Dual-probe Fluorescence In Situ Hybridization Research Articles

HER2 Status Assessment in Endometrial Serous Carcinoma: Comparative Analysis of Two Proposed Testing and Interpretation Algorithms.

HER2 status is now routinely assessed in endometrial serous carcinoma (ESC) due to the reported predictive value of HER2 protein overexpression and/or gene amplification. Herein the authors compare 2 proposed testing and interpretation guidelines for HER2 in ESC. Forty-three consecutive cases of ESC that had been dually tested by both HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were interpreted using 2 sets of guidelines. Guideline set 1 (GS1) is the 2018 American Society of Clinical Oncology/College of American Pathologists guidelines for breast cancer. Guideline set 2 (GS2) is a recent proposal that is a slight modification of the enrollment criteria for the clinical trial (NCT01367002) that demonstrated a survival benefit for anti-HER2 therapy in ESC. By IHC, GS1 and GS2, respectively classified 39.5% (17/43) and 28% (12/43) of ESC as HER2-negative, 37.2% (16/43) and 53.4% (23/43) as HER2 equivocal, and 23.2% (10/43) and 18.6% (8/43) as HER2-positive (P > 0.05 for all). IHC and FISH were highly concordant at the extremes using either set of guidelines, as no cases were found to be IHC3+/FISH-negative or IHC 0-1+/FISH-positive. GS1 and GS2 were comparable regarding the proportion of IHC equivocal cases that were HER2 amplified by FISH (19% vs 23% respectively; [P = 0.71]). GS1 and GS2 displayed 98% (42/43) concordance regarding the final (IHC and/or FISH-based) classification of tumors as being HER2-positive or negative, and the same 13 cases were ultimately classified as HER2 amplified using either GS1 or GS2. One "discordant" case was classified as HER2-positive using GS2 but HER2-negative using GS1 (HER2 IHC score 2+ using both guidelines, HER2:CEP17 signal ratio of 3, HER2 signal number of 3.4). Six (14%) of the 43 cases (FISH Groups: 2, 3, and 4) would require IHC results to interpret the FISH findings using GS1. Because GS1 requires that the HER2 IHC staining be observed within a homogeneous and contiguous invasive cell population, and this is not a requirement in GS2, GS2 may be better suited for ESC given its frequently heterogeneous staining pattern. Additional studies may be required on the optimal interpretation of problematic dual-probe FISH scenarios in GS2 and the necessity for IHC correlation in such scenarios. Using either set of guidelines, our findings support a reflex testing strategy of restricting FISH testing to cases that are IHC equivocal.

HER2 fluorescent in situ hybridization signal degradation: a 10-year retrospective study.

Fluorescence in situ hybridization (FISH) analysis is recommended for invasive breast carcinomas with equivocal (2+) immunohistochemical expression of human epidermal growth factor receptor 2 (HER2). However, existing guidelines for the retention and storage requirements for HER2 FISH slides vary widely among countries and laboratories. To determine the degradation rateof HER2 FISH signals, and the optimal retention time and storage conditions for HER2 FISH slides. Dual-probe HER2 FISH slides from March 2009 to June 2019 were retrieved from the archive to assess the presence, intensity and quantity of the green chromosome enumeration probe 17 (CEP 17) and orange HER2 signals. Per the institutional policy, FISH slides are placed in slide boxes and stored in -80°C freezers for up to 4years, whereas older slides are stored at room temperature. After excluding HER2 FISH slides that were deemed uninterpretable due to technical issues, a total of 6255 slides were assessed. Slides from 2009 to 2014 were stored at room temperature, while slides from 2015 to 2019 were stored in -80°C freezers. Slides stored in freezers showed retention of both the green and the orange signals. Slide stored at room temperature demonstrated significant decrease in the signal retention rate and the loss of signal did not progress in a linear fashion. The CEP17 signal was quenched much faster than the HER2 signal. Our study is the first to demonstrate HER2 FISH signal degradation with time and slide storage conditions. Storing HER2 FISH slides in a -80°C freezer allows for retention of both HER2 and CEP17 signals. At room temperature, the signals start to degrade with CEP17 signals lost at a faster rate. The results of the study may be used in official guidelines for storage conditions and retention time for HER2 FISH slides.

Abstract ES1-1: What is a HER2-positive in breast cancer in 2018?

Abstract Remarkable progress has been made in the treatment of patients with HER2-positive breast cancer since trastuzumab was approved by the U.S. Food and Drug Administration 20 years ago. Among patients with HER2-positive disease, HER2-targeted therapy has been associated with substantial improvements in overall survival in the adjuvant setting, a high rate of pathologic complete response (pCR) after neoadjuvant therapy, and improvements in survival in patients with metastatic disease. While much of these improvements in outcome is due to more effective therapies, improvements in patient selection as a result of more accurate HER2 testing has also contributed to the better prognosis of patients with this disease. Data from clinical trials examining the benefit of trastuzumab in the adjuvant setting and published in the early 2000s (e.g., NSABP B31; NCCTG 9831) demonstrated that up to 25% of community-based assays reported as HER2-positive by immunohistochemistry (IHC) and up to 15% reported as HER2-positive by fluorescence in situ hybridization (FISH) could not be confirmed upon central laboratory testing. To address this high frequency of false-positive results and to improve the accuracy of HER2 testing, the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) in 2007 published guideline recommendations for HER2 testing. These guidelines were subsequently updated in 2013 and, more recently, in 2018. Since the implementation of these guidelines, the accuracy of HER2 testing has improved. In fact, in current clinical practice, when HER2 IHC and FISH testing are performed according to the ASCO-CAP guidelines, approximately 95% of breast cancers can ultimately be categorized as either unequivocally HER2-positive or HER2-negative. In the remainder of the cases, combined IHC and FISH assay results provide a less straightforward picture of the HER2 status and, in turn, create uncertainty regarding the likelihood of benefit from HER2-targeted therapy. These include cases which on dual-probe FISH testing show: 1) HER2/CEP17 ratio >2.0 and an average HER2 copy number <4.0 signals/cell (monosomy); 2) HER2/CEP17 ratio <2.0 and an average HER2 copy number >6.0 signals/cell (polysomy); and 3) HER2/CEP17 ratio <2.0 and an average HER2 copy number >4.0 and <6.0 signals/cell. However, the most recent (2018) update of the ASCO-CAP guidelines provides pragmatic recommendations to resolve the HER2 status of such cases, and this, in turn, should result in even fewer cases in which the HER2 status remains in doubt. It should be noted, however, that not all patients whose tumors are HER2-positive by IHC and/or FISH respond similarly to HER2-targeted therapy and that some patients who initially respond subsequently develop resistance. Active efforts are underway to understand the mechanisms of de novo and acquired resistance to HER2-targeted treatments and to identify biomarkers that can predict resistance to therapy. Thus, the clinically relevant question in 2018 is not “what is a HER2-positive breast cancer ”? Rather, the question that now needs to be addressed is “which HER2-positive breast cancers will respond to HER2 targeted-treatments and to which HER2-targeted treatments are they most likely to respond? ”. Citation Format: Schnitt S. What is a HER2-positive in breast cancer in 2018? [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr ES1-1.

Impact of repeat HER2 testing after initial equivocal HER2 FISH results using 2013 ASCO/CAP guidelines.

The updated 2013 American Society of Clinical Oncology/College of American Pathologists guideline recommendations for human epidermal growth factor receptor 2 (HER2) testing have made some major changes in HER2 fluorescence in situ hybridization (FISH) interpretation criteria with additional FISH equivocal cases. Repeat HER2 testing is recommended after initial HER2 FISH equivocal results; however, little is known about its impact on final HER2 status. The aim of this study is to investigate whether reflex test clarifies HER2 status, and to characterize clinicopathological features of the newly defined HER2 equivocal group. A total of 886 consecutive cases of primary invasive breast cancer conducted with dual-probe HER2 FISH testing between November 2013 and December 2015 were reviewed. HER2 immunohistochemistry (IHC) and FISH testing were performed on a different tissue block or a new specimen after initial HER2 FISH equivocal results. Compared to 2007 guideline, 85 (9.6%) cases changed their category by using 2013 guideline. The major change of the 85 cases is that 57 (6.4%) cases in HER2 FISH-negative category changed to equivocal, and the equivocal category cases increased from 36 to 67. HER2 FISH equivocal was significantly associated with HER2 IHC equivocal (2+) and chromosome 17 polysomy (P<0.01). Repeat testing by IHC and FISH clarified HER2 status in 33 and 42% of HER2 equivocal cases, respectively. Overall 32 (48%) initial HER2 equivocal cases stayed HER2 equivocal after repeat FISH and or IHC testing. These tumors were ER/PR+, with high KI-67 index. New guidelines classify more HER2 FISH equivocal cases. Repeat HER2 testing clarifies HER2 status in about 50% of initial HER2 FISH equivocal cases. In addition, HER2 equivocal cases merit further study as there is limited information about prognosis and optimal treatment strategy for this population.

Impact of the 2013 ASCO/CAP HER2 Guideline Updates at an Academic Medical Center That Performs Primary HER2 FISH Testing: Increase in Equivocal Results and Utility of Reflex Immunohistochemistry.

The 2013 American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guideline updates lowered the threshold for HER2 positivity and altered the equivocal category. The goal of this study was to evaluate the impact of these changes on the distribution of HER2 fluorescence in situ hybridization (FISH) status. The utility of reflex HER2 immunohistochemistry (IHC) for FISH equivocal cases was also examined. We retrospectively reviewed all invasive breast cancers analyzed for HER2 via dual-probe FISH (PathVysion; Abbott Laboratories. Abbott Park, IL) 12 months before and after the HER2 guidelines updates were implemented. Reflex HER2 IHC results were recorded for HER2 FISH equivocal cases. There was a significant increase in the number of HER2 FISH equivocal results after the guideline updates (4.9% vs 1.4%, P = .0087) that was independent of specimen type (core vs surgical, P = .6). All 17 FISH equivocal cases after the updates had reflex HER2 IHC: two (12%) of 17 were positive, 12 (71%) of 17 remained equivocal, and three (18%) of 17 were negative. Implementation of the 2013 ASCO/CAP HER2 guideline updates resulted in an increase in HER2 FISH equivocal results, which can be attributed to HER2 copy number, regardless of the HER2/CEP17 ratio. Reflex IHC for FISH equivocal cases is of limited utility; however, IHC does assign HER2 positivity or negativity in a small percentage of cases.

576: Simultaneous fetal cell detection and genetic diagnosis by immunophenotyping and chromosomal fluorescence in situ hybridization (FISH)

To confirm application of a novel monoclonal anti-fetal erythroblast antibody (4B9 mAb) for specific detection of fetal erythroblasts in nucleated cell fraction of maternal blood and simultaneous analysis of chromosomal status of the identified cells by single or dual-probe FISH.

Detection of chromosomal aneuploidies in fetal cells isolated from maternal blood using single‐chromosome dual‐probe FISH analysis

Detection of chromosomal aneuploidies using fetal cells isolated from maternal blood, for prenatal non-invasive genetic investigation, has been a long-sought goal of clinical genetics to replace amniocentesis and chorionic villous sampling to avoid any risk to the fetus. The purpose of this study was to develop a sensitive and specific new assay for diagnosing aneuploidy with circulating fetal cells isolated from maternal blood as previously reported using two novel approaches: (i) simultaneous immunocytochemistry (ICC) evaluation using a monoclonal antibody for i-antigen, followed by fluorescence in situ hybridization (FISH); (ii) dual-probe FISH analysis of interphase nuclei using two differently labeled probes, specific for different loci of chromosomes 21 and 18; in addition, short tandem repeats (STR) analysis on single cells isolated by micromanipulation was applied to confirm the presence of fetal cells in the cell sample enriched from maternal blood. Blood samples were obtained from women carrying trisomic fetuses, and from non-pregnant women and men as controls. Using ICC-FISH approach, a large heterogeneity in immunostaining pattern was observed, which is a source of very subjective signal interpretation. Differently, dual-probe FISH analysis provided for a correct diagnosis of all pregnancies: the mean percentage of trisomic cells was 0.5% (range, 0.36-0.76%), while the mean percentage of trisomic cells in the control group (normal pregnancies or non-pregnant women) was ≤0.20%. The application of the dual-probe FISH protocol on fetal cells isolated from maternal blood enables accurate molecular detection of fetal aneuploidy, thus providing a foundation for development of non-invasive prenatal diagnostic testing.

Abstracts and Case Studies From the College of American Pathologists 2011 Annual Meeting (CAP '11)

Abstracts and Case Studies From the College of American Pathologists 2011 Annual Meeting (CAP '11)

Comparison between analysis of HER2 gene and chromosome 17 in breast cancer by dual-probe chromogenic in situ hybridization and fluorescence in situ hybridization

To evaluate the application of dual-probe chromogenic in situ hybridization (dual-probe CISH) in analysis of HER2 gene status of breast cancer patients by comparison with fluorescence in situ hybridization (FISH). The potential impact of chromosome 17 polysomy in the determination of HER2 status was also studied. One hundred and forty-six cases of paraffin-embedded breast cancer tissues were retrieved. Analysis of HER2 gene and chromosome 17 copy numbers using CE-approved commercial kits of dual-probe FISH (for 146 cases) and dual-probe CISH (for 73 cases) were carried out. The results were interpreted according to ASCO/CAP, 2007 either HER2 gene copy number or the ratio of HER2/centromere 17 (CEN17). Of the 73 cases analyzed by both FISH and dual-probe CISH, the concordance rates for negative and positive results was 91.7% (33/36) and 97.4% (37/38) respectively, while the overall concordance rate between the two methods was 95.9% (70/73). Of the 146 cases analyzed by FISH, 13 cases were interpreted as equivocal if only HER2 copies were counted, compared with 8 equivocal cases by calculating the ratio of HER2/CEN 17. Moreover, 3 cases (4.8%) of the 63 HER2-positive cases determined by HER2 copies turned out to be HER2-negative when determined by the ratio of HER2/CEN 17; while using dual-probe CISH, 1 (3.0%) of the 33 positive cases turned out to be negative. In addition, when using FISH, there were more chromosome 17 polysomy cases (63.5%, 40/63) in the HER2-positive subgroup than HER2-negative subgroup (37.3%, 28/75) (P = 0.002). Dual-probe CISH can achieve similar results as compared to FISH, indicating that this technology is a reliable alternative to FISH in HER2 testing. The accuracy can further be improved when HER2 and chromosome 17 are simultaneously tested and counted.

Genetic Mechanisms of TP53 Loss of Heterozygosity in Barrett's Esophagus: Implications for Biomarker Validation

17p (TP53) loss of heterozygosity (LOH) has been reported to be predictive of progression from Barrett's esophagus to esophageal adenocarcinoma, but the mechanism by which TP53 LOH develops is unknown. It could be (a) DNA deletion, (b) LOH without copy number change, or (c) tetraploidy followed by genetic loss. If an alternative biomarker assay, such as fluorescence in situ hybridization (FISH), provided equivalent results, then translation to the clinic might be accelerated, because LOH genotyping is presently limited to research centers. We evaluated mechanisms of TP53 LOH to determine if FISH and TP53 LOH provided equivalent results on the same flow-sorted samples (n = 43) representing established stages of clonal progression (diploid, diploid with TP53 LOH, aneuploid) in 19 esophagectomy specimens. LOH developed by all three mechanisms: 32% had DNA deletions, 32% had no copy number change, and 37% had FISH patterns consistent with a tetraploid intermediate followed by genetic loss. Thus, FISH and LOH are not equivalent (P < 0.000001). LOH develops by multiple chromosome mechanisms in Barrett's esophagus, all of which can be detected by genotyping. FISH cannot detect LOH without copy number change, and dual-probe FISH is required to detect the complex genetic changes associated with a tetraploid intermediate. Alternative biomarker assay development should be guided by appreciation and evaluation of the biological mechanisms generating the biomarker abnormality to detect potential sources of discordance. FISH will require validation in adequately powered longitudinal studies before implementation as a clinical diagnostic for esophageal adenocarcinoma risk prediction.

Determination of HER2 Gene Amplification by Fluorescence In situ Hybridization and Concordance with the Clinical Trials Immunohistochemical Assay in Women with Metastatic Breast Cancer Evaluated for Treatment with Trastuzumab

To evaluate the concordance between HER2 gene amplification, determined by fluorescence in situ hybridization (FISH), and HER2 protein overexpression assessed by an immunohistochemical (IHC) assay. The IHC protocol used was a research assay, known as the Clinical Trial Assay (CTA), developed to select women with metastatic breast cancer (MBC) for three pivotal clinical trials of trastuzumab therapy. A direct-labeled, dual-probe FISH assay was used to determine HER2 amplification in 623 fixed breast cancer tissue specimens. These specimens had been stored as paraffin-embedded sections for 25 years. All specimens had been analyzed for HER2 protein expression by the CTA. To assess the reproducibility of FISH results in archived material, we evaluated a separate group of 617 breast cancer tissue specimens at two different laboratories. Informative FISH results were available for 529 (85%) of the 623 specimens. Overall concordance between FISH and IHC results was 82% (95% CI; 7885%). Assay agreement between FISH results and specimens with immunostaining scores of 0, 1+, and 3+ were 97, 93 and 89%, respectively. However, only 24% of specimens with 2+ immunostaining scores had HER2 amplification by FISH; there was assay disagreement in 76% of specimens in this IHC subgroup. Interlaboratory FISH concordance was 92% (95% CI; 8994%), indicating very good assay reproducibility in these archived specimens. HER2 status determined by CTA-IHC and FISH are significantly correlated; however, differences between these two assays can a ect patient selection for trastuzumab therapy.

Evaluation of Clinical Outcomes According to HER2 Detection by Fluorescence In Situ Hybridization in Women with Metastatic Breast Cancer Treated with Trastuzumab

Background We evaluated the influence of HER2 gene amplification, as determined by fluorescence in situ hybridization (FISH), on clinical outcomes (objective response rates, time to disease progression, and overall survival time) in women with metastatic breast cancer treated with trastuzumab in 3 clinical trials. Breast cancer tissue specimens were evaluated using a direct labeled, dual-probe FISH assay. Materials and Methods Specimens with a HER2:CEP17 ratio of ≥ 2:0 were considered positive for gene amplification. All specimens had previously demonstrated overexpression of HER2 protein at the 2+ or 3+ level by immunohistochemistry using the Clinical Trials Assay. Response rate, time to disease progression, and survival times were then compared between the FISH-positive and FISH-negative cohorts in each of the 3 clinical trials. Results Informative FISH results were obtained in 765 (96%) of the 799 patients enrolled in the 3 clinical trials. Overall, 596 (78%) were FISH-positive and 169 (22%) were FISH-negative. The proportion of FISH-positive patients was comparable in all 3 trials. Clinical benefit from trastuzumab therapy appeared to be restricted to patients with FISH-positive metastatic breast cancer. In each clinical trial, the cohort of FISH-positive patients had higher overall response rates and longer durations of survival compared with FISH-negative patients. Conclusion These data indicate that assessment of HER2 amplification by FISH is the preferred method to select patients for trastuzumab therapy.

Dual-probe fluorescence in situ hybridization assay for detecting deletions associated with VCFS/DiGeorge syndrome I and DiGeorge syndrome II loci

Over 90% of patients with DiGeorge syndrome (DGS) or velocardiofacial syndrome (VCFS) have a microdeletion at 22q11.2. Given that these deletions are difficult to visualize at the light microscopic level, fluorescence in situ hybridization (FISH) has been instrumental in the diagnosis of this disorder. Deletions on the short arm of chromosome 10 are also associated with a DGS-like phenotype. Since deletions at 22q11.2 and at 10p13p14 result in similar findings, we have developed a dual-probe FISH assay for screening samples referred for DGS or VCFS in the clinical laboratory. This assay includes two test probes for the loci, DGSI at 22q11.2 and DGSII at 10p13p14, and centromeric probes for chromosomes 10 and 22. Of 412 patients tested, 54 were found to be deleted for the DGSI locus on chromosome 22 (13%), and a single patient was found deleted for the DGSII locus on chromosome 10 (0.24%). The patient with the 10p deletion had facial features consistent with VCFS, plus sensorineural hearing loss, and renal anomalies. Cytogenetic analysis showed a large deletion of 10p [46,XX,del(10)(p12.2p14)] and FISH using a 10p telomere region-specific probe confirmed the interstitial nature of the deletion. Analysis for the DGSI and the DGSII loci suggests that the deletion of the DGSII locus on chromosome 10 may be 50 times less frequent than the deletion of DGSI on chromosome 22. The incidence of deletions at 22q11.2 has been estimated to be 1 in 4000 newborns; therefore, the deletion at 10p13p14 may be estimated to occur in 1 in 200,000 live births. Am. J. Med. Genet. 91:313–317, 2000. © 2000 Wiley-Liss, Inc.

Dual-probe fluorescence in situ hybridization assay for detecting deletions associated with VCFS/DiGeorge syndrome I and DiGeorge syndrome II loci

Over 90% of patients with DiGeorge syndrome (DGS) or velocardiofacial syndrome (VCFS) have a microdeletion at 22q11.2. Given that these deletions are difficult to visualize at the light microscopic level, fluorescence in situ hybridization (FISH) has been instrumental in the diagnosis of this disorder. Deletions on the short arm of chromosome 10 are also associated with a DGS-like phenotype. Since deletions at 22q11.2 and at 10p13p14 result in similar findings, we have developed a dual-probe FISH assay for screening samples referred for DGS or VCFS in the clinical laboratory. This assay includes two test probes for the loci, DGSI at 22q11.2 and DGSII at 10p13p14, and centromeric probes for chromosomes 10 and 22. Of 412 patients tested, 54 were found to be deleted for the DGSI locus on chromosome 22 (13%), and a single patient was found deleted for the DGSII locus on chromosome 10 (0. 24%). The patient with the 10p deletion had facial features consistent with VCFS, plus sensorineural hearing loss, and renal anomalies. Cytogenetic analysis showed a large deletion of 10p [46, XX,del(10)(p12.2p14)] and FISH using a 10p telomere region-specific probe confirmed the interstitial nature of the deletion. Analysis for the DGSI and the DGSII loci suggests that the deletion of the DGSII locus on chromosome 10 may be 50 times less frequent than the deletion of DGSI on chromosome 22. The incidence of deletions at 22q11.2 has been estimated to be 1 in 4000 newborns; therefore, the deletion at 10p13p14 may be estimated to occur in 1 in 200,000 live births.