Adjuvant Trastuzumab Emtansine Versus Paclitaxel Plus Trastuzumab for Stage I Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer: 5-Year Results and Correlative Analyses From ATEMPT

Novel treatment approaches utilizing antibody-drug conjugates in breast cancer

Antibody-drug conjugates (ADCs) are rapidly changing the way we treat patients with breast cancer. Despite this progress, many unanswered questions remain regarding the sequencing of different ADCs with similar payloads, optimal combinations, drug design strategies to limit off-target toxicities, biomarkers to define antigen positivity, and the use of ADCs in the neoadjuvant and adjuvant settings. In this review, we summarize novel ADC approaches in breast cancer treatment, including potential improvements in ADC payloads, linkers, targets, and drug delivery. We also evaluate novel strategies to combine ADCs with other agents, such as targeted drugs and immune checkpoint inhibitors. To improve patient selection, the development of quantitative biomarkers is reviewed, including HER2 mRNA, immunofluorescence-based assays, mass spectrometry, liquid biopsies, digital pathology, and molecular imaging-based approaches. Lastly, we evaluate the potential to incorporate ADCs into the early-stage setting, including evaluating currently published and ongoing clinical trials. This review highlights the potential for ADCs to shift the treatment paradigm in both the advanced and early-stage settings. We further demonstrate the complexity and challenges of improving ADCs to enhance targeting of tumor vulnerabilities while limiting toxicity through rationale drug development strategies to enhance the therapeutic window, linker technology, and payload variability to continue to improve outcomes for patients with breast cancer.

HER2DX ERBB2 mRNA score in first-line advanced HER2-positive breast cancer treated with chemotherapy, trastuzumab, and pertuzumab

In advanced HER2-positive breast cancer, the standard taxane-trastuzumab-pertuzumab (THP) regimen faces competition from new therapies, emphasizing the need for biomarkers to guide treatment. This study evaluates the HER2DX ERBB2 mRNA score as a prognostic predictor, aiming to tailor treatment strategies. We retrospectively analyzed 94 patients treated with the THP regimen between 2010 and 2024. The HER2DX ERBB2 mRNA score was categorized as low (n = 14), medium (n = 20), or high (n = 60), and its correlation with progression-free survival (PFS) and overall survival (OS) was assessed using Cox regression models. The median follow-up was 31.5 months. Patients with ERBB2-high scores had significantly better median PFS (33.9 vs. 10.6 months, hazard ratio [HR] = 0.40, 95% CI: 0.24-0.69, p < 0.001) and OS (not reached vs. 30.8 months, HR = 0.26, 95% CI: 0.13-0.49, p < 0.001) compared to ERBB2-low patients. Based on these findings, further validation of this biomarker in tumor samples from the CLEOPATRA phase III trial is ongoing, which could help optimize treatment strategies in this population.

The necessity of adjuvant chemotherapy in young patients with T1N0M0 breast cancer: a population-based study

Chemotherapy clearly adversely affects fertility in women of childbearing age. But it is not yet clear whether chemotherapy at the expense of fertility can benefit younger patients with early-stage breast cancer. We conducted a retrospective cohort study utilizing the Surveillance, Epidemiology, and End Results database and the Shanghai Jiao Tong University Breast Cancer Data Base spanning from 2010 to 2020 to investigate early-stage breast malignant carcinoma in patients aged between 20 and 39 years. To address covariate imbalance, propensity score matching (PSM) was employed with a ratio of 1:1 and caliper set at 0.02 standard deviation of propensity score. Univariate and multivariate analyses were performed to evaluate the impact of chemotherapy on both breast cancer-specific survival (BCSS) and overall survival (OS). We identified a total of 6265 patients with complete information about breast cancer. Among them, 3855 patients received chemotherapy. Following successful PSM, we obtained a matched cohort comprising 3038 patients where the characteristics between the two groups were balanced except for race. Kaplan-Meier survival analysis revealed no significant differences in BCSS (P = 0.183) and OS (P = 0.295) between the chemotherapy group and no-chemotherapy group. Similarly, in matched dataset. multivariate COX analysis revealed that chemotherapy did not significantly reduce the risk of BCSS (HR 1.332; 95% CI [0.865-2.051], P = 0.193) and OS (HR 1.225; 95% CI [0.818-1.833], P = 0.324). The chemotherapy group did not demonstrate a superior benefit in any of the subgroups when stratified analyses were conducted based on molecular subtype, tumor size, age, and ethnicity. Chemotherapy fails to significantly improve prognostic outcomes in young patients diagnosed with early-stage breast cancer. With the help of genetic testing, these patients can expect further step-down therapy in the future.

Tumor-infiltrating lymphocytes in HER2-positive breast cancer: potential impact and challenges

INTRODUCTION

In this review, we evaluate the role of stromal tumor-infiltrating lymphocytes (sTILs) as a biomarker in human epidermal growth factor receptor 2 (HER2)-positive breast cancer, exploring the prognostic and predictive potential in various treatment settings.

METHODS

Data from multiple clinical trials in the early and metastatic settings, focusing on TILs' correlation with pathologic complete response (pCR), progression-free survival (PFS), and overall survival across early and metastatic HER2-positive breast cancer were summarized. This review also discusses TILs' assessment methods, interobserver variability, and emerging technologies to assess TILs.

RESULTS

TILs have been identified as a highly reproducible biomarker that predicts pCR in patients receiving neoadjuvant therapy and serves as a prognostic indicator for long-term outcomes in several breast cancer subtypes, including HER2-positive. Studies indicate that higher TIL levels correlate with better recurrence-free survival rates. Despite these findings, there is no consensus on the optimal TIL threshold for clinical decision making, and further research is required on how to incorporate TILs into routine clinical practice.

CONCLUSIONS

TILs represent a promising biomarker in HER2-positive breast cancer, particularly in early disease settings. This assessment could guide treatment de-escalation or intensification, tailoring therapies to individual patient profiles. Due to their prognostic importance, TILs can be added to pathology reports. However, further validation in clinical trials is essential for the widespread adoption of TILs in clinical practice.

HER2DX in HER2-positive inflammatory breast cancer: correlative insights and comparative analysis with noninflammatory breast cancers

BACKGROUND

The HER2DX assay predicts long-term prognosis and pathologic complete response (pCR) in patients with early-stage human epidermal growth factor receptor 2 (HER2)-positive breast cancer receiving neoadjuvant systemic therapy but has not been evaluated in inflammatory breast cancer (IBC).

PATIENTS AND METHODS

HER2DX was analyzed in baseline biopsy tissues from 23 patients with stage III HER2-positive IBC on a phase II trial (NCT01796197) treated with neoadjuvant trastuzumab, pertuzumab, and paclitaxel (THP). To assess the assay's predictive accuracy for pCR in IBC, clinical-pathological features and outcomes from this IBC cohort were compared with 156 patients with stage III HER2-positive non-IBC from four different cohorts. Comparative analyses included HER2DX scores, gene signatures, and expression of individual genes between patients with IBC and non-IBC.

RESULTS

Notable differences in clinicopathological characteristics included higher pertuzumab and chemotherapy usage and lower axillary burden in patients with IBC compared with non-IBC. In the combined cohort (n = 179), HER2DX pCR score and pertuzumab use were significant predictors of pCR, but not IBC status. The pCR rates in patients treated with trastuzumab-based chemotherapy (including IBC and non-IBC) were 68.9%, 58.5%, and 16.3% in the HER2DX pCR-high, -medium, and -low groups, respectively. Comparative gene expression analysis indicated minor differences between IBC and non-IBC affecting individual HER2, immune, and proliferation genes.

CONCLUSIONS

The HER2DX pCR score could predict pCR in stage III HER2-positive IBC following treatment with de-escalated neoadjuvant systemic therapy and in stage III HER2-positive non-IBC. Elevated pCR rates in HER2-positive IBC with high HER2DX pCR scores suggest there may be a role for treatment de-escalation in these patients and confirmatory studies are justified.

HER2DX genomic test in early-stage HER2-positive breast cancer

Therapies targeting human epidermal growth factor receptor 2 (HER2)-positive breast cancer significantly impact patient outcomes, quality of life, and health care systems. While chemotherapy and trastuzumab improve survival in early-stage HER2-positive breast cancer, variability in clinical and biological characteristics leads to different response to therapies and outcomes. Clinical guidelines provide general recommendations, but significant uncertainty persists in identifying an optimal treatment plan for individual patients. The HER2DX genomic test informs treatment decisions for stage 1-3 HER2-positive breast cancer by integrating biological factors and clinical factors (tumor size and nodal status). It provides three scores relevant to patient management: long-term prognosis (risk score), likelihood of achieving pathological complete response (pCR score), and ERBB2 mRNA expression (ERBB2 score). This article offers an expert overview of HER2DX, covering score interpretation, clinical applications, ongoing studies, and future directions. By analyzing the genomic profiles of HER2-positive tumors, HER2DX provides independent information regarding therapeutic responses and disease prognosis, thereby enabling physicians to navigate the increasing complexity of managing patients with HER2-positive early breast cancer. Key findings show that HER2DX predicts relapse-free survival and probability of pCR to a variety of neoadjuvant therapy regimens, which aids in personalizing treatment plans that could reduce over-treatment and under-treatment. The article underscores expert recommendations to help integrate HER2DX into clinical practice, aiming to enhance decision making and clinical outcomes.

Dual HER2 inhibition: mechanisms of synergy, patient selection, and resistance

HER2-targeted therapies for patients with HER2+ breast cancer are rapidly evolving, offering a range of more complex and personalized treatment options. Currently, an array of anti-HER2 monoclonal antibodies, tyrosine kinase inhibitors and antibody-drug conjugates are administered, sometimes alongside chemotherapy or endocrine therapy, both in curative and palliative contexts. However, the heterogeneous nature of HER2+ breast cancer demands a deeper understanding of disease biology and its role in responsiveness to novel HER2-targeted agents, as well as non-HER2-targeted therapies, in order to optimize patient outcomes. In this Review, we revisit the mechanisms of action of HER2-targeted agents, examine the evidence supporting the use of dual HER2 blockade in patients with HER2-amplified tumours, and explore the role of biomarkers in guiding future treatment strategies. We also discuss potential implications for the future treatment of patients with HER2+ breast cancer.

Nodal involvement in patients with small, clinically node-negative HER2-positive breast cancer after staging with FDG-PET/CT and neoadjuvant systemic therapy

BACKGROUND

Guidelines recommend systemic therapy for stage I HER2+ breast cancer (BC). Neoadjuvant systemic treatment (NAST) allows response-guided adjuvant treatment. However, prior to NAST only clinical nodal staging is available, risking undertreatment if ypN+ is observed. Here, we aim to evaluate the impact of FDG-PET/CT and NAST on nodal disease status in patients with small, node-negative HER2+ BC.

METHODS

This retrospective study included patients with small (≤3 cm), clinically node-negative HER2+ BC diagnosed between 2011 and 2023. Primary outcome was the proportion of patients with nodal disease on final pathology after upfront surgery or NAST followed by surgery with or without FDG-PET/CT. Patients received either paclitaxel + trastuzumab (PT) or a more extensive regimen.

RESULTS

Of the 370 included patients, 183 underwent FDG-PET/CT, detecting regional or distant metastases in 14 patients (7.7 %). Among 356 patients with cN0 disease, 44.1 % (n = 157/356) had upfront surgery, with only 3 % (5/157) having an FDG-PET/CT. The remaining 55.9 % (199/356) started with NAST, with 82 % (n = 164/199) having an FDG-PET/CT. Among patients treated with NAST, 36 % received PT. Nodal involvement on pathology was seen in 19.1 % (n = 29/152) after upfront surgery without FDG-PET/CT and 6.1 % (10/164) after NAST combined with FDG-PET/CT. After NAST, 58 % had a pCR (PT: 49 %, other: 63 %). Nodal involvement on final pathology was seen in 6.9 % after PT and in 5.5 % after more extensive regimen.

CONCLUSIONS

The proportion of patients with ypN + after NAST combined with FDG-PET/CT was only 6.1 %. Neoadjuvant treatment can be a safe treatment strategy for patients with stage I HER2+ BC.

De-Escalating Treatment Strategies for Patients with Human Epidermal Growth Factor Receptor-2 (HER2)-Positive Early-Stage Breast Cancer

Almost one-fifth of breast cancer cases express Human Epidermal Growth Factor-2 (HER2), and such expression is associated with highly proliferative tumors and poor prognosis. The introduction of anti-HER2 therapies has dramatically changed the natural course of this aggressive subtype of breast cancer. However, anti-HER2 therapy can be associated with substantial toxicities, mostly cardiac, and high cost. Over the past few years, there has been growing interest in de-escalation of anti-HER2 therapies to minimize adverse events and healthcare costs, while maintaining the efficacy of treatment. Data from clinical observations and single-arm studies have eluted to the minimal impact of anti-HER2 therapy in low-risk patients, like those with node-negative and small tumors. Though single-arm, the APT trial, in which patients with node-negative, small tumors received single-agent paclitaxel for 12 cycles plus trastuzumab for 1 year, was a practice-changing study. Several other recently published studies, like the PERSEPHONE trial, have shown more convincing data that 6 months of trastuzumab is not inferior to 12 months, in terms of disease-free survival (DFS), suggesting that de-escalating strategies with shorter treatment may be appropriate for some low-risk patients. Other de-escalating strategies involved an adaptive, response-directed approach, and personalized therapy that depends on tumor genomic profiling.