Distinct clinical and somatic mutational features of breast tumors with high-, low-, or non-expressing human epidermal growth factor receptor 2 status

Molecular and clinical traits of HER2-low breast cancer patients and their relationship with neoadjuvant treatment effectiveness

BACKGROUND

We aimed to investigate the clinical and molecular characteristics of different degrees of human epidermal growth factor receptor 2 (HER2) protein expression in HER2-negative breast cancer and the related factors affecting the efficacy of neoadjuvant chemotherapy in HER2-low breast cancer patients.

METHODS

The study endpoint was pathological complete remission (PCR). Blood specimens and fresh cancer tissue samples were collected before neoadjuvant chemotherapy for whole-exon sequencing (WES) and RNA sequencing (RNA-seq), and patients were divided into a human epidermal growth factor receptor 2 (HER2)-low group and a HER2-0 group according to their HER2 expression status via bioinformatics analysis.

RESULTS

A total of 409 HER2-negative breast cancer patients were included in the analysis, and HER2 status (HER2-0 vs. HER2-low) was significantly different between hormone receptor status, the Ki-67 index, and the PCR rate. A total of 18 patients who underwent WES and RNA testing were included, and the WES results suggested that the HER2-low group had a significantly higher rate of PIK3CA mutations and a greater frequency of PI3K pathway variants than the other groups and the HER2-low group had a greater number of concomitant mutations and reached statistical significance ( P  = 0.03). In terms of expression profiles, HER2-low and HER2-0 patients had different expression profiles. Overall, suggesting that the low PCR rate in the HER2-low group may also be related to chemoresistance.

CONCLUSION

Our investigation highlights the possibility that HER2-low breast cancer may indicate a unique clinical and biological phenomenon.

Comparative analysis of the clinicopathological features and prognostic implications of invasive breast carcinoma of nonspecial type exhibiting HER2-low and HER2-zero expressions

PURPOSE

This retrospectively study aimed to investigate the clinicopathological features, treatments, prognostic differences, and influencing factors between invasive breast carcinoma of nonspecial type (IBC-NST) with low and zero HER2 expressions.

METHODS

Clinical data of patients with IBC-NST exhibiting low and zero HER2 expression were obtained from the Shanghai Jiao Tong University Breast Cancer Database spanning July 2009 to December 2019. The Kaplan-Meier method, log-rank test and Cox regression analyses were performed.

RESULTS

Of the 2071 patients with IBC-NST, 1618 (78.1%) had low HER2 expression and 453 (21.9%) had zero HER2 expression. A higher proportion of patients aged below 40 years, with Ki67 >20%, and with tumor grade III were observed in the HER2-zero group. Higher percentages of estrogen receptor-positive, progesterone receptor-positive, hormone receptor (HR)-positive, and receipt of endocrine therapy were observed in the HER2-low group. The breast cancer-free interval (BCFI) and overall survival (OS) were similar between the groups. In the HR-positive subgroup, no significant differences were observed in the clinical pathological characteristics, treatment types, BCFI, and OS. In the HR-negative subgroup, higher proportions of patients aged over 40 years and patients in the postmenopausal stage were observed in the HER2-low group. Multivariate analysis revealed that the lymph node stage (N2-N3) was an independent risk factor for BCFI and OS regardless of the HER2 status. Meanwhile, HER2-low was an independent risk factor for BCFI in the HR-negative subgroup (hazard ratio, 1.781, 95% confidence interval, 1.061-2.989, P = 0.029).

CONCLUSION

The clinical biological characteristics of HER2-low IBC-NST could be influenced by the HR status. The clinicopathological features and prognosis of HER2-low and HER2-zero IBC-NST were comparable at the same HR status.

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.

Intratumoral and peritumoral radiomics based on automated breast volume scanner for predicting human epidermal growth factor receptor 2 status

Purpose

To develop an intratumoral and peritumoral radiomics model using Automated Breast Volume Scanner (ABVS) for noninvasive preoperative prediction of Human Epidermal Growth Factor Receptor 2 (HER2) status.

Methods

This retrospective study analyzed 384 lesions from 379 patients with pathologically confirmed breast cancer across four hospitals. Two tasks were defined: Task 1 to distinguish HER2-negative from HER2-positive cases and Task 2 to differentiate HER2-zero from HER2-low status. For each classification task, three models were built: Model 1 included radiomics features from the tumor region alone; Model 2 included features from both the tumor region and a 5mm peritumoral region; and Model 3 incorporated features from the tumor region, the 5mm peritumoral region, and the 5-10mm peritumoral region. The performance of the model was evaluated using receiver operating characteristic (ROC) curves, with key metrics including the area under the curve (AUC), sensitivity, specificity, and accuracy.

Results

In the classification tasks, Model 2 demonstrated superior predictive performance across multiple datasets. For Task 1, it achieved the highest AUC (0.844), exceptional sensitivity (0.955), and satisfactory accuracy (0.787) in the validation set, and outperformed other models in the test set with an AUC of 0.749 and sensitivity of 0.885, highlighting its robustness and clinical applicability. For Task 2, Model 2 exhibited the highest AUC (0.801), sensitivity (0.862), and accuracy (0.808) in the test set, with consistent performance across the training (AUC 0.850) and validation sets (AUC 0.801). Model 3, which combines intratumoral and peritumoral features, did not demonstrate significant improvements over the intratumoral-only model in the two classification tasks. These results underscore the value of incorporating peritumoral radiomics features, particularly within a 5mm margin, to enhance predictive performance compared to intratumoral-only models.

Conclusion

The radiomics model integrating intratumoral and appropriate peritumoral features significantly outperformed the model based on intratumoral features alone. This integrated approach holds strong potential for noninvasive, preoperative prediction of HER2 status.

Quantitative Parameters of Intravoxel Incoherent Movement Imaging and Dynamic Contrast Enhancement MRI for the Prediction of HER2-Zero, -Low, and -Positive Breast Cancers

RATIONALE AND OBJECTIVES

To explore the predictive value of quantitative parameters from intravoxel incoherent movement (IVIM) imging and dynamic contrast enhancement MRI (DCE-MRI) for HER2 expression in breast cancer.

MATERIALS AND METHODS

This retrospective study included 167 women with breast cancer who underwent MRI from December 2019 to December 2023, categorized into 48 HER2-positive, 78 HER2-low and 41 HER2-zero cancers. All patients underwent IVIM imaging and DCE-MRI. Statistical analyses, including one-way ANOVA, Kruskal-Wallis test and χ2 test, were employed to compare clinical data, MRI features, and MRI quantitative parameters including standard ADC(ADC), pure diffusion coefficient(D), perfusion-related diffusion coefficient(D*), perfusion fraction(f), volume transfer constant(Ktrans), extravascular extracellular interstitial volume ratio(Ve) and rate constant(Kep) between the three groups. Multivariable logistic regression was used to identify independent predictors for distinguishing HER2 expressions. The diagnostic efficacy of significant IVIM and DCE parameters for different HER2 expressions was analyzed using receiver operator characteristic (ROC) curves.

RESULTS

Peritumoral edema, histological grade and Kep achieved an AUC of 0.86(95%CI:0.78,0.91) in distinguishing HER2-positive tumors from HER2-low expressing tumors and were independent predictors for differentiating these two groups. Among HER2-positive and -zero breast cancers, the combined model of D*, Ktrans and Kep had an AUC of 0.74(95%CI:0.63,0.82) for the prediction of HER2-positive versus HER2-zero cancers, and its prediction efficiency was not improved compared with that of a single parameter(P > .05).

CONCLUSION

Quantitative parameters from intravoxel incoherent movement imaging and dynamic contrast enhancement MRI can predict different HER2 expressions in breast cancer from different perspectives, with implications for therapy.

Prognostic difference between early breast cancer patients with HER2 low and HER2 zero status

We aimed to investigate the differences in prognosis between patients with HER2-low and HER2-zero status. This retrospective cohort study conducted at multi-institution included 1627 patients diagnosed with HER2-low or HER2-zero breast cancer (stages I-III). Survival analysis after propensity score matching was used. In total, 445 patients with HER2-low and 707 patients with HER2-zero status were included. The median follow-up was 92.7 months. Locoregional and distant recurrence-free survival were comparable between patients with HER2-low and HER2-zero status (p = 0.872, p = 0.746, respectively). HER2-low status did not affect overall survival. However, in subgroups with lymph node metastases, patients with HER2-low status showed better recurrence-free survival compared with that of patients with HER2-zero status (p = 0.033). In conclusion, survival outcomes were comparable between patients with HER2-low and HER2-zero breast cancer. More studies are needed to validate our findings and examine the biological mechanism underlying these prognostic differences.

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.

Distinguishing Low Expression Levels of Human Epidermal Growth Factor Receptor 2 in Breast Cancer: Insights from Qualitative and Quantitative Magnetic Resonance Imaging Analysis

BACKGROUND

The discovery of novel antibody-drug conjugates for low-expression human epidermal growth factor receptor 2 (HER2-low) breast cancer highlights the inadequacy of the conventional binary classification of HER2 status as either negative or positive. Identification of HER2-low breast cancer is crucial for selecting patients who may benefit from targeted therapies. This study aims to determine whether qualitative and quantitative magnetic resonance imaging (MRI) features can effectively reflect low-HER2-expression breast cancer.

METHODS

Pre-treatment breast MRI images from 232 patients with pathologically confirmed breast cancer were retrospectively analyzed. Both clinicopathologic and MRI features were recorded. Qualitative MRI features included Breast Imaging Reporting and Data System (BI-RADS) descriptors from dynamic contrast-enhanced MRI (DCE-MRI), as well as intratumoral T2 hyperintensity and peritumoral edema observed in T2-weighted imaging (T2WI). Quantitative features were derived from diffusion kurtosis imaging (DKI) using multiple b-values and included statistics such as mean, median, 5th and 95th percentiles, skewness, kurtosis, and entropy from apparent diffusion coefficient (ADC), Dapp, and Kapp histograms. Differences in clinicopathologic, qualitative, and quantitative MRI features were compared across groups, with multivariable logistic regression used to identify significant independent predictors of HER2-low breast cancer. The discriminative power of MRI features was assessed using receiver operating characteristic (ROC) curves.

RESULTS

HER2 status was categorized as HER2-zero (n = 60), HER2-low (n = 91), and HER2-overexpressed (n = 81). Clinically, estrogen receptor (ER), progesterone receptor (PR), hormone receptor (HR), and Ki-67 levels significantly differed between the HER2-low group and others (all p < 0.001). In MRI analyses, intratumoral T2 hyperintensity was more prevalent in HER2-low cases (p = 0.009, p = 0.008). Mass lesions were more common in the HER2-zero group than in the HER2-low group (p = 0.038), and mass shape (p < 0.001) and margin (p < 0.001) significantly varied between the HER2 groups, with mass shape emerging as an independent predictive factor (HER2-low vs. HER2-zero: p = 0.010, HER2-low vs. HER2-over: p = 0.012). Qualitative MRI features demonstrated an area under the curve (AUC) of 0.763 (95% confidence interval [CI]: 0.667-0.859) for distinguishing HER2-low from HER2-zero status. Quantitative features showed distinct differences between HER2-low and HER2-overexpression groups, particularly in non-mass enhancement (NME) lesions. Combined variables achieved the highest predictive accuracy for HER2-low status, with an AUC of 0.802 (95% CI: 0.701-0.903).

CONCLUSIONS

Qualitative and quantitative MRI features offer valuable insights into low-HER2-expression breast cancer. While qualitative features are more effective for mass lesions, quantitative features are more suitable for NME lesions. These findings provide a more accessible and cost-effective approach to noninvasively identifying patients who may benefit from targeted therapy.

Intratumoral and peritumoral ultrasound-based radiomics for preoperative prediction of HER2-low breast cancer: a multicenter retrospective study

OBJECTIVES

Recent advances in human epidermal growth factor receptor 2 (HER2)-targeted therapies have opened up new therapeutic options for HER2-low cancers. This study aimed to establish an ultrasound-based radiomics model to identify three different HER2 states noninvasively.

METHODS

Between May 2018 and December 2023, a total of 1257 invasive breast cancer patients were enrolled from three hospitals. The HER2 status was divided into three classes: positive, low, and zero. Four peritumoral regions of interest (ROI) were auto-generated by dilating the manually segmented intratumoral ROI to thicknesses of 5 mm, 10 mm, 15 mm, and 20 mm. After image preprocessing, 4720 radiomics features were extracted from each image of every patient. The least absolute shrinkage and selection operator and LightBoost algorithm were utilized to construct single- and multi-region radiomics signatures (RS). A clinical-radiomics combined model was developed by integrating discriminative clinical-sonographic factors with the optimal RS. A data stitching strategy was used to build patient-level models. The Shapley additive explanations (SHAP) approach was used to explain the contribution of internal prediction.

RESULTS

The optimal RS was constructed by integrating 12 tumor features and 9 peritumoral-15mm features. Age, tumor size, and seven qualitative ultrasound features were retained to construct the clinical-radiomics combined model with the optimal RS. In the training, validation, and test cohorts, the patient-level combined model showed the best discrimination ability with the macro-AUCs of 0.988 (95% CI: 0.983-0.992), 0.915 (95% CI: 0.851-0.965), and 0.862 (95% CI: 0.820-0.899), respectively.

CONCLUSION

This study built a robust and interpretable clinical-radiomics model to evaluate three classes of HER2 status based on ultrasound images.

CRITICAL RELEVANCE STATEMENT

Ultrasound-based radiomics method can noninvasively identify three different states of HER2, which may guide treatment decisions and the implementation of personalized HER2-targeted treatment for invasive breast cancer patients.

KEY POINTS

Determination of HER2 status can affect treatment options for breast cancer. The ultrasound-based clinical-radiomics model can discriminate the three different HER2 statuses. Our developed model can assist in providing personalized recommendations for novel HER2-targeted therapies.

Activity and Efficacy of Neoadjuvant Chemotherapy in Luminal-HER2 Negative Early Breast Cancer According to HER2 Score (Low vs. Score 0): A Retrospective Study

BACKGROUND

The predictive and prognostic role of HER2 status in patients with luminal-HER2 negative early breast cancer (BC) undergoing neoadjuvant chemotherapy is unclear. A retrospective analysis evaluating the correlation between HER2 status (low vs. score 0) and pCR/IDFS was conducted.

METHODS

Patients with BC undergoing neoadjuvant chemotherapy and surgery were included. HER2 low BC was defined as IHC 1+ or 2+ with negative FISH. Logistic regression model and Cox proportional hazard model were adopted to investigate the independent role of HER2 status and outcomes of interest (pCR, CPS-EG and IDFS).

RESULTS

About 566 patients were included: 60% were HER2 low and 40% were HER2 0. pCR was achieved in 13.2% of HER2 low versus 17.7% of HER2 0 (P = .15). There was no correlation between baseline HER2 status and CPS-EG score (P = .18). A trend toward improved IDFS for HER2 low BC was observed (P = .07). The relapse rate of the HER2 0 cohort peaked at 12 months after surgery, similar to the HER2 low cohort, which showed an additional peak at 36 months after surgery.

CONCLUSIONS

Among Luminal-HER2 negative early BCs, our results do not support a clear predictive and prognostic effect of HER2 status, although a trend of worse pCR and better survival for HER2 low BCs cannot be ruled out.

Predictive factors for outcome in HER2-low breast cancer patients after neoadjuvant chemotherapy

Objective

The present study aimed to evaluate the predictive factors that predict outcomes of HER2-low breast cancer patients who did not achieve pathological complete response(pCR) after neoadjuvant chemotherapy (NAC).

Methods

This study included patients with HER2-low breast cancer who received NAC from January 2017 to December 2020. Analysis of the clinicopathological features, NAC response and outcome of the patients were retrospectively analyzed. Univariate and multivariable Cox analysis were used to determine factors that predict outcomes of HER2-low breast cancer patients who did not exhibit pCR.

Results

293 Asian patients were included. The proportion of patients with hormone receptor (HR) positive and triple negative breast cancer (TNBC) among HER2-low patients was 75.8% and 24.2%, respectively. The pCR rate of HR positive cases was significantly lower than TNBC (27.5% vs. 53.5%, P=0.000). The patients who obtained pCR after NAC showed better disease-free survival(DFS) (5-year DFS 93.9% vs. 83.1%, p=0.039). For patients not achieving pCR, multivariable analysis showed that Miller/Payne (MP) grading system (hazard ratio: 0.094; 95% CI: 0.037-0.238; p=0.000) and HR status (hazard ratio: 2.561; 95% CI: 1.100-5.966; p=0.029) were significant independent predictors for DFS. Additionally, The MP grading system was also an independent predictor of overall survival (OS) (hazard ratio: 0.071; 95% CI: 0.019-0.260; p=0.000).

Conclusions

The results of our study show that pathological assessment following NAC offers valuable insights into the survival outcome of HER2-low breast cancer. According to these findings, responses to NAC should be considered when choosing systemic treatment for patients with HER2-low breast cancer.

Induction chemotherapy followed by camrelizumab plus apatinib and chemotherapy as first-line treatment for extensive-stage small-cell lung cancer: a multicenter, single-arm trial

Chemo-immunotherapy is the current first-line treatment for patients with extensive-stage small cell lung cancer (ES-SCLC), but survival benefits are modest. We aimed to evaluate the safety, antitumor activity and biomarkers of first-line camrelizumab and apatinib plus chemotherapy in untreated ES-SCLC patients. In this single-arm trial (ClinicalTrials.gov NCT05001412), eligible patients received 2 cycles of etoposide and carboplatin (EC) as induction treatment followed by 2-4 cycles of camrelizumab, apatinib plus EC, then maintenance camrelizumab plus apatinib. Primary endpoint was safety. Secondary endpoints included objective response rate (ORR), duration of response, progression-free survival (PFS), and overall survival (OS). Targeted sequencing and whole transcriptome sequencing were performed to explore biomarkers. All enrolled 40 patients were treated and analyzed for safety. During the entire treatment, treatment-emergent adverse events (TEAEs) occurred in 40 patients (100%), and 30 (75.0%) were grade ≥3. The most common grade ≥3 TEAEs were neutropenia (35.0%), anemia (15.0%) and increased alanine aminotransferase (15.0%). No treatment-related deaths occurred. Among 36 evaluable patients, ORR was 88.9% (95% CI: 73.9%-96.9%), median PFS was 7.3 months (95% CI: 6.6-9.2) and median OS was 17.3 months (11.8-not reached). Mutations in RB1, high levels of tumor mutation burden, natural killer cells, and interferons, and low levels of cancer-associated fibroblasts, correlated with prolonged PFS. Induction chemotherapy followed by camrelizumab, apatinib plus EC demonstrated acceptable safety and promising antitumor activity in untreated ES-SCLC patients. The identified biomarkers need further validation.Trial Registration ClinicalTrials.gov Identifier: NCT05001412.

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.

Prognostic value of HER2 2 + expression in patients with TNBC receiving adjuvant capecitabine

BACKGROUND

In triple-negative breast cancer (TNBC) patients receiving adjuvant capecitabine, the impact of HER2 expression on survival outcomes is unclear.

METHODS

 Between June 2017 and December 2023, 112 patients with TNBC who received adjuvant capecitabine due to residual masses after neoadjuvant chemotherapy (NACT) in three hospitals were identified. HER2 is analyzed through immunohistochemistry (IHC) and/or in situ hybridization in the core biopsy and/or post-surgical histopathologies. Relapse-free survival (RFS) and overall survival (OS), according to HER2 expression (0, 1 + , 2 +) status, were calculated (Kaplan-Meier method).

RESULTS

 Seventy-eight (69.6%) patients had HER2 zero, 20 (17.9%) patients had HER2 + 1, and 14 (12.5%) patients had HER2 + 2/ISH- BC. The 5-year OS was 62.6%, and the 5-year RFS was 55.8%. HER2 2 + expression was associated with worse OS (27.5 vs. 84.5 months; HR 4.82, 95% CI 2.15-10.80, p < 0.001) and worse RFS (11.90 months vs. not reached; HR 4.30, 95% CI 2.06-8.99, p < 0.001) compared with HER2 0/1 + expression. The 5-year OS rates were 32.7% and 72.1%, and the 5-year RFS rates were 30.6% and 64.7% in the HER2 2 + and HER2 0/1 + groups, respectively. No statistically significant differences were detected in clinicopathologic features or pathologic responses to NACT according to the HER2 expression level.

CONCLUSIONS

 Despite the use of the adjuvant capecitabine in HER2 2 + TNBC patients, these poor results will pave the way for further investigations of anti-HER2 therapeutic agents in adjuvant treatment.

Comparative analysis of metabolic characteristics and prognostic stratification of HER2-low and HER2-zero breast cancer using 18F-FDG PET/CT imaging

BACKGROUND

Recent advancements in novel anti-human epidermal growth factor receptor 2 (HER2) antibody-drug conjugates (ADCs) have highlighted the emerging HER2-low breast cancer subtype with promising therapeutic efficacy. This study aimed to comparatively analyze the metabolic characteristics and prognostic stratification of HER2-low and HER2-zero breast cancer using baseline fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) imaging.

METHODS

Consecutive patients with newly diagnosed breast cancer who underwent 18F-FDG PET/CT prior to therapy in our hospital were retrospectively reviewed. The relationship between metabolic parameters (maximum standardized uptake value (SUVmax), tumor-to-liver SUV ratio (TLR), total lesion glycolysis (TLG), and metabolic tumor volume (MTV)) in primary lesions and HER2 expression was analyzed. The survival analyses were performed to identify the prognostic factors for disease-free survival (DFS) in patients with HER2-negative (HER2-low versus -zero).

RESULTS

In total, 258 patients (mean age: 54 ± 12 years) were included. In hormone receptor (HR)-positive subgroup, SUVmax and TLR were significantly higher in HER2-low than in HER2-zero (P = 0.045 and 0.03, respectively). But in HR-negative subgroup, there was no significant metabolic difference between HER2-low and HER2-zero (All P > 0.05). The four metabolic parameters were significant predictors of DFS in HER2-negative patients (All P < 0.01), but there was no significant difference in DFS between HER2-low and -zero, regardless of tumor metabolism. Moreover, in HER2-zero patients, the DFS of patients with high metabolism was significantly shorter than that of patients with low metabolism (PSUVmax = 0.002, PMTV = 0.03, PTLG= 0.005, PTLR < 0.001, respectively), but without a similar finding in HER2-low patients.

CONCLUSION

Our study demonstrated the HR-positive HER2-low breast cancer exhibited a particularity in glucose metabolic profile. Additionally, HER2-zero patients with elevated metabolism were associated with inferior prognosis and warranted careful attention in clinical evaluations.

The Clinical Study of Intratumoral and Peritumoral Radiomics Based on DCE-MRI for HER-2 Positive and Low Expression Prediction in Breast Cancer

Background

Core biopsy sampling may not fully capture tumor heterogeneity. Radiomics provides a non-invasive method to assess tumor characteristics, including both the core and surrounding tissue, with the potential to improve the accuracy of HER-2 status prediction.

Objective

To explore the clinical value of intratumoral and peritumoral radiomics features from dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) for preoperative prediction of human epidermal growth factor receptor-2 (HER-2) expression status in breast cancer.

Methods

Two tasks were designed, including Task1-distinguished HER-2 positive and HER-2 negative from 382 breast cancer patients and Task2-distinguished HER-2 low and HER-2 zero expression from 249 patients with HER-2 negative. Three radiomics models (intratumoral, peritumoral 5 mm, intratumoral+peritumoral 5 mm) were constructed based on decision tree, and clinical combined radiomics models were constructed with logistic regression based on clinicopathological features and radscore. The area under the curve (AUC), sensitivity, specificity, accuracy and decision curve analysis (DCA) were used to evaluate the predictive performance of models.

Results

Estrogen receptor (ER), progesterone receptor (PR) and Ki67 showed statistically significant in the different groups of HER-2 expression. Additionally, magnetic resonance imaging-reported axillary lymph nodes (MRI-reported ALN) in the positive and negative groups and histological grade in the low and zero expression groups showed significant differences (all P < 0.05). For task 1, the peritumoral radiomics model outperformed the other two radiomics models, with AUC values of 0.774 and 0.727 in the training and testing sets, respectively. For task 2, intratumoral + peritumoral radiomics model in the testing set showed the best predictive performance among the three radiomics models, and the AUC values were 0.777. The addition of clinicopathological features slightly altered the AUC values in both tasks.

Conclusion

Both radiomics methods based on DCE-MRI and the nomogram are helpful for preoperative prediction of HER-2 expression status.

Genomic landscape of circulating tumor DNA in HER2-low metastatic breast cancer

The large population of HER2-low breast cancer patients necessitates further research to provide enhanced clinical guidance. In this study, we retrospectively analyzed 1071 metastatic breast cancer (MBC) patients and the circulating tumor DNA (ctDNA) to investigate clinicopathological and genetic alterations of HER2-low MBC patients. The effect of HER2-low status on different treatment modalities was explored in two prospective clinical trials (NCT03412383, NCT01917279) and a retrospective study. Our findings suggest TP53, PIK3CA, and ESR1 are frequently mutated genes in HER2-low MBC. Compared to the HER2-0 group, mutations observed in the HER2-low group are more closely associated with metabolic pathway alterations. Additionally, among patients with ERBB2 mutations and treated with pyrotinib, the HER2-low group may experience superior prognosis when compared to the HER2-0 group. Notably, we did not find any statistically significant disparity in the response to chemotherapy, endocrine therapy, or CDK4/6 inhibitor therapy between HER2-0 and HER2-low breast cancer patients. Interestingly, within the subgroup of individuals with metabolic pathway-related gene mutations, we found that HER2-low group exhibited a more favorable response to these treatments compared to HER2-0 group. Additionally, dynamic analysis showed the HER2-low MBC patients whose molecular tumor burden index decreased or achieved early clearance of ctDNA after the initial two treatment cycles, exhibited prolonged survival. Moreover, we classified HER2-low MBC into three clusters, providing a reference for subsequent treatment with enhanced precision. Our study offers valuable insights into the biology of HER2-low MBC and may provide reference for personalized treatment strategies.

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 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.

Deciphering HER2-low breast cancer (BC): insights from real-world data in early stage breast cancer

Background

Human epidermal growth factor receptor 2 (HER2)-low has emerged as a potential new entity in breast cancer (BC). Data on this subset are limited, and prognostic results are controversial, evidencing the need of further data in a BC real-world cohort.

Methods

Patients with HER2-negative stage I-III BC diagnosed between 2006 and 2016 were retrospectively reviewed in a single cohort from the Catalan Institute of Oncology Badalona. Demographics and clinicopathological characteristics were examined via medical charts/electronic health records. We aim to describe and compare HER2-0/HER2-low populations through Chi-square or Fisher test, and explore its prognostic impact using Kaplan-Meier curves and Cox regression models.

Results

From a cohort of 1755 BC patients, 1401 invasive HER2-negative, stage I-III cases were evaluated. 87% were hormone receptor (HR)-positive versus 13% triple negative (TNBC). Overall, 43% were HER2-0 and 57% HER2-low (61% immunohistochemistry (IHC) 1+ and 39% IHC 2+). Comparing HER2-low versus HER2-0, HER2-low showed higher proportion of estrogen receptor (ER)-positive (91.6% vs 79.9%, p ⩽ 0.001) and progesterone receptor (PR)-positive (79.8% vs 68.9%, p ⩽ 0.001) cases. HER2-0 exhibited higher proportion of TNBC (20.1% vs 8.4%, p = 0.001), grade III tumors (28.8% vs 23.5%, p = 0.039), and higher Ki67 median value (26.47% vs 23.88%, p = 0.041). HER2-low was associated with longer time to distant recurrence (TTDR) compared to HER2-0 (67.8 vs 54.1 months; p = 0.015) and better BC-related survival (19.2 vs 16.3 years; p = 0.033). In the multivariable analysis, HER2-low was not an independent prognostic factor for TTDR and BC-related survival. ER expression showed a strong association with longer TTDR (Hazard Ratio: 0.425, p ⩽ 0.001) and improved BC-related survival (Hazard Ratio: 0.380, p ⩽ 0.001). PR expression was also associated with longer TTDR (Hazard Ratio: 0.496, p ⩽ 0.001), and improved BC-related survival (Hazard Ratio: 0.488, p ⩽ 0.001). Histological grade III was significantly associated with shorter TTDR (Hazard Ratio: 1.737, p = 0.002). Positive nodal status was the strongest factor correlated with worse BC-related survival (Hazard Ratio: 2.747, p ⩽ 0.001).

Conclusion

HER2-low was significantly associated with HR-positive disease, whereas HER2-0 group had higher incidence of TNBC, histological grade III and higher Ki67%. Although HER2-low group was associated with longer TTDR and improved BC-related survival, these findings could be explained by the greater proportion of favorable prognostic features in this subgroup compared to HER2-0.

Comparison of the Pathological Complete Response Rate and Survival Between HER2-Low and HER2-Zero Breast Cancer in Neoadjuvant Chemotherapy Setting: A Systematic Review and Meta-Analysis

Although HER2-low breast cancer (BC) constitutes almost 50% of all BC types, its impact on the pathological complete response (pCR) rate and survival in early BC is uncertain. As a result, a systematic review was conducted to compare the pCR rate and survival of HER2-low and HER2-zero BC in the neoadjuvant chemotherapy (NACT) setting. Two reviewers independently performed literature searches using EMBASE, PubMed, and Cochrane Libraries internet databases up to June 2023. Finally, 29 studies with 178,294 patients were included. HER2-low BC had a considerably lower pCR rate compared to HER2-zero BC in the entire population (Risk Ratio [RR] = 0.68, P < .001) and in the hormone receptor (HR)-positive subgroup (RR = 0.73, P = .009), but not in the HR-negative subgroup (RR = 0.99, P = .755). Furthermore, patients with HER2-low BC exhibited prolonged disease-free survival (DFS) and overall survival (OS) compared to those with HER2-zero BC, observed in both the entire cohort (DFS: P = .004; OS: P = .008) and the HR-negative subgroup (DFS: P = .009; OS: P < .001). In the HR-positive population, OS was superior in HER2-low BC patients (P < .001), whereas no significant differences in DFS were observed (P = .064). Our findings imply that the pCR rate and prognosis of HER2-low BC are distinguished from those of HER2-zero BC in early BC treated with NACT, which contributes to a better knowledge of the BC subgroup.

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.

A Nationwide Study on HER2-Low Breast Cancer in South Korea: Its Incidence of 2022 Real World Data and the Importance of Immunohistochemical Staining Protocols

PURPOSE

Notable effectiveness of trastuzumab deruxtecan in patients with human epidermal growth factor receptor 2 (HER2)-low advanced breast cancer (BC) has focused pathologists' attention. We studied the incidence and clinicopathologic characteristics of HER2-low BC, and the effects of immunohistochemistry (IHC) associated factors on HER2 IHC results.

MATERIALS AND METHODS

The Breast Pathology Study Group of the Korean Society of Pathologists conducted a nationwide study using real-world data on HER2 status generated between January 2022 and December 2022. Information on HER2 IHC protocols at each participating institution was also collected.

RESULTS

Total 11,416 patients from 25 institutions included in this study. Of these patients, 40.7% (range, 6.0% to 76.3%) were classified as HER2-zero, 41.7% (range, 10.5% to 69.1%) as HER2-low, and 17.5% (range, 6.7% to 34.0%) as HER2-positive. HER2-low tumors were associated with positive estrogen receptor and progesterone receptor statuses (p < 0.001 and p < 0.001, respectively). Antigen retrieval times (≥ 36 minutes vs. < 36 minutes) and antibody incubation times (≥ 12 minutes vs. < 12 minutes) affected on the frequency of HER2 IHC 1+ BC at institutions using the PATHWAY HER2 (4B5) IHC assay and BenchMark XT or Ultra staining instruments. Furthermore, discordant results between core needle biopsy and subsequent resection specimen HER2 statuses were observed in 24.1% (787/3,259) of the patients.

CONCLUSION

The overall incidence of HER2-low BC in South Korea concurs with those reported in previously published studies. Significant inter-institutional differences in HER2 IHC protocols were observed, and it may have impact on HER2-low status. Thus, we recommend standardizing HER2 IHC conditions to ensure precise patient selection for targeted therapy.

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.

Efficacy and prognosis of neoadjuvant chemotherapy in HER2 low-expressing breast cancer: a retrospective single-center study

Purpose

Human epidermal growth factor receptor 2 (HER2) is vital for breast cancer prognosis. The aim of this study was to analyze the clinicopathological data of HER2-negative breast cancer patients receiving neoadjuvant chemotherapy and the associated factors affecting the pathological complete response rate (pCR) and prognosis.

Methods

Clinical data of 173 patients with primary HER2-negative breast cancer, who initially received neoadjuvant chemotherapy followed by surgical treatment at the Breast Surgery Department of Bethune Hospital in Shanxi Province from January 2012 to December 2022, were collected.

Results

Compared to HER2-0 patients, HER2-low patients had higher T staging (p = 0.008), higher Ki67 proliferation index (p < 0.001), lower N staging (p = 0.001), and lower pCR rate (p < 0.001). Univariate analysis revealed that T stage, TNM stage, HR status, HER2 status, and Ki67 are risk factors that affect the pCR rate in HER-2 negative. Multivariate analysis identified HR status as an independent predictor of pCR rate. Kaplan-Meier survival curves showed that menstrual status, N staging, T staging, TNM staging, and pCR status affected the prognosis of HER2-low breast cancer patients (p < 0.05).

Conclusion

HER2-low breast cancer exhibits distinct biological behaviors, suggesting personalized treatment approaches.

Ultrasound-based radiomics nomogram for predicting HER2-low expression breast cancer

Purpose

Accurate preoperative identification of Human epidermal growth factor receptor 2 (HER2) low expression breast cancer (BC) is critical for clinical decision-making. Our aim was to use machine learning methods to develop and validate an ultrasound-based radiomics nomogram for predicting HER2-low expression in BC.

Methods

In this retrospective study, 222 patients (108 HER2-0 expression and 114 HER2-low expression) with BC were included. The enrolled patients were randomly divided into a training cohort and a test cohort with a ratio of 8:2. The tumor region of interest was manually delineated from ultrasound image, and radiomics features were subsequently extracted. The features underwent dimension reduction using the least absolute shrinkage and selection operator (LASSO) algorithm, and rad-score were calculated. Five machine learning algorithms were applied for training, and the algorithm demonstrating the best performance was selected to construct a radiomics (USR) model. Clinical risk factors were integrated with rad-score to construct the prediction model, and a nomogram was plotted. The performance of the nomogram was assessed using receiver operating characteristic curve and decision curve analysis.

Results

A total of 480 radiomics features were extracted, out of which 11 were screened out. The majority of the extracted features were wavelet features. Subsequently, the USR model was established, and rad-scores were computed. The nomogram, incorporating rad-score, tumor shape, border, and microcalcification, achieved the best performance in both the training cohort (AUC 0.89; 95%CI 0.836-0.936) and the test cohort (AUC 0.84; 95%CI 0.722-0.958), outperforming both the USR model and clinical model. The calibration curves showed satisfactory consistency, and DCA confirmed the clinical utility of the nomogram.

Conclusion

The nomogram model based on ultrasound radiomics exhibited high prediction value for HER2-low BC.

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.

Machine learning models for differential diagnosing HER2-low breast cancer: A radiomics approach

To develop machine learning models based on preoperative dynamic enhanced magnetic resonance imaging (DCE-MRI) radiomics and to explore their potential prognostic value in the differential diagnosis of human epidermal growth factor receptor 2 (HER2)-low from HER2-positive breast cancer (BC). A total of 233 patients with pathologically confirmed invasive breast cancer admitted to our hospital between January 2018 and December 2022 were included in this retrospective analysis. Of these, 103 cases were diagnosed as HER2-positive and 130 cases were HER2 low-expression BC. The Synthetic Minority Oversampling Technique is employed to address the class imbalance problem. Patients were randomly split into a training set (163 cases) and a validation set (70 cases) in a 7:3 ratio. Radiomics features from DCE-MRI second-phase imaging were extracted. Z-score normalization was used to standardize the radiomics features, and Pearson's correlation coefficient and recursive feature elimination were used to explore the significant features. Prediction models were constructed using 6 machine learning algorithms: logistic regression, random forest, support vector machine, AdaBoost, decision tree, and auto-encoder. Receiver operating characteristic curves were constructed, and predictive models were evaluated according to the area under the curve (AUC), accuracy, sensitivity, and specificity. In the training set, the AUC, accuracy, sensitivity, and specificity of all models were 1.000. However, in the validation set, the auto-encoder model's AUC, accuracy, sensitivity, and specificity were 0.994, 0.976, 0.972, and 0.978, respectively. The remaining models' AUC, accuracy, sensitivity, and specificity were 1.000. The DeLong test showed no statistically significant differences between the machine learning models in the training and validation sets (Z = 0, P = 1). Our study investigated the feasibility of using DCE-MRI-based radiomics features to predict HER2-low BC. Certain radiomics features showed associations with HER2-low BC and may have predictive value. Machine learning prediction models developed using these radiomics features could be beneficial for distinguishing between HER2-low and HER2-positive BC. These noninvasive preoperative models have the potential to assist in clinical decision-making for HER2-low breast cancer, thereby advancing personalized clinical precision.

Preliminary study on DCE-MRI radiomics analysis for differentiation of HER2-low and HER2-zero breast cancer

Purpose

This study aims to evaluate the utility of radiomic features from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in distinguishing HER2-low from HER2-zero breast cancer.

Patients and methods

We retrospectively analyzed 118 MRI cases, including 78 HER2-low and 40 HER2-zero patients confirmed by immunohistochemistry or fluorescence in situ hybridization. From each DCE-MRI case, 960 radiomic features were extracted. These features were screened and reduced using intraclass correlation coefficient, Mann-Whitney U test, and least absolute shrinkage to establish rad-scores. Logistic regression (LR) assessed the model's effectiveness in distinguishing HER2-low from HER2-zero. A clinicopathological MRI characteristic model was constructed using univariate and multivariate analysis, and a nomogram was developed combining rad-scores with significant MRI characteristics. Model performance was evaluated using the receiver operating characteristic (ROC) curve, and clinical benefit was assessed with decision curve analysis.

Results

The radiomics model, clinical model, and nomogram successfully distinguished between HER2-low and HER2-zero. The radiomics model showed excellent performance, with area under the curve (AUC) values of 0.875 in the training set and 0.845 in the test set, outperforming the clinical model (AUC = 0.691 and 0.672, respectively). HER2 status correlated with increased rad-score and Time Intensity Curve (TIC). The nomogram outperformed both models, with AUC, sensitivity, and specificity values of 0.892, 79.6%, and 82.8% in the training set, and 0.886, 83.3%, and 90.9% in the test set.

Conclusions

The DCE-MRI-based nomogram shows promising potential in differentiating HER2-low from HER2-zero status in breast cancer patients.

Association between Homologous Recombination Repair Defect Status and Long-Term Prognosis of Early HER2-Low Breast Cancer: A Retrospective Cohort Study

BACKGROUND

As a newly identified subtype of HER2-negative tumors associated with a less favorable prognosis, it remains crucial to evaluate potential prognostic and predictive factors, particularly non-invasive biomarkers, for individuals with human epidermal growth factor 2 (HER2) low early-stage breast cancer (EBC). Multiple investigations have highlighted that HER2-negative patients with EBC exhibiting high homologous recombination deficiency (HRD) scores display lower rates of pathological complete response (PCR) to neoadjuvant chemotherapy (NAC). Nevertheless, no study to date has explored the correlation between HRD and the long-term prognosis in HER2-low patients with EBC.

PATIENTS AND METHODS

This retrospective observational study focuses on primary EBC sourced from The Cancer Genome Atlas dataset (TCGA). It reveals the gene mutation landscape in EBC with low HER2 expression and elucidates the tumor immune landscape across different HRD states. Utilizing bioinformatics analysis and Cox proportional models, along with the Kaplan-Meier method, the study assesses the correlation between HRD status and disease-specific survival (DSS), disease-free interval (DFI), and progression-free interval (PFI). Subgroup analyses were conducted to identify potential variations in the association between HRD and prognosis.

RESULTS

In the patients with HER2-low breast cancer, patients with homologous recombination related genes (HRRGs) defects had an HRD score about twice that of those without related genes mutations, and were at higher risk of acquiring ARID1A, ATM, and BRCA2 mutations. We also found that most immune cell abundances were significantly higher in EBC tumors with high HRD than in EBC tumors with low HRD or HRD-medium, particularly plasma B-cell abundance, CD8 T-cell abundance, and M1 macrophages. In addition, these tumors with HRD-high also appear to have significantly higher tumor immune scores and lower interstitial scores. Then, we analyzed the relationship between different HRD status and prognosis. There was statistical significance (P = .036 and P = .046, respectively) in DSS and PFI between the HRD-low and HRD-high groups, and patients with HRD-high EBC showed relatively poor survival outcomes. A medium HRD score (hazard ratio, HR = 2.15, 95% CI: 1.04-4.41, P = .038) was a significant risk factor for PFI. Hormone receptor positivity is an important factor in obtaining medium-high HRD score and poor prognosis.

CONCLUSION

Higher HRD scores were associated with poorer PFI outcomes, particularly in people with HR+/HER2-low. Varied HRD states exhibited distinctions in HRRGs and the tumor immune landscape. These insights have the potential to assist clinicians in promptly identifying high-risk groups and tailoring personalized treatments for patients with HER2-low EBC, aiming to enhance long-term outcomes.

Relationship between HER2-low status and efficacy of CDK4/6 inhibitors in advanced breast cancer: a real-world study

AIMS AND OBJECTIVES

Human epidermal growth factor receptor 2 (HER2)-low breast cancer (BC) is a new entity considered a biologically distinct subtype from HER2-zero BC. However, the importance of HER2 low expression on the activity of cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) remains unclear.

METHODS/MATERIALS

We conducted a single-center retrospective study including hormone receptor-positive (HR +) /HER2- metastatic BC (mBC) patients treated with CDK4/6i plus endocrine treatment (ET) as first-line therapy. Clinical outcomes were analyzed according to HER2 expression.

RESULTS

258 women were analyzed with a median follow-up of 25.4 months; 39.9% had HER2 low, and 60.1% had HER2 zero BC. Median progression-free survival (mPFS) in the HER2-low group was 27.6 months compared with 44.3 months in the HER2-zero group (p = 0.341). In patients receiving ribociclib, the mPFS in the HER2-low group was 24.2 months compared with 53.1 months in the HER2-zero group (multivariate-adjusted HR: 1.981, 95 Cl 1.094-3.586; p = 0.024). The survival probabilities at 24, 36 and 48 months for the HER2 low and HER2 zero groups were 82%, 69%, 69% and 83%, 75% and 69%, respectively (p = 0.336). Objective response rate (p = 0.179) and disease control rate (p = 0.338) did not significantly differ between HER-2-low and HER-2-zero groups.

CONCLUSIONS

The mPFS in the Her2-zero group was almost twice that of the Her2-low group, but the difference was not statistically significant. mPFS was significantly longer in the HER2-zero group compared to the HER2-low group in patients receiving ribociclib. More prospective studies are needed to understand the actual consequences of this biomarker.

Performance evaluation of ML models for preoperative prediction of HER2-low BC based on CE-CBBCT radiomic features: A prospective study

To explore the value of machine learning (ML) models based on contrast-enhanced cone-beam breast computed tomography (CE-CBBCT) radiomics features for the preoperative prediction of human epidermal growth factor receptor 2 (HER2)-low expression breast cancer (BC). Fifty-six patients with HER2-negative invasive BC who underwent preoperative CE-CBBCT were prospectively analyzed. Patients were randomly divided into training and validation cohorts at approximately 7:3. A total of 1046 quantitative radiomic features were extracted from CE-CBBCT images and normalized using z-scores. The Pearson correlation coefficient and recursive feature elimination were used to identify the optimal features. Six ML models were constructed based on the selected features: linear discriminant analysis (LDA), random forest (RF), support vector machine (SVM), logistic regression (LR), AdaBoost (AB), and decision tree (DT). To evaluate the performance of these models, receiver operating characteristic curves and area under the curve (AUC) were used. Seven features were selected as the optimal features for constructing the ML models. In the training cohort, the AUC values for SVM, LDA, RF, LR, AB, and DT were 0.984, 0.981, 1.000, 0.970, 1.000, and 1.000, respectively. In the validation cohort, the AUC values for the SVM, LDA, RF, LR, AB, and DT were 0.859, 0.880, 0.781, 0.880, 0.750, and 0.713, respectively. Among all ML models, the LDA and LR models demonstrated the best performance. The DeLong test showed that there were no significant differences among the receiver operating characteristic curves in all ML models in the training cohort (P > .05); however, in the validation cohort, the DeLong test showed that the differences between the AUCs of LDA and RF, AB, and DT were statistically significant (P = .037, .003, .046). The AUCs of LR and RF, AB, and DT were statistically significant (P = .023, .005, .030). Nevertheless, no statistically significant differences were observed when compared to the other ML models. ML models based on CE-CBBCT radiomics features achieved excellent performance in the preoperative prediction of HER2-low BC and could potentially serve as an effective tool to assist in precise and personalized targeted therapy.

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.

The effects of low HER2 expression on survival in patients with metastatic breast cancer treated with CDK 4/6 inhibitors: a multicenter retrospective study

PURPOSE

Endocrine therapy (ET) in combination with CDK 4/6 inhibitors (CDK 4/6i) is the standard treatment modality for hormone receptor (HR)-positive and HER2-negative metastatic breast cancer (mBC). There is uncertainty about the prognostic and predictive value of HER2-low status and whether HER2-low BC is an individual biologic subtype. In this study, we aimed to investigate the prognostic effect of HER2 expression status on survival in mBC patients treated with first-line ET plus CDK 4/6i.

METHODS

This multicenter retrospective study included patients with HR + /HER2-negative mBC cancer who were treated with first-line CDK 4/6i in combination with ET from January 2016 to March 2023. Patients were divided into two groups (HER2-low and zero), and survival and safety analyses were performed.

RESULTS

A total of 201 patients were included in this study; of these, 73 (36.3%) had HER2-low disease and 128 (63.7%) had HER2-zero. There were 135 patients (67.2%) treated with ribociclib and 66 (32.8%) with palbociclib. Most of the patients (75.1%) received aromatase inhibitors as combination-endocrine therapy. Baseline characteristics were similar between the two groups. The median follow-up was 19.1 months (range: 2.5-78.4). The most common side effect was neutropenia (22.4%). The frequency of grade 3-4 toxicity was similar between the HER2-zero and low patients (32% vs 31.5%; p = 0.939). Visceral metastases were present in 44.8% of patients. Between the HER2-low and zero groups, median PFS (25.2 vs 22.6 months, p = 0.972) and OS (not reached vs 37.5 months, p = 0.707) showed no statistically significant differences.

CONCLUSION

The prognostic value of HER2-low status remains controversial. Our study showed no significant effect of HER2 low expression on survival in patients receiving CDK 4/6i plus ET.

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.

Human epidermal growth factor receptor 2 expression level and combined positive score can evaluate efficacy of advanced gastric cancer

BACKGROUND

Although treatment options for gastric cancer (GC) continue to advance, the overall prognosis for patients with GC remains poor. At present, the predictors of treatment efficacy remain controversial except for high microsatellite instability.

AIM

To develop methods to identify groups of patients with GC who would benefit the most from receiving the combination of a programmed cell death protein 1 (PD-1) inhibitor and chemotherapy.

METHODS

We acquired data from 63 patients with human epidermal growth factor receptor 2 (HER2)-negative GC with a histological diagnosis of GC at the Cancer Hospital, Chinese Academy of Medical Sciences between November 2020 and October 2022. All of the patients screened received a PD-1 inhibitor combined with chemotherapy as the first-line treatment.

RESULTS

As of July 1, 2023, the objective response rate was 61.9%, and the disease control rate was 96.8%. The median progression-free survival (mPFS) for all patients was 6.3 months. The median overall survival was not achieved. Survival analysis showed that patients with a combined positive score (CPS) ≥ 1 exhibited an extended trend in progression-free survival (PFS) when compared to patients with a CPS of 0 after receiving a PD-1 inhibitor combined with oxaliplatin and tegafur as the first-line treatment. PFS exhibited a trend for prolongation as the expression level of HER2 increased. Based on PFS, we divided patients into two groups: A treatment group with excellent efficacy and a treatment group with poor efficacy. The mPFS of the excellent efficacy group was 8 months, with a mPFS of 9.1 months after excluding a cohort of patients who received interrupted therapy due to surgery. The mPFS was 4.5 months in patients in the group with poor efficacy who did not receive surgery. Using good/poor efficacy as the endpoint of our study, univariate analysis revealed that both CPS score (P = 0.004) and HER2 expression level (P = 0.015) were both factors that exerted significant influence on the efficacy of treatment the combination of a PD-1 inhibitor and chemotherapy in patients with advanced GC (AGC). Finally, multivariate analysis confirmed that CPS score was a significant influencing factor.

CONCLUSION

CPS score and HER2 expression both impacted the efficacy of immunotherapy combined with chemotherapy in AGC patients who were non-positive for HER2.

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.

Clinical sequencing defines the somatic and germline mutation landscapes of Chinese HER2-Low Breast Cancer

More than half of the breast cancer initially labeled as human epidermal growth factor receptor 2 (HER2)-negative actually exhibited low HER2 levels (IHC 1+ or IHC 2+/FISH-) and were classified as HER2-low breast cancer. Previous research emphasized the significant biological heterogeneity in HER2-low breast cancer, highlighting the importance of accurately characterizing HER2-low tumors to promote the precise management of antibody‒drug conjugates. In this study, we established a large-scale targeted sequencing cohort (N = 1907) representing Chinese HER2-low breast cancer patients with detailed clinical annotation. Our research findings revealed that HER2-low breast cancer demonstrated distinct clinical pathological characteristics and mutation landscapes compared to HER2-zero group. When compared to HER2-zero tumors, HER2-low tumors exhibited a higher proportion of Luminal B subtypes and better disease-free survival. In hormone receptor (HR)-positive breast cancer, HER2-low group showed a higher frequency of GATA3 somatic mutations, BRCA2 germline mutations, and mutations in the DNA damage repair pathway. In contrast, in HR-negative breast cancer, the HER2-low group displayed a higher frequency of PIK3CA mutations and PI3K pathway alterations. These findings offered valuable insights for the precise targeted treatment of HER2-low breast cancer in different HR statuses.

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.

Effect of HER2-low expression on neoadjuvant efficacy in operable breast cancer

OBJECTIVE

To investigate the effects of HER2-low expression (HER2-low) and HER2-zero expression (HER2-0) on the pathological complete response (pCR) rate and survival of patients following neoadjuvant chemotherapy.

METHODS

Eighty-six patients were followed up. Patients were divided into HER2-0 (immunohistochemistry (IHC) score of 0 (IHC0)) and HER2-low (IHC1+ or IHC2+/in situ hybridization non-amplified (ISH-)) groups according to the IHC detection of puncture tissues. After neoadjuvant chemotherapy, the clinical characteristics, pCR rate and DFS were compared between the two groups.

RESULTS

There were 24 (27.9%) cases with HER2-0 and 62 (72.1%) cases with HER2-low. Hormone receptor-positive (HR+) patients accounted for 77.4% of the HER2-low group, which was higher than 70.8% in the HER2-0 group, and there was no significant difference between the two groups (p = 0.524). There were statistical differences in the pT and pN stages between HER2-low and HER2-0 subgroups in the triple-negative breast cancer (TNBC) group after neoadjuvant chemotherapy. The HER2-low subgroup had an earlier T stage (p = 0.009), and the ratio of N0 to N1 in the HER2-low and HER2-0 subgroups was 92.9% and 71.4%, respectively (p = 0.037). The Ki-67 index and median PR value were significantly lower in the HER2-low group after neoadjuvant chemotherapy (p = 0.002, p = 0.018). The HER2 IHC score was altered in the HER2-low group, and the HER-2 (2+) score changed significantly (p = 0.002). Seventy-eight patients with complete immunohistochemical data were analyzed. The discordance rate of the IHC score of HER2 after neoadjuvant chemotherapy was 38.5%, and eight patients with HER2-low showed HER2-0 status, with a discordance rate of 10.3%. After neoadjuvant chemotherapy, The pCR rate was significantly lower in the HER2-low group compared with that in the HER2-0 group (4.8% vs. 8.3%; p = 0.914), but the recurrence and metastasis rates were lower in the HER2-low group (9.7% vs. 20.8%; p = 0.165). There were no differences in DFS between the two groups at 6, 12, 24, and 36 months (p = 0.076; p = 0.518; p = 0.245; p = 0.406). The subgroup analysis demonstrated no significant difference in DFS between HER2-low and HER2-0 subgroups in the HR + and TNBC groups (p = 0.141, p = 0.637).

CONCLUSION

This retrospective study indicates that HER2-low has no significant effect on neoadjuvant efficacy in operable breast cancer. There were no statistical differences in clinical characteristics, pCR rate, and DFS between the HER2-low and the HER2-0 groups. There was no evidence that a HER2-low status constitutes a unique biological subtype, suggesting that more clinical data might be needed to verify these observations.

Development and Validation of MRI Radiomics Models to Differentiate HER2-Zero, -Low, and -Positive Breast Cancer

BACKGROUND. Breast cancer HER2 expression has been redefined using a three-tiered system, with HER2-zero cancers considered ineligible for HER2-targeted therapy, HER2-low cancers considered candidates for novel HER2-targeted drugs, and HER2-positive cancers treated with traditional HER2-targeted medications. OBJECTIVE. The purpose of this study was to assess MRI radiomics models for a three-tiered classification of HER2 expression of breast cancer. METHODS. This retrospective study included 592 patients with pathologically confirmed breast cancer (mean age, 47.0 ± 18.0 [SD] years) who underwent breast MRI at either of a health system's two hospitals from April 2016 through June 2022. Three-tiered HER2 status was pathologically determined. Radiologists assessed the conventional MRI features of tumors and manually segmented the tumors on multiparametric sequences (T2-weighted images, DWI, ADC maps, and T1-weighted delayed contrast-enhanced images) to extract radiomics features. Least absolute shrinkage and selection operator analysis was used to develop two radiomics signatures, to differentiate HER2-zero cancers from HER2-low or HER2-positive cancers (task 1) as well as to differentiate HER2-low cancers from HER2-positive cancers (task 2). Patients from hospital 1 were randomly assigned to a discovery set (task 1: n = 376; task 2: n = 335) or an internal validation set (task 1: n = 161; task 2: n = 143); patients from hospital 2 formed an external validation set (task 1: n = 55; task 2: n = 50). Multivariable logistic regression analysis was used to create nomograms combining radiomics signatures with clinicopathologic and conventional MRI features. RESULTS. AUC, sensitivity, and specificity in the discovery, internal validation, and external validation sets were as follows: for task 1, 0.89, 99.4%, and 69.0%; 0.86, 98.6%, and 76.5%; and 0.78, 100.0%, and 0.0%, respectively; for task 2, 0.77, 93.8%, and 32.3%; 0.75, 92.9%, and 6.8%; and 0.77, 97.0%, and 29.4%, respectively. For task 1, no nomogram was created because no clinicopathologic or conventional MRI feature was associated with HER2 status independent of the MRI radiomics signature. For task 2, a nomogram including an MRI radiomics signature and three pathologic features (histologic grade of III, high Ki-67 index, and positive progesterone receptor status) that were independently associated with HER2-low expression had an AUC of 0.87, 0.83, and 0.80 in the three sets. CONCLUSION. MRI radiomics features were used to differentiate HER2-zero from HER2-low cancers or HER2-positives cancers as well as to differentiate HER2-low cancers from HER2-positive cancers. CLINICAL IMPACT. MRI radiomics may help select patients for novel or traditional HER2-targeted therapies, particularly those patients with ambiguous results of immunohistochemical staining results or limited access to fluorescence in situ hybridization.

Convenient determination of serum HER-2 status in breast cancer patients using Raman spectroscopy

Given the significant therapeutic efficacy of anti-HER-2 treatment, the HER-2 status is a crucial piece of information that must be obtained in breast cancer patients. Currently, as per guidelines, HER-2 status is typically acquired from breast tissue of patients. However, there is growing interest in obtaining HER-2 status from serum and other samples due to the convenience and potential for dynamic monitoring. In this study, we have developed a serum Raman spectroscopy technique that allows for the rapid acquisition of HER-2 status in a convenient manner. The established HER-2 negative and positive classification model achieved an area under the curve of 0.8334. To further validate the reliability of our method, we replicated the process using immunohistochemistry and in situ hybridization. The results demonstrate that serum Raman spectroscopy, coupled with artificial intelligence algorithms, is an effective technical approach for obtaining HER-2 status.

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.

Impact of HER2-low expression on the efficacy of endocrine therapy with or without CDK4/6 inhibitor in HR-positive/HER2-negative metastatic breast cancer: A prospective study

BACKGROUND

CDK4/6 inhibitors in combination with traditional endocrine therapy (ET) have become the recommended first-line therapy for HR-positive/HER2-negative metastatic breast cancer (MBC). The aim of this prospective study was to evaluate the relationship between HER2-low expression and clinical outcomes in HR-positive/HER2-negative MBC patients receiving ET with or without CDK4/6 inhibitors.

METHODS

Between April 2016 and November 2019, 233 women with HR-positive/HER2-negative MBC who received ET with or without CDK4/6 inhibitors were enrolled into the study. The primary endpoint was progression-free survival (PFS). Statistical analysis included descriptive statistics, Kaplan-Meier curves, and Cox proportional hazards models.

RESULTS

HER2-low and HER2-zero subgroups in the CDK4/6 inhibitor plus ET cohort showed no significant difference in the median PFS (10.9 vs. 8.0 months; hazard ratio: 0.92; 95% confidence interval [CI]: 0.64-1. 30; p = 0.65), while HER2-low subgroup showed a significantly shorter median PFS compared to the HER2-zero subgroup in the ET alone cohort (5.6 vs. 17.0 months; hazard ratio: 2.82; 95% CI: 1.34-5.93; p = 0.0044). Moreover, the objective response rate was significantly lower in the HER2-low subgroup than the HER2-zero subgroup in the ET alone cohort (10.5% vs. 40.0%, p = 0.047). Lastly, no significant difference was observed in the overall survival between the HER2-low and HER2-zero subgroups in both cohorts.

CONCLUSION

This study suggested that HER2-low expression may predict the efficacy of ET but not that of CDK4/6 inhibitor plus ET in HR-positive/HER2-negative MBC patients. The results of this study highlight the importance of integrating HER2 status in tailoring personalized treatment strategies for HR-positive MBC.

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.

HER2-Low Status Was Associated With Better Breast Cancer-Specific Survival in Early-Stage Triple-Negative Breast Cancer

BACKGROUND

Based on the association between the hormone receptor and the status of human epidermal growth factor receptor 2 (HER2)-low, we investigated the clinicopathological and prognostic characteristics of the HER2-low status in early-stage triple-negative breast cancer (TNBC).

METHODS

We collected the data of patients with TNBC who received treatment at our hospital and compared the pathological complete response (pCR) rate, overall survival (OS), and breast cancer-specific survival (BCSS) between the HER2-0 and HER2-low subtypes.

RESULTS

A total of 1445 patients were included in the study, of which 698 patients (48.3%) showed HER2-low status. A similar pCR rate was observed between HER2-0 and HER2-low patients (34.9% vs. 37.4%; P = .549). T staging, N staging, and HER2 status were associated with BCSS, whereas T staging and N staging were associated with OS. Patients with the HER2-low status showed better BCSS than those with the HER2-0 status (96.6% vs. 93.7%; log-rank P = .027). In patients with non-pCR, the BCSS of the HER2-low subgroup was better than that of the HER2-0 subgroup (log-rank P = .047); however, no similar result was observed in patients with pCR. In patients with stage III, the BCSS and OS of the HER2-low subgroup were better than those of the HER2-0 subgroup (BCSS, log-rank P = .010; OS, log-rank P = .047). No similar results were observed in patients with stages I and II.

CONCLUSION

The HER2-low expression was associated with better BCSS in TNBC, especially in the high-risk groups, suggesting that HER2-low breast cancer is a potential independent biological subtype.

Prognostic value and relapse pattern of HER2-low in hormone receptor-positive breast cancer

BACKGROUND

A new concept of HER2-low has emerged in recent years. However, the prognostic value and the relapse pattern of HER2-low is unclear.

METHODS

Our study included patients diagnosed with HER2-negative/hormone receptor-positive breast cancer to explore the differences in survival outcomes between the HER2-low group and the HER2-zero group. More importantly, we explored different recurrence patterns, including the comparison of metastatic sites and recurrence time curve between the two groups.

RESULTS

A total of 797 patients with hormone receptor-positive breast cancer were analyzed. Similar disease-free survival (DFS) was observed between the HER2-low group and HER2-zero group (HR 0.84, 95% CI: 0.61-1.16, p = 0.290). There was also no significant difference in OS between the HER2-low group and the HER2-zero group (HR 0.77, 95% CI: 0.46-1.28, p = 0.310). When IHC 1+ and 0 were taken as a group, the IHC 2+ group had significantly better DFS than the IHC 1+ and 0 group in some subgroups. The risk of bone metastasis in patients with HER2 IHC 1+ and 0 was significantly higher than that of patients with HER2 IHC 2+ (12.7% vs. 4.7%, p < 0.001). Compared with the HER2-zero group, we found that the HER2-low group had a more obvious peak in mortality at the time of postoperative 80th-100th month.

CONCLUSIONS

No significant difference in DFS and OS between the HER2-low group and the HER2-zero group was observed. Patients with HER2 IHC 1+ and 0 tend to develop bone metastasis. The HER2-low group had a more obvious second peak in mortality.

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.