Impact of decalcification on receptor status in breast cancer

Open questions, current challenges, and future perspectives in targeting human epidermal growth factor receptor 2-low breast cancer

Approximately 60% of traditionally defined human epidermal growth factor receptor 2 (HER2)-negative breast cancers express low levels of HER2 [HER2-low; defined as immunohistochemistry (IHC) 1+ or IHC 2+/in situ hybridization (ISH)-]. HER2-low breast cancers encompass a large percentage of both hormone receptor-positive (up to 85%) and triple-negative (up to 63%) breast cancers. The DESTINY-Breast04 trial established that HER2-low tumors are targetable, leading to the approval of trastuzumab deruxtecan (T-DXd) as the first HER2-directed therapy for the treatment of HER2-low breast cancer in the United States and Europe. This change in the clinical landscape results in a number of questions and challenges-including those related to HER2 assessment and patient identification-and highlights the need for careful assessment of HER2 expression to identify patients eligible for T-DXd. This review provides context for understanding how to identify patients with HER2-low breast cancer with respect to sample types, scoring and reporting HER2 status, and testing methods and assays. It also discusses management of important T-DXd-related adverse events. Available evidence supports the efficacy of T-DXd in patients with any history of IHC 1+ or IHC 2+/ISH- scores; however, future research may further refine the population who could benefit from T-DXd or other HER2-directed therapies and identify novel methods for patient identification. Because HER2 expression can change with disease progression or treatment, and variability exists in scoring and interpretation of HER2 status, careful re-evaluation in certain scenarios may help to identify more patients who may benefit from T-DXd.

HER2 Intratumoral Heterogeneity in Breast Cancer, an Evolving Concept

Amplification and/or overexpression of human epidermal growth factor receptor 2 (HER2) in breast cancer is associated with an adverse prognosis. The introduction of anti-HER2 targeted therapy has dramatically improved the clinical outcomes of patients with HER2-positive breast cancer. Unfortunately, a significant number of patients eventually relapse and develop distant metastasis. HER2 intratumoral heterogeneity (ITH) has been reported to be associated with poor prognosis in patients with anti-HER2 targeted therapies and was proposed to be a potential mechanism for anti-HER2 resistance. In this review, we described the current definition, common types of HER2 ITH in breast cancer, the challenge in interpretation of HER2 status in cases showing ITH and the clinical applications of anti-HER2 agents in breast cancer showing heterogeneous HER2 expression. Digital image analysis has emerged as an objective and reproducible scoring method and its role in the assessment of HER2 status with ITH remains to be demonstrated.

Effect of Surface Decalcification With Hydrochloric Acid on the Determination of Estrogen Receptor, Progesterone Receptor, Ki67, and Human Epidermal Growth Factor Receptor 2 Expressions in Invasive Breast Carcinoma Based on Immunohistochemistry and Fluorescence In Situ Hybridization

BACKGROUND

Bone is the most common site of metastatic breast cancer (MBC). EDTA is often used to decalcify bony tissue samples to ensure the accurate assessment of antigenicity in MBC. It takes ~24 to 48 hours to decalcify small bone tissues such as bone marrow, which is considered unacceptable given the priority that is often placed on the rapid processing of bone marrow trephine cores. Thus, an effective decalcification method that preserves genetic material is needed.

AIM

We performed immunohistochemical studies on surface decalcification (SD) in breast tumors and evaluated the effect of SD on receptor status and human epidermal growth factor receptor 2 (HER2). Fluorescence in situ hybridization was performed on a subset of these tumors to establish a protocol for handling bone specimens for MBC.

MATERIALS AND METHODS

Forty-four cases of invasive breast tumors were studied. We compared the immunohistochemical expressions of estrogen receptor (ER), progesterone receptor (PR), Ki67, and HER2 between control tissue (nondecalcified) and parallel tissue subjected to SD with hydrochloric acid. We also evaluated the effect of SD on the fluorescence in situ hybridization expression of HER2.

RESULTS

Categorical decreases in ER and PR expression were identified in 9/31 (29.0%) cases without SD and 10/26 (38.5%) cases with SD. HER2 expression changed from equivocal to negative in 4/12 (33.4%) cases. Among the HER2-positive cases, all remained positive after SD. The most significant declines in immunoreactivity occurred with Ki67, with an average decrease from 22% to 13%. The average HER2 copy numbers were 5.37 and 4.76 in the control and SD groups, respectively, and the average HER2/CEP17 ratios were 2.35 and 2.08, respectively.

CONCLUSIONS

Overall, SD is an alternative decalcification method in bony metastases to assess ER, PR, and HER2 in MBC.

Comprehensive Review of Metastatic Breast Carcinoma in Cytology Specimens

Breast carcinomas are known to metastasize to various organs of the human body. Fine needle aspiration cytology or exfoliative cytology often are the standard method for diagnosis at these metastatic sites due to ease of procurement of diagnostic material, accessibility, less complications, high sensitivity, and specificity of diagnosis and evaluation of biomarker status needed to guide future management. This comprehensive review article discusses in detail metastatic patterns, cytomorphology of metastatic breast cancer at different body sites, immunohistochemistry needed for diagnosis of breast carcinoma, sensitivity and specificity of diagnosis and breast biomarker assays in the cytology material.

Update on prognostic and predictive biomarkers of breast cancer

Breast cancer represents a heterogeneous group of human cancer at both histological and molecular levels. Estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) are the most commonly used biomarkers in clinical practice for making treatment plans for breast cancer patients by oncologists. Recently, PD-L1 testing plays an important role for immunotherapy for triple-negative breast cancer. With the increased understanding of the molecular characterization of breast cancer and the emergence of novel targeted therapies, more potential biomarkers are needed for the development of more personalized treatments. In this review, we summarized several main prognostic and predictive biomarkers in breast cancer at genomic, transcriptomic and proteomic levels, including hormone receptors, HER2, Ki67, multiple gene expression assays, PD-L1 testing, mismatch repair deficiency/microsatellite instability, tumor mutational burden, PIK3CA, ESR1 andNTRK and briefly introduced the roles of digital imaging analysis in breast biomarker evaluation.

Unusual Patterns of HER2 Expression in Breast Cancer: Insights and Perspectives

The biomarker human epidermal growth factor receptor-2 (HER2) has represented the best example of successful targeted therapy in breast cancer patients. Based on the concept of "oncogene addiction," we have learnt how to identify patients likely benefitting from anti-HER2 agents. Since HER2 gene amplification leads to marked overexpression of the HER2 receptors on the cell membrane, immunohistochemistry with clinically validated antibodies and scoring system based on intensity and completeness of the membranous expression constitute the screening method to separate negative (score 0/1+) and positive (score 3+) carcinomas and to identify those tumours with complete yet only moderate HER2 expression (score 2+, equivocal carcinomas), which need to be investigated further in terms of gene status to confirm the presence of a loop of oncogene addiction. This process has demanded quality controls and led to recommendations by Scientific Societies, which pathologists routinely need to follow to guarantee reproducibility. In this review, we will span from the description of classical HER2 evaluation to the discussion of those scenarios in which HER2 expression is unusual and/or difficult to define. We will dissect HER2 heterogeneity, HER2 conversion from primary to relapsed/metastatic breast cancer, and we will introduce the new category of HER2-low breast carcinomas.

Effect of EDTA decalcification on estrogen receptor and progesterone receptor immunohistochemistry and HER2/neu fluorescence in situ hybridization in breast carcinoma

Bone is the most common site of metastasis in breast carcinoma (BC). Treatments for metastatic BC depend on various factors, including the tumor's estrogen receptor (ER), progesterone receptor (PR), and HER2 status. Bone biopsies require decalcification which may affect the accuracy of ER and PR immunohistochemistry (IHC) and HER2 situ hybridization (FISH) studies. Ethylenediaminetetraacetic acid (EDTA) decalcifying solutions have been theorized to have no significant impact on ER and PR IHC or HER2 FISH analyses. We completed a prospective study of the effect of EDTA decalcification on ER and PR IHC and HER2 FISH in 29 cases of BC. Samples from 29 BC resections were collected and formalin fixed between 12 and 24 h. Control samples were routinely processed, whereas test samples were placed in EDTA for 48 h. ER and PR slides were blinded, randomized, and evaluated. Blinded samples underwent HER2 FISH assays where an average HER2 copy number and HER2/CEP17 ratio were calculated. Paired differences between EDTA and control samples were compared for ER and PR positivity, average HER2 copy number, and HER2/CEP17 ratios using paired-samples t-tests (PST) and Wilcoxon signed-rank test (WSR). PST and WSR tests yielded no significant difference between EDTA and control tissue for ER% (PST: P = 1; WSR: P = 0.916), PR% (PST: P = 0.973; WSR: P = 0.984), HER2 copy number (PST: P = 0.124; WSR: P = 0.103), and HER2/CEP17 ratio (PST: P = 0.25; WSR: P = 0.105). The use of EDTA in bony tissue is therefore a valid decalcification method to ensure accurate assessment of ER and PR IHC and HER2 FISH in metastatic BC.

Estrogen, progesterone, and human epidermal growth factor receptor 2 discordance between primary and metastatic breast cancer

Background

The estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) statuses are frequently discordant between the primary tumor and metastatic lesions in metastatic breast cancer. This can have important therapeutic implications.

Patients and methods

In all, 541 patients with available receptor statuses from both primary tumor and metastatic lesion treated at Heidelberg and Tuebingen University Hospitals between 1982 and 2018 were included.

Results

Statistically significant discordance rates of 14% and 32% were found for ER and PR. HER2 status was statistically insignificantly discordant in 15% of patients. Gain in HER2 positivity was associated with an improved overall survival, whereas loss of HR positivity was associated with worse overall survival. Antiendocrine treatment differed in 20% of cases before and after biopsy and HER2-directed treatment in 14% of cases.

Conclusions

Receptor statuses are discordant between primary tumor and metastasis in a considerable fraction of patients with metastatic breast cancer. Next to a highly presumed predictive value with respect to efficacy of endocrine and HER2-targeted therapy, discordance seems to provide prognostically relevant information. Where feasible, metastatic lesions should be biopsied in accordance with current guidelines.

Electronic supplementary material

The online version of this article (10.1007/s10549-020-05746-8) contains supplementary material, which is available to authorized users.

Applying the New Guidelines of HER2 Testing in Breast Cancer

PURPOSE OF REVIEW

The human epidermal growth factor receptor 2 (HER2) is an important prognostic and predictive biomarker in the breast cancer. The American Society of Clinical Oncology/College of American Pathology (ASCO/CAP) has published HER2 testing guidelines in breast cancer. We herein reviewed the HER2 testing guidelines in breast cancer with a focus on the application of the current guidelines.

RECENT FINDINGS

The continual investigation of HER2 testing in breast cancer has resulted in updates in the HER2 testing guidelines. The current guidelines focus on the uncommon clinical scenarios and emphasize the coordination between immunohistochemistry and in situ hybridization results, in an effort to improve clarity and accuracy. The ASCO/CAP guidelines provide valuable recommendations to ensure the accurate evaluation of HER2 status in breast cancer patients through standardization. Additional studies, particularly those with long-term outcome data are still needed to validate the guideline recommendations, especially the uncommon cases.

Hormone receptor and HER2 assessment in breast carcinoma metastatic to bone: A comparison between FNA cell blocks and decalcified core needle biopsies

BACKGROUND

Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) guide the clinical management of breast cancer metastases. Decalcification of bone core needle biopsies (CNBs) can affect IHC. In the current study, the authors sought to define whether fine-needle aspiration (FNA) would be a better alternative to CNB for reliable IHC.

METHODS

Patients with breast cancer metastases to bone that were sampled by both CNB and FNA were selected. ER, PR, and HER2 were performed in FNA cell blocks (FNA-CBs) and concurrent decalcified CNBs. Discrepancies were classified as minor when there was a difference of up to 30% nuclear staining in IHC for ER and PR between paired samples and as major when a clinically relevant change was observed (ie, positive vs negative). Quantitative reverse transcriptase-polymerase chain reaction of ESR1 messenger RNA levels was performed on FNA/CNB pairs with discrepancies for ER IHC. IHC status of the primary breast carcinoma was recorded.

RESULTS

Concordance rates for ER, PR, and HER2 were 89%, 67%, and 93%, respectively, between FNA-CB and CNB pairs from 27 patients. Major discrepancies were noted in approximately 11% of FNA/CNB pairs for ER IHC and in 33% of FNA/CNB pairs for PR. ESR1 messenger RNA levels of FNA/CNB matched samples were similar and did not explain the differences in ER IHC expression in the majority of cases. Two of 27 FNA/CNB pairs had different results for HER2 IHC that changed from negative on CNB to equivocal (2+) on FNA-CB. Both cases had prior HER2 amplification by fluorescence in situ hybridization.

CONCLUSIONS

FNA-CB and CNB appear to constitute acceptable methods for the assessment of ER, PR, and HER2 for clinical decision making.

89Zr-Trastuzumab PET/CT for Detection of Human Epidermal Growth Factor Receptor 2-Positive Metastases in Patients With Human Epidermal Growth Factor Receptor 2-Negative Primary Breast Cancer

PURPOSE

The aim of this study was to determine if imaging with Zr-trastuzumab, a human epidermal growth factor receptor 2 (HER2)-targeting PET tracer, can detect HER2-positive metastases in patients with HER2-negative primary breast cancer.

METHODS

As part of an institutional review board-approved, prospective clinical trial of Zr-trastuzumab PET/CT (ClinicalTrials.gov identifier NCT02286843), a second group of 11 patients with HER2-negative primary breast cancer and known metastatic disease were recruited. Patients with confirmed HER2-negative primary breast cancer underwent Zr-trastuzumab PET/CT to screen for Zr-trastuzumab-avid lesions suggestive of unsuspected HER2-positive metastases. Zr-trastuzumab-avid lesions on PET/CT were biopsied and pathologically examined to determine HER2 status.

RESULTS

All 11 patients had confirmed HER2-negative primary breast cancer. Four patients demonstrated suspicious foci on Zr-trastuzumab PET/CT. Of these 4 patients, 1 patient had biopsy-proven HER2-positive metastases. The other 3 patients with suspicious Zr-trastuzumab-avid foci had biopsy demonstrating a metastasis that was HER2-negative and were considered false-positive Zr-trastuzumab PET foci. Combined with a published report of the first 9 patients, there have been a total of 20 HER2-negative primary breast cancer patients, with 3 patients (15%) having pathologically confirmed HER2-positive distant metastases and 6 (30%) with suspicious Zr-trastuzumab-avid foci that were HER2-negative on pathology, which were thus considered false-positive Zr-trastuzumab findings.

CONCLUSIONS

This second group of patients confirms the proof of concept that Zr-trastuzumab PET/CT detects unsuspected HER2-positive metastases in a subset of patients with HER2-negtive primary breast cancer. False-positive Zr-trastuzumab-avid foci present a challenge to using this tracer.

Estrogen, progesterone, and HER2/neu receptor discordance between primary and metastatic breast tumours-a review

Discordance in estrogen (ER), progesterone (PR), and HER2/neu status between primary breast tumours and metastatic disease is well recognized. In this review, we highlight how receptor discordance between primary tumours and paired metastasis can help elucidate the mechanism of metastasis but can also effect patient management and the design of future trials. Discordance rates and ranges were available from 47 studies (3384 matched primary and metastatic pairs) reporting ER, PR, and HER2/neu expression for both primary and metastatic sites. Median discordance rates for ER, PR, and HER2/neu were 14 % (range 0-67 %, IQR 9-25 %), 21 % (range 0-62 %, IQR 15-41 %), and 10 % (range 0-44 %, IQR 4-17 %), respectively. Loss of receptor expression was more common (9.17 %) than gain (4.51 %). Discordance rates varied amongst site of metastasis with ER discordance being highest in bone metastases suggesting that discordance is a true biological phenomenon. Discordance rates vary for both the biomarker and the metastatic site. Loss of expression is more common than gain. This can affect patient management as it can lead to a reduction in both the efficacy and availability of potential therapeutic agents. Future studies are recommended to explore both the mechanisms of discordance as well as its impact on patient outcome and management.

Influence of decalcification procedures on immunohistochemistry and molecular pathology in breast cancer

Distant breast cancer metastases are nowadays routinely biopsied to reassess receptor status and to isolate DNA for sequencing of druggable targets. Bone metastases are the most frequent subgroup. Decalcification procedures may negatively affect antigenicity and DNA quality. We therefore evaluated the effect of several decalcification procedures on receptor status and DNA/RNA quality. In 23 prospectively collected breast tumors, we compared ERα, PR and HER2 status by immunohistochemistry in (non-decalcified) tissue routinely processed for diagnostic purposes and in parallel tissue decalcified in Christensen's buffer with and without microwave, EDTA and Formical-4. Furthermore, HER2 fluorescence in situ hybridization and DNA/RNA quantity and quality were assessed. We found that the percentage of ERα-positive cells were on average lower in EDTA (P=0.049) and Formical-4 (P=0.047) treated cases, compared with controls, and PR expression showed decreased antigenicity after Christensen's buffer treatment (P=0.041). Overall, a good concordance (weighted kappa) was seen for ERα, PR and HER2 immunohistochemistry when comparing the non-decalcified control tissues with the decalcified tissues. For two patients (9%), there was a potential influence on therapeutic decision making with regard to hormonal therapy or HER2-targeted therapy. HER2 fluorescence in situ hybridization interpretation was seriously hampered by Christensen's buffer and Formical-4, and DNA/RNA quantity and quality were decreased after all four decalcification procedures. Validation on paired primary breast tumor specimens and EDTA-treated bone metastases showed that immunohistochemistry and fluorescence in situ hybridization were well assessable and DNA and RNA yield and quality were sufficient. With this, we conclude that common decalcification procedures have only a modest negative influence on hormone and HER2 receptor immunohistochemistry in breast cancer. However, they may seriously affect DNA/RNA-based diagnostic procedures. Overall, EDTA-based decalcification is therefore to be preferred as it best allows fluorescence in situ hybridization and DNA/RNA isolation.

Detection of HER2-Positive Metastases in Patients with HER2-Negative Primary Breast Cancer Using 89Zr-Trastuzumab PET/CT

Our objective was to determine whether imaging with a human epidermal growth factor receptor 2 (HER2)-targeted PET tracer can detect HER2-positive metastases in patients with HER2-negative primary breast cancer.

METHODS

Patients with HER2-negative primary breast cancer and evidence of distant metastases were enrolled in an Institutional Review Board-approved prospective clinical trial. Archived pathologic samples from the patient's primary breast cancer were retested to confirm HER2-negative disease. Patients with confirmed HER2-negative primary breast cancer underwent ⁸⁹Zr-trastuzumab PET/CT to screen for ⁸⁹Zr-trastuzumab metastases. Metastases avid for ⁸⁹Zr-trastuzumab by PET/CT were biopsied and pathologically examined to define HER2 status. Patients with pathologically proven HER2-positive metastases subsequently received off-protocol HER2-targeted therapy to evaluate treatment response.

RESULTS

Nine patients were enrolled, all of whom had pathologic retesting that confirmed HER2-negative primary breast cancer. Five demonstrated suggestive foci on ⁸⁹Zr-trastuzumab PET/CT. Of these 5 patients, 2 had biopsy-proven HER2-positive metastases and went on to benefit from HER2-targeted therapy. In the other 3 patients, biopsy showed no evidence of HER2-positive disease, and their foci on ⁸⁹Zr-trastuzumab PET were considered false-positive.

CONCLUSION

In this proof-of-concept study, we demonstrated that ⁸⁹Zr-trastuzmab PET/CT detects unsuspected HER2-positive metastases in patients with HER2-negative primary breast cancer. Although these are only initial results in a small sample, they are a proof of the concept that HER2-targeted imaging can identify additional candidates for HER2-targeted therapy. More specific HER2-targeted agents will be needed for clinical use.

Use of Biomarkers to Guide Decisions on Systemic Therapy for Women With Metastatic Breast Cancer: American Society of Clinical Oncology Clinical Practice Guideline

PURPOSE

To provide recommendations on the appropriate use of breast tumor biomarker assay results to guide decisions on systemic therapy for metastatic breast cancer.

METHODS

A literature search and prospectively defined study selection identified systematic reviews, meta-analyses, randomized controlled trials (RCTs), prospective-retrospective studies, and prospective comparative observational studies published from 2006 through September 2014.

RESULTS

The literature search revealed 17 articles that met criteria for further review: 11 studies reporting discordances between primary tumors and metastases in expression of hormone receptors or human epidermal growth factor receptor 2 (HER2), one RCT that addressed the use of a biomarker to decide whether to change or continue a treatment regimen, and five prospective-retrospective studies that evaluated the clinical utility of biomarkers.

RECOMMENDATIONS

In patients with accessible metastases, biopsy for confirmation of disease process and retesting of estrogen receptor, progesterone receptor, and HER2 status should be offered, but evidence is lacking to determine whether changing anticancer treatment on the basis of change in receptor status affects clinical outcomes. With discordance of results between primary and metastatic tissues, the Panel consensus is to use preferentially the estrogen receptor, progesterone receptor, and HER2 status of the metastasis to direct therapy if supported by the clinical scenario and patient's goals for care. Carcinoembryonic antigen, cancer antigen 15-3, and cancer antigen 27-29 may be used as adjunctive assessments, but not alone, to contribute to decisions regarding therapy. Recommendations for tumor rebiopsy and use of circulating tumor markers are based on clinical experience and Panel informal consensus in the absence of studies designed to evaluate the clinical utility of the markers. As such, it is also reasonable for clinicians to not use these markers as adjunctive assessments.

Testing for her2 in breast cancer: current pathology challenges faced in Canada

This review is designed to highlight several key challenges in the diagnosis of human epidermal growth factor receptor 2 (her2)-positive breast cancer currently faced by pathologists in Canada: Pre-analysis issues affecting the accuracy of her2 testing in non-excision sample types: core-needle biopsies, effusion samples, fine-needle aspirates, and bone metastasesher2 testing of core-needle biopsies compared with surgical specimensCriteria for retesting her2 status upon disease recurrenceLiterature searches for each topic were carried out using the medline, Embase, International Pharmaceutical Abstracts, and biosis databases. In addition, the congress databases of the American Society of Clinical Oncology (2005-2011) and the San Antonio Breast Cancer Symposium (2007-2011) were searched for relevant abstracts.All authors are expert breast pathologists with extensive experience of her2 testing, and several participated in the development of Canadian her2 testing guidelines. For each topic, the authors present an evaluation of the current data available for the guidance of pathology practice, with recommendations for the optimization or improvement of her2 testing practice.