HER2-low breast cancers: incidence, HER2 staining patterns, clinicopathologic features, MammaPrint and BluePrint genomic profiles

Association of HER2-low with clinicopathological features in patients with early invasive lobular breast cancer: an international multicentric study

PURPOSE

The antibody-drug conjugate trastuzumab deruxtecan has proven to be not only efficient in patients with HER2+ breast cancers (BC), but also in those patients with so-called HER2-low BC. HER2-low tumors are well described in the general BC population, but not in patients with invasive lobular carcinoma (ILC). Here, we aimed at analyzing the association of HER2-low with clinicopathological features and survival outcomes in patients with early-stage pure ILC.

METHODS

A multicentric retrospective cohort of patients diagnosed with stage I-III estrogen receptor positive (ER+) HER2 negative (HER2-) ILC between 01/01/2000 and 12/31/2020 was assembled. HER2- disease was categorized further by immunohistochemical (IHC) score into HER2 0, HER2 1+ and HER2 2+ following time appropriate ASCO/CAP guidelines from 2007 onward and by local guidelines prior to 2007. The association of HER2-low (HER2 1+ and 2+) with clinicopathological variables was assessed using multinomial logistic regression. Survival analyses were performed to evaluate the association of HER2-low with disease-free (DFS), distant recurrence-free (DRFS) and overall survival (OS).

RESULTS

The data of 2098 patients with ER+ HER2- ILC was collected of which 1103 (52.6%) had a HER2-low tumor. Of these 716 (34.1%) had an IHC score of HER2 1+ and 387 (18.4%) of HER2 2+. In multivariable analysis, both tumor size of ≥ 2cm (OR: 1.37; 95%CI 1.01 - 1.87; p-value 0.042) and multifocality (OR: 1.55; 95%CI 1.11 - 2.15; p-value 0.009) were associated with HER2-low. HER2-low was associated with worse DFS (HR: 1.32; 95%CI 1.06 - 1.66; p-value 0.015) and OS (HR: 1.42; 95%CI 1.12 - 1.81; p-value 0.004) as compared to HER2 0. No association of HER2-low with DRFS was observed.

CONCLUSIONS

HER2-low is present in more than half of the patients with early ER+ HER2- pure ILCs and is associated with larger tumor size and multifocality. HER2-low is associated with a worse DFS and OS as compared to HER2 0.

The impact of HER2-Low expression in salivary duct carcinoma: Clinicopathologic features, survival outcomes, and association with androgen receptor-targeted therapy

OBJECTIVES

Recent advances in systemic therapy for salivary duct carcinoma (SDC) have been driven by the development of HER2- and androgen receptor (AR)-targeted therapies. Trastuzumab deruxtecan has proven effective not only in HER2-positive but also HER2-low breast and gastro-esophageal cancers. However, the significance of HER2-low expression in SDC remains unknown. This study aimed to investigate the clinicopathologic characteristics, prognostic implications, and impact on efficacy to AR-targeted therapy in HER2-low SDC.

MATERIALS AND METHODS

This was a multi-center, observational study. HER2 status was reclassified as follows: HER2-positive (IHC3+ or 2+/ISH+ ), HER2-low (IHC1+ or 2+/ISH-), and HER2-zero (IHC0). The subjects were compared in three groups: total population, curative treatment cohort, and AR-targeted therapy cohort.

RESULTS

The total population consisted of 526 patients, of whom, 271 (52 %), 184 (35 %), and 71 (13 %) had HER2-positive, -low, and -zero tumors, respectively. Sex, M category, histological origin, Ki67, and p53 expression differed significantly between the HER2-low and HER2-positive cases. No differences in relapse-free or overall survival were observed for HER2 status in the curative treatment cohort; however, in the AR-targeted therapy cohort, the HER2-low group had significantly better response rates (41.6 % vs. 18.9 %, Odds ratio = 0.30, P = 0.012) and longer median progression-free survival (6.9 vs. 4.2 months, Hazard ratio = 1.61, P = 0.029) than those of the HER2-positive group.

CONCLUSION

HER2-low showed different clinicopathologic features from HER2-positive cases, with no prognostic differences observed in patients who underwent curative treatment. Still, HER2-low may be associated with the efficacy of AR-targeted therapy.

A Comparative Analysis of the Value of HER2 Immunohistochemistry Scoring in Primary and Metastatic Breast Cancer, in the Era of HER2 "Low" Breast Cancers

BACKGROUND

In the DESTINY-B04 trial, patients with pretreated HER2 low metastatic breast cancer (defined as immunohistochemistry score of 1+ or 2+ and negative in situ hybridization) had significant survival improvement with Trastuzumab therapy.

METHODS

The goal of our study was to compare the HER2 immunohistochemistry scores of paired primary and metastatic breast cancer, with emphasis on HER2 low criteria and its implications for detailed immunohistochemistry interpretation. Using the pathology database from 2011, we identified 272 cases of primary breast cancers with paired metastases. We reviewed and performed immunohistochemistry concordance between the primary and metastases and calculated the HER2 low incidence.

RESULTS

Compared to the primary, HER2 immunohistochemistry score in the metastases remained the same in 156/272 cases (57%) and by immunohistochemistry was: 0 (67/114 = 59%), 1+ (22/52 = 42%), 2+ (34/67 = 51%), 3+ (33/39 = 85%) and HER2 low (85/119 = 71%). The HER2 score changed from 0 to HER2 low in 46 cases (17%) and vice versa in 30 (11%).

CONCLUSIONS

The concordance rate of HER2 immunohistochemistry scores was 57%, highest in 3+ cases, followed by HER2 low and then HER2 negative. The incidence of HER2 low was higher in the metastases by 6% compared to the primary. HER2 should be tested in all metastases and compared with the primary, due to differences in scores as seen in 28% of our cases, which may have clinical implications in the new HER2 low era.

HER2 testing: evolution and update for a companion diagnostic assay

Human epidermal growth factor receptor 2 (HER2; encoded by ERBB2) testing has been a cornerstone of patient selection for HER2-targeted therapies, principally in breast cancer but also in several other solid tumours. Since the introduction of HercepTest as the original companion diagnostic for trastuzumab, HER2 assessment methods have evolved substantially, incorporating various testing modalities, from western blots, immunohistochemistry and fluorescence in situ hybridization, to early chromogenic quantitative methods and, probably in the future, fully quantitative methods. The advent of highly effective HER2-targeted antibody-drug conjugates with clinical activity at low levels of HER2 expression, such as trastuzumab deruxtecan, has necessitated the re-evaluation of HER2 testing, particularly for HER2-low tumours. In this Review, we provide an in-depth overview of the evolution of HER2 testing, the current clinical guidelines for HER2 testing across various solid tumours, challenges associated with current testing methodologies and the emerging potential of quantitative techniques. We discuss the importance of accurately defining HER2-low expression for therapeutic decision-making and how newer diagnostic approaches, such as quantitative immunofluorescence and RNA-based assays, might address the limitations of traditional immunohistochemistry-based methods. As the use of HER2-targeted therapies continues to expand to a wider range of tumour types, ensuring the precision and accuracy of HER2 testing will be crucial for guiding treatment strategies and improving patient outcomes.

Best pathology practices for HER2 testing interpretation, including HER2-low and ultralow, in the era of HER2-directed antibody drug conjugates (ADCs), aligned with the 2018 CAP/ASCO HER2 guidelines

With the emergence of studies showing clinical response to novel human epidermal growth factor receptor 2(HER2)-targeted treatments among HER2-low and HER2-ultralow metastatic breast cancer patients, this gives hope to patients failing to respond to conventional treatment. Hence, the interest in identifying these group of patients is becoming important. Pathologists' interpretation and scoring of HER2 immunohistochemistry (IHC) was challenged from a dichotomous way to a ternary way of reporting. But HER2 IHC testing is affected by a number of pre-analytic, analytic and post-analytic challenges that could affect interpretation at the lower HER2 protein expression range. Interobserver variability among pathologists and inter-assay variabilities likewise posses a challenge since prior guidelines' emphasis were focused on recognizing HER2-overexpressed from HER2-non-overexpressed tumours. In consideration of these clinical trials, the American Society of Clinical Oncologists and College of American Pathologists (ASCO/CAP) updated and reaffirmed the guideline on HER2 testing in 2018 and in 2023, with the criteria for HER2 categories redefined. Here, we reviewed the definition and differences among HER2-low, HER2-ultralow and HER2-null breast cancer cases as well as the different challenges on HER2 IHC testing encountered and reported, including best pathology practice recommendations to avaoid or minimize these challenges.

Prevalence and clinicopathological features of human epidermal growth factor receptor-2-low breast cancers: A single-center experience

ObjectiveHuman epidermal growth factor receptor-2-low breast cancer, characterized by low-level human epidermal growth factor receptor-2 expression and immunohistochemistry score 1+ or immunohistochemistry score 2+ without amplification, has been proposed as a distinct subgroup. This study investigated the prevalence and clinicopathological characteristics of human epidermal growth factor receptor-2-low breast cancers.MethodsA retrospective observational cohort study was conducted on patients diagnosed with invasive breast carcinoma between 2021 and 2023 at a single tertiary center. Data on histological type, tumor grade, human epidermal growth factor receptor-2 status, and Ki-67 proliferation index were collected.ResultsAmong the 181 patients who were included, 54.7% were classified as human epidermal growth factor receptor-2-low, 27.6% as human epidermal growth factor receptor-2-negative, and 17.7% as human epidermal growth factor receptor-2-positive. Human epidermal growth factor receptor-2-low tumors were predominantly those classified into grade 2 (69.7%). The mean age of patients with human epidermal growth factor receptor-2-low tumors was 60 years. The Ki-67 index was significantly lower in human epidermal growth factor receptor-2-low tumors than in human epidermal growth factor receptor-2-positive and human epidermal growth factor receptor-2-negative groups (p = 0.001). No significant differences were observed in the rates of axillary lymph node metastasis among the groups (p = 0.13).ConclusionHuman epidermal growth factor receptor-2-low breast cancers constitute a significant proportion of breast cancer cases and are associated with distinct clinicopathological features, including high estrogen reception positivity and lower Ki-67 proliferation rates.

Incidence, Clinicopathologic Features, and Follow-Up Results of human epidermal growth factor receptor-2-Ultralow Breast Carcinoma

The preliminary result of DESTINY-Breast06 trial demonstrated the effectiveness of antibody-drug conjugate in patients with human epidermal growth factor receptor-2 (HER2)-ultralow breast carcinoma (BC), defined by the presence of ≤10% of infiltrating cancer cells showing incomplete and faint/weak membrane staining on HER2 immunohistochemistry. In this study, we investigated the pathologic features and clinical outcomes in patients with HER2-ultralow, HER2-null, and HER2-low expression. The incidence of HER2 ultralow was 17.5% (260/1486). The incidence of other groups is as follows: 7.7% for HER2 null, 56.8% for HER2 low, and 18% for HER2 positive. HER2-ultralow cases showed similarity to HER2-low cases but a significant difference from HER2-null cases, including older age (61.1 vs 57.3 years; P = .0099), fewer grade 3 BCs (18.1% vs 53.9%; P < .0001), triple-negative BCs (16.2% vs 42.6%; P < .0001), estrogen receptor (ER)-negative BCs (16.5% vs 47.8%; P < .0001), and progesterone receptor-negative BCs (26.2% vs 54.8%; P < .0001). When cases were stratified based on ER positivity, these differences between HER2-null and HER2-ultralow groups were confined to ER+ but not ER- cases. There were no discernible differences in response to neoadjuvant chemotherapy (n = 125) among HER2-null, HER2-ultralow, and HER2-low BCs. HER2-null/ER-BCs displayed a lower probability of overall survival than HER2-ultralow and HER2-low/ER-BCs, but no statistically significant difference was observed in disease-free survival among the 3 groups. HER2-ultralow BCs exhibit distinct features that align more closely with HER2-low BCs than HER2-null BCs. These findings contribute to the evolving classification of HER2 expression in BC and may have implications for refining treatment strategies in this subgroup.

Prevalence and concordance of HER2-low and HER2-ultralow status between historical and rescored results in a multicentre study of breast cancer patients in China

BACKGROUND

Accurately assessing HER2-low (immunohistochemistry [IHC] 1 + and IHC 2+/in situ hybridization [ISH]-) and HER2-ultralow (IHC > 0 < 1+) is essential given the emergence of novel therapies. Thorough understanding of the reproducibility of rescoring IHC stained slides or re-staining archived tissue slides is essential.

METHODS

2,869 breast cancer patients diagnosed between July 2021 and July 2022 from 10 hospitals in China were included in this multicentre study. The prevalence of different HER2 expression levels and distribution of HER2 IHC scores were assessed by HER2 status determination from rescored historical slides. Concordance was evaluated across historical results versus rescored results, historical results versus re-stained results, and leading center results versus local site results. Clinicopathological characteristics were retrospectively analyzed as well.

RESULTS

HER2 IHC 0, IHC 1+, IHC 2+, and IHC 3 + were identified in 682 (23.8%), 871 (30.4%), 801 (27.9%), and 515 (18.0%) cases, respectively. HER2-positive, HER2-low, and HER2 IHC 0 (HER2-ultralow and IHC null) were identified in 21.7%, 54.5%, and 23.8% of cases, respectively. The prevalence of HER2-ultralow and IHC null was 10.6% and 13.2%, respectively. The concordance for HER2-ultralow was 43.3%; 30% of cases that were scored as HER2-ultralow at local sites were rescored as HER2-null and 26.7% of cases were rescored as IHC 1 + at the leading site. Overall, there was substantial agreement (83.1%) between rescored and historical IHC results. A high concordance rate of 91.7% was observed for HER2-low classification.

CONCLUSIONS

This is the first multicenter study to determine the prevalence of HER2-low and HER2-ultralow based on rescored results in the Chinese breast cancer population. The concordance analysis carries important implications for the diagnosis of HER2-low and HER2-ultralow cases in clinical practice. The relatively low concordance in identifying HER2-ultralow suggested that the reproducibility of scoring HER2-ultralow needed to be improved through training.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT05203458.

Comprehensive analysis of HER2 Low Breast Cancer Response to Neoadjuvant Chemotherapy, a Retrospective Cohort Study

BACKGROUND

This study aimed to identify the response and survival outcomes of HER2-low patients following neoadjuvant chemotherapy (NAC).

METHOD

A retrospective cohort of patients who received NAC in the Department of Breast Surgery at Peking Union Medical College Hospital (PUMCH) from September 27, 2016, to January 23, 2024, was reviewed. Multivariate logistic regression and Cox proportional hazards models were used to identify factors associated with pathological complete response (pCR) and survival outcomes. The Kaplan-Meier method was applied to compare survival outcomes between HER2-zero and HER2-low patients.

RESULT

Four hundred and twenty-one patients meeting the inclusion criteria. The pCR rate of HER2-zero patients was significantly higher than that of HER2-low patients after adjusting for confounders (OR = 2.83, 95% CI: 1.44-5.65, adjusted P = .003). HER2-low patients demonstrated the most stable status after NAC within the hormone receptor (HR)-positive subset (80.82%) and the most unstable status within the HR-negative subset (57.69%). HER2-zero status was associated with worse disease-free survival (DFS) (HR = 1.94, 95% CI: 1.13-3.32, adjusted P = .02), but not with overall survival (OS) (HR = 1.18, 95% CI: 0.59-2.37, P = .65). HER2-zero patients had significantly worse DFS than HER2-low patients in the entire cohort (P = .014) and the HR-positive subset (P < .001). pCR could serve as a surrogate endpoint of favorable survival outcomes for HER2-zero patients, but not for HER2-low patients.

CONCLUSION

HER2-low patients might exhibit distinct characteristics compared with HER2-zero patients following NAC. Further multicenter, prospective studies are warranted to validate the conclusions of this exploratory research and assess whether HER2-low expression could serve as a new clinical subtype for evaluating NAC treatment outcomes.

Pathologic response rates in HER2-low versus HER2-zero early breast cancer patients receiving neoadjuvant therapy: a systematic review and meta-analysis

BACKGROUND

Currently, the primary methods for detecting HER2 expression levels are immunohistochemistry (IHC) and in situ hybridization (ISH), with the traditional standard being a HER2-positive score of 3 + accompanied by ERBB2 gene amplification detected through ISH. However, a new entity has recently emerged: HER2-low, defined as HER2 IHC 1 + or 2 + with negative ISH. HER2-low breast cancer, representing 45-60% of all HER2-negative tumors, has distinct biological characteristics and uncertain responses to conventional HER2-targeted therapies. Recent studies suggest varied clinical outcomes, highlighting the need for further investigation into the impact of HER2-low status on treatment efficacy and prognosis.

OBJECTIVE

This meta-analysis evaluates the difference in complete pathological response (pCR), disease-free survival (DFS), and overall survival (OS) between HER2-low and HER2-zero phenotypes.

METHODS

We systematically searched the main databases PubMed, Scopus, and Web of Science for articles evaluating women in neoadjuvant therapy expressing HER2-low and HER2-zero. We computed odds ratios (ORs) or hazard ratios (HRs) using DerSimonian and Laird random-effect models for all endpoints, with 95% confidence intervals (CIs). We assessed the heterogeneity using I2 statistics. R, version 4.2.3, was used for statistical analyses.

RESULTS

38 studies totaling 70,104 patients were included. The HER2-low group accounted for 61.3% of patients while HR + status represented 52.4% in the whole research. In 67,839 women, the pCR was analyzed, which in the overall cohort analysis favored the HER2-zero group (OR 0.84; 95% CI 0.78-0.90; p = 0.000005; I2 = 15%). Subgroup analyses for triple-negative breast cancer (TNBC) and HR + patients also favored HER2-zero expression, with an OR of 0.91 (95% CI 0.83-1.0; p < 0.041; I2 = 12%) and 0.75 (95% CI 0.70-0.81; p < 0.000001; I2 = 0%), respectively. In the multivariate analysis across all patients, both DFS and OS outcomes were significantly favorable for the HER2-low expression group, with HR 0.8317 (95% CI 0.7036-0.9832; p = 0.031) for DFS and HR 0.806 (95% CI 0.663-0.979; p = 0.03) for OS.

CONCLUSION

Based on our findings, HER2-zero status is associated with a significantly higher pathological complete response (pCR) rate compared to HER2-low in early-stage breast cancer, and other survival outcomes. These results suggest that HER2-zero should be considered a prognostic factor in early-stage breast cancer and taken into account in neoadjuvant treatment planning and future clinical research.

Machine learning-based prediction of distant metastasis risk in invasive ductal carcinoma of the breast

More than 90% of deaths due to breast cancer (BC) are due to metastasis-related complications, with invasive ductal carcinoma (IDC) of the breast being the most common pathologic type of breast cancer and highly susceptible to metastasis to distant organs. BC patients who develop cancer metastases are more likely to have a poor prognosis and poor quality of life, so it is extremely important to recognize and diagnose whether distant metastases have occurred in IDC as early as possible. In this study, we develop a non-invasive breast cancer classification system for detecting cancer metastasis. We used Anaconda-Jupyter notebooks to develop various Python programming modules for text mining, data processing, and machine learning (ML) methods. A risk prediction model was constructed based on four algorithms: Random Forest, XGBoost, Logistic Regression, and SVM. Additionally, we developed a hybrid model based on a voting mechanism using these four algorithms as the base models. The models were compared and evaluated by the following metrics: accuracy, precision, recall, F1-score, and area under the ROC curve (AUC) values. The experimental results show that the hybrid model based on the voting mechanism exhibits the best prediction performance (accuracy: 0.867, precision: 0.929, recall: 0.805, F1-score: 0.856, AUC: 0.94). This stable risk prediction model provides a valuable reference support for doctors in assessing and diagnosing the risk of IDC hematogenous metastasis. It also improves the work efficiency of doctors and strives to provide patients with increased chances of survival.

Impact of HER2-Low Status on Pathologic Complete Response and Survival Outcome Among Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy

PURPOSE

This study analyzed the pathological complete response (pCR) rates, long-term outcomes, and biological features of human epidermal growth factor receptor 2 (HER2)-zero, HER2-low, and HER2-positive breast cancer patients undergoing neoadjuvant treatment.

METHODS

This single-center study included 1,667 patients who underwent neoadjuvant chemotherapy from 2008 to 2014. Patients were categorized by HER2 status, and their clinicopathological characteristics, chemotherapy responses, and recurrence-free survival (RFS) rates were analyzed.

RESULTS

Patients with HER2-low tumors were more likely to be older (p = 0.081), have a lower histological grade (p < 0.001), and have hormone receptor (HorR)-positive tumors (p < 0.001). The HER2-positive group exhibited the highest pCR rate (23.3%), followed by the HER2-zero (15.5%) and HER2-low (10.9%) groups. However, the pCR rate did not differ between HER2-low and HER2-zero tumors in the HorR-positive or HorR-negative subgroups. The 5-year RFS rates increased in the following order: HER2-low, HER2-positive, and HER2-zero (80.0%, 77.5%, and 74.5%, respectively) (log-rank test p = 0.017). A significant survival difference between patients with HER2-low and HER2-zero tumors was only identified in HorR-negative tumors (5-year RFS for HER2-low, 74.5% vs. HER2-zero, 66.0%; log-rank test p-value = 0.04). Multivariate survival analysis revealed that achieving a pCR was the most significant factor associated with improved survival (hazard ratio [HR], 4.279; p < 0.001). Compared with HER2-zero, the HRs for HER2-low and HER2-positive tumors were 0.787 (p = 0.042) and 0.728 (p = 0.005), respectively. After excluding patients who received HER2-targeted therapy, patients with HER2-low tumors exhibited better RFS than those with HER2-zero (HR 0.784, p = 0.04), whereas those with HER2-positive tumors exhibited no significant difference compared with those with HER2-low tumors (HR, 0.975; p = 0.953).

CONCLUSION

Patients with HER2-low tumors had no significant difference in pCR rate compared to HER2-zero but showed better survival, especially in HorR-negative tumors. Further investigation into biological differences is warranted.

Clinicopathological characteristics and long-term prognosis of triple-negative breast cancer patients with HER2-Low expression: a retrospective propensity score-matched cohort study

PURPOSE

The objective of the current research was to assess the clinicopathological characteristics and long-term prognosis of triple-negative breast cancer (TNBC) patients with human epidermal growth factor receptor 2 (HER2)-low status following breast surgery.

METHODS

A total of 202 TNBC patients treated at Qingdao Central Hospital from January 2010 to December 2019 were included, comprising 71 HER2-low and 131 HER2-zero patients. Propensity score matching (PSM) was applied to minimize differences between the cohorts.

RESULTS

HER2-low TNBC patients had lower histological grade, lower Ki-67 expression levels, and a higher prevalence of hypertension compared to HER2-zero TNBC patients. Before and after PSM, the HER2-low group consistently exhibited a lower recurrence rate and longer RFS compared to HER2-zero TNBC patients. HER2-low status was validated as an independent low-risk factor for RFS both pre-PSM (HR 0.354, 95% CI 0.178-0.706, p = 0.003) and post-PSM (HR 0.405, 95% CI 0.185-0.886, p = 0.024). No statistically significant differences in mortality rate and OS were observed, both before and after PSM.

CONCLUSIONS

HER2-low and HER2-zero TNBC patients show significant clinicopathological differences. Compared to HER2-zero, HER2-low status is linked to better long-term prognosis and serves as an independent low-risk factor for RFS in TNBC patients.

HER2-low prevalence among Hispanic/Latino women with breast cancer: A systematic review and meta-analysis

PURPOSE

HER2-low has garnered significant attention for the treatment of HER2-negative breast cancer. We aimed to determine the prevalence of HER2-low expression in Hispanic/Latino women with breast cancer (BC).

METHODS

We searched in Embase, LILACS, and Medline databases for articles reporting the expression of HER2 immunohistochemistry with scores reported as 0, 1+, 2+, or 3+, with equivocal cases (2+) confirmed through in situ hybridization (ISH).

RESULTS

A total of 12 articles were finally included, comprising 73,467 individuals. The prevalence of HER2-zero, HER2-low and HER2 positive cases among all BC (0, 1+, 2+/ISH-, 2+/ISH+ and 3+), was 45.0%, 32.0%, and 23.0%, respectively. The prevalence of HER2-zero and HER2-low expression among negative cases (0, 1+ and 2+/ISH-), was 53.0% and 47.0%, respectively.

CONCLUSION

There is an important percentage of Hispanic/Latino individuals who would benefit from HER2-targeted therapies, even in HER2 negative cases. Additional research on the prevalence of HER2-low tumors across a wider range of Latin American countries is required to better understand the molecular epidemiology of this biomarker within the Hispanic/Latino population.

Patient characteristics and treatment patterns of patients with locally advanced or metastatic HER2-low breast cancer, a single site descriptive study

PURPOSE

To evaluate the prevalence and characteristics of different HER2 categories among patients with advanced breast cancer (aBC) and describe treatment patterns and outcomes of those with HER2-low disease.

METHODS

A retrospective cohort study was conducted via chart review at the Huntsman Cancer Institute, including patients diagnosed with aBC (stages IIIB, IIIC and IV) between 2010 and 2019. All patients with IHC1+ were considered HER2-low unless FISH was positive. Patients with IHC2+ were only classified as HER2-low if a negative FISH was documented. The prevalence and characteristics of each HER2 category were reported. Treatment patterns and survival outcomes of HER2-low patients who received first line treatment in 2017 or later were presented.

RESULTS

A total of 240 of 414 patients (58%) with aBC were HER2-low, with the majority of patients (83%) classified as hormone receptor (HR)-positive. In first line, most HR-positive patients received endocrine therapy with chemotherapy for stage IIIB/IIIC (47%) and with CDK4/6 inhibitors for stage IV breast cancer (50%) Most HR-negative patients received chemotherapy alone (92% for stage IIIB/IIIC, 60% for stage IV). In second line, chemotherapy alone was the most common modality (21.4% for HR-positive; 45.5% for HR-negative). Median overall survival was 37.7 months while median progression-free survival from first line was 18.0 months, decreasing to 8.0 months in second line.

CONCLUSION

A substantial proportion of patients previously classified as HER2-negative have low but detectable HER2 expression and may benefit from novel HER2-directed agents, which have demonstrated clinical benefit in this population post-chemotherapy.

Clinicopathological characteristics, evolution, and treatment outcomes of hormone receptor-negative/HER2-low metastatic breast cancer: a pooled analysis of individual patient data from three prospective clinical trials

Objective

With the approval of trastuzumab deruxtecan for the treatment of unresectable/metastatic HER2-low breast cancer, human epidermal growth factor receptor 2 (HER2)-low has emerged as a clinically actionable biomarker. There is an urgent need for a deeper understanding of HER2-low breast cancer patients. Therefore, this study was conducted to explore the clinicopathological characteristics, the evolution of HER2-low status, and its impact on the prognosis of hormone receptor (HoR)-negative/HER2-low metastatic breast cancer (MBC) patients.

Methods

This pooled analysis included 350 metastatic triple-negative breast cancer (mTNBC) patients who received first-line platinum-based chemotherapy at Fudan University Shanghai Cancer Center from November 2007 to July 2022. Patients were categorized into HER2-0 and HER2-low groups based on their HER2 status. Baseline clinicopathological characteristics, evolution of HER2 status between primary and metastatic lesions, and treatment efficacy were compared between the two groups.

Results

Among the 350 mTNBC patients, 34.9% (122/350) were HER2-low and 65.1% (228/350) were HER2-0. Significant differences were observed between HER2-low and HER2-0 patients in terms of age and menopausal status. HER2-low patients were older (54 vs. 49 years, p=0.002) and had a lower proportion of premenopausal patients (32.8% vs. 52.6%, p<0.001) compared to HER2-0 patients. No significant differences were observed in progression-free survival (PFS) and overall survival (OS) between HER2-low and HER2-0 patients receiving first-line platinum-based chemotherapy (mPFS: 7.43 vs. 8.30 months, p=0.389, HR=1.11, 95% CI 0.88-1.40; mOS: 25.37 vs. 26.63 months, p=0.907, HR=1.02, 95% CI 0.76-1.37). Additionally, 32.3% (41/127) of patients exhibited discordant HER2 status between primary and metastatic lesions, primarily evolving from HER2-0 to HER2-low. Notably, patients with discordant HER2 status had significantly longer PFS compared to those with concordant status (mPFS: 11.07 vs. 7.53 months, p=0.020). The Cox multivariate analysis showed that HER2 status consistency (p=0.026) was an independent predictor of PFS.

Conclusion

In mTNBC patients, those with HER2-low status had similar responses to platinum-based chemotherapy as HER2-0 patients. There was significant discordance in HER2 status between primary and metastatic lesions. Patients with discordant HER2 status had better responses to platinum-based chemotherapy. Therefore, for patients with HER2-0 primary lesions, re-evaluation of HER2 status in metastatic lesions through biopsy may offer new treatment opportunities.

The prognostic impact of Her2 status in early triple negative breast cancer: a Turkish Oncology Group (TOG) study

The studies evaluating the impact of Her2 levels in neoadjuvant setting have conflicting data. The aim of the study was to evaluate the prognostic impact of Her2 status in early triple negative breast cancer(TNBC). In the study TNBC patients who were treated with neoadjuvant chemotherapy (NAC) and surgery were analyzed retrospectively. The primary aim of the study was to analyze the impact of Her2 status(Her2-0 and Her2-low) on pathological complete response (pCR). The secondary objectives were disease free survival (DFS) and overall survival (OS). 620 female triple negative breast cancer patients were evaluated. 427 patients (68.9%) had Her2-0 and 193(31.1%) had her2-low pathology. The pCR rates were similar between Her2-0 and Her2-low patients (33.0% vs. 27.5%, p = 0.098). Although Her2-0 group has better DFS (106 vs. 50 months, p = 0.002), in multivariate analysis it had a HR of 0.74 (p = 0.06). In addition, OS was similar (131 vs. 105 months, p = 0.13) with a HR of 0.88 (p = 0.61). In multivariate analysis; presence of LVI (HR:2.2 (95% CI 1.1-3.5) p = 0.001), Clinical stage T1/T2 (HR:0.39 (95% CI 0.2-0.6) p < 0.001) and lymph node negativity (HR:0.35 (95% CI 0.1-0.9) p = 0.03) were independent factors for OS. Although there were pathological and clinical differences, the pCR, DFS and OS were similar between Her2-0 and Her2-low TNBC patients. The importance of Her2 status of TNBC in neoadjuvant setting should be further studied.

Potential Use of Extracellular Vesicles for the HER2 Status Assessment in Breast Cancer Patients

Human epithelial growth factor receptor 2 (HER2)-targeted therapies are effective in patients with HER2-positive breast cancer. Recent advances have shown that HER2-targeted therapies can also be of benefit when treating tumors expressing low levels of HER2, highlighting the importance of identifying the HER2-low subgroup. This clinical trend has opened new therapeutic avenues for patients who were previously ineligible for HER2-targeted therapies. Thus, the development of new diagnostic methods for real-time HER2 profiling is crucial for accurately tailoring the treatment for these patients. We hypothesized that tumor-derived extracellular vesicles (TEVs) could reflect the HER2 profiles of primary tumors and potentially serve as diagnostic tools for HER2 status. This approach was validated using six breast cancer cell lines, which confirmed that the TEVs accurately reflected the HER2 profiles of the tumor cells. TEVs were isolated using an immunoaffinity method, and copy number variation (CNV) in the ERBB2/EIF2C ratio was assessed using droplet digital PCR of DNA from these vesicles. Clinical validation using plasma samples from 33 breast cancer patients further reinforced the diagnostic potential of our method. Pearson's correlation coefficient analysis of the flow cytometry results demonstrated that TEVs reflected HER2 expression in primary cells. To distinguish between HER2-negative and HER2-low patients, the area under the curve (AUC) of the ROC curve in our method was 0.796, with a sensitivity of 53.8% and a specificity of 100%. These findings suggest the clinical utility of extracellular vesicles derived from plasma and emphasize the need for further research to distinguish HER2-negative from HER2-low patients.

Landscape of HER2-low breast cancer: Insights from a six-year study on prevalence and clinicopathological characteristics

Human epidermal growth factor receptor 2 (HER2)-low breast cancer has emerged as a subtype of breast cancer, defined by HER2 1+/2+ in immunohistochemistry (IHC) and absence of ERBB2 gene amplification on fluorescence in situ hybridization (FISH). Recent trials showed marked response of HER2-low breast cancer to novel anti-HER2 antibody-drug-conjugates. Data on characteristics of HER2-low breast cancer subtype is limited. Real-world data from the Anatomic Pathology Department of Hotel-Dieu de France, spanning 2017-2023, was retrospectively collected. HER2-positive patients were excluded to compare HER2-low to HER2-zero breast cancer subtypes. Clinicopathological characteristics between the groups were compared using a Chi-Squared test. Out of 1195 patients, we observed 341 (28.5 %) HER2-low breast cancers cases. HER2-positive breast cancer cases (n = 178; 14.9 %) were excluded. There was no significant difference in age and sex between HER2-low and HER2-zero group (p = 0.33 and 0.79, respectively). HER2-low breast cancer was associated with positive estrogen receptor status and positive progesterone receptor status (p < 0.001 and p = 0.01, respectively). Ductal adenocarcinomas were more commonly observed in HER2-low group (p < 0.001). When stratified by hormone (HR) status, 87.4 % of patients had HR-positive status and 12.6 % were HR-negative. Among the HR-negative group, HER2-low tumors tended to show lower proliferation index compared to HER2-zero tumors (25%vs.10 %, p = 0.04). This study showed that HER2-low is distinct from HER2-zero and is common among patients with breast cancer. Clinicopathological features such as histological type differ between HER2-zero and HER2-low breast cancer. Within HR-negative breast cancer, those with low HER2 expression exhibit a less aggressive profile compared to HER2-zero tumors.

Understanding the spectrum of HER2 status in breast cancer: From HER2-positive to ultra-low HER2

HER2 (human epidermal growth factor receptor 2) status in breast cancer spans a spectrum from HER2-positive to ultra-low HER2, each category influencing prognosis and treatment decisions differently. Approximately 20 % of breast cancers overexpress HER2, correlating with aggressive disease and poorer outcomes without targeted therapy. HER2 status is determined through immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), guiding therapeutic strategies. HER2-positive breast cancer exhibits HER2 protein overexpression or gene amplification, benefiting from HER2-targeted therapies like trastuzumab and pertuzumab. In contrast, HER2-negative breast cancer lacks HER2 overexpression and amplification, treated based on hormone receptor status. HER2-low breast cancer represents a newly recognized category with low HER2 expression, potentially benefiting from evolving therapies. Ultra-low HER2 cancers, characterized by minimal expression without gene amplification, challenge conventional classifications and treatment paradigms. Their distinct molecular profiles and clinical behaviors suggest unique therapeutic approaches. Recent diagnostic guideline updates refine HER2 assessment, enhancing precision in identifying patients for targeted therapies. Challenges remain in accurately classifying HER2-low tumors and optimizing treatment efficacy, necessitating ongoing research and innovative diagnostic methods. Understanding the heterogeneity and evolving landscape of HER2 status in breast cancer is crucial for advancing personalized treatment strategies and improving patient outcomes.

Comparison of neoadjuvant chemotherapy response and prognosis among pegylated liposomal doxorubicin, epirubicin and pirarubicin in HR ⩽ 10%/HER2-negative breast cancer: an exploratory real-world multicentre cohort study

BACKGROUND

Pegylated liposomal doxorubicin (PLD), epirubicin and pirarubicin are the main anthracyclines widely used in China. PLD demonstrates therapeutic response comparable to epirubicin and pirarubicin in neoadjuvant chemotherapy (NAC) of breast cancer.

OBJECTIVES

The objectives of our study were to retrospectively assess the real-world effectiveness and prognostic characteristics of PLD as NAC for HR ⩽ 10%/human epidermal growth factor receptor 2 (HER2)-negative breast cancer.

DESIGN

This was a retrospective study.

METHODS

Our study enrolled patients with HR ⩽ 10%/HER2-negative breast cancer who received PLD-, epirubicin- or pirarubicin-based NAC from three centres in Hunan Province, China, between 2015 and 2022. We employed inverse probability of treatment weighting to balance the differences in patients' characteristics among the PLD, epirubicin, and pirarubicin groups. The endpoints were pathological complete response (pCR), event-free survival (EFS), and overall survival (OS).

RESULTS

A total of 267 patients were included. After NAC, the pCR rates in PLD group were superior to epirubicin group (PLD, 34.1%; epirubicin, 20.8%, p = 0.038). The differences in EFS (log-rank p = 0.99) and OS (log-rank p = 0.33) among the three groups were not statistically significant. Among the three groups, non-pCR patients had worse EFS than pCR patients (log-rank p = 0.014). For patients with pCR, the differences in EFS (log-rank p = 0.47) and OS (log-rank p = 0.38) were not statistically significant among the three groups, and the EFS (log-rank p = 0.59) and OS (log-rank p = 0.14) of non-pCR patients in the PLD group were similar to those in the epirubicin and pirarubicin groups.

CONCLUSION

PLD had a similar therapeutic response and prognosis compared to epirubicin or pirarubicin in NAC for patients with HR ⩽ 10%/HER2 negative breast cancer, which means that PLD represents a potential NAC option.

Prognosis in HR-positive metastatic breast cancer with HER2-low versus HER2-zero treated with CDK4/6 inhibitor and endocrine therapy: a meta-analysis

Background

The combination of CDK4/6 inhibitors (CDK4/6i) and endocrine therapy (ET) is currently the standard first-line treatment for patients with metastatic hormone receptor positive (HR+), and HER2-negative (HER2-) breast cancer. However, the impact of HER2 status on the prognosis of patients receiving CDK4/6i and ET remains unclear. The meta-analysis was conducted to evaluate different outcomes between HER2-low and HER2-zero patients in advanced HR+ breast cancer receiving CDK4/6i and ET.

Methods

A systematic search was performed in PubMed and EMBASE databases for relevant published literature. Objective response rate (ORR), overall survival (OS), and progression-free survival (PFS) were pooled by fixed or random effects models.

Results

Overall, 12 studies with 3567 patients were eligible for analysis. The pooled analysis suggested that no significant differences were observed in terms of ORR and OS between HER2-low and HER2-zero patients who underwent CDK4/6i and ET. Similarly, no significant difference in PFS was found between HER2-low and HER2-zero patients who underwent post-line CDK4/6i and ET or first-line Palbociclib and ET. However, in patients who received mixed-line (not a single treatment line) or first-line CDK4/6i and ET, the PFS was significantly shorter in the HER2-low subgroup than in the HER2-zero subgroup (mixed-line: HR = 1.36; 95% CI = 1.11-1.65; P = 0.002; first-line: HR = 1.14; 95% CI = 1.01-1.28; P = 0.04). A similar phenomenon was observed in patients who received mixed-line or post-line Palbociclib and ET (mixed-line: HR = 1.60; 95% CI = 1.09-2.34; P = 0.02; post-line: HR = 1.43; 95% CI = 1.03-2.00; P = 0.03).

Conclusion

These results indicated that HER2-low status did not have a significant association with ORR and OS, but it may have a worse impact on PFS in patients who received mixed-line or first-line CDK4/6i and ET, as well as mixed-line or post-line palbociclib plus ET.

Alteration of HER2 Status During Breast Cancer Progression: A Clinicopathological Analysis Focusing on HER2-Low Status

Recent studies have shown that novel antibody-drug conjugates (ADCs) can improve clinical outcomes in patients with HER2-low breast cancers. This study aimed to investigate alteration of HER2 status during breast cancer progression with an emphasis on HER2-low status. Using 386 paired samples of primary and recurrent breast cancers, HER2 discordance rate between primary and matched recurrent samples, the relationships between HER2 discordance and clinicopathological characteristics and clinical outcomes of the patients were analyzed. HER2 discordance rate between primary breast cancer and first recurrence was 25.9% (κ = 0.586) with mostly zero-to-low (10.6%) or low-to-zero (9.3%) conversion. There was no significant difference in the discordant rates according to type or location of the recurrence. Of 70 cases with a second recurrence, HER2 discordance rate between the primary tumor and the second recurrence was 27.1% (κ = 0.554). HER2 discordance was associated with lower HER2 level, lymphovascular invasion, and progesterone receptor positivity of the primary tumor. In further analyses, HER2-zero-to-low conversion was associated with lymph node metastasis and hormone receptor (HR) positivity, whereas HER2-low-to-zero conversion was associated with HR negativity and triple-negative subtype. In survival analyses, HER2 discordance was associated with decreased overall survival of patients in the HR-positive group but not in the HR-negative group. Furthermore, patients with HER2-low-to-zero converted tumors showed worse overall survival compared with those with HER2-low concordant tumors. In conclusion, HER2 status changes during breast cancer progression in significant proportions, mostly between zero and low status. As HER2 instability increases during progression and affects clinical outcome, HER2 status needs to be reevaluated in recurrent settings.

The Prognostic Impact of HER2-Low and Menopausal Status in Triple-Negative Breast Cancer

TNBC is noted for its aggressive behavior and poor prognosis. Recently developed HER2 target agents have shown potential benefit even in HER2-low expressing breast cancers. This study retrospectively analyzed 2542 non-metastatic TNBC patients from 2008 to 2020, revealing that 26.0% were HER2-low. Data on demographics, tumor characteristics, pathologic complete response (pCR) rates and disease-free survival (DFS), distant metastasis-free survival (DMFS), overall survival (OS), and breast cancer-specific survival (BCSS) were analyzed. The HER2-low group, compared to the HER2-0 group, showed significantly better DFS, DMFS, OS, BCSS (p = 0.0072, p = 0.0096, p = 0.0180, and p = 0.0001, respectively) with older age and higher rates of postmenopausal status (p < 0.0001). No significant differences in pCR rates were observed. Multivariate analyses identified HER2 status as a significant prognostic factor for DFS (p = 0.048), DMFS (p = 0.018), OS (p = 0.049), and BCSS (p = 0.008). Subgroup analysis revealed that these effects varied with menopausal status, showing more pronounced benefits in postmenopausal women. Our findings suggest that HER2-low TNBC patients exhibit a distinct clinical profile and improved survival compared to HER2-0 TNBC patients, especially in postmenopausal patients. Further research on estrogen and HER2 interaction is needed.

HER2-Low Breast Cancer: Now and in the Future

Breast cancer is a heterogeneous disease, and its subtypes are characterized by hormone receptor and human epidermal growth factor receptor 2 (HER2) expression status. "HER2-low" tumors, which exhibit a low level of HER2 expression (immunohistochemistry 1+ or 2+ without gene amplification), were conventionally considered not amenable to anti-HER2 targeting agents based on the results of a phase III trial of trastuzumab. However, this perspective is being challenged by the emergence of novel anti-HER2 antibody-drug conjugates, such as trastuzumab-deruxtecan. These innovative therapies have demonstrated remarkable efficacy against HER2-low breast cancer, shedding new light on a previously overlooked category of breast cancer. Such promising results highlight the need for in-depth investigations of the biology and prognostic implications of HER2-low tumors. In this review, we comprehensively summarize the current evidence surrounding this topic and highlight areas that warrant further exploration and research in the future.

Concordance of HER2 status between core needle biopsy and surgical resection specimens of breast cancer: an analysis focusing on the HER2-low status

BACKGROUND

Human epidermal growth factor receptor 2 (HER2)-low status has recently gained attention because of the potential therapeutic benefits of antibody-drug conjugates (ADCs) in breast cancer patients. We aimed to investigate the concordance of HER2 status between core needle biopsy (CNB) and subsequent surgical resection specimens focusing on the HER2-low status.

METHODS

This retrospective study was conducted in 1,387 patients with invasive breast cancer whose HER2 status was evaluated in both CNB and surgical resection specimens. The discordance rates between CNB and surgical resection specimens and the clinicopathological features associated with HER2 status discordance were analyzed.

RESULTS

The overall concordance rates of HER2 status between CNB and surgical resection specimens were 99.0% (κ = 0.925) for two-group classification (negative vs. positive) and 78.5% (κ = 0.587) for three-group classification (zero vs. low vs. positive). The largest discordance occurred in CNB-HER2-zero cases with 42.8% of them reclassified as HER2-low in surgical resection. HER2 discordance was associated with lower histologic grade, tumor multiplicity, and luminal A subtype. In multivariate analysis, tumor multiplicity and estrogen receptor (ER) positivity were independent predictive factors for HER2-zero to low conversion.

CONCLUSIONS

Incorporation of HER2-low category in HER2 status interpretation reduces the concordance rate between CNB and surgical resection specimens. Tumor multiplicity and ER positivity are predictive factors for conversion from HER2-zero to HER2-low status. Therefore, HER2 status should be re-evaluated in resection specimens when considering ADCs in tumors exhibiting multiplicity and ER positivity.

The Emergence of the Potential Therapeutic Targets: Ultrasound-Based Radiomics in the Prediction of Human Epidermal Growth Factor Receptor 2-Low Breast Cancer

RATIONALE AND OBJECTIVES

To evaluate whether ultrasound-based radiomics features can effectively predict HER2-low expression in patients with breast cancer (BC).

MATERIAL AND METHODS

Between January 2021 and June 2023, patients who received US scans with pathologically confirmed BC in this multicenter study were included. In total, 383 patients from institution 1 were comprised of training set, 233 patients from institution 2 were comprised of validation set and 149 patients from institution 3 were comprised of external validation set. Radiomics features were derived from conventional ultrasound (US) images. The minimum redundancy and maximum relevancy and the least absolute shrinkage and selector operation algorithm were used to generate an US-based radiomics score (RS). Multivariable logistic regression analysis was used to select variables associated with HER2 expressions. The diagnostic performance of the RS was evaluated through the area under the receiver operating characteristic curve (AUC).

RESULTS

In the training set, the RS yield an AUC of 0.81 (95%CI: 0.76-0.84) for differentiation HER2-zero from HER2-low and -positive cases, and performed well in validation set (AUC 0.84, 95%CI: 0.78-0.88) and external validation set (AUC 0.82, 95%CI: 0.73-0.90). In the subgroups analysis, the RS showed good performance in distinguishing HER2-zero from HER2 1 + , HER2 2 + and HER2-low tumors (AUC range, 0.79-0.87).

CONCLUSION

The RS based on conventional US is proven effective for predicting HER2-low expression in BC.

Concordance between pathologists and between specimen types in detection of HER2-low breast carcinoma by immunohistochemistry

CONTEXT

Recent clinical trials indicate that HER2-targeted therapy may benefit HER2-low breast cancer patients including HER2 score 1+ or 2+ and no gene amplification. Concordance between pathologists and between core biopsy and surgical excision in establishing HER2-low status was evaluated.

DESIGN

57 patients with HER2 negative breast cancer (IHC 0, 1+, or 2+, no gene amplification) by core biopsy were included. Core biopsy and representative tumor from corresponding surgical excision was immunostained for HER2. Original HER2 IHC scores were interpreted using 2018 guidelines. Three pathologists independently interpreted again under 2023 guidelines. Kappa statistic evaluated agreement of HER2 IHC scores.

RESULTS

Applying 2023 guidelines, HER2 IHC scores were concordant among study pathologists in 46 of 57 (81 %) core biopsy and 50 of 57 (88 %) surgical resections. Kappa statistics were 0.78 and 0.85 (substantial agreement), for inter-pathologist agreement of core biopsy and surgical resections under 2023 guidelines; 0.55 (moderate agreement) for agreement between first interpretation by 2018 guidelines and second interpretation by 2023 guidelines; and 0.13 (slight agreement) for agreement in HER2 consensus scores between outside core and surgical resection and 0.49 (moderate agreement) for inside core and surgical resection. Low HER2 expression was found in 28 of 57 (49 %) core biopsy and in 25 of 57 (44 %) surgical excisions.

CONCLUSIONS

Interobserver agreement among study pathologists was good in core biopsy and surgical excisions, applying updated 2023 guidelines. Intratumoral heterogeneity in protein expression and preanalytical factors may result in variable identification of HER2-low status in core biopsy and surgical excision specimens.

Clinical significance of KRT7 in bladder cancer prognosis

BACKGROUND

Typically, the overexpressed keratin 7 (KRT7) is considered a validated therapeutic target and prognosis marker in bladder cancer. However, the crucial roles of KRT7 in the clinical prognosis and immune microenvironment in bladder cancer remain unclear.

METHODS

Initially, the expression levels of KRT7 in public databases were analyzed that is,Tumor Immune Estimation Resource (TIMER) 2.0 and Gene Expression Profiling Interactive Analysis (GEPIA). Further, the clinical tissue samples from patients (n = 10 pairs) were collected to confirm the expression trends of KRT7 and detected by immunohistochemistry (IHC) analysis. Meanwhile, the relationship between KRT7 and the prognosis of bladder cancer patients was analyzed by Kaplan-Meier plotter estimation and Cox regression analysis. Finally, TIMER 2.0 and IHC staining analyses were performed to calculate the infiltration abundances of three kinds of immune cells in eligible bladder tumor samples.

RESULTS

The TIMER 2.0 and GEPIA datasets suggested the differences in the expression levels of KRT7 in tumors, in which KRT7 was significantly upregulated in bladder cancer. The KRT7 expression was closely associated with patients' gender, tumor histologic subtypes, T status, and American Joint Committee on Cancer stages. Notably, the increased KRT7 indicated poor overall survival and disease-free survival rates. Moreover, KRT7 expression could be responsible for immune infiltration in the cancer microenvironment of the bladder. Finally, the high expression level of KRT7 increased the presence of regulatory T cells (Tregs) but reduced the infiltration of CD8+ T and natural killer cells.

CONCLUSION

KRT7 as a biomarker potentiated the prediction of bladder cancer prognosis and the immune microenvironment.

Neoadjuvant chemotherapy efficacy and prognosis in HER2-low and HER2-zero breast cancer patients by HR status: a retrospective study in China

Background

The promising efficacy of novel anti-HER2 antibody-drug conjugates (ADC) in HER2-low breast cancer has made HER2-low a research hotspot. However, controversy remains regarding the neoadjuvant chemotherapy (NAC) efficacy, prognosis, and the relationship with hormone receptor (HR) status of HER2-low.

Methods

A retrospective analysis was conducted on 975 patients with HER2-negative breast cancer undergoing NAC at Tianjin Medical University Cancer Institute and Hospital, evaluating pathological complete response (pCR) rate and prognosis between HER2-low and HER2-zero in the overall cohort and subgroups.

Results

Overall, 579 (59.4%) and 396 (40.6%) patients were HER2-low and HER2-zero disease, respectively. Compared with HER2-zero, the HER2-low cohort consists of more postmenopausal patients, with lower histological grade and higher HR positivity. In the HR-positive subgroup, HER2-low cases remain to exhibit lower histological grade, while in the HR-negative subgroup, they show higher grade. The HER2-low group had lower pCR rates than the HER2-zero group (16.4% vs. 24.0%). In the HR-positive subgroup, HER2-low consistently showed lower pCR rate (8.1% vs. 15.5%), and served as an independent suppressive factor for the pCR rate. However, no significant difference was observed in the pCR rates between HER2-low and HER2-zero in the HR-negative breast cancer. In the entire cohort and in stratified subgroups based on HR and pCR statuses, no difference in disease-free survival were observed between HER2-low and HER2-zero.

Conclusions

In the Chinese population, HER2-low breast cancer exhibits distinct characteristics and efficacy of NAC in different HR subgroups. Its reduced pCR rate in HR-positive subgroup is particularly important for clinical decisions. However, HER2-low is not a reliable factor for assessing long-term survival outcomes.

HER2-Low Luminal Breast Carcinoma Is Not a Homogenous Clinicopathological and Molecular Entity

BACKGROUND

With the development of some new antibody-drug conjugates, the HER2 classification of breast carcinomas now includes the HER2-low (H2L) category: IHC 1+, 2+ non-amplified by ISH, and double-equivocal carcinomas, mostly luminal, expressing hormone receptors (HR+).

METHODS

We analyzed mutational status and transcriptomic activities of three HER2 effector pathways: PI3K-AKT, MAPK, and JAK-STAT, in association with clinicopathologic features, in 62 H2L carcinomas compared to 43 HER2-positive and 20 HER2-negative carcinomas, all HR+.

RESULTS

H2L carcinomas had significantly lower histoprognostic grades and mitotic and Ki67 proliferation indexes than HER2-positive carcinomas. Their PIK3CA mutation rates were close to those of HER2-negative and significantly higher than in HER2-positive carcinomas, contrary to TP53 mutations. At the transcriptomic level, we identified three distinct groups which did not reflect the new HER2 classification. H2L and HER2-negative carcinomas shared most of clinicopathological and molecular characteristics, except HER2 membrane expression (mRNA levels). The presence of a mutation in a signaling pathway had a strong pathway activation effect. PIK3CA mutations were more prevalent in H2L carcinomas, leading to a strong activation of the PI3K-AKT signaling pathway even in the absence of HER2 overexpression/amplification.

CONCLUSION

PIK3CA mutations may explain the failure of conventional anti-HER2 treatments, suggesting that new antibody-drug conjugates may be more effective.

Molecular and Clinical Portrait of HER2-low Invasive Lobular Carcinomas

Invasive lobular carcinomas (ILCs) have a low frequency of ERBB2 amplification, therefore restricting the use of conventional anti-HER2 therapies for this histologic special type. Conversely, ILCs with low HER2 overexpression may represent a broader target for the use of emerging antibody drug conjugate therapies targeting HER2, since these treatments have proven effective in HER2-low breast cancers. Very scarce data about HER2-low ILCs have been so far published, although these tumors could have different prevalence and histomolecular specificities compared with invasive breast carcinoma of no special type (IBC-NST). Our aims in that context were to decipher the clinicopathological and molecular features of a large series of HER2-low ILCs. Comparative evaluation of HER2-low prevalence was done based on a retrospective series of 7970 patients from Institut Curie, with either primary invasive lobular (N = 1103) or no special type (N = 6867) invasive carcinoma. Clinicopathological and molecular analyses of HER2-zero, HER2-low, and HER2-positive ILCs were performed on a subgroup of 251 patients who underwent surgery for a primary ILC between 2005 and 2008. The mutational profile of these 251 cases was determined from RNAseq data. Compared with HER2-negative IBC-NSTs, the HER2-negative ILCs were found to display a higher frequency of HER2-zero cases (59.4% vs 53.7%) and a lower frequency of HER2-low (40.6% vs 46.3%) (P < .001). Clinicopathological features associated with HER2-low status (vs HER2-zero) in ILC were older age, postmenopausal status, nonclassic ILC histological types, higher grade, proliferation, and estrogen receptor expression levels. Survival curve analysis showed a significantly lower risk of local recurrence for HER2-low (vs HER2-zero) ILCs, but no association was found between HER2 status and either breast cancer-specific survival or distant metastasis-free interval. ERBB3 was the unique mutated gene exclusively associated with HER2-low ILCs yet being mutated at a low frequency (7.1%) (false discovery rate < 0.05). In conclusion, HER2-low ILCs exhibit their own particularities, both on clinical-pathological and molecular levels. Our findings call for larger multicenter validation studies.

Navigating HER2-Low Testing in Invasive Breast Cancer: Update Recommendations for Pathologists

The article discusses the importance of accurately distinguishing HER2-low from HER2-negative breast cancer, as novel ADCs have demonstrated activity in a large population of patients with HER2-low-expressing BC. While current guidelines recommend a dichotomous classification of HER2 as either positive or negative, the emergence of the HER2-low concept calls for standardization of HER2 testing in breast cancer, using currently available assays to better discriminate HER2 levels. This review covers the evolution and latest updates of the ASCO/CAP guidelines relevant to this important biomarker in breast cancer, including still-evolving concepts such as HER2 low, HER2 heterogeneity, and HER2 evolution. Our group presents the latest Mexican recommendations for HER2 status evaluation in breast cancer, considering the ASCO/CAP guidelines and introducing the HER2-low concept. In the era of personalized medicine, accurate HER2 status assessment remains one of the most important biomarkers in breast cancer, and the commitment of Mexican pathologists to theragnostic biomarker quality is crucial for providing the most efficient care in oncology.

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.

Do HER2-Low Tumors Have a Distinct Clinicopathologic Phenotype?

BACKGROUND

Breast cancer subtypes, distinguished by hormone receptor (HR) and HER2 status, have different clinicopathologic features. With recognition of the clinical relevance of HER2-low, there is debate as to whether this is a distinct subtype. Our study aimed to determine whether HER2-low breast cancers have specific clinicopathologic features that differ from those of HER2-negative and HER2-positive cancers.

PATIENTS AND METHODS

A total of 11,072 patients undergoing upfront surgery from 1998 to 2010 were identified from a single-institution prospectively maintained database. HER2 status was classified by immunohistochemistry (IHC)/fluorescence in situ hybridization (FISH) as HER2 negative (41.2%), HER2 low (45%; IHC 1+ or 2+ with negative FISH), and HER2 positive (13.7%), and stratified by HR status. Univariate (UVA) and multivariable multinomial logistic regression analysis (MVA) were performed to determine associations among variables and subtypes.

RESULTS

Compared with HER2-negative tumors, HER2 low was associated with lymphovascular invasion [odds ratio (OR) 1.2, 95% confidence interval (CI) 1.06-1.36; p = 0.003], multifocality (OR 1.26, 95% CI 1.12-1.42; p < 0.001), nodal micrometastasis (OR 1.15, 95% CI 1.02-1.31; p = 0.024), and lower rates of ≥ 3 positive nodes (OR 0.77, 95% CI 0.66-0.90, p = 0.001). When stratified by HR expression, in both HR-positive and HR-negative tumors, age and multifocality were associated with HER2 low on UVA. On MVA, no variables were independently associated with both HR-negative and HR-positive/HER2-low tumors compared with HER2-negative tumors. In contrast, HER2-positive tumors, regardless of HR status, were associated with multifocality and an extensive intraductal component.

CONCLUSION

Clinicopathologic features of HER2-low tumors appear to be primarily related to HR status. Our findings do not support the characterization of HER2 low as a separate subtype.

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.

Clinicopathological characteristics and value of HER2-low expression evolution in breast cancer receiving neoadjuvant chemotherapy

OBJECTIVE

The present study aimed to evaluate the clinicopathological characteristics and value of HER2-low expression evolution in breast cancer receiving neoadjuvant chemotherapy (NAC).

METHODS

Patients with HER2 negative breast cancer receiving NAC from January 2017 to December 2020 were enrolled in this study. The clinicopathological characteristics, response to NAC, evolution of HER2 and prognostic value were retrospectively analyzed.

RESULTS

410 patients were included. The proportion of HR positive disease in HER2-low cases was higher than in HER2-zero population (75.8 % vs. 65.8 %, P = 0.040). No statistical significant difference in pCR rate was observed between HER2-low and HER2-zero patients (33.8 % vs. 39.3 %, P = 0.290) when pCR was defined as ypTis/0ypN0. Exploratory analysis revealed that the pCR rate of HER2-low cases was significantly lower than HER2-zero patients in the entire population (19.8 % vs. 33.3 %, P = 0.004) and HR positive population (12.6 % vs. 29.9 %, P = 0.001) when pCR was defined as ypT0ypN0. The evolution rate of HER2 expression after NAC was 31.0 % in HER2-zero patients and 24.7 % in HER2-low patients. Compared with patients with HR positive disease, patients with TNBC had higher evolution rate of HER2 expression after NAC (37.7 % vs. 23.6 %). Significant association was observed between HER2 evolution with histology type and Ki-67 index in HER2-zero patients and with lymph node involvement, HR status and Ki-67 index in HER2-low patients. Prognostic impact of HER2 evolution was not observed.

CONCLUSIONS

HR positive and HR negative HER2-low breast cancer exhibit different clinicopathological features, response to NAC and HER2 evolution after treatment.

New insights into HER2-low breast cancer brain metastasis: A retrospective analysis

BACKGROUND

A considerable number of patients with breast cancer will suffer from brain metastasis in the advanced setting. The HER2 status serves as a significant prognostic factor and the reference of applying treatment for patients with breast cancer brain metastasis (BCBM).

METHODS

Between January 2010 and July 2021, patients with BCBM who had available HER2 status were identified. The patients with HER2 1+ in immunohistochemistry (IHC) or IHC 2+ and fluorescence in situ hybridization (FISH) negative were categorized as HER2-low. Comparisons were conducted between the HER2-low and HER2-zero population. The primary endpoint was overall survival (OS) after the diagnosis of BCBM. Survival outcomes were assessed using Kaplan-Meier curves with log-rank test and Cox proportional hazards model.

RESULTS

In this study, we analyzed 71 patients with the HER2-low breast cancer subtype and 64 patients with the HER2-zero subtype. Despite the limited sample size, our findings revealed a significantly better OS for patients with HER2-low cancer compared to their HER2-zero counterparts (26 m vs 20 m, p = 0.0017). This trend was particularly notable in the HR-negative group (26 m vs 13 m, p = 0.0078), whereas no significant difference was observed among the HR-positive patients. Furthermore, Cox regression analysis revealed that the HER2-low status was an independent prognostic factor for better survival in the HR-negative patients (p = 0.046 in multivariate analysis).

CONCLUSIONS

Patients diagnosed with HER2-low BCBM exhibited a more favorable prognosis than those with HER2-zero BCBM, particularly within the HR-negative subgroup. The low expression of HER2 is supposed to be linked to the prolonged survival of BCBM patients.

Emerging Landscape of Targeted Therapy of Breast Cancers With Low Human Epidermal Growth Factor Receptor 2 Protein Expression

CONTEXT.—

Human epidermal growth factor receptor 2 (HER2) status in breast cancer is currently classified as negative or positive for selecting patients for anti-HER2 targeted therapy. The evolution of the HER2 status has included a new HER2-low category defined as an HER2 immunohistochemistry score of 1+ or 2+ without gene amplification. This new category opens the door to a targetable HER2-low breast cancer population for which new treatments may be effective.

OBJECTIVE.—

To review the current literature on the emerging category of breast cancers with low HER2 protein expression, including the clinical, histopathologic, and molecular features, and outline the clinical trials and best practice recommendations for identifying HER2-low-expressing breast cancers by immunohistochemistry.

DATA SOURCES.—

We conducted a literature review based on peer-reviewed original articles, review articles, regulatory communications, ongoing and past clinical trials identified through ClinicalTrials.gov, and the authors' practice experience.

CONCLUSIONS.—

The availability of new targeted therapy potentially effective for patients with breast cancers with low HER2 protein expression requires multidisciplinary recognition. In particular, pathologists need to recognize and identify this category to allow the optimal selection of patients for targeted therapy.

cGAS-STING pathway expression correlates with genomic instability and immune cell infiltration in breast cancer

Genomic instability, as caused by oncogene-induced replication stress, can lead to the activation of inflammatory signaling, involving the cGAS-STING and JAK-STAT pathways. Inflammatory signaling has been associated with pro-tumorigenic features, but also with favorable response to treatment, including to immune checkpoint inhibition. In this study, we aim to explore relations between inflammatory signaling, markers of replication stress, and immune cell infiltration in breast cancer. Expression levels of cGAS-STING signaling components (STING, phospho-TBK1, and phospho-STAT1), replication stress markers (γH2AX and pRPA), replication stress-related proto-oncogenes (Cyclin E1 and c-Myc) and immune cell markers (CD20, CD4, and CD57) are determined immunohistochemically on primary breast cancer samples (n = 380). RNA-sequencing data from TCGA (n = 1082) and METABRIC (n = 1904) are used to calculate cGAS-STING scores. pTBK1, pSTAT1 expression and cGAS-STING pathway scores are all increased in triple-negative breast cancers compared to other subtypes. Expression of γH2AX, pRPA, Cyclin E1, c-Myc, and immune cell infiltration positively correlate with p-STAT1 expression (P < 0.001). Additionally, we observe significant positive associations between expression of pTBK1 and γH2AX, pRPA, c-Myc, and number of CD4+ cells and CD20+ cells. Also, cGAS-STING scores are correlated with genomic instability metrics, such as homologous recombination deficiency (P < 0.001) and tumor mutational burden (P < 0.01). Moreover, data from the I-SPY2 clinical trial (n = 71) confirms that higher cGAS-STING scores are observed in breast cancer patients who responded to immunotherapy combined with chemotherapy. In conclusion, the cGAS-STING pathway is highly expressed in TNBCs and is correlated with genomic instability and immune cell infiltration.

Clinicopathological features and prognostic analysis of HER2 low and fibrotic focus in HER2-negative breast cancer

OBJECTIVE

The aim of this study is to evaluate the clinicopathological features and prognostic significance of HER2 low, fibrotic focus (FF), and tumor-infiltrating lymphocytes (TILs) in patients with HER2-negative breast cancer.

METHODS

We retrospectively reviewed the data of 293 patients with HER2-negative, stage I-II, invasive breast cancer of non-specific types. The HER2-negative cases were classified into HER2 low and HER2 0. Digital analysis of hematoxylin-eosin stained whole slide images was used to evaluate the FF expression. TILs were also evaluated using the Whole Slide Image. Furthermore, the association between HER2 low, FF, and TILs as well as their prognostic significance were analyzed.

RESULTS

The study cohort included 178 cases (60.8%) with HER2 low and 115 cases (39.2%) with HER2 0. Older age, lower Nottingham histological grade (NHG), estrogen receptor (ER) positivity, progesterone receptor (PR) positivity, and hormone receptor (HR) positivity were all associated with HER2 low. FF was correlated with older age, intermediate and low NHG, vascular invasion, HR positivity, HER2 low status, high Ki67 expression, and low TILs. Univariate survival analysis showed that FF was significantly associated with shorter progression-free survival (PFS). Stratified analysis indicated that in the HR-negative and HR-positive groups, HER2 status and TILs did not affect PFS. DFS was longer in patients without FF compared to those with FF in the HR-positive (hazard ratio [HR] = 0.313) and HER2 low (HR = 0.272) groups. DFS was also significantly longer in patients without FF compared to those with FF in the HR-negative (HR = 0.069) and HER2 0 groups (HR = 0.129).

CONCLUSION

The results indicated that the HER2 low status and the TILs expression did not impact prognosis. However, patients with FF exhibited distinct biological characteristics and prognostic significance, particularly in the HR-negative and HER2 0 groups. This provides a rationale for accurate diagnosis and treatment of HER2-negative breast cancer.

Standardized pathology report for HER2 testing in compliance with 2023 ASCO/CAP updates and 2023 ESMO consensus statements on HER2-low breast cancer

Since the release of the DESTINY-Breast04 (DB-04) trial findings in June 2022, the field of pathology has seen a renaissance of HER2 as a predictive biomarker in breast cancer. The trial focused on patients with metastatic breast cancer who were classified as "HER2-low," i.e., those with immunohistochemistry (IHC) HER2 1 + or 2 + and negative in situ hybridization (ISH) results. The study revealed that treating these patients with trastuzumab deruxtecan (T-DXd) instead of the oncologist's chosen chemotherapy led to outstanding improvements in survival. This has challenged the existing binary HER2 pathological classification system, which categorized tumors as either positive (overexpression/amplification) or negative, as per the ASCO/CAP 2018 guideline reaffirmed by ASCO/CAP 2023 guideline update. Given that DB-04 excluded patients with HER2 IHC score 0 status, the results of the ongoing DB-06 trial may shed further light on the potential benefits of T-DXd therapy for these patients. Roughly half of all breast cancers are estimated to belong to the HER2-low category, which does not represent a distinct or specific subtype of cancer. Instead, it encompasses a diverse group of tumors that exhibit clinical, morphological, immunohistochemical, and molecular variations. However, HER2-low offers a distinctive biomarker status that identifies a specific therapeutic regimen (i.e., T-DXd) linked to a favorable prognosis in breast cancer. This unique association emphasizes the importance of accurately identifying these tumors. Differentiating between a HER2 IHC score 0 and score 1 + has not been clinically significant until now. To ensure accurate classification and avoid misdiagnosis, it is necessary to adopt standardized procedures, guidelines, and specialized training for pathologists in interpreting HER2 expression in the lower spectrum. Additionally, the utilization of artificial intelligence holds promise in supporting this endeavor. Here, we address the current state of the art and unresolved issues in assessing HER2-low status, with a particular emphasis on the score 0. We explore the dilemma surrounding the exclusion of HER2-zero patients from potentially beneficial therapy based on traditional HER2 testing. Additionally, we examine the clinical context, considering that DB-04 primarily involved heavily pretreated late-stage metastatic breast cancers. We also delve into emerging evidence suggesting that extrapolating HER2-low status from the original diagnosis may lead to misleading results. Finally, we provide recommendations for conducting high-quality testing and propose a standardized pathology report in compliance with 2023 ASCO/CAP updates and 2023 ESMO consensus statements on HER2-low breast cancer.

An Analysis of Clinical and Pathologic Features, RecurIndex Genomic Profiles, and Survival Outcomes in HER2-Low Breast Cancer

BACKGROUND

In recent years, breast cancer has become the most common cancer in the world, increasing women's health risks. Approximately 60% of breast cancers are categorized as human epidermal growth factor receptor 2 (HER2)-low tumors. Recently, antibody-drug conjugates have been found to have positive anticancer efficacy in patients with HER2-low breast cancer, but more studies are required to comprehend their clinical and molecular characteristics.

METHODS

In this study, we retrospectively analyzed the data of 165 early breast cancer patients with pT1-2N1M0 who had undergone the RecurIndex testing. To better understand HER2-low tumors, we investigated the RecurIndex genomic profiles, clinicopathologic features, and survival outcomes of breast cancers according to HER2 status.

RESULTS

First, there were significantly more hormone receptor (HR)-positive tumors, luminal-type tumors, and low Ki67 levels in the HER2-low than in the HER2-zero. Second, RI-LR (P = .0294) and RI-DR (P = .001) scores for HER2-low and HER2-zero were statistically significant. Third, within HER2-negative disease, HR-positive/HER2-low tumors showed highest ESR1, NFATC2IP, PTI1, ERBB2, and OBSL1 expressions. Fourth, results of the survival analysis showed that lower expression of HER2 was associated with improved relapse-free survival for HR-positive tumors, but not for HR-negative tumors.

CONCLUSIONS

The present study highlights the unique features of HER2-low tumors in terms of their clinical characteristics as well as their gene expression profiles. HR status may influence the prognosis of patients with HER2-low expression, and patients with HR-positive/HER2-low expression may have a favorable outcome.

Characterisation of luminal and triple-negative breast cancer with HER2 Low protein expression

BACKGROUND

Breast cancer (BC) expressing low levels of human epidermal growth factor receptor 2 (HER2 Low) is an emerging category that needs further refining. This study aims to provide a comprehensive clinico-pathological and molecular profile of HER2 Low BC including response to therapy and patient outcome in the adjuvant and neoadjuvant settings.

METHODS

Two different independent and well-characterised BC cohorts were included. Nottingham cohort (A) (n = 5744) and The Cancer Genome Atlas (TCGA) BC cohort (B) (n = 854). The clinical, molecular, biological and immunological profile of HER2 Low BC was investigated. Transcriptomic and pathway enrichment analyses were performed on the TCGA BC cohort and validated through next-generation sequencing in a subset of Nottingham cases.

RESULTS

Ninety percent of HER2 Low tumours were hormone receptor (HR) positive (HR+), enriched with luminal intrinsic molecular subtype, lacking significant expression of HER2 oncogenic signalling genes and of favourable clinical behaviour compared to HER2 negative (HER2-) BC. In HR+ BC, no significant prognostic differences were detected between HER2 Low and HER2- tumours. However, in HR- BC, HER2 Low tumours were less aggressive with longer patient survival. Transcriptomic data showed that the majority of HR- /HER2 Low tumours were of luminal androgen receptor (LAR) intrinsic subtype, enriched with T-helper lymphocytes, activated dendritic cells and tumour associated neutrophils, while most HR-/HER2- tumours were basal-like, enriched with tumour associated macrophages.

CONCLUSION

HER2 Low BC is mainly driven by HR signalling in HR+ tumours. HR-/HER2 Low tumours tend to be enriched with LAR genes with a unique immune profile.

Integrated Molecular Characterization of HER2-Low Breast Cancer Using Next Generation Sequencing (NGS)

Based on immunohistochemistry (IHC) and in situ hybridization (ISH), HER2-low breast cancers (BC) subtype-defined as IHC1+ or IHC2+/ISH- tumors-emerged and represent more than half of all BC. We evaluated the performance of NGS for integrated molecular characterization of HER2-low BC, including identification of actionable molecular targets, copy number variation (CNV), and microsatellite instability (MSI) analysis. Thirty-one BC specimens (11 HER2+, 10 HER2-, and 10 HER2-low) were routinely analyzed using IHC and ISH, and were selected and analyzed using NGS for gene mutations including ESR1, PIK3CA, AKT1, ERBB2, TP53, BRCA1, and BRCA2, CNV, and MSI. CNV values for the ERBB2 gene were significantly (p < 0.001) different between HER2+, and either HER2-low or HER2- tumors with mean values of 7.8 (SD = 6.8), 1.9 (SD = 0.3), and 2.0 (SD = 0.3), respectively. Using 3.25 as the cutoff value, 96.8% overall concordance of HER2 status was achieved between IHC and NGS compared to IHC and ISH. Using NGS, gene mutations and amplifications were detected in 68% (21/31) and 19% (6/31) of the cases, respectively. One case of MSI was detected in a HER2-negative and ISH unamplified case. Beside IHC, NGS allows the identification of HER2-low subtype simultaneously, with the detection of multiple actionable gene mutations being helpful for molecular board treatment selection.

The Impact of HER2-Low Expression on Oncologic Outcomes in Hormone Receptor-Positive Breast Cancer

Breast cancer is a prevalent malignancy with increasing incidence, particularly in Asian countries. Classification based on estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status is pivotal in determining treatment. Recent advances have challenged the traditional dichotomy in HER2 classification, prompting investigation into the HER2-low subtype's characteristics and outcomes. This retrospective study analyzed 10,186 non-metastatic hormone receptor (HR)-positive, HER2-negative breast cancer cases treated from 2008 to 2020. Data encompassed clinical, pathological, and treatment information. Oncologic outcomes included disease-free survival (DFS), overall survival (OS), and breast cancer-specific survival (BCSS). In total, 56.5% were HER2-low cases. Differences in patient characteristics were noted, with more BRCA1/2 mutations and higher mastectomy rates in the HER2-low group (p = 0.002, p < 0.001, respectively). Fewer received adjuvant chemotherapy or radiation therapy, and fewer histologic and nuclear grade 1 tumors were identified (all p < 0.001). With a median follow-up of 64 months (range: 13-174), HER2-low cases exhibited better DFS, OS, and BCSS than HER2-0 cases (p = 0.012, p = 0.013, and p = 0.013, respectively). Notably, the prognosis differed between premenopausal and postmenopausal subgroups, with BCSS benefitting premenopausal patients (p = 0.047) and DFS and OS benefitting postmenopausal patients in the HER2-low group (p = 0.004, p = 0.009, respectively). Multivariate analysis confirmed HER2 status as an independent predictor of these outcomes (p = 0.010, p = 0.008, and p = 0.014, respectively). This extensive single-center study elucidates the favorable prognosis associated with HER2-low status in HR-positive breast cancer. However, this effect differs among premenopausal and postmenopausal patients, necessitating further research into the underlying tumor biology.

Is HER2 ultra-low breast cancer different from HER2 null or HER2 low breast cancer? A study of 1363 patients

OBJECTIVE

This study aims to analyze whether there are any differences in clinicopathological features and prognosis between HER2 ultra-low, HER2-null, and HER2-low expression in Chinese breast cancer (BC) patients.

METHODS

The clinicopathological data of 1363 HER2-negative BC patients were retrospectively collected (from January 2018 to December 2019). HER2 status was further classified into HER2-null, HER2 ultra-low, and HER2-low. HER2-null expression is defined as infiltrating cancer cells completely free of staining. HER2 ultra-low expression is defined as ≤10% of infiltrating cancer cells showing incomplete and faint/weak membrane staining. HER2-low expression is defined as HER2 immunohistochemistry (IHC) 1+ or 2+ with negative in situ hybridization (ISH) assay.

RESULTS

Of 1363 patients, there were 86 (6.3%) HER2-null patients, 395 (29.0%) HER2 ultra-low patients, and 882 (64.7%) HER2-low patients. HER2 ultra-low patients were different from HER2-low patients in terms of N stage, hormone receptor (HR) status, Ki-67 expression, and type of surgery. There were also significant differences in histologic type and postoperative endocrine therapy between HER2 ultra-low and HER2-null patients. HR+ (81.0%) tumors was more common than HR- (19.0%) in HER2 ultra-low patients. In addition, there was a significant difference in HR status between HER2 ultra-low and HER2-low patients (P = 0.001). The survival analysis showed that HER2 status had no effect on disease-free survival (DFS) in HER2-negative patients (all P > 0.05). However, regardless of HER2 status, HR+ patients had better DFS than HR- patients (P = 0.003). Cox multivariate analysis revealed that age (HR [95% CI] = 0.950 [0.928, 0.972], P < 0.001), HR status (HR [95% CI] = 3.342 [1.658, 6.736], P = 0.001), and postoperative endocrine therapy (HR [95% CI] = 0.048 [0.048, 0.023], P < 0.001) were important influencing factors of DFS in HER2-negative BC patients.

CONCLUSION

HER2 ultra-low BC patients demonstrated distinct clinicopathological features from HER2-null and HER2-low tumors; while, HER2 status (null, ultra-low, or low) had no prognostic value in these HER2-negative BC population. Consistent with the published literature, HR status was an independent prognostic factor for DFS in HER2-negative BC patients.

The Significance of Recognition of Human Epidermal Growth Factor 2 Low in Breast Cancer Therapy

In response to recent clinical trials that demonstrate the clinical benefit of antibody-drug conjugate drug therapy in breast cancer (BC) with human epidermal growth factor 2 (HER2) immunohistochemical scores of 1+ or 2+ and negative in situ hybridization results, a new concept of "HER2-low BC" has emerged to describe this newly relevant therapeutic category of BC. Clinical recognition of HER2-low BC has caused a paradigm shift in the therapeutic landscape and management of patients with BC and resulted in rapid changes in clinical practice guidelines. In addition the American Society of Clinical Oncology-College of American Pathologists (ASCO-CAP) recently updated their HER2 Guidelines Recommendations to specifically address HER2-low BC. A literature search in PubMed of peer-reviewed articles, regulatory communications, and relevant practice guidelines pertaining to HER2-low BC was conducted. In this review, we have summarized current published knowledge regarding the clinicopathologic and molecular features, diagnostic criteria, and most current guideline recommendations regarding HER2-low BC, and also highlight ongoing practical and diagnostic challenges when identifying HER2-low BC in routine clinical practice.

The dynamics of HER2-low expression during breast cancer progression

PURPOSE

Low HER2 expression is emerging as an actionable target for the treatment of breast cancer (BC) with the antibody drug conjugate Trastuzumab deruxtecan. The aim of the study was to characterize the dynamics of HER2 expression during BC progression.

METHODS

We evaluated the evolution of HER2 expression in 171 paired primary and metastatic BCs (pBCs/mBCs) by including the HER2-low category.

RESULTS

The proportions of HER2-low cases were 25.7% in pBCs and 23.4% in mBCs, respectively, while those of HER2-0 cases were 35.1% and 42.7%, respectively. The overall conversion rate between HER2-0 and HER2-low was 31.7%. HER2-low switching to HER2-0 was more frequent than the reverse (43.2% vs. 23.3%; P = 0.03). Two (3.3%) and 9 (20.5%) cases of pBCs with a HER2-0 and a HER2-low status, respectively, were converted to HER2-positive mBCs. In contrast, 10 (14.9%) HER2-positive pBCs were converted to HER2-0 and an identical number to HER2-low mBCs, respectively, significantly higher than that when compared to the HER2-0 to HER2-positive (P = 0.03), but not HER2-low to HER2-positive conversion. No significant difference was found when comparing the conversion rates among the common organs of relapse. Of the 17 patients with multiorgan metastases, 41.2% had discordance among the different sites of relapse.

CONCLUSIONS

HER2-low BCs constitute a heterogeneous group of tumors. Low HER2 expression is dynamic, with significant discordance between primary tumors and advanced disease as well as the distant sites of relapse. Repeat biomarker studies from advanced disease are warranted in making appropriate treatment plans in the pursuit of precision medicine.

Clinical Genetic Features and Neoadjuvant Chemotherapy Response in HER2-Low Breast Cancers: A Retrospective, Multicenter Cohort Study

BACKGROUND

The objective of this work is to reveal differences in clinical and genetic features, as well as neoadjuvant chemotherapy (NAC) response, between HER2-low and HER2-zero or HER2-positive breast cancers.

PATIENTS AND METHODS

A total of 245 female patients with breast cancer were retrospectively enrolled from seven hospitals. Core needle biopsy (CNB) samples were collected before NAC and used for next-generation sequencing by a commercial gene panel. Clinical and genetic features, as well as NAC response, were compared between HER2-low and HER2-zero or HER2-positive breast cancers. The nonnegative matrix factorization (NMF) method was applied to cluster the C-Score of enrolled cases to reveal the intrinsic features of each HER2 subgroup.

RESULTS

A total of 68 (27.8%) cases are HER2-positive, 117 (47.8%) cases are HER2-low, and 60 (24.5%) cases are HER2-zero. HER2-low breast cancers have a significantly lower pathologic complete response (pCR) rate than HER2-positive and HER2-zero breast cancers (p < 0.050 for all comparisons). Compared with HER2-low breast cancers, HER2-positive cases have higher rates of TP53 mutation, TOP2A amplification, and ERBB2 amplification, as well as lower rates of MAP2K4 mutation, ESR1 amplification, FGFR1 amplification, and MAPK pathway alteration (p < 0.050 for all comparisons). After clustering HER2-low cases by the NMF method, 56/117 (47.9%) are in cluster 1, 51/117 (43.6%) are in cluster 2, and 10/117 (8.5%) are in cluster 3. HER2-low cases in cluster 2 have the lowest pCR rate among the three clusters (p < 0.050).

CONCLUSIONS

HER2-low breast cancers have significant genetic differences from HER2-positive cases. Genetic heterogeneity exists in HER2-low breast cancers and impacts on NAC response in this subgroup.