Instant-quality fluorescence in-situ hybridization as a new tool for HER2 testing in breast cancer: a comparative study

Complementary Tumor Diagnosis by Single Cell-Based Cytogenetics Using Multi-marker Fluorescence In Situ Hybridization (mFISH)

Multi-color (or multi-marker) fluorescence in situ hybridization (mFISH) is a well-established, valuable, complementary tool for prenatal and pathological (tumor) diagnosis. A variety of chromosomal abnormalities, such as partial or total chromosomal gains, losses, inversions, or translocations, which are considered to cause genetic syndromes, can relatively easily be detected on a cell-by-cell basis. Individual cells either in suspension (e.g., in the form of a cytological specimen derived from body fluids) or within a tissue (e.g., a solid tumor specimen or biopsy) can be quantitatively evaluated with respect to the chromosomal hybridization markers of interest (e.g., a gene or centromeric region) and with due consideration of cellular heterogeneity. FISH is helpful or even essential for the (sub-)classification, stratification, and unambiguous diagnosis of a number of malignant diseases and contributes to treatment decision in many cases. Here, the diagnostic power and limitations of typical FISH and mFISH approaches (except chromosome painting and RNA hybridization) are discussed, with special emphasis on tumor and single-cell diagnostics. Well-established and novel FISH protocols, the latter addressed to accelerate and flexibilize the preparation and hybridization of formalin-fixed and paraffin-embedded tissues, are provided. Moreover, guidelines and molecular aspects important for data interpretation are discussed. Finally, sophisticated multiplexed approaches and those that analyze very rare single-cell events, which are not yet implemented in diagnostic procedures, will be touched upon. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: (m)FISH applied to formaldehyde-fixed paraffin-embedded tissues Basic Protocol 2: (m)FISH applied to cytological specimens.

Advances in HER2 testing

HER2-positive breast cancer is a particularly aggressive type of breast cancer. Indication of HER2 positivity is essential for its treatment. In addition to a few FDA-approved methods such as immunohistochemical (IHC) detection of HER2 protein expression and in situ hybridization (ISH) assessment of HER2 gene amplification, several novel methods have been developed for HER2 testing in recent years. This chapter provides an overview of HER2 testing with emphasis on those new methods.

Assessment of HER2 amplification status in breast cancer using a new automated HER2 IQFISH pharmDx™ (Dako Omnis) assay

In breast cancer the human epidermal growth factor receptor 2 (HER2) is an important target for a number of different HER2 inhibitors. Different slide-based assays are available for assessment of treatment eligibility, which include fluorescence in situ hybridization (FISH) or other in situ hybridization (ISH) methods for assessment of the HER2 gene status. Here we report a summary of the validation data on HER2 IQFISH pharmDx™ (Dako Omnis), a newly developed assay for the automated staining platform Dako Omnis. The assay uses a non-toxic buffer that significantly reduces the hybridization time, which results in a total turnaround time of 3½ to 4h from deparaffinization to counting of the gene and centromere signals. The data reported in the current summary covers method comparison, assessment of staining quality, observer-to-observer reproducibility as well as reproducibility within and between laboratories. Based on data from the different studies it was concluded that HER2 IQFISH pharmDx (Dako Omnis) is a reliable and robust assay with a high precision that is at least comparable to the manual HER2 IQFISH pharmDx™ assay and the PathVysion(®)HER-2 DNA Probe Kit.

The FlexISH assay brings flexibility to cytogenetic HER2 testing

AIMS

Fluorescence in-situ hybridization (FISH) is the method of choice for quantitative human epidermal growth factor receptor 2 (HER2) (also known as ERBB2) gene testing in invasive breast cancer. HER2 testing has great clinical impact, and is often claimed to expeditiously complete the entire diagnostic procedure for an individual patient. Against this background, the aim of this study was to evaluate the usefulness and performance of a novel dual-colour HER2/cen17 FISH assay designed to facilitate flexible (overnight) and rapid (<2 h of hybridization) FISH.

METHODS AND RESULTS

We quantitatively and qualitatively compared counting results and the performance of the FlexISH SPEC ERBB2/CEN 17 dual-colour hybridization kit with well-established HER2FISH assays, by using 90 malignant (polysomic and non-polysomic) and 19 benign paraffin-embedded breast tissue specimens. We used long (overnight) and short (2 h) hybridization periods, and found an excellent correlation between the FISH results obtained with FlexISH, ZytoLight and PathVysion hybridization probes.

CONCLUSIONS

The results obtained with both the short-run and long-run application of FlexISH are in excellent accordance with the results obtained with other commercially available FISH kits. This appears to be true in all relevant respects: signal counts, signal-to-noise ratio, brightness, and distinctness of HER2 and cen17 signals. As FlexISH probes can be equivalently used as a short-run or long-run application, the FlexISH probe kit provides the highest flexibility in terms of time and laboratory management. If required, a reliable HER2 finding can be delivered within 4.5 h, but the standard workflow (including overnight hybridization) does not negatively affect the performance, specimen quality or diagnostic result.

Advantages and disadvantages of technologies for HER2 testing in breast cancer specimens

OBJECTIVES

Human epidermal growth factor receptor 2 (HER2) plays a central role as a prognostic and predictive marker in breast cancer specimens. Reliable HER2 evaluation is central to determine the eligibility of patients with breast cancer to targeted anti-HER2 therapies such as trastuzumab and lapatinib. Presently, several methods exist for the determination of HER2 status at different levels (protein, RNA, and DNA level).

METHODS

In this review, we discuss the main advantages and disadvantages of the techniques developed so far for the evaluation of HER2 status in breast cancer specimens.

RESULTS

Each technique has its own advantages and disadvantages. It is therefore not surprising that no consensus has been reached so far on which technique is the best for the determination of HER2 status.

CONCLUSIONS

Currently, emphasis must be put on standardization of procedures, internal and external quality control assessment, and competency evaluation of already existing methods to ensure accurate, reliable, and clinically meaningful test results. Development of new robust and accurate diagnostic assays should also be encouraged. In addition, large clinical trials are warranted to identify the technique that most reliably predicts a positive response to anti-HER2 drugs.

Quantification of HER family receptors in breast cancer

The clinical success of trastuzumab in breast cancer taught us that appropriate tumor evaluation is mandatory for the correct identification of patients eligible for targeted therapies. Although HER2 protein expression by immunohistochemistry (IHC) and gene amplification by fluorescence in situ hybridization (FISH) assays are routinely used to select patients to receive trastuzumab, both assays only partially predict response to the drug. In the case of epidermal growth factor receptor (EGFR), the link between the presence of the receptor or its amplification and response to anti-EGFR therapies could not be demonstrated. Even less is known for HER3 and HER4, mainly due to lack of robust and validated assays detecting these proteins. It is becoming evident that, besides FISH and IHC, we need better assays to quantify HER receptors and categorize the patients for individualized treatments. Here, we present the current available methodologies to measure HER family receptors and discuss the clinical implications of target quantification.

Rapid fluorescence in situ hybridisation (FISH) for HER2 (ERBB2) assessment in breast and gastro-oesophageal cancer

Evaluation of HER2 (ERBB2) gene amplification or protein expression is standard of care in breast (BR) and advanced stage gastro-oesophageal cancers to identify patients eligible for anti-HER2 therapies. Here, we evaluate a rapid fluorescence in situ hybridisation (FISH) technology (HER2 instant quality (IQ) FISH pharmDx Kit) for detection of HER2 in patients with BR and gastro-oesophageal cancer using 30 FFPE samples that had been previously evaluated with the PathVysion HER2 DNA Probe Kit. Cases were scored as positive (HER2:CEN-17 ≥2.0), negative (HER2:CEN-17 <2.0) or equivocal according to the ASCO/CAP 2013 BR cancer guidelines. Ten samples were positive for HER2 amplification while 20 were negative; none were equivocal. The IQ FISH was able to detect low level amplification (HER2:CEN-17 ratio 2.4). The HER2 IQ FISH pharmDx Kit is a FDA approved kit that offers a rapid turnaround time (approximately 3.5 h) and in our laboratory was 100% concordant with prior PathVysion results.

The human epidermal growth factor receptor 2 screening tests for breast cancer suggested by the new updated recommendation of the american society of clinical oncology/college of american pathologists will involve a rise of the in-situ hybridization tests for the European laboratories of pathology

Aims. The differences between the 2007 and the 2013 ASCO/CAP HER2 guidelines have been compared. We also discussed the potential consequences in our pathological practice. Material and Methodology. 189 HER2 fluorescence in situ hybridisation (FISH) tests were performed from 1016 preliminary HER2 immunohistochemical tests (IHC). All cases were reviewed and reclassed following the 2007 and 2013 ASCO/CAP recommendations. Results. The 2013 version decreased false-negative IHC (3/118 versus 1/54, P = ns) and created more 2+ IHC (40/186 versus 89/186, P = 0.001) or more 3+ IHC (9/186 versus 39/186, P = 0.001). One false-positive IHC was described for the 2013 version (0/9 versus 1/39, P = ns). Equivocal FISH was reduced (8/186 versus 2/186, P = ns). An estimation based on our data for 1000 patients showed a rise of our FISH tests for the control of 2+ IHC (180 tests for the 2007 version versus 274 tests for the 2013 version or FISH work overflow is +52%) and for the control of 2+/3+ IHC (300 for the 2007 version versus 475 for the 2013 version or FISH work overflow is +58%). Conclusions. The new 2013 ASCO/CAP guidelines have detected more HER2 positive cases but have increased the number of FISH tests.