of 11 years of experience using QIA for both diagnostic and research purposes.

The guideline features 11 primary statements, seven of which are recommendations and four of which are expert consensus opinions. They are summarized as follows:

  1. Laboratories that choose to implement QIA for HER2 immunohistochemistry interpretation for clinical testing should select a QIA system that is validated for diagnostic interpretation. The final reporting schema should be consistent with the ASCO/CAP guideline on HER2 testing in breast cancer. Expert consensus opinion

  2. Laboratories should validate their QIA results for clinical use by comparing them to an alternative, validated method(s) such as HER2 FISH or consensus images for HER2 immunohistochemistry. Recommendation

  3. Laboratories should ensure that the results produced by a QIA system are reproducible within and between different batch analyses. Recommendation

  4. Laboratories should ensure that the results produced by a QIA system are reproducible between operators when they select regions of interest for analysis and/or perform annotation. Recommendation

  5. Laboratories should monitor and document the performance of their QIA system. Recommendation

  6. Laboratories should have procedures in place to address changes to the QIA system that could impact clinical results. Recommendation

  7. The pathologist should document in the pathology report that results were obtained using QIA. Expert consensus opinion

  8. Personnel involved in the QIA process should be trained specifically in the use of the technology. Recommendation

  9. Laboratories should retain QIA results and the algorithm metadata in accordance with local requirements and applicable regulations. Expert consensus opinion

  10. The pathologist who oversees the entire HER2 QIA process used for clinical practice should have appropriate expertise in this area. Recommendation

  11. The pathologist finalizing the case should be knowledgable in the use of the HER2 QIA system and visually verify that the correct region of interest was analyzed, the algorithm annotated image produced, and the image analysis results. Expert consensus opinion

Bui serves as a consultant to Rosen Louik & Perry, PC, and de la Parte & Gilbert, PA, and has multiple patent applications in the field. Other authors have disclosed financial relationships with industry, including companies with QIA technology.

Arch Pathol Lab Med. Published online January 15, 2019. Full text

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