Implications of the Updated 2013 American Society of Clinical Oncology/College of American Pathologists Guideline Recommendations on Human Epidermal Growth Factor Receptor 2 Gene Testing Using Immunohistochemistry and Fluorescence In Situ Hybridization for Breast Cancer

Abstract

Context.-Human epidermal growth factor receptor 2 (HER2/neu) amplification is used as a predictive marker for trastuzumab treatment in breast cancer. Objective.-To assess the impact of the revised ASCO/ CAP recommendations on both IHC and FISH results by using the dual-color HER2/neu and centromeric FISH probes.Design.-Retrospective analysis of 590 invasive carcinomas with concurrent IHC and dual-color HER2/neu and centromeric 17 (CEP17) FISH results, based on 2007 ASCO/CAP guidelines, was conducted from July 2011 to June 2013. With the revised guidelines, patients were recategorized and concordance rates between the 2 assays were recalculated.Results.-Overall concordance rates for FISH and IHC decreased from 94.9% to 93.8% with reclassification. Negative FISH cases decreased from 79.1% to 69.3%. However, equivocal FISH cases were significantly increased from 0.7% to 9.5%, leading to more retesting. Both positive IHC and FISH cases were also noted to be increased, leading to more patients being eligible for trastuzumab treatment, especially those patients with concurrent HER2/neu and CEP17 polysomy. Approximately 1% of patients with initial FISH negative results were reclassified as having positive results when both the ratios and average copy number of HER2/neu were considered under the revised guidelines.Conclusions.-The revised 2013 ASCO/CAP guidelines can potentially lead to more patients being eligible for trastuzumab therapy but additional retesting is to be expected owing to an increased number of equivocal FISH cases.

Genomic profiling of ER + breast cancers after short-term estrogen suppression reveals alterations associated with endocrine resistance

“…We measured ER, PR, and Ki67 expression in pre- and post-letrozole tumor samples by automated quantitative immunofluorescence (AQUA) (14, 15). This method utilizes multiplexed immunofluorescence to delineate invasive cancer cells with tagged antibodies against pan-cytokeratin and nuclei with DAPI staining in 10-25 regions of interest on whole tumor sections identified by a breast pathologist, scoring approximately 10,000 tumor nuclei (7).…”

“…This method utilizes multiplexed immunofluorescence to delineate invasive cancer cells with tagged antibodies against pan-cytokeratin and nuclei with DAPI staining in 10-25 regions of interest on whole tumor sections identified by a breast pathologist, scoring approximately 10,000 tumor nuclei (7). As all tumors were clinically HER2 negative (not amplified), this allowed for allocation of molecular subtype (luminal A or B) by the AQUA-IHC4 algorithm (14) (Fig. 1B).…”

“…Fluorescent multiplexed IHC was conducted at Genoptix, Inc. Medical Laboratories according to clinical standards on both the diagnostic biopsy and post-treatment surgical biopsy for ER, PR, HER2, and Ki67 (antibody clone SP6, Ventana) (14, 15). This method utilizes multiplexed immunoflurorescence to delineate invasive cancer cells with tagged pan-cytokeratin and nuclei with DAPI staining in 10-25 regions of interest on whole tumor sections identified by a breast pathologist, measuring approximately 10,000 tumor nuclei (7).…”

Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: American Society of Clinical Oncology/College of American Pathologists Clinical Practice Guideline Focused Update

“…1,4 The number of such cases within a laboratory varies based on the patient population referred for ISH testing, but it seems to be approximately 5% of cases (range, 1% to 16%). 15,[19][20][21][32][33][34][35][36][37][38][39][40][41][42] The use of alternative probes to adjudicate these cases has also increased since 2013.…”

Molecular Diagnostics in Breast Cancer Routine Practice

“…Staining is usually scored according to the DAKO guidelines as 0 (no staining or <10% of the tumour cells are weak and incomplete, not circumferential), 1+ (≥10% of the tumour cells is weak and incompletely stained), 2+ (≥10% of the tumour cells are stained moderately intense [complete, or incomplete], or <10% complete and intense), or 3+ (>10% is stained strongly and circumferentially). 35 However, membrane staining can be influenced by fixation conditions, and IHC may miss amplified cases. 36 FISH is an effective and sensitive method to assess HER2 gene amplification status.…”