Updated UK Guidelines for HER2 Assessment in Breast Cancer
This update to UK breast cancer HER2 testing guidelines refines the two-tiered IHC/ISH diagnostic approach, addresses the clinically important distinction between HER2-low (IHC 1+) and HER2-negative (IHC 0) status, and provides guidance on HER2 heterogeneity reporting and repeat testing. The recommendations evaluate the potential role of next-generation sequencing and other molecular assays for routine HER2 testing, as well as image analysis for IHC scoring. These distinctions have become therapeutically relevant with the emergence of antibody-drug conjugates targeting HER2-low tumours.
The original study
UK recommendations for HER2 assessment in breast cancer: an update.
- Authors
- Rakha EA, Tan PH, Quinn C, Provenzano E, Shaaban AM, Deb R, et al.
- Journal
- Journal of clinical pathology
- Type
- Journal Article, Review
- PMID
- 36564170
Original abstract
The last UK breast cancer (BC) human epidermal growth factor receptor 2 (HER2) testing guideline recommendations were published in 2015. Since then, new data and therapeutic strategies have emerged. The American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) published a focused update in 2018 that reclassified in situ hybridisation (ISH) Group 2 (immunohistochemistry (IHC) score 2+and HER2/chromosome enumeration probe 17 (CEP17) ratio ≥2.0 and HER2 copy number <4.0 signals/cell), as well as addressed other concerns raised by previous guidelines. The present article further refines UK guidelines, with specific attention to definitions of HER2 status focusing on eight key areas: (1) HER2 equivocal (IHC 2+) and assignment of the ASCO/CAP ISH group 2 tumours; (2) the definition of the group of BCs with low IHC scores for HER2 with emphasis on the distinction between IHC score 1+ (HER2-Low) from HER2 IHC score 0 (HER2 negative); (3) reporting cases showing HER2 heterogeneity; (4) HER2 testing in specific settings, including on cytological material; (5) repeat HER2 testing, (6) HER2 testing turnaround time targets; (7) the potential role of next generation sequencing and other diagnostic molecular assays for routine testing of HER2 status in BC and (8) use of image analysis to score HER2 IHC. The two tiered system of HER2 assessment remains unchanged, with first line IHC and then ISH limited to IHC equivocal cases (IHC score 2+) but emerging data on the relationship between IHC scores and levels of response to anti-HER2 therapy are considered. Here, we present the latest UK recommendations for HER2 status evaluation in BC, and where relevant, the differences from other published guidelines.