Clinicopathological Characteristics and Prognosis of HER2-Low Early-Stage Breast Cancer: A Single-Institution Experience

The efficacy of trastuzumab-deruxtecan for the treatment of patients with advanced HER2-low breast cancer

INTRODUCTION

Until recently, the available human receptor epidermal growth factor 2 (HER2) targeted agents were ineffective for treating patients with HER2-low expressing breast cancer (defined as immunohistochemical expression of 1+ or 2+ without amplification). The development of novel and potent HER2-directed antibody-drug conjugates, affective at treating HER2-low expressing breast cancers, have changed the way we think about HER2-low expression and expanded the treatment options for many patients with advanced disease.

AREAS COVERED

In this review, we summarize the current management of HER2-low breast cancer and commonly encountered challenges such as treatment sequencing and toxicity management.

EXPERT OPINION

trastuzumab deruxtecan (T-DXd) is a treatment option for patients with advanced, HER2-low breast cancer, irrespective of the hormone receptor status. The current optimal place in treatment algorithms is after the first line of chemotherapy, both in HR-positive and triple-negative breast cancer; however, other agents are available in this setting and risks and benefits for each should be considered in shared decision making. Up to 10-15% of patients receiving T-DXd develop interstitial lung disease. Patient and clinician education are key to safely implement T-DXd in clinical practice.

HER2-low non-metastatic breast cancer in Qatar-a nationwide retrospective cohort study to evaluate the response to neoadjuvant chemotherapy: a real-world analysis

Globally, breast cancer is the most prevalent cancer and one of the leading causes of cancer-related death among women. HER2-low breast cancer represents a recently identified molecular category within breast cancer characterized by tumors displaying only slight overexpression of HER2 or lacking gene amplification. To illustrate, HER2-low tumors typically have an IHC (immune histochemistry) score of 1+ or 2+ with negative amplification. Nonetheless, recent findings indicate that even a slight amplification of HER2 could notably influence both therapeutic responses and prognostic outcomes. Our study aims to unveil the impact of HER2-low expression on the response to anthracycline and taxane-based neoadjuvant chemotherapy (NACT) in comparison to the HER2-negative group in non-metastatic breast cancer. This is a retrospective cohort study. All patients' profiles with non-metastatic, HER2-low, and HER2-negative breast cancers who were administered neo-adjuvant chemotherapy and had surgery performed within the period spanning from 1 January 2018 to 30 August 2022 were enrolled. HER2-positive breast cancer patients were excluded. The evaluation of patients' responses was conducted through the examination of surgical pathology reports to compare the two study groups (HER2-low and HER2-negative). The primary objective was evaluating the response to NACT comparing the objective response rate (ORR) in each of the two groups of HER2-low and HER2-negative patients. The total number of patients included was 262 patients; the majority were HER2-low 89% (233/262) vs. 11% (29/262) HER2-negative. An ORR (complete and partial response) to NACT was shown in 71% (185/262) of all patients. The ORR was similar in both groups, 70% (164/233) in the HER2-low group vs. 73% (21/29) in the HER2-negative group, with a statistical difference, OR: 1 (95% CI: 0.8-1), p-value 0.8. Similarly, the pathological complete response (pCR) rate was the same in both study groups at 14%, OR: 0.7 (95% CI: 0.2-3), p-value: 0.6. Interestingly, patients with hormone-positive tumors across both study groups had a higher response rate compared to hormone-negative patients. In the HER2-low cohort, the ORR was higher in patients with hormone-positive tumors in comparison with those with hormone-negative tumors [73% vs. 27%, OR: 0.8 (95% CI:0.8-1), p-value: 0.001]. Comparatively, in the HER2-negative cohort, ORR was also higher in patients with hormone-positive tumors compared to hormone-negative tumors [52% vs. 48%, OR: 2 (95% CI: 1-5), p-value: 0.05]. Subsequently, the ORR of all hormone-positive tumors with a positive outcome (CR or PR) was assessed categorizing the patients based on their HER2 expression. Concerning patients who expressed partial response (N = 115), a statistically significant difference was observed in HER2- low hormone-positive tumors as opposed to HER2-negative hormone-positive tumors [90% vs. 10%, OR: 0.7 (95% CI: 0.5-0.9), p-value: 0.001]. Remarkably, all patients with complete responses were from the HER2-low cohort. Our findings demonstrated a significant influence of HER2-low expression on the response to neoadjuvant chemotherapy among patients with hormone-positive HER2-low breast cancer within the studied cohort. Further studies are needed to evaluate the influence of hormonal expression on the response rate to NACT in the HER2-low patients in our population.

Prognostic Impact of HER2 Low Status in Male Breast Cancer: Prospective Cohort Analysis

BACKGROUND

Male breast cancer (MBC) is a rare disease, and the potential influence of low expression of human epidermal growth factor receptor 2 (HER2 low) remains unexplored.

METHODS

In this prospective cohort study, we evaluated 870 patients treated for MBC between May 2009 and June 2023 to assess HER2 low status and its prognostic implications.

RESULTS

With a median follow-up of 43 months (range 1-175 months), 659 eligible patients were categorized into three groups based on HER2 status: 501 (76%) HER2 low, 81 (12.3%) HER2 zero, and 77 (11.7%) HER2 positive. HER2 positivity correlated with younger age, higher proliferation index, non-specific type histology, lymphovascular invasion (LVSI), and low differentiation grade. Notably, all these parameters were equally distributed between the HER2 zero and HER2 low groups. Additionally, HER2 positivity was significantly associated with increased occurrences of regional and distant lymph nodes and pulmonary metastases. However, no statistically significant difference was observed between HER2 zero and HER2 low. Disease-free and overall survival showed no significant disparities between the groups.

CONCLUSIONS

Our findings suggest that HER2 low status is frequently detected in MBC. Despite this, HER2 low did not correlate with clinical and pathological parameters, nor did it impact patients' survival.

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.

Comparison of clinicopathological characteristics, efficacy of neoadjuvant therapy, and prognosis in HER2-low and HER2-ultralow breast cancer

BACKGROUND

This study aims to analyze potential differences in clinicopathology, efficacy of neoadjuvant therapy (NAT), and clinical outcome among HER2-null, HER2-ultralow and HER2-low breast cancers.

METHODS

Consecutive cases of HER2-negative breast cancer that received NAT were included. They were classified as HER2-null (no staining), HER2-ultralow (incomplete faint staining in ≤ 10% of tumour cells) and HER2-low (HER2-1 + or HER2-2+, in situ hybridisation negative). Subgroup analysis was performed based on the HER2 expression level.

RESULTS

Out of 302 patients, 215 (71.19%) were HER2-low, 59 (19.54%) were HER2-ultralow, and 28 (9.27%) were HER2-null. In comparison to the HER2-ultralow group, the HER2-low group exhibited higher expression frequencies of ER (p < 0.001), PR (p < 0.001), and AR (p = 0.004), along with a greater prevalence of the luminal subtype (p < 0.001). The HER2-ultralow group also demonstrated a higher prevalence of lymph node metastasis compared to the HER2-null group (p = 0.026). Varied rates of pathologic complete response (pCR) were observed among the three subgroups: HER2-null, HER2-ultralow, and HER2-low, with rates of 35.71%, 22.03%, and 12.56%, respectively. Only the HER2-low subgroup exhibited a significant difference compared to HER2-null (p = 0.001). Despite variations in pCR rates, the three subgroups exhibited comparable disease-free survival (DFS) (p = 0.571). Importantly, we found HER2-low patients with better treatment response (RCB-0/I) exhibited significantly better DFS than those with significant residual disease (RCB-II/III) (P = 0.036). The overall rate of HER2 immunohistochemical score discordance was 45.24%, mostly driven by the conversion between HER2-0 and HER2-low phenotype. Notably, 32.19% of cases initially classified as HER2-0 phenotype on baseline biopsy were later reclassified as HER2-low after neoadjuvant therapy, and it is noteworthy that 22 out of these cases (78.57%) originally had an HER2-ultralow status in the pretreatment biopsy sample.

CONCLUSIONS

Our results demonstrate the distinct clinicopathological features of HER2-low and HER2-ultralow breast tumors and confirm that RCB is an effective predictor of prognosis in HER2-low populations for the first time. Notably, our findings demonstrate high instability in both HER2-low and HER2-ultralow expression from the primary baseline biopsy to residual disease after NAT. Furthermore, this study is the first to investigate the clinicopathological feature and the effectiveness of NAT for HER2-ultralow breast cancer.

Incidence and Prognostic Values in Human Epidermal Growth Factor Receptor 2-Low Expression Metastatic Breast Cancer in Southeast Asian Population: A 10-Year Retrospective Study

PURPOSE

Breast cancer progression varies across molecular subtypes, and treatment options for human epidermal growth factor receptor 2 (HER2)-low expression tumors are limited compared with those of HER2 overexpression tumors. Comprehensive information regarding the epidemiology and clinical outcomes of metastatic HER2-low expression breast cancer in a Southeast Asian population is lacking.

METHODS

This retrospective cohort study was performed to analyze data from patients with de novo advanced breast cancer, including HER2 expression, tumor stage, and metastatic pattern. Statistical analyses, including chi-square tests and survival analyses, were used to compare HER2-low expression and HER2-negative groups.

RESULTS

Of the 491 patients, 21.2% had HER2-low expression, 30% had HER2 overexpression, and 50% had HER2-negative expression. Among the hormone receptor (HR)-positive patients, 34% had HER2-low expression; in the triple-negative patients, the HER2-low incidence was 20.6%. No significant differences in clinical characteristics between HER2-low and HER2-negative groups were observed, except for more HR-positive patients in the HER2-low group. HER2-low patients had a longer overall survival (OS) than HER2-negative patients (43 v 23 months; hazard ratio, 0.7; P < .001), especially in HR-positive patients. After adjusting for HR status, HER2-low patients maintained improved outcomes. HR-positive HER2-low patients showed nonsignificant OS gains compared with HR-positive HER2-negative patients, regardless of first-line chemotherapy or endocrine therapy.

CONCLUSION

This study revealed the incidence and clinical outcomes of HER2-low expression in de novo advanced breast cancer, suggesting favorable outcomes, particularly in HR-positive breast cancer. These findings may inform personalized treatment strategies. Further research into the mechanisms and implications of HER2-low expression in breast cancer is required.

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.

A retrospective analysis of clinicopathological characteristics and risk factors for recurrence in young patients with breast cancer

Background

Younger and older patients with breast cancer often present with different clinicopathological characteristics and exhibit different risk factors for recurrence. This study sought to evaluate the biological characteristics and identify the recurrence risk factors in patients with operable breast cancer who were ≤40 years of age.

Methods

This retrospective study investigated the biological characteristics and clinical outcomes of young patients (aged ≤40 years) with operable breast cancer who had been admitted to the Second Affiliated Hospital of Soochow University for treatment from January 2015 to December 2019. Clinicopathological and follow-up data were collected and statistically analyzed using IBM SPSS 27.0 software. The disease-free survival (DFS) rates were evaluated, and regression analyses were conducted to identify risk factors associated with adverse outcomes.

Results

A total of 154 young patients (aged ≤40 years) with operable breast cancer were included in this study, of whom 68 (44.2%) were aged ≤35 years. In terms of breast cancer subtypes, there were 19 (12.3%) patients with luminal A-like disease, 74 (48.1%) patients with luminal B-like disease, 17 (11.0%) patients with human epidermal growth factor receptor 2 (HER2)-positive (non-luminal) disease, and 44 (28.6%) patients with triple-negative breast cancer (TNBC). The 5-year DFS rate of all the patients was 88%; among those with TNBC, the rate was slightly lower at 76%. According to the results of the log-rank test, tumor (T) stage, node (N) status (N0 or N+), the biological subtype, and the Ki-67 index (with a 14% cut-off value between high and low expression levels) were risk factors for recurrence. The Cox regression analysis showed that the biological subtype was the only risk factor for recurrence. The multiple linear regression analysis demonstrated that the pathological type, tumor grade, estrogen receptor (ER) labeling intensity, and progesterone receptor (PR) expression level significantly affected the level of Ki-67 expression.

Conclusions

This retrospective study showed that biological subtype was the most important risk factor for recurrence in operable breast cancer patients ≤40 years. The Ki-67 index is influenced by the pathological type, primary tumor grade, ER labeling intensity, and PR expression level. Fourteen percent is recommended as the cut-off value for the high and low expression of Ki-67 in clinical practice.

Insights Into the Emerging Entity of HER2-Low Breast Cancer

Human epidermal growth factor receptor 2 (HER2)-low breast cancer (BC) is a subtype of BC that has been recently recognized as a separate clinical entity with distinct clinical and molecular characteristics. It is defined by a low level of HER2 protein expression, which distinguishes it from other more aggressive BC subtypes. Early studies suggest that it may have a more favorable prognosis than HER2-positive BC, as it is less likely to spread to other parts of the body and may be more responsive to standard BC treatments such as chemotherapy, radiation therapy, and hormone therapy. Given the relative new emergence of HER2-low BC, there is still much to be learned about this subtype; ongoing research is focused on identifying the underlying genetic mutations that contribute to HER2-low BC as well as developing targeted therapies that can improve outcomes for patients with this disease. This review is aimed at summarizing the current clinical knowledge on HER2-low BC, with the aim of creating a better understanding of this entity and paving the way for potential interventions and a new standard of care.

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.

Survival outcomes in HER2-low versus HER2-zero breast cancer after neoadjuvant chemotherapy: a meta-analysis

BACKGROUND

The survival outcomes in HER2-low versus HER2-zero breast cancer (BC) after neoadjuvant chemotherapy (NACT) remain unclear. The meta-analysis was conducted to summarize current evidence about the survival outcomes in HER2-low versus HER2-zero BC.

METHODS

We conducted a systematic search in PubMed and EMBASE databases to identify relevant studies.

RESULTS

A total of 14 studies with 53,714 patients were included. Overall, 34,037 patients (63.37%) were HER2-low, and 19,677 patients (36.63%) were HER2-zero. Patients with HER2-low tumors had a significantly lower pathological complete response (pCR) rate than patients with HER2-zero tumors, regardless of the hormone receptor status. Compared with HER2-zero breast cancer, the overall survival (OS) and disease-free survival (DFS) of HER2-low BC were longer in the overall cohort (HR = 0.72; 95% CI = 0.61-0.85; P < 0.0001; HR = 0.83; 95% CI = 0.75-0.92; P = 0.0002); however, no differences were observed in terms of OS and DFS between HER2-low and HER2-zero BC in the HR-negative group. In the HR-positive group, HER2-low status had no significant impact on OS, while significantly associated with increased DFS (HR = 0.85; 95% CI = 0.76-0.96; P = 0.007).

CONCLUSION

These results suggest that although HER2-low BC has a poor response to NACT, it is correlated with favorable OS and DFS after NACT in the overall cohort as well as longer DFS in the HR-positive group.

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.

The Modified Neo-Bioscore System for Staging Breast Cancer Treated with Neoadjuvant Therapy Based on Prognostic Significance of HER2-Low Expression

Background: Recently, the classification of HER2 status evolves from binary to ternary, and HER2-low expression may exhibit prognostic significance. We aimed to investigate whether HER2-low tumor is distinct from HER2-zero or HER2-positive tumors, and then to develop a modified staging system (mNeo-Bioscore) that incorporates HER2-low status into Neo-Bioscore. Patients and Methods: This cohort study was conducted using data from the prospective database on breast cancer patients between January 2014 and February 2019. Results: Among 259 patients enrolled in the study, the HER2-low tumor exhibited significantly lower histological grade, pathological staging and Ki-67 level than the other two groups. HER2-low patients and HER2-positive patients receiving concurrent HER2-directed therapy may have similar LRFS (p = 0.531) and OS (p = 0.853), while HER2-zero peers may have significantly worse LRFS (p = 0.006) and OS (p = 0.017). In particular, a similar trend was also found in the patients without pathological complete response after surgery. Incorporation of HER2-low status made improvement in fit: 5-year OS rate estimates ranged from 33.33% to 100% for mNeo-Bioscore vs 61.36% to 100% for Neo-Bioscore. Conclusions: This study demonstrated that HER2-low tumor may exhibit prognostic significance. The innovative mNeo-Bioscore, based on a new classification of HER2 status, may serve as a prognostic staging system superior to Neo-Bioscore.

Prognostic Impact of HER2-Low and HER2-Zero in Resectable Breast Cancer with Different Hormone Receptor Status: A Landmark Analysis of Real-World Data from the National Cancer Center of China

BACKGROUND

The prognostic impact of HER2-low on overall survival (OS) and disease-free survival (DFS) in patients with resectable breast cancer (BC) remains controversial, partly resulting from the hormone receptor (HR) status.

OBJECTIVE

To investigate the prognostic impact of HER2-low in different HR subgroups.

PATIENTS AND METHODS

We retrospectively retrieved medical records of treatment-naive primary HER2-low and HER2-zero BC patients who were diagnosed with invasive ductal carcinoma and underwent surgery in the Cancer Hospital of the Chinese Academy of Medical Sciences from January 2009 to September 2017 (n = 7371). We compared the clinicopathologic features and performed Cox regression and landmark survival analyses to explore the prognostic impact of HER2-low on survival outcomes during distinct post-surgery intervals-36 months, 60 months, and 120 months.

RESULTS

HER2-low BC, compared to HER2-zero BC, exhibited less aggressive clinicopathologic features, such as smaller invasion size, lower grade, increased nerve invasion, higher HR positivity, and a higher proportion of low-Ki67 cases. In the HR-positive subgroup, HER2-low demonstrated improved OS (p = 0.046) and DFS (p = 0.026) within 60 months. Conversely, HER2-low displayed worse DFS (p = 0.046) in the HR-negative subgroup after 36 months from surgery. The findings remained robust in uni- and multi-variable Cox models.

CONCLUSIONS

HER2-low BCs manifested less aggressive clinicopathologic features than the HER2-zero cases. The prognostic impact of HER2-low in resectable BCs exhibits variability contingent upon the patients' HR status.

Consensus on clinical diagnosis and medical treatment of HER2-low breast cancer (2022 edition)

Treatment of breast cancer with low expression of human epidermal growth factor receptor 2 (HER2; HER2-low) has drawn much attention in recent years. With the proven therapeutic effect of trastuzumab deruxtecan (T-DXd) in patients with HER2-low (immunohistochemistry [IHC] 1+, or IHC2+/in situ hybridization [ISH]-) breast cancer, HER2-low may become a new subtype of targeted therapy for breast cancer. The expert committee formulated this consensus based on the current clinical studies and clinical medication experience. The current consensus is the collaborative work of an interdisciplinary working group, including experts in the fields of pathology and oncology. The purpose of this consensus was to guide the clinical diagnosis and treatment of HER2-low breast cancer, thereby prolonging the overall survival of patients.

Prognosis difference between HER2-low and HER2-zero breast cancer patients: a systematic review and meta-analysis

BACKGROUND

HER2-low breast cancer (BC) is proposed to be a special population of patients with an immunohistochemistry (IHC) score of 1 + or 2 + and non-amplified in situ hybridization (ISH) results. The role and prognostic impact of HER2-low BC is still controversial. This meta-analysis aims to explore the prognostic difference between of HER2-low and HER2-zero characteristic in BC patients.

METHODS

A meta-analysis was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and eligible studies were search in PubMed, Web of Science and EMBASE databases. Quality assessment of included studies were performed by Quality in Prognostic Studies (QUIPS) tool. Hazard ratios (HRs) and corresponding 95% confidence interval (CI) for overall survival (OS) and disease-free survival (DFS) were pooled in a meta-analysis. Furthermore, subgroup analysis, sensitivity analysis, and analysis for publication bias were conducted.

RESULTS

Eighteen studies comprising a total of 93,317 patients were included for meta-analysis. BC patients with HER2-low characteristic have longer OS (HRs 0.87, 95% CI 0.81-0.93, p < 0.0001) and DFS (HRs 0.82, 95% CI 0.73-0.93, p = 0.001) compared to those with HER2-zero characteristic. Subgroup analysis indicate that the source of heterogeneity may come from the hormone receptor (HR) status group. Although, the publication bias was detected, sensitivity analysis and the trim-and-fill method analysis demonstrated the stability and reliability of the results.

CONCLUSION

HER2-low BC patients have longer OS and DFS compared to HER2-zero BC patients, and its prognostic value is consistent among different HR status patients. Whether HER2-low breast cancer is an independent subtype of breast cancer is still a subject of ongoing research, and more studies are needed to fully understand the molecular and clinical features of this subtype.

Clinicopathological characteristics, evolution, treatment pattern and outcomes of hormone-receptor-positive/HER2-low metastatic breast cancer

Objective

Despite the promising efficacy of the novel antibody-drug conjugate trastuzumab deruxtecan in treating Hormone Receptor (HoR)-positive/Human Epidermal Growth Factor Receptor 2 (HER2)-low metastatic breast cancer (MBC), its categorization as a distinct entity remains disputed, as does the divergence in its endocrine and chemotherapy outcomes. This study aimed to elucidate the clinical characteristics, primary/metastatic lesion HER2 expression, and treatment outcomes of HoR-positive/HER2-low patients.

Methods

We included HoR-positive/HER2-negative MBC patients who underwent 1st and 2nd line endocrine treatment from July 2010 to October 2022 at the Fudan University Shanghai Cancer Center, comparing the clinical pathological characteristics, HER2 expression in primary/metastatic lesions, treatment, and therapeutic effects of the HER2-low and HER2-zero groups.

Results

Among the 458 HoR-positive/HER2-negative MBC patients, 54.37% (249/458) were HER2-low. The HER2-low group and the HER2-zero group had similar clinical pathological characteristics and similar progression-free survival (PFS) of 1st and 2nd line endocrine treatment (median PFS: 8.05 months vs 10.12 months, p=0.114, HR 1.257, 95% CI 0.771 to 1.028). The PFS of the HER2-low and HER2-zero groups was also similar, treated with different endocrine drugs (including aromatase inhibitors, tamoxifen/toremifene, fulvestrant, palbociclib, and everolimus). However, the HER2-low group had significantly shorter PFS during 1st and 2nd line chemotherapy compared to the HER2-zero group (median PFS: 8.64 vs 9.03 months, p=0.027, HR 0.841, 95% CI 0.721-0.980). Additionally, 41.18% (63/153) of patients exhibited a change in HER2 expression between primary and metastatic lesions. Notably, patients whose HER2 status changed from zero to low expression had significantly prolonged PFS during chemotherapy compared to those who maintained low HER2 expression (median PFS: 14.29 vs 11.27 months, p=0.048, HR 0.597, 95% CI 0.358-0.996).

Conclusion

In HoR-positive MBC, patients with low and zero HER2 expression have similar clinical characteristics and respond similarly to endocrine treatment, but the chemotherapy effect is worse in the HER2-low patients. Moreover, the transformation of HER2 status from primary to metastatic lesions may have potential influence on chemotherapy outcomes. Therefore, the expression and heterogeneity of HER2 should be considered in clinical decisions.

Molecular Characterization of HER2-Low Invasive Breast Carcinoma by Quantitative RT-PCR Using Oncotype DX Assay

BACKGROUND

HER2 immunohistochemistry (IHC) reproducibility is suboptimal for HER-low cases (IHC 1+ or 2+).

METHODS

The Yale cohort included 214 stages I-II estrogen receptor positive breast cancers with IHC scores 0, 1+, and 2+ and routine Oncotype DX Recurrence Score (RS) results. The Exact Sciences (ES) cohort included 9 57 624 patients who had an Oncotype DX RS assay that assigns HER2-negative, equivocal, or positive status based on HER2 mRNA levels.

RESULTS

HER2 mRNA levels varied across IHC categories but with increasing medians of 9.10 (n = 89), 9.20 (n = 71), and 9.45 (n = 54) in IHC 0, 1+, and 2+, respectively. 22.4% of HER2-low (1+/2+) cancer had RS > 25. Over 98% of HER-low cancers were HER2-negative by Oncotype DX assignment.

CONCLUSIONS

Cancers with higher mRNA levels exist within IHC 0 and low categories, most of the HER2-low patients by IHC have low RS indicating no benefit from current adjuvant chemotherapies.

The trichotomy of HER2 expression confers new insights into the understanding and managing for breast cancer stratified by HER2 status

Human epidermal growth factor receptor 2 (HER2) is a tyrosine kinase receptor that plays a carcinogenic role in breast cancer (BC) through gene amplification, mutation, or overexpression. Traditional methods of HER2 detection were divided into positive (immunohistochemistry (IHC) 3+/fluorescence in situ hybridization (FISH) amplification) and negative (IHC 2+/FISH-, IHC 1+, IHC 0) according to the dichotomy method. Anti-HER2-targeted therapies, such as trastuzumab and pertuzumab, have significantly improved the prognosis of HER2-positive patients. However, up to 75% to 85% of patients remain HER2-negative. In recent years, with the rapid development of molecular biology, gene detection technology, targeted therapy, and immunotherapy, researchers have actively explored the clinicopathological characteristics, molecular biological characteristics, treatment methods, and HER2 detection methods of HER2-low/zero breast cancer. With the clinical efficacy of new anti-HER2 targeted drugs, accurate classification of breast cancer is very important for the treatment choice. Therefore, the following review summarizes the necessity of developing HER2 detection methods, and the clinicopathological and drug treatment characteristics of patients with HER2-low/zero, to light the dawn of the treatment of breast cancer patients with HER2-low/zero expression.

Comparisons of clinical characteristics, prognosis, epidemiological factors, and genetic susceptibility between HER2-low and HER2-zero breast cancer among Chinese females

BACKGROUND

Traditional human epidermal growth factor receptor 2 (HER2)-negative breast cancer (BC) is recommended to be divided into HER2-low and HER2-zero subtypes due to different prognosis. However, few studies investigated their differences in clinical characteristics and prognosis among Chinese HER2-negative BC and their stratified differences by hormone receptor (HR), while fewer studies investigated their differences in epidemiological factors and genetic susceptibility.

METHODS

A total of 11,911 HER2-negative BC were included to compare the clinical characteristics and prognosis between HER2-zero and HER2-low BC, and 4227 of the 11,911 HER2-negative BC were further compared to 5653 controls to investigate subtype-specific epidemiological factors and single nucleotide polymorphisms(SNPs).

RESULTS

Overall, 64.2% of HER2-negative BC were HER2-low BC, and the stratified proportions of HER2-low BC were 61.9% and 75.2% for HR-positive and HR-negative BC, respectively. Compared to HER2-zero BC, HER2-low BC among HR-positive BC showed younger age at diagnosis, later stage, poorer differentiation, and higher Ki-67, while elder age at diagnosis and lower mortality were observed for HER2-low BC among HR-negative BC (all p values <0.05). Compared to healthy controls, both HER2-low and HER2-zero BC are associated with similar epidemiological factors and SNPs. However, stronger interaction between epidemiological factors and polygenic risk scores were observed for HER2-zero BC than HER2-low BC among either HR-positive [odds ratios: 10.71 (7.55-15.17) and 8.84 (6.19-12.62) for the highest risk group compared to the lowest risk group] or HR-negative BC [7.00 (3.14-15.63) and 5.70 (3.26-9.98)].

CONCLUSIONS

HER2-low BC should deserve more attention than HER2-zero BC, especially in HR-negative BC, due to larger proportion, less clinical heterogeneity, better prognosis, and less susceptibility to risk factors.

Survival differences between HER2-0 and HER2-low-expressing breast cancer - A meta-analysis of early breast cancer patients

BACKGROUND

HER2-low (human epidermal growth factor receptor 2) breast cancer takes up 40-50% in all breast cancer subtypes. The survival difference between HER2-low and HER2-zero breast cancers remain uncertain. Therefore, the aim of this study was to compare survival outcome of the two subtypes and to explore the impact of hormone receptor status.

METHODS

A comprehensive medical literature search was performed by searching PubMed, EMBASE, and the Cochrane Libraries up to August 2022. We included observational studies reporting hazard ratios (HRs) with corresponding 95% confidence intervals (CIs). The results of individual studies were pooled by random-effects models using Stata 16.0. Seventeen articles with a total of 78984 breast cancer patients were included in the meta-analysis.

RESULTS

We observed a statistically significant association between low HER2 expression and better breast cancer survival outcomes (OS: HR: 0.83; 95% confidence interval: 0.75, 0.90; DFS/RFS: HR: 0.83; 95% confidence interval: 0.75, 0.91). In a subgroup analysis, we found that HER2-low patients had better survival outcomes relative to hormone receptor-positive breast cancer patients (OS: HR: 0.87; 95% confidence interval: 0.81, 0.93; DFS/RFS: HR: 0.91; 95% confidence interval: 0.85, 0.96). Similarly, in triple-negative breast cancer patients, we also observed a positive association between HER2 low expression and better survival (OS: HR: 0.85; 95% confidence interval: 0.71, 0.98; DFS/RFS: HR: 0.85; 95% confidence interval: 0.74, 0.95).

CONCLUSIONS

Our study showed that HER2-low breast cancer had better survival outcomes compared to HER2 negative breast cancer in patients with early stage breast cancer, regardless of hormone receptor status.

REGISTRATION

This meta-analysis was registered with PROSPERO (CRD42022335704) on June 10, 2022.

AVAILABILITY OF DATA AND MATERIALS

All data generated or analysed during this study are included in this published article [and its supplementary information files].

The association between HER2-low expression and prognosis of breast cancer: a systematic review and meta-analysis

Background

The use of antibody-drug conjugates for the treatment of advanced-stage human epidermal growth factor receptor 2 (HER2)-low expression in breast cancer (BC) has shown prominent curative effects, which has led to increased academic interest. However, the role of HER2-low expression in the prognosis of BC remains controversial.

Methods

We conducted a systematic search of the PubMed, Embase, and Cochrane library databases and several oncology conferences until 20 September 2022. We used fixed- and random-effects models to calculate odds ratio (OR) or hazard ratio (HR) with 95% confidence interval (CI) for overall survival (OS), disease-free survival (DFS), progression-free survival (PFS), and pathological complete response (pCR) rates.

Results

Overall, 26 studies encompassing 677,248 patients were included in the meta-analysis. Patients with HER2-low BC showed significantly better OS than those with HER2-zero BC in the overall population (HR = 0.90; 95% CI: 0.85-0.97) and hormone receptor-positive population (HR = 0.98; 95% CI: 0.96-0.99), whereas no significant difference was observed in the OS of the hormone receptor-negative population (p > 0.05). In addition, there was no significant difference in the DFS of the overall and hormone receptor-negative population (p > 0.05), but better DFS than those with HER2-zero BC in the hormone receptor-negative population (HR = 0.96; 95% CI: 0.94-0.99). There was also no significant difference in the PFS of the overall population, hormone receptor-positive, and hormone receptor-negative population (p > 0.05). Patients with HER2-low BC had a lower pCR rate after neoadjuvant treatment than those with HER2-zero BC.

Conclusions

Compared to patients with HER2-zero BC, those with HER2-low BC had better OS in the overall population and hormone receptor-positive population, DFS in hormone receptor-positive population and lower pCR in the overall population. The biological differences between HER2-low and HER2-zero BCs, particularly in hormone receptor-positive patients, and the relationship between HER2-low expression status and prognosis need to be explored further.

Bioinformatics combined with clinical data to analyze clinical characteristics and prognosis in patients with HER2 low expression breast cancer

Background

Human epidermal growth factor receptor 2 (HER2) is a landmark protein in determining the targeted treatment of breast cancer (BC). However, the latest research shows that different intensity of HER2 protein expression levels in BC leads to different clinical characteristics, treatment, and prognosis, especially in HER2 low expression patients. Therefore, this study intends to analyze and compare the clinicopathologic features and prognosis of BC patients with low and zero HER2 expression from The Cancer Genome Atlas (TCGA) database and the data collected by our center.

Methods

First, the BC dataset was downloaded from TCGA database, including 345 eligible and with complete clinical information BC patients, to compare the difference between HER2 low expression groups and HER2 zero expression groups and their correlation with estrogen receptor (ER) and progesterone receptor (PR) expression. Then, the clinicopathological data and follow-up of 405 patients with HER2 low expression and HER2 zero expression diagnosed with BC admitted to the Affiliated Hospital of Youjiang Medical University for Nationalities (YJMU) from January 2017 to December 2021 were collected to verify the consistency of the results of the two data sets.

Results

Both the clinical samples and the TCGA data showed that the ER and PR rates were higher in the HER2 low expression group compared with the HER2 zero expression group. There were no significant differences in tumor size, lymph node metastasis, distant metastasis, and disease-free survival (DFS). In addition, the data analysis of 405 clinical samples also showed that the HER2 low expression group had a lower 3-year recurrence or metastasis rate compared with the HER2 zero expression group.

Conclusions

Compared with HER2 zero expression, HER2 low patients express more ER and PR, and have less short-term recurrence and metastasis, but there is no obvious difference in DFS between the two groups.

Discordance of HER2-Low between Primary Tumors and Matched Distant Metastases in Breast Cancer

We examined differences in HER2 expression between primary tumors and distant metastases, particularly within the HER2-negative primary breast cancer cohort (HER2-low and HER2-zero). The retrospective study included 191 consecutive paired samples of primary breast cancer and distant metastases diagnosed between 1995 and 2019. HER2-negative samples were divided into HER2-zero (immunohistochemistry [IHC] score 0) and HER2-low (IHC score 1+ or 2+/in situ hybridization [ISH]-negative). The main objective was to analyze the discordance rate between matched primary and metastatic samples, focusing on the site of distant metastasis, molecular subtype, and de novo metastatic breast cancer. The relationship was determined by cross-tabulation and calculation of Cohen's Kappa coefficient. The final study cohort included 148 paired samples. The largest proportion in the HER2-negative cohort was HER2-low [primary tumor 61.4% (n = 78), metastatic samples 73.5% (n = 86)]. The discordance rate between the HER2 status of primary tumors and corresponding distant metastases was 49.6% (n = 63) (Kappa -0.003, 95%CI -0.15-0.15). Development of a HER2-low phenotype occurred most frequently (n = 52, 40.9%), mostly with a switch from HER2-zero to HER2-low (n = 34, 26.8%). Relevant HER2 discordance rates were observed between different metastatic sites and molecular subtypes. Primary metastatic breast cancer had a significantly lower HER2 discordance rate than secondary metastatic breast cancer [30.2% (Kappa 0.48, 95%CI 0.27-0.69) versus 50.5% (Kappa 0.14, 95% CI -0.03-0.32)]. This highlights the importance of evaluating potentially therapy-relevant discordance rates between a primary tumor and corresponding distant metastases.

Clinicopathologic characteristics and prognostic significance of HER2-low expression in patients with early breast cancer: A systematic review and meta-analysis

Background

HER2-low expression breast cancer (BC) accounts for approximately 45%-55% of all BC cases. The purpose of this study was to investigate the prognostic difference between patients with HER2-low expression and HER2-zero BC.

Methods

An electronic search of Pubmed, Embase, Cochrane Library, and Web of Science databases was performed to screen studies that included prognostic comparisons between HER2-zero and HER2-low expression groups. A total of 14 studies involving 52106 patients were included.

Results

Our results indicated that HER2-low expression was associated with a significant benefit in OS among all patients with early BC (HR, 0.83; 95% CI, 0.78-0.88), patients with hormone-receptor positive BC (HR, 0.83; 95% CI, 0.77-0.89), and patients with TNBC (HR, 0.78; 95% CI, 0.70-0.87). HER2-low expression was associated with a significant benefit in DFS among all patients (HR, 0.81; 95% CI, 0.71-0.93), patients with hormone receptor-positive BC (HR, 0.81; 95% CI, 0.72-0.90), but no significant difference in DFS was found in patients with TNBC (HR, 0.87; 95% CI, 0.65-1.17). HER2-low expression was associated with a significant benefit in RFS among all patients (HR, 0.90; 95% CI, 0.85-0.95), patients with hormone receptor-positive BC (HR, 0.90; 95% CI, 0.84-0.96), but no significant difference in RFS was found in patients with TNBC (HR, 0.80; 95% CI, 0.55-1.16).

Conclusions

Among patients with early-stage BC, patients with HER2-low expression BC had better OS in the overall population, hormone receptor-positive and TNBC subgroups. Besides, favorable DFS and RFS were observed in both the overall population and hormone receptor-positive subgroup.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier (CRD 42022349458).

Molecular Classification, Treatment, and Genetic Biomarkers in Triple-Negative Breast Cancer: A Review

Breast cancer is the most common malignancy and the second most common cause of cancer-related mortality in women. Triple-negative breast cancers do not express estrogen receptors, progesterone receptors, or human epidermal growth factor receptor 2 and have a higher recurrence rate, greater metastatic potential, and lower overall survival rate than those of other breast cancers. Treatment of triple-negative breast cancer is challenging; molecular-targeted therapies are largely ineffective and there is no standard treatment. In this review, we evaluate current attempts to classify triple-negative breast cancers based on their molecular features. We also describe promising treatment methods with different advantages and discuss genetic biomarkers and other prediction tools. Accurate molecular classification of triple-negative breast cancers is critical for patient risk categorization, treatment decisions, and surveillance. This review offers new ideas for more effective treatment of triple-negative breast cancer and identifies novel targets for drug development.

Comparison of the pCR Rate and DFS Among Breast Cancer Patients with Different Hormone Receptor and HER2 Statuses

Background

Recent studies have investigated the features of breast cancer (BC) with low human epidermal growth factor receptor 2 (HER2) expression or HER2-0 expression. However, the results were inconsistent. In this study, we investigated the differences in the pathological complete response (pCR) rate and disease-free survival (DFS) between HER2-low and HER2-0 BC patients and between subgroups.

Methods

HER2-negative BC patients who received neoadjuvant chemotherapy between January 2013 and December 2019 in our hospital were retrospectively reviewed. First, the pCR rate and DFS were compared between HER2-low and HER2-0 patients and among different hormone receptor (HR) and HER2 statuses. Subsequently, DFS was compared between different HER2 status populations with or without pCR. Finally, a Cox regression model was used to identify the prognostic factors.

Results

Overall, 693 patients were selected: 561 were HER2-low, and 132 were HER2-0. Between the two groups, there were significant differences in N stage (P = 0.008) and HR status (P = 0.007). No significant difference in the pCR rate (12.12% vs 14.39%, P = 0.468) or DFS was observed, independent of HR status. HR+/HER2-low patients had a significantly worse pCR rate (P < 0.001) and longer DFS (P < 0.001) than HR-/HER2-low or HER2-0 patients. In addition, a longer DFS was found in HER2-low patients versus HER2-0 patients among those who did not achieve pCR. Cox regression showed that N stage and HR status were prognostic factors in the overall and HER2-low populations, while no prognostic factor was found in the HER2-0 group.

Conclusion

This study suggested that HER2 status is not associated with the pCR rate or DFS. Longer DFS was found only among patients who did not achieve pCR in the HER2-low versus HER2-0 population. We speculated that the interaction of HR and HER2 might have played a crucial role in this process.

Lentiviral vector–based xenograft tumors as candidate reference materials for detection of HER2-low breast cancer

The human epidermal growth factor receptor 2 (HER2) is an important biomarker that plays a pivotal role in therapeutic decision-making for patients with breast cancer (BC). Patients with HER2-low BC can benefit from new HER2 targeted therapy. For ensuring the accurate and reproducible detection of HER2-low cancer, reliable reference materials are required for monitoring the sensitivity and specificity of detection assays. Herein, a lentiviral vector was used to transduce the HER2 gene into MDA-MB-231 cells that exhibited low HER2 density, and the cells were characterized by droplet digital PCR to accurately determine the copy number variation. Then, the formalin-fixed paraffin-embedded (FFPE) samples from xenografts were prepared and evaluated for suitability as candidate reference materials by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). The FFPE reference materials were selected on the basis of IHC score of 2+ and negative FISH result to meet the requirement for HER2-low BC detection. Furthermore, the FFPE reference materials exhibited typical histological structures that resembled the clinical BC specimens. These novel FFPE reference materials displayed the high stability and homogeneity, and they were produced in high quantity. In summary, we generated high-quality reference materials for internal quality control and proficiency testing in HER2-low detection.