Selecting patients with HER2-low breast cancer: Getting out of the tangle

Evolution of HER2 expression between pre-treatment biopsy and residual disease after neoadjuvant therapy for breast cancer

INTRODUCTION

We have previously found that HER2 expression is dynamic, and can change from the primary breast tumor to matched recurrences. With this work, we aimed to assess the dynamics of HER2 during neoadjuvant treatment.(NAT).

METHODS

We reviewed HER2 expression in pre- and post-treatment samples from consecutive patients with early-stage breast cancer that received NAT and underwent surgery at Dana-Farber Brigham Cancer Center between 01/2016-08/2022. The primary outcome was evolution of HER2 expression from pre- to post-NAT specimens in patients with residual disease.

RESULTS

Among 1613 patients receiving NAT, 1080 had residual disease at surgery. A total of 319 patients (29.5%) experienced a change in HER2 expression (HER2 0 vs. HER2-low vs. HER2-positive) from the pre-treatment sample to residual disease, with roughly equal distribution between decreased (50.5%) and increased HER2 expression (49.5%). Similar rates of change in HER2 expression were observed with anthracycline-based (31.8%) or taxane/platinum-based regimens (32.4%). Patients with HER2-0 or HER2-low tumors at diagnosis were likelier to experience a change in HER2 expression post-NAT compared to HER2-positive (32.3% vs. 21.3%, p < 0.001). Changes in HER2 expression post-NAT were prognostic among patients with HER2-positive tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 71.6% vs. 89.6%, p = 0.006) but not among those with HER2-negative tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 79.3% vs. 81.1%, p = 0.31).

CONCLUSIONS

Nearly 30% of patients with early-stage breast cancer showed a change in HER2 expression after NAT. Changes in HER2 expression post-NAT were only prognostic in the setting of HER2-positive tumors becoming HER2-negative at surgery.

HER2-low breast cancer and response to neoadjuvant chemotherapy: a population-based cohort study

About half of breast cancers (BC) without amplification of the human epidermal growth factor receptor 2 (HER2) have a low HER2 protein expression level (HER2-low). The clinical impact of HER2-low and the response to neoadjuvant chemotherapy (NAC) is unclear. This study aimed to assess the association between HER2-low BC and pathological response to NAC. Data from the Dutch Pathology Registry were collected for 11,988 BC patients treated with NAC between 2014 and 2022. HER2-low BC was defined as an immunohistochemical score of 1+ or 2+ and a negative molecular reflex test. We compared clinicopathological features of HER2-0 versus HER2-low BC and assessed the correlation between HER2 status and the pathological complete response (pCR) rate after NAC, including overall survival. Among hormone receptor (HR)-positive tumours, 67% (n=4,619) were HER2-low, compared to 47% (n=1,167) in the HR-negative group. Around 32% (n=207) of patients had a discordant HER2 status between the pre-NAC biopsy and the corresponding post-NAC resection, within which 87% (n=165) changed from HER2-0 to HER2-low or vice versa. The pCR rate was significantly lower in HER2-low BC compared to HER2-0 BC within the HR-positive group (4% versus 5%; p=0.022). However, the absolute difference was limited, so the clinical relevance is questionable. In HR-negative cases, the difference in pCR was not significant (32% versus 34%; p=0.266). No significant difference in overall survival was observed between HER2-low and HER2-0 tumours, regardless of hormone receptor status. The antibody-drug conjugate trastuzumab deruxtecan (T-DXd) has improved survival outcomes of patients with HER2-low metastatic BC. The finding that one-third of the patients in this study had a discordant HER2 status between the pre-NAC biopsy and the post-NAC resection specimen could impact clinical decision-making should T-DXd be used in early BC treatment.

HER2-low and tumor infiltrating lymphocytes in triple-negative breast cancer: Are they connected?

Most patients with triple-negative breast cancer (TNBC) are not candidates for targeted therapy, leaving chemotherapy as the primary treatment option. Recently, immunotherapy has demonstrated promising results in TNBC, due to its immunogenicity. In addition, a novel antibody-drug conjugate, namely, trastuzumab-deruxtecan, has shown effectiveness in TNBC patients with low-HER2 expression (HER2-low). These novel treatment options raise the question about the potential association between the density of stromal tumor-infiltrating lymphocytes (sTILs) and the level of HER2 expression. We aimed to evaluate the association between the level of HER2 expression (HER2-low versus HER2-0) and density of sTILs in TNBC patients, and how they impact the response to neoadjuvant chemotherapy (NAC). This was a retrospective multicenter study including all TNBC patients diagnosed between 2018 and 2022. Central pathology review included sTILs percentages and level of HER2 expression. Tumors were reclassified as either HER2-0 (HER2 IHC 0) or HER2-low (IHC 1 + or 2 + with negative reflex test). Various clinicopathologic characteristics, including sTILs density, and response to NAC were compared between HER2-0 and HER2-low cases. In total, 753 TNBC patients were included in this study, of which 292 patients received NAC. Interobserver agreement between the original pathology report and central review was moderate (77% had the same IHC status after reclassification in either HER2-0 or HER2-low; k = 0.45). HER2-low TNBC represented about one third (36%) of the tumors. No significant difference in sTILs density or complete pathologic response rate was found between HER2-0 and HER2-low cases (p = 0.476 and p = 0.339, respectively). The density of sTILs (≥ 10% sTILs vs. < 10%) was independently associated with achieving a pCR (p = 0.011). In conclusion, no significant association was found between HER2-low status and density of sTILs nor response to NAC. Nonetheless, sTILs could be an independent biomarker for predicting NAC response in TNBC patients.

High contrast breast cancer biomarker semi-quantification and immunohistochemistry imaging using upconverting nanoparticles

Breast cancer is the second leading cause of cancer death in women. Current clinical treatment stratification practices open up an avenue for significant improvements, potentially through advancements in immunohistochemistry (IHC) assessments of biopsies. We report a high contrast upconverting nanoparticles (UCNP) labeling to distinguish different levels of human epidermal growth factor receptor 2 (HER2) in HER2 control pellet arrays (CPAs) and HER2-positive breast cancer tissue. A simple Fourier transform algorithm trained on CPAs was sufficient to provide a semi-quantitative HER2 assessment tool for breast cancer tissues. The UCNP labeling had a signal-to-background ratio of 40 compared to the negative control.

Multiplexed RNA-FISH-guided Laser Capture Microdissection RNA Sequencing Improves Breast Cancer Molecular Subtyping, Prognostic Classification, and Predicts Response to Antibody Drug Conjugates

On a retrospective cohort of 1,082 FFPE breast tumors, we demonstrated the analytical validity of a test using multiplexed RNA-FISH-guided laser capture microdissection (LCM) coupled with RNA-sequencing (mFISHseq), which showed 93% accuracy compared to immunohistochemistry. The combination of these technologies makes strides in i) precisely assessing tumor heterogeneity, ii) obtaining pure tumor samples using LCM to ensure accurate biomarker expression and multigene testing, and iii) providing thorough and granular data from whole transcriptome profiling. We also constructed a 293-gene intrinsic subtype classifier that performed equivalent to the research based PAM50 and AIMS classifiers. By combining three molecular classifiers for consensus subtyping, mFISHseq alleviated single sample discordance, provided near perfect concordance with other classifiers (κ > 0.85), and reclassified 30% of samples into different subtypes with prognostic implications. We also use a consensus approach to combine information from 4 multigene prognostic classifiers and clinical risk to characterize high, low, and ultra-low risk patients that relapse early (< 5 years), late (> 10 years), and rarely, respectively. Lastly, to identify potential patient subpopulations that may be responsive to treatments like antibody drug-conjugates (ADC), we curated a list of 92 genes and 110 gene signatures to interrogate their association with molecular subtype and overall survival. Many genes and gene signatures related to ADC processing (e.g., antigen/payload targets, endocytosis, and lysosome activity) were independent predictors of overall survival in multivariate Cox regression models, thus highlighting potential ADC treatment-responsive subgroups. To test this hypothesis, we constructed a unique 19-feature classifier using multivariate logistic regression with elastic net that predicted response to trastuzumab emtansine (T-DM1; AUC = 0.96) better than either ERBB2 mRNA or Her2 IHC alone in the T-DM1 arm of the I-SPY2 trial. This test was deployed in a research-use only format on 26 patients and revealed clinical insights into patient selection for novel therapies like ADCs and immunotherapies and de-escalation of adjuvant chemotherapy.

High inter-laboratory variability in the assessment of HER2-low breast cancer: a national registry study on 50,714 Danish patients

BACKGROUND

Considering the recent advancements in the treatment of breast cancer with low expression of human epidermal growth factor receptor 2 (HER2), we aimed to examine inter-laboratory variability in the assessment of HER2-low breast cancer across all Danish pathology departments.

METHODS

From the Danish Breast Cancer Group, we obtained data on all women diagnosed with primary invasive breast cancer in 2007-2019 who were subsequently assigned for curatively intended treatment.

RESULTS

Of 50,714 patients, HER2 score and status were recorded for 48,382, among whom 59.2% belonged to the HER2-low group (score 1+ or 2+ without gene amplification), 26.8% had a HER2 score of 0, and 14.0% were HER2 positive. The proportion of HER2-low cases ranged from 46.3 to 71.8% among pathology departments (P < 0.0001) and from 49.3 to 65.6% over the years (P < 0.0001). In comparison, HER2 positivity rates ranged from 11.8 to 17.2% among departments (P < 0.0001) and from 12.6 to 15.7% over the years (P = 0.005). In the eight departments with the highest number of patients, variability in HER2-low cases increased from 2011 to 2019, although the same immunohistochemical assay was used. By multivariable logistic regression, the examining department was significantly related to both HER2 score 0 and HER2 positivity (P < 0.0001) but showed greater dispersion in odds ratios in the former case (range 0.25-1.41 vs. 0.84-1.27).

CONCLUSIONS

Our data showed high inter-laboratory variability in the assessment of HER2-low breast cancer. The findings cast doubt on whether the current test method for HER2 is robust and reliable enough to select HER2-low patients for HER2-targeted treatment in daily clinical practice.

Can we define breast cancer HER2 status by liquid biopsy?

Human Epidermal growth factor Receptor 2 (HER2) assessment is crucial for breast cancer treatment. Therapeutic decisions for recurrent cases often rely on primary tumor status. However, mounting evidence suggests that tumors show dynamic changes and up to 10% of breast cancer modify their initial status during progression. It is still debated whether these changes reflect a biological evolution of the disease or are secondary to primary tumor heterogeneity. Certainly, repeating HER2 assessment during breast cancer trajectory is important for the increasing availability of effective anti-HER2 drugs. In response to this need, circulating biomarkers such as circulating tumor cells (CTCs) and cell-free circulating tumor DNA (ctDNA) offer the potential to safely and repeatedly assess HER2 status over time. This chapter outlines current methods for testing HER2 in CTCs and ctDNA, and reviews clinical trials evaluating its prognostic and predictive value in patients with breast cancer, as well as recent advances in the field.

Delineating intra-tumoral heterogeneity and tumor evolution in breast cancer using precision-based approaches

The burden of breast cancer continues to increase worldwide as it remains the most diagnosed tumor in females and the second leading cause of cancer-related deaths. Breast cancer is a heterogeneous disease characterized by different subtypes which are driven by aberrations in key genes such as BRCA1 and BRCA2, and hormone receptors. However, even within each subtype, heterogeneity that is driven by underlying evolutionary mechanisms is suggested to underlie poor response to therapy, variance in disease progression, recurrence, and relapse. Intratumoral heterogeneity highlights that the evolvability of tumor cells depends on interactions with cells of the tumor microenvironment. The complexity of the tumor microenvironment is being unraveled by recent advances in screening technologies such as high throughput sequencing; however, there remain challenges that impede the practical use of these approaches, considering the underlying biology of the tumor microenvironment and the impact of selective pressures on the evolvability of tumor cells. In this review, we will highlight the advances made thus far in defining the molecular heterogeneity in breast cancer and the implications thereof in diagnosis, the design and application of targeted therapies for improved clinical outcomes. We describe the different precision-based approaches to diagnosis and treatment and their prospects. We further propose that effective cancer diagnosis and treatment are dependent on unpacking the tumor microenvironment and its role in driving intratumoral heterogeneity. Underwriting such heterogeneity are Darwinian concepts of natural selection that we suggest need to be taken into account to ensure evolutionarily informed therapeutic decisions.

HER2-low metastases of HER2-negative primary tumors: a single institution analysis of intertumoral and internodal heterogeneity in node-positive breast cancer

Objective

HER2 status in breast cancer is an essential parameter in individual therapeutic decision-making and is routinely assessed in primary tumors in accordance with international recommendations. Reports of HER2 heterogeneity raise the question of basing treatment decisions on HER2 status in metastases, if present. We investigated the degree and clinical implications of HER2 heterogeneity in lymph node-positive breast cancer. Because of recent recognition of therapeutic opportunities in this group of tumors, we especially focused on cases involving low-level HER2 expression.

Methods

The HER2 status of primary tumors and of corresponding lymph node metastases was determined in archived material at the protein and gene levels using the gene- protein assay and interpreted in accordance with 2018 ASCO/CAP criteria. HER2-low status was defined as protein expression levels 1+ or 2+ with negative amplification status.

Results

We analyzed a series of 43 cases of primary infiltrating breast cancer, each with at least two axillary nodes harboring macrometastases (>2 mm), in total 206 such nodes. In 7% of cases, we detected intertumoral HER2 heterogeneity. Three of nine HER2-positive primary tumors were associated with HER2-negative metastases. No cases with HER2-negative primary tumors had HER2-positive metastases, but 55% (6/11) of HER2 0 primary tumors had HER2 1+ and/or 2+ metastases, and 19% (3/16) HER2 1+ cases had exclusively HER2 0 metastases. All metastases in HER2 2+ cases showed HER2-low protein expression levels. Internodal HER2 heterogeneity at low protein expression levels (presence of HER2 0, HER2 1+, and/or HER2 2+ metastatic deposits within the same axilla) was seen in 40% (17/43) of cases. We found no statistically significant association between HER2 heterogeneity and other tumor-related parameters. Survival data indicated worse outcomes in the HER2-low group compared with the rest of the cohort.

Conclusion

Our results indicate a substantial instability of HER2 protein expression, leading to considerable intertumoral and internodal HER2 heterogeneity in lymph node-positive breast carcinomas. This heterogeneity is particularly relevant in HER2-low tumors in which the corrective effects of HER2 gene copy number analysis definitionally is absent. Our findings suggest that determining HER2 status in metastatic lymph nodes may generate relevant information for therapeutic decision-making.

Concordance of HER2-low scoring in breast carcinoma among expert pathologists in the United Kingdom and the republic of Ireland -on behalf of the UK national coordinating committee for breast pathology

BACKGROUND

Recent clinical evidence showed that breast cancer with low HER2 expression levels responded to trastuzumab deruxtecan therapy. The HER2-low cancers comprise immunohistochemistry (IHC) score 1+ and 2+ ISH non-amplified tumours, currently classified as HER2 negative. Little data exists on the reproducibility of pathologists reporting of HER2-low cancer.

PATIENT AND METHODS

Sixteen expert pathologists of the UK National Coordinating Committee for Breast Pathology scored 50 digitally scanned HER2 IHC slides. The overall level of agreement, Fleiss multiple-rater kappa statistics and Cohen's Kappa were calculated. Cases with low concordance were re-scored by the same pathologists after a washout period.

RESULTS

Absolute agreement was achieved in 6% of cases, all of which scored 3+. Poor agreement was found in 5/50 (10%) of cases. This was due to heterogeneous HER2 expression, cytoplasmic staining and low expression spanning the 10% cut-off value. Highest concordance (86%) was achieved when scores were clustered as 0 versus others. Improvement in kappa of overall agreement was achieved when scores 1+ and 2+ were combined. Inter-observer agreement was moderate to substantial in the whole cohort but fair to moderate in the HER2-low group. Similarly, consensus-observer agreement was substantial to almost perfect in the whole cohort and moderate to substantial in the HER2-low group.

CONCLUSION

HER2-low breast cancer suffers from lower concordance among expert pathologists. While most cases can reproducibly be classified, a small proportion (10%) remained challenging. Refining the criteria for reporting and consensus scoring will help select appropriate patients for targeted therapy.

Diagnostic quality model (DQM): an integrated framework for the assessment of diagnostic quality when using AI/ML

BACKGROUND

Laboratory medicine has reached the era where promises of artificial intelligence and machine learning (AI/ML) seem palpable. Currently, the primary responsibility for risk-benefit assessment in clinical practice resides with the medical director. Unfortunately, there is no tool or concept that enables diagnostic quality assessment for the various potential AI/ML applications. Specifically, we noted that an operational definition of laboratory diagnostic quality - for the specific purpose of assessing AI/ML improvements - is currently missing.

METHODS

A session at the 3rd Strategic Conference of the European Federation of Laboratory Medicine in 2022 on "AI in the Laboratory of the Future" prompted an expert roundtable discussion. Here we present a conceptual diagnostic quality framework for the specific purpose of assessing AI/ML implementations.

RESULTS

The presented framework is termed diagnostic quality model (DQM) and distinguishes AI/ML improvements at the test, procedure, laboratory, or healthcare ecosystem level. The operational definition illustrates the nested relationship among these levels. The model can help to define relevant objectives for implementation and how levels come together to form coherent diagnostics. The affected levels are referred to as scope and we provide a rubric to quantify AI/ML improvements while complying with existing, mandated regulatory standards. We present 4 relevant clinical scenarios including multi-modal diagnostics and compare the model to existing quality management systems.

CONCLUSIONS

A diagnostic quality model is essential to navigate the complexities of clinical AI/ML implementations. The presented diagnostic quality framework can help to specify and communicate the key implications of AI/ML solutions in laboratory diagnostics.

Triple-Negative Breast Cancer and Predictive Markers of Response to Neoadjuvant Chemotherapy: A Systematic Review

Around 40-50% of all triple-negative breast cancer (TNBC) patients achieve a pathological complete response (pCR) after treatment with neoadjuvant chemotherapy (NAC). The identification of biomarkers predicting the response to NAC could be helpful for personalized treatment. This systematic review provides an overview of putative biomarkers at baseline that are predictive for a pCR following NAC. Embase, Medline and Web of Science were searched for articles published between January 2010 and August 2022. The articles had to meet the following criteria: patients with primary invasive TNBC without distant metastases and patients must have received NAC. In total, 2045 articles were screened by two reviewers resulting in the inclusion of 92 articles. Overall, the most frequently reported biomarkers associated with a pCR were a high expression of Ki-67, an expression of PD-L1 and the abundance of tumor-infiltrating lymphocytes, particularly CD8+ T cells, and corresponding immune gene signatures. In addition, our review reveals proteomic, genomic and transcriptomic markers that relate to cancer cells, the tumor microenvironment and the peripheral blood, which also affect chemo-sensitivity. We conclude that a prediction model based on a combination of tumor and immune markers is likely to better stratify TNBC patients with respect to NAC response.

Current Biological, Pathological and Clinical Landscape of HER2-Low Breast Cancer

HER2-low breast cancer (BC) is a newly defined subset of HER2-negative BC that has HER2 immunohistochemical (IHC) score of 1+ or score of 2+/in situ hybridization (ISH) negative phenotype. Recent clinical trials have demonstrated significant clinical benefits of novel HER2 directing antibody-drug conjugates (ADCs) in treating this group of tumors. Trastuzumab-deruxtecan (T-Dxd), a HER2-directing ADC was recently approved by the U.S. Food and Drug Administration as the first targeted therapy to treat HER2-low BC. However, HER2-low BC is still not well characterized clinically and pathologically. This review aims to update the current biological, pathological and clinical landscape of HER2-low BC based on the English literature published in the past two years and to propose the future directions on clinical management, pathology practice, and translational research in this subset of BC. We hope it would help better understand the tumor biology of HER2-low BC and the current efforts for identifying and treating this newly recognized targetable group of BC.

HER2-Low Status Is Not Accurate in Breast Cancer Core Needle Biopsy Samples: An Analysis of 5610 Consecutive Patients

Background: HER2-Low status is found in approximately half of breast cancer patients and shows potential benefits from novel antibody−drug conjugates (ADCs). Data on the accuracy of HER2-Low status between core needle biopsy (CNB) and surgical excision specimen (SES) samples are lacking. We aimed to investigate the accuracy of HER2-Low status diagnosis between CNB and SES samples. Methods: Consecutive early-stage breast cancer patients who underwent surgery from January 2009 to March 2022 with paired CNB and SES samples were retrospectively reviewed. HER2-Low was defined as IHC 1+ or IHC2+ and FISH-negative. Concordance rates were analyzed by the Kappa test. Further clinicopathological characteristics were compared among different HER2 status and their changes. Results: A total of 5610 patients were included, of whom 3209 (57.2%) and 3320 (59.2%) had HER2-Low status in CNB and SES samples, respectively. The concordance rate of HER2 status in the whole population was 82.37% (Kappa = 0.684, p < 0.001), and was 76.87% in the HER2-Negative patients (Kappa = 0.372, p < 0.001). Among 1066 HER2-0 cases by CNB, 530 patients were classified as HER2-Low tumors. On the contrary, in 3209 patients with HER2-Low tumor by CNB, 387 were scored as HER2-0 on the SES samples. ER-negative or Ki67 high expression tumor by CNB had a high concordance rate of HER2-Low status. Conclusions: A relatively low concordance rate was found when evaluating HER2-Low status between CNB and SES samples in HER2-Negative breast cancer patients, indicating the necessity of retesting HER2 low status at surgery, which may guide further therapy in the era of anti-HER2 ADCs.