Higher efficacy of letrozole in combination with trastuzumab compared to letrozole monotherapy as first-line treatment in patients with HER2-positive, hormone-receptor-positive metastatic breast cancer - results of the eLEcTRA trial

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.

The evolving landscape of metastatic HER2-positive, hormone receptor-positive Breast Cancer

Therapeutic agents targeting Human Epidermal Growth Factor Receptor 2 (HER2) demonstrated to positively impact the prognosis of HER2-positive breast cancer. HER2-positive breast cancer can present either as hormone receptor-negative or positive, defining Triple-positive breast cancer (TPBC). TPBC demonstrate unique gene expression profiles, showing reduced HER2-driven gene expression, as recapitulated by a higher proportion of Luminal-type intrinsic subtypes. The different molecular landscape of TPBC dictates distinctive clinical features, including reduced chemotherapy sensitivity, different patterns of recurrence, and better overall prognosis. Cross-talk between HER2 and hormone receptor signaling seems to be critical to determine resistance to HER2-directed agents. Accordingly, superior outcomes have been achieved with the use of endocrine therapy, representing the first subtype-specific pharmacological intervention unique to this subgroup. Additional targeted agents capable to tackle resistance mechanisms to anti-HER2, hormone agents, or both might further improve the efficacy of treatments, such as PI3K/AKT/mTOR inhibitors, particularly in a biomarker-enriched setting, and CDK4/6-inhibitors, with preliminary data suggesting a role of PAM50 subtyping to predict higher benefits in luminal tumors. Finally, the distinct biology of triple-positive tumors may yield the rationale for considering combinations within antibody-drug conjugate regimens. Accordingly, in this review, we summarized the current evidence and rationale for considering TPBC as a different entity, in which distinct therapeutical approaches leveraging on the different biological profile of TPBC may result in superior anticancer regimens and improved patient-centric outcomes.

Combining Endocrine Therapy with Trastuzumab Emtansine Improves Progression-Free Survival and Overall Survival in HER2-Positive, Hormone Receptor-Positive Metastatic Breast Cancer

Background and Objectives: Patients with human epidermal growth factor receptor 2 (HER2) -positive, hormone receptor-positive (HR-positive) metastatic breast cancer (MBC) usually undergo trastuzumab emtansine (T-DM1) therapy in subsequent lines. Combining endocrine therapy (ET) with T-DM1 can improve treatment outcomes in this subtype. Therefore, this study aimed to investigate the benefits of using T-DM1 with ET in HER2-positive and HR-positive MBC. This study was the first to investigate the benefits of combining ET with T-DM1. Material and Methods: This study analyzed the medical records of patients with HER2-positive and HR-positive MBC who were treated with T-DM1 from June 2010 to December 2021. The patients were divided into groups based on whether they received concomitant ET with T-DM1. The primary endpoint was to determine the progression-free survival (PFS), while the secondary endpoints were overall survival (OS), objective response rate, and safety of the treatment. Results: Our analysis examined 88 patients, of whom 32 (36.4%) were treated with T-DM1 in combination with ET. The combination therapy showed a significant improvement in median PFS (15.4 vs. 6.4 months; p = 0.00004) and median OS (35.0 vs. 23.1 months; p = 0.026) compared to T-DM1 alone. The ORR was also higher in the combination group (65.6% vs. 29.3%; p = 0.026). Patients treated with pertuzumab priorly had reduced median PFS on T-DM1 compared to those who were not treated with pertuzumab (11.7 vs. 5.4 months, respectively; p < 0.01). T-DM1 demonstrated better median PFS in HER2 3+ patients compared to HER2 2+ patients, with an amplification ratio of >2.0 (10.8 vs 5.8 months, respectively; p = 0.049). The safety profiles were consistent with previous T-DM1 studies. Conclusions: The combination of T-DM1 with ET can significantly improve PFS and OS in patients with HER2-positive and HR-positive MBC. Our study suggests that prior pertuzumab treatment plus trastuzumab treatment might decrease T-DM1 efficacy.

heredERA Breast Cancer: a phase III, randomized, open-label study evaluating the efficacy and safety of giredestrant plus the fixed-dose combination of pertuzumab and trastuzumab for subcutaneous injection in patients with previously untreated HER2-positive, estrogen receptor-positive locally advanced or metastatic breast cancer

BACKGROUND

HER2-positive, estrogen receptor-positive breast cancer (HER2+, ER+ BC) is a distinct disease subtype associated with inferior response to chemotherapy plus HER2-targeted therapy compared with HER2+, ER-negative BC. Bi-directional crosstalk leads to cooperation of the HER2 and ER pathways that may drive treatment resistance; thus, simultaneous co-targeting may optimize treatment impact and survival outcomes in patients with HER2+, ER+ BC. First-line (1L) treatment for patients with HER2+ metastatic BC (mBC) is pertuzumab, trastuzumab, and taxane chemotherapy. In clinical practice, dual HER2 blockade plus a fixed number of chemotherapy cycles are given as induction therapy to maximize tumor response, with subsequent HER2-targeted maintenance treatment given as a more tolerable regimen for long-term disease control. For patients whose tumors co-express ER, maintenance endocrine therapy (ET) can be added, but uptake varies due to lack of data from randomized clinical trials investigating the superiority of maintenance ET plus dual HER2 blockade versus dual HER2 blockade alone. Giredestrant, a novel oral selective ER antagonist and degrader, shows promising clinical activity and manageable safety across phase I-II trials of patients with ER+, HER2-negative BC, with therapeutic potential in those with HER2 co-expression.

METHODS

This phase III, randomized, open-label, two-arm study aims to recruit 812 patients with HER2+, ER+  locally advanced (LA)/mBC into the induction phase (fixed-dose combination of pertuzumab and trastuzumab for subcutaneous injection [PH FDC SC] plus a taxane) to enable 730 patients to be randomized 1:1 to the maintenance phase (giredestrant plus PH FDC SC or PH FDC SC [plus optional ET]), stratified by disease site (visceral versus non-visceral), type of LA/metastatic presentation (de novo versus recurrent), best overall response to induction therapy (partial/complete response versus stable disease), and intent to give ET (yes versus no). The primary endpoint is investigator-assessed progression-free survival. Secondary endpoints include overall survival, objective response rate, clinical benefit rate, duration of response, safety, and patient-reported outcomes.

DISCUSSION

heredERA BC will address whether giredestrant plus dual HER2 blockade is superior to dual HER2 blockade alone, to inform the use of this combination in clinical practice for maintenance 1L treatment of patients with HER2+, ER+ LA/mBC.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05296798; registered on March 25, 2022. Protocol version 3.0 (November 18, 2022).

SPONSOR

F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124 4070, Basel, Switzerland.

Hormone Receptor-Positive/HER2-Positive Breast Cancer: Hormone Therapy and Anti-HER2 Treatment: An Update on Treatment Strategies

Hormone receptor (HR)-positive/HER2-positive breast cancer represents a distinct subtype expressing estrogen and progesterone receptors with an overexpression of HER2. Approximately 14% of female breast cancer cases are HER2-positive, with the majority being HR-positive. These tumors show a cross-talk between the hormonal and HER2 pathways; the interaction has implications for the treatment options for the disease. In this review, we analyze the biology of HR-positive/HER2-positive breast cancer and summarize the evidence concerning the standard of care options both in neoadjuvant/adjuvant settings and in advanced disease. Additionally, we focus on new trials and drugs for HR-positive/HER2-positive breast cancer and the new entity: HER2-low breast cancer.

The breast cancer tumor microenvironment and precision medicine: immunogenicity and conditions favoring response to immunotherapy

Some main recent researches that have dissected tumor microenvironment (TME) by imaging mass cytometry (IMC) in different subtypes of primary breast cancer samples were considered. The many phenotypic variants, clusters of epithelial tumor and immune cells, their structural features as well as the main genetic aberrations, sub-clonal heterogeneity and their systematic classification also have been examined. Mutational evolution has been assessed in primary and metastatic breast cancer samples. Overall, based on these findings the current concept of precision medicine is questioned and challenged by alternative therapeutic strategies. In the last two decades, immunotherapy as a powerful and harmless tool to fight cancer has received huge attention. Thus, the tumor immune microenvironment (TIME) composition, its prognostic role for clinical course as well as a novel definition of immunogenicity in breast cancer are proposed. Investigational clinical trials carried out by us and other findings suggest that G0-G1 state induced in endocrine-dependent metastatic breast cancer is more suitable for successful immune manipulation. Residual micro-metastatic disease seems to be another specific condition that can significantly favor the immune response in breast and other solid tumors.

Efficacy and safety of first-line therapy in patients with HER2-positive advanced breast cancer: a network meta-analysis of randomized controlled trials

PURPOSE

The numerous first-line treatment regimens for human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer (ABC) necessitate a comprehensive evaluation to inform clinical decision-making. We conducted a Bayesian network meta-analysis (NMA) to compare the efficacy and safety of different interventions.

METHODS

We systematically searched for relevant randomized controlled trials (RCTs) in Pubmed, Embase, Cochrane Library and online abstracts from inception to June 1, 2023. NMA was performed to calculate and analyze progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and adverse events of grade 3 or higher (≥ 3 AEs).

RESULTS

Out of the 10,313 manuscripts retrieved, we included 28 RCTs involving 11,680 patients. Regarding PFS and ORR, the combination of trastuzumab with tyrosine kinase inhibitors (TKIs) was more favorable than dual-targeted therapy. If only using trastuzumab, combination chemotherapy is superior to monochemotherapy in terms of PFS. It is important to note that the addition of anthracycline did not result in improved PFS. For patients with hormone receptor-positive HER2-positive diseases, dual-targeted combined with endocrine therapy showed better benefit in terms of PFS compared to dual-targeted alone, but it did not reach statistical significance. The comprehensive analysis of PFS and ≥ 3 AEs indicates that monochemotherapy combined with dual-targeted therapy still has the optimal balance between efficacy and safety.

CONCLUSION

Monochemotherapy (Docetaxel) plus dual-target (Trastuzumab and Pertuzumab) therapy remains the optimal choice among all first-line treatment options for ABC. The combination of trastuzumab with TKIs (Pyrotinib) demonstrated a significant improvement in PFS and ORR, but further data are warranted to confirm the survival benefit.

Endocrine therapy plus HER2-targeted therapy, another favorable option for HR+/HER2+ advanced breast cancer patients

Advanced breast cancer (ABC) that is positive for hormone receptors (HRs) and human epidermal growth factor receptor 2 (HER2) is a cancer subtype with distinctive characteristics. The primary treatment guidelines suggest that a combination therapy comprising anti-HER2 therapy and chemotherapy should be administered as the initial treatment for HR-positive/ HER2-positive (HR+/HER2+) ABC. However, crosstalk between the HR and HER2 pathways can partially account for the resistance of HR+/HER2+ disease to HER2-targeted therapy. This, in turn, provides a rationale for the concomitant administration of HER2-targeted therapy and endocrine therapy (ET). Many clinical studies have confirmed that the combination of HER2-targeted therapy and ET as a first-line treatment is not inferior to the combination of HER2-targeted therapy and chemotherapy, and support its use as a first-line treatment choice for HR+/HER2+ ABC. Other drugs, such as antibody-drug conjugates, cyclin-dependent kinase 4/6 inhibitors, phosphatidylinositol 3-kinase-protein kinase B (AKT)-mammalian target of rapamycin inhibitors, and programmed cell death protein 1 or programmed cell death ligand 1 inhibitors, may also improve the prognosis of patients with breast cancer by blocking signaling pathways associated with tumor proliferation and break new ground for the treatment of HR+/HER2+ ABC.

Unraveling Vulnerabilities in Endocrine Therapy-Resistant HER2+/ER+ Breast Cancer

Breast tumors overexpressing human epidermal growth factor receptor (HER2) confer intrinsic resistance to endocrine therapy (ET), and patients with HER2/estrogen receptor-positive (HER2+/ER+) breast cancer (BCa) are less responsive to ET than HER2-/ER+. However, real-world evidence reveals that a large subset of patients with HER2+/ER+ receive ET as monotherapy, positioning this treatment pattern as a clinical challenge. In the present study, we developed and characterized 2 in vitro models of ET-resistant (ETR) HER2+/ER+ BCa to identify possible therapeutic vulnerabilities. To mimic ETR to aromatase inhibitors (AIs), we developed 2 long-term estrogen deprivation (LTED) cell lines from BT-474 (BT474) and MDA-MB-361 (MM361). Growth assays, PAM50 subtyping, and genomic and transcriptomic analyses, followed by validation and functional studies, were used to identify targetable differences between ET-responsive parental and ETR-LTED HER2+/ER+ cells. Compared to their parental cells, MM361 LTEDs grew faster, lost ER, and increased HER2 expression, whereas BT474 LTEDs grew slower and maintained ER and HER2 expression. Both LTED variants had reduced responsiveness to fulvestrant. Whole-genome sequencing of aggressive MM361 LTEDs identified mutations in genes encoding transcription factors and chromatin modifiers. Single-cell RNA sequencing demonstrated a shift towards non-luminal phenotypes, and revealed metabolic remodeling of MM361 LTEDs, with upregulated lipid metabolism and ferroptosis-associated antioxidant genes, including GPX4. Combining a GPX4 inhibitor with anti-HER2 agents induced significant cell death in both MM361 and BT474 LTEDs. The BT474 and MM361 AI-resistant models capture distinct phenotypes of HER2+/ER+ BCa and identify altered lipid metabolism and ferroptosis remodeling as vulnerabilities of this type of ETR BCa.

HER2-positive breast cancer: cotargeting to overcome treatment resistance

PURPOSE OF REVIEW

The introduction in clinical practice of anti-HER2 agents changed the prognosis of patients with HER2-positive (HER2+) breast cancer in both metastatic and early setting. Although the incomparable results obtained in the last years with the approval of new drugs targeting HER2, not all patients derive benefit from these treatments, experiencing primary or secondary resistance. The aim of this article is to review the data about cotargeting HER2 with different pathways (or epitopes of receptors) involved in its oncogenic signaling, as a mechanism to overcome resistance to anti-HER2 agents.

RECENT FINDINGS

Concordantly to the knowledge of the HER2+ breast cancer heterogeneity as well as new drugs, novel predictive biomarkers of response to anti-HER2 treatments are always raised helping to define target to overcome resistance. Cotargeting HER2 and hormone receptors is the most well known mechanism to improve benefit in HER2+/HR+ breast cancer. Additional HER2-cotargeting, such as, with PI3K pathway, as well as different HERs receptors or immune-checkpoints revealed promising results.

SUMMARY

HER2+ breast cancer is an heterogenous disease. Cotargeting HER2 with other signaling pathways involved in its mechanism of resistance may improve patient outcomes. Research efforts will continue to investigate novel targets and combinations to create more effective treatment regimes.

Efficacy and Safety of Anti-HER2 Targeted Therapy for Metastatic HR-Positive and HER2-Positive Breast Cancer: A Bayesian Network Meta-Analysis

Despite the development of HER2-targeted drugs, achieving favorable outcomes for patients with HR+/HER2+MBC remains challenging. This study utilized Bayesian Network Meta-analysis to compare the efficacy and safety of anti-HER2 combination regimens. The primary analysis focused on progression-free survival (PFS), while secondary analyses included objective response rate, overall survival (OS) and the incidence rate of grade 3/4 adverse events (AEs). A comprehensive search across seven databases identified 25 randomized controlled trials for inclusion in this meta-analysis. For patients eligible for endocrinotherapy, our findings revealed that dual-target combined endocrine therapy, such as Her2-mAb+Her2-mAb+Endo (HR = 0.38; 95%CrI: 0.16-0.88) and Her2-mAb+Her2-tki+Endo (HR = 0.45; 95%CrI: 0.23-0.89), significantly improved PFS compared to endocrine therapy alone. According to the surface under the cumulative ranking curves (SUCRAs), Her2-mAb+Her2-mAb+Endo and Her2-mAb+Her2-tki+Endo ranked highest in terms of PFS and OS, respectively. For patients unsuitable for endocrine therapy, anti-HER2 dual-target combined chemotherapy, such as Her2-mAb+Her2-mAb+Chem (HR = 0.76; 95%CrI: 0.6-0.96) and Her2-mAb+Her2-tki+Chem (HR = 0.48; 95%CrI: 0.29-0.81), demonstrated significant improvements in PFS compared to Her2-mAb+Chem. The results were the same when compared with Her2-tki+Chem. According to the SUCRAs, Her2-mAb+Her2-tki+Chem and Her2-mAb+Her2-mAb+Chem ranked highest for PFS and OS, respectively. Subgroup analyses consistently supported these overall findings, indicating that dual-target therapy was the optimal approach irrespective of treatment line.

SEOM-GEICAM-SOLTI clinical guidelines in advanced breast cancer (2022)

Advanced breast cancer represents a challenge for patients and for physicians due its dynamic genomic changes yielding to a resistance to treatments. The main goal is to improve quality of live and survival of the patients through the most appropriate subsequent therapies based on the knowledge of the natural history of the disease. In these guidelines, we summarize current evidence and available therapies for the medical management of advanced breast cancer.

Unraveling Vulnerabilities in Endocrine Therapy-Resistant HER2+/ER+ Breast Cancer

Background

Breast tumors overexpressing human epidermal growth factor receptor (HER2) confer intrinsic resistance to endocrine therapy (ET), and patients with HER2/ estrogen receptor-positive (HER2+/HR+) breast cancer (BCa) are less responsive to ET than HER2-/ER+. However, real-world evidence reveals that a large subset of HER2+/ER+ patients receive ET as monotherapy, positioning this treatment pattern as a clinical challenge. In the present study, we developed and characterized two distinct in vitro models of ET-resistant (ETR) HER2+/ER+ BCa to identify possible therapeutic vulnerabilities.

Methods

To mimic ETR to aromatase inhibitors (AI), we developed two long-term estrogen-deprived (LTED) cell lines from BT-474 (BT474) and MDA-MB-361 (MM361). Growth assays, PAM50 molecular subtyping, genomic and transcriptomic analyses, followed by validation and functional studies, were used to identify targetable differences between ET-responsive parental and ETR-LTED HER2+/ER+ cells.

Results

Compared to their parental cells, MM361 LTEDs grew faster, lost ER, and increased HER2 expression, whereas BT474 LTEDs grew slower and maintained ER and HER2 expression. Both LTED variants had reduced responsiveness to fulvestrant. Whole-genome sequencing of the more aggressive MM361 LTED model system identified exonic mutations in genes encoding transcription factors and chromatin modifiers. Single-cell RNA sequencing demonstrated a shift towards non-luminal phenotypes, and revealed metabolic remodeling of MM361 LTEDs, with upregulated lipid metabolism and antioxidant genes associated with ferroptosis, including GPX4. Combining the GPX4 inhibitor RSL3 with anti-HER2 agents induced significant cell death in both the MM361 and BT474 LTEDs.

Conclusions

The BT474 and MM361 AI-resistant models capture distinct phenotypes of HER2+/ER+ BCa and identify altered lipid metabolism and ferroptosis remodeling as vulnerabilities of this type of ETR BCa.

Evolving perspectives on the treatment of HR+/HER2+ metastatic breast cancer

Breast cancer (BC) with expression of the estrogen receptor (ER) and/or progesterone receptor (PR) protein and with overexpression/amplification of the human epidermal growth factor receptor 2 (HER2), termed hormone receptor-positive (HR+)/HER2+ BC, represents ∼10% of all BCs in the United States. HR+/HER2+ BC includes HER2+ BCs that are ER+, PR+, or both ER+ and PR+ (triple-positive BC). Although the current guideline-recommended treatment combination of anti-HER2 monoclonal antibodies plus chemotherapy is an effective first-line therapy for many patients with HER2+ advanced disease, intratumoral heterogeneity within the HR+/HER2+ subtype and differences between the HR+/HER2+ subtype and the HR-/HER2+ subtype suggest that other targeted combinations could be investigated in randomized clinical trials for patients with HR+/HER2+ BC. In addition, published data indicate that crosstalk between HRs and HER2 can lead to treatment resistance. Dual HR and HER2 pathway targeting has been shown to be a rational approach to effective and well-tolerated therapy for patients with tumors driven by HER2 and HR, as it may prevent development of resistance by blocking receptor pathway crosstalk. However, clinical trial data for such approaches are limited. Treatments to attenuate other signaling pathways involved in receptor crosstalk are also under investigation for inclusion in dual receptor targeting regimens. These include cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, based on the rationale that association of CDK4/6 with cyclin D1 may play a role in resistance to HER2-directed therapies, and others such as phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway inhibitors. Herein, we will review the scientific and clinical rationale for combined receptor blockade targeting HER2 and ER for patients with advanced-stage HR+/HER2+ disease.

Estrogen/HER2 receptor crosstalk in breast cancer: combination therapies to improve outcomes for patients with hormone receptor-positive/HER2-positive breast cancer

The human epidermal growth factor receptor 2 (HER2) is overexpressed in 13-22% of breast cancers (BC). Approximately 60-70% of HER2+ BC co-express hormone receptors (HRs). HR/HER2 co-expression modulates response to both anti-HER2-directed and endocrine therapy due to "crosstalk" between the estrogen receptor (ER) and HER2 pathways. Combined HER2/ER blockade may be an effective treatment strategy for patients with HR+/HER2+ BC in the appropriate clinical setting(s). In this review, we provide an overview of crosstalk between the ER and HER2 pathways, summarize data from recently published and ongoing clinical trials, and discuss clinical implications for targeted treatment of HR+/HER2+ BC.

Identifying the optimal therapeutics for patients with hormone receptor-positive, HER2-positive advanced breast cancer: a systematic review and network meta-analysis

INTRODUCTION

Hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-positive (HER2+) breast cancer is a distinct subtype with different prognosis and response to treatment. HER2-targeted therapy is currently recommended for patients with HR+/HER2+ advanced breast cancer. However, there is debate over which drugs to add on the basis of HER2 blockade yield the optimal efficacy. This systematic review and network meta-analysis was conducted to solve the problem.

METHODS

Eligible randomized controlled trials (RCTs) comparing different interventions in HR+/HER2+ metastatic breast cancer were included. The outcomes of interest included progression-free survival (PFS), overall survival (OS) and treatment-related adverse events (TRAEs). Pooled hazard ratios or odds ratios with credible intervals (CrIs) were calculated to estimate the predefined outcomes. The optimal therapeutics were identified by comparing the surface under the cumulative ranking curves (SUCRA).

RESULTS

Totally, 23 literatures of 20 RCTs were included. Regarding PFS, significant differences were detected between single or dual HER2 blockade plus endocrine therapy (ET) versus ET alone and dual HER2 blockade plus ET versus physician's choice. Trastuzumab, pertuzumab plus chemotherapy significantly improved PFS than trastuzumab plus chemotherapy (hazard ratio 0.69, 95% CrI 0.50-0.92). The SUCRA values suggested the relatively better efficacy of dual HER2-targeted therapy plus ET (86%-91%) than chemotherapy (62%-81%) in prolonging PFS and OS. The HER2 blockade-containing regimens showed similar safety profiles in eight documented TRAEs.

CONCLUSIONS

Prominent status of dual-targeted therapy for patients with HR+/HER2+ metastatic breast cancer was revealed. Compared with chemotherapy-containing regimens, the ET-containing ones showed better efficacy and similar safety profiles, which could be recommended in clinical practice.

Addition of endocrine therapy to dual anti-HER2 targeted therapy in initial treatment of HER2 + /HR + metastatic breast cancer

PURPOSE

Dual anti-HER2 targeted therapy and chemotherapy is the current first-line standard of care for HER2 + metastatic breast cancer (MBC), with endocrine therapy (ET) the backbone of treatment in hormone receptor positive (HR +) disease. The potential ET benefit in HER2 + /HR + patients is unknown as pivotal dual anti-HER2 clinical trials precluded ET use.

METHODS

Real-world data from a multi-site registry of consecutive HER2 + MBC patients treated at clinician discretion were examined. Patients that were HR + (ER + and/or PR +) and had received first-line chemotherapy alongside trastuzumab and pertuzumab were explored. Of 362 patients in the registry, 215 were excluded due to being HR- (n = 210) or not receiving chemotherapy (n = 5).

RESULTS

Of the 147 patients included, 91 (62%) received concurrent ET and 56 (38%) had not. Comparing the groups, there were no significant differences in age, performance status, metastatic sites, use of previous therapy and de novo metastatic disease. More patients with ER + PR + disease versus those with ER + PR- or ER-PR + received ET (73 vs 45%). The addition of ET was associated with significantly improved 5-year PFS (HR 0.58, CI 0.37-0.89, p = 0.014) and OS (HR 0.52, CI 0.31-0.90, p = 0.018), with no increase in adverse events noted.

CONCLUSION

The addition of ET to first-line dual anti-HER2 therapy post chemotherapy in patients with HER2 + /HR + MBC was associated with major gains in PFS and OS with no safety concerns evident. Further studies of this combination are justified, along with studies of how best to integrate other agents that are active in this patient subset, including CDK4/6 inhibitors.

Efficacy and safety of pyrotinib-containing regimen in the patients with HER2-positive metastatic breast cancer: A multicenter real-world study

BACKGROUND

Pyrotinib, a novel irreversible epidermal growth factor receptor 2 (EGFR)/HER2 dual tyrosine kinase inhibitor, has shown promising antitumor efficacy with tolerable toxicity in HER2-positive metastatic breast cancer (MBC) in several clinical trials. However, the clinical trials do not usually well reflect the patients in real clinical settings. Despite several small-sample studies in real world, the data on pyrotinib as first-line and third-or-later-line treatment and the efficacy comparison of pyrotinib combined with different regimens are still lacking. Therefore, this study aimed to investigate the efficacy and safety of pyrotinib for the HER2-positive MBC in real world to replenish more comprehensive data.

METHODS

A total of 172 HER2-positive MBC patients treated with pyrotinib-based therapy were recruited from multiple centers in nonclinical trial settings from September 2017 to June 2020.

RESULTS

The median progression-free survival (mPFS) of 172 patients was 8.83 months. The patients, receiving first-line pyrotinib treatment, had the longest mPFS (20.93 months) compared with those receiving second-line (8.67 months, p = 0.0339) and third-or-later-line (7.13 months, p = 0.0075) treatments, respectively. Prior treatment with lapatinib (p = 0.012) and site of metastasis (visceral vs. nonvisceral) (p = 0.033) were the independent prognostic factors for PFS. The prior treatment with lapatinib compared with lapatinib-native treatment (5.96 vs. 10.97 months, p = 0.0036) and those with visceral metastasis compared with nonvisceral metastasis (8.40 vs. 23.70 months, p = 0.0138) had worse mPFS. Among 146 patients evaluated for efficacy, 2.1%, 58.9%, and 32.9% showed complete response, partial response, and stable disease, respectively. Adverse events occurred in 92.4% of the patients with 33.3% Grade 3 and higher adverse events and diarrhea (57.0%), anemia (44.8%), and leukopenia (40.7%) as the most frequent ones.

CONCLUSIONS

Pyrotinib-containing regimen could effectively treat HER2-positive MBC with acceptable toxicity, including the patients who progressed after lapatinib treatment and with brain metastasis.

A phase II study of palbociclib plus letrozole plus trastuzumab as neoadjuvant treatment for clinical stages II and III ER+ HER2+ breast cancer (PALTAN)

Patients with ER+/HER2+ breast cancer (BC) are less likely to achieve pathological complete response (pCR) after chemotherapy with dual HER2 blockade than ER-/HER2+ BC. Endocrine therapy plus trastuzumab is effective in advanced ER+/HER2+ BC. Inhibition of CDK4/6 and HER2 results in synergistic cell proliferation reduction. We combined palbociclib, letrozole, and trastuzumab (PLT) as a chemotherapy-sparing regimen. We evaluated neoadjuvant PLT in early ER+/HER2+ BC. Primary endpoint was pCR after 16 weeks. Research biopsies were performed for whole exome and RNA sequencing, PAM50 subtyping, and Ki67 assessment for complete cell cycle arrest (CCCA: Ki67 ≤ 2.7%). After 26 patients, accrual stopped due to futility. pCR (residual cancer burden-RCB 0) was 7.7%, RCB 0/I was 38.5%. Grade (G) 3/4 treatment-emergent adverse events occurred in 19. Among these, G3/4 neutropenia was 50%, hypertension 26.9%, and leucopenia 7.7%. Analysis indicated CCCA in 85% at C1 day 15 (C1D15), compared to 27% at surgery after palbociclib was discontinued. Baseline PAM50 subtyping identified 31.2% HER2-E, 43.8% Luminal B, and 25% Luminal A. 161 genes were differentially expressed comparing C1D15 to baseline. MKI67, TK1, CCNB1, AURKB, and PLK1 were among the genes downregulated, consistent with CCCA at C1D15. Molecular Signatures Database gene-sets analyses demonstrated downregulated processes involved in proliferation, ER and mTORC1 signaling, and DNA damage repair at C1D15, consistent with the study drug's mechanisms of action. Neoadjuvant PLT showed a pCR of 7.7% and an RCB 0/I rate of 38.5%. RNA sequencing and Ki67 data indicated potent anti-proliferative effects of study treatments. ClinicalTrials.gov- NCT02907918.

Treatment strategies for hormone receptor-positive, human epidermal growth factor receptor 2-positive (HR+/HER2+) metastatic breast cancer: A review

Hormone receptor-positive HER2-positive (HR+/HER2+) metastatic breast cancer (MBC) is a unique subtype of breast cancer. Most current guidelines recommend that combination regimens based on anti-HER2 therapy should be used as first-line treatment for HER2+ MBC, irrespective of HR status. Endocrine therapy can be applied as maintenance therapy for patients who are intolerant to chemotherapy or post-chemotherapy. Increasing evidence suggests that complex molecular crosstalk between HR and HER2 pathways may affect the sensitivity to both HER2-targeted and endocrine therapy in patients with HR+/HER2+ breast cancer. Recent research and clinical trials have revealed that a combination of endocrine therapy and anti-HER2 approaches without chemotherapy provides along-term disease control for some patients, but the challenge lies in how to accurately identify the subsets of patients who can benefit from such a de-chemotherapy treatment strategy. In this review, we aim to summarize the results of preclinical and clinical studies in HR+/HER2+ MBC and discuss the possibility of sparing chemotherapy in this subgroup of patients.

The adverse effects of trastuzumab-containing regimes as a therapy in breast cancer: A piggy-back systematic review and meta-analysis

BACKGROUND

Trastuzumab is a valuable therapy option for women with ERBB2(HER2)+ breast cancer tumours, often used in combination with chemotherapy and alongside other therapies. It is known to have adverse effects, but these have proved difficult to separate from the effects of other concurrent therapies patients are usually taking. This study aims to assess the adverse effects specifically attributable to trastuzumab, and whether they vary by patient subgroup or concurrent therapies.

METHODS

As registered on PROSPERO (CRD42019146541), we used previous systematic reviews as well as the clinicaltrials.gov registry to identify randomised controlled trials in breast cancer which compared treatment regimes with and without trastuzumab. Neoadjuvant, adjuvant and metastatic settings were examined. Data was extracted from those which had, as of July 2022, reported adverse events. Risk of bias was assessed using ROB2. Primary outcomes were adverse events of any type or severity (excluding death). A standard random-effects meta-analysis was performed for each outcome independently. In order to ascertain whether adverse effects differed by individual factors such as age or tumour characteristics, or by use of trastuzumab concurrently with hormone therapy, we examined individual-level patient data for one large trial, HERA.

RESULTS

79 relevant trials were found, of which 20 contained comparable arms of trastuzumab-containing therapy and corresponding matched therapy without trastuzumab. This allowed a comparison of 8669 patients receiving trastuzumab versus 9556 receiving no trastuzumab, which gave a list of 25 statistically and clinically significant adverse effects related to trastuzumab alone: unspecified pain, asthenia, nasopharyngitis, skin disorders (mainly rash), dyspepsia, paraesthesia, infections (often respiratory), increased lacrimation, diarrhoea, myalgia, oedema (limb/peripheral), fever, nose bleeds, cardiac events, insomnia, cough, back pain, dyspnoea, chills, dizziness or vertigo, hypertension, congestive heart failure, increased levels of aspartate aminotransferase, gastrointestinal issues and dehydration. Analysis of individual patient-level data from 5102 patients suggested that nausea is slightly more likely for women taking trastuzumab who are ER+ /also taking hormone therapy than for those who are ER-/not taking hormone therapy; no other potential treatment-subgroup interactions were detected. We found no evidence for significantly increased rates of neutropenia, anaemia or lymphopenia in patients on trastuzumab-containing regimes compared to those on comparable regimes without trastuzumab.

CONCLUSIONS

This meta-analysis should allow clinicians and patients to better identify and quantify the potential adverse effects of adding trastuzumab to their treatment regime for breast cancer, and hence inform their decision-making. However, limitations include serious risk of bias due to heterogeneity in reporting of the outcomes and the open-label nature of the trials.

The role of HER2 alterations in clinicopathological and molecular characteristics of breast cancer and HER2-targeted therapies: a comprehensive review

Breast cancer (BC) is the most common malignancy in women and one of the leading causes of cancer mortality, despite significant treatment advancements over the last decades. Human epidermal growth factor receptor-2 (HER2) is a member of the ERBB family of receptor tyrosine kinases which have long been known to mediate cancer cell growth and invasion through constitutive activation of oncogenic downstream signaling, such as PI3K/Akt/mTOR and MAPK. Overexpression/amplification of HER2 in various tumors, especially BC, offers the possible therapeutic potential for target therapies. HER2-targeted therapies, either with a combination of chemotherapy or through multi-anti-HER2 therapies without chemotherapy, have significantly improved the prognosis of HER2-positive tumors. In recent years, novel anti-HER2 agents and combination therapies have garnered much attention, especially for heavily treated advanced or metastatic BCs. HER2-positive BC is biologically a heterogeneous group depending on HER2 activation mechanisms, hormone receptor status, genome variations, tumor heterogeneity, and treatment resistance, which affect the treatment benefit and patients' outcomes. This review will discuss HER2 alternations (gene amplification or receptor overexpression) in BC, their correlation with clinicopathological characteristics and molecular characteristics, and HER2-based therapies in tumors with HER2 overexpression/amplification.

Systemic Treatment of Breast Cancer. 1st Central-Eastern European Professional Consensus Statement on Breast Cancer

This text is based on the recommendations accepted by the 4th Hungarian Consensus Conference on Breast Cancer, modified based on the international consultation and conference within the frames of the Central-Eastern European Academy of Oncology. The professional guideline primarily reflects the resolutions and recommendations of the current ESMO, NCCN and ABC5, as well as that of the St. Gallen Consensus Conference statements. The recommendations cover classical prognostic factors and certain multigene tests, which play an important role in therapeutic decision-making. From a didactic point of view, the text first addresses early and then locally advanced breast cancer, followed by locoregionally recurrent and metastatic breast cancer. Within these, we discuss each group according to the available therapeutic options. At the end of the recommendations, we summarize the criteria for treatment in certain rare clinical situations.

Combined analysis of receptor expression reflects inter-and intra-tumor heterogeneity in HR+/HER2+ breast cancer

BACKGROUND

Hormone receptor-positive and human epidermal growth factor receptor 2-positive (HR+/HER2+ breast cancer comprise approximately 5-10% of all invasive breast cancers. However, the lack of knowledge regarding the complexity of tumor heterogeneity in HR+/HER2+ disease remains a barrier to more accurate therapies. This study aimed to describe the tumor heterogeneity of HR+/HER2+ breast cancer and to establish a novel indicator to identify the HER2-enriched subtype in patients with HR+/HER2+ breast cancer.

METHODS

First of all, a comprehensive analysis was performed on HR+/HER2+ breast cancer samples from the TCGA (n = 141) and METABRIC (n = 104) databases. We determined the distribution of PAM50 intrinsic subtypes within the two cohorts and compared the somatic mutational profile and RNA expression features between HER2-enriched and non-HER2-enriched subtypes. From this, we constructed a novel marker termed rH/E, which was calculated as ERBB2 expression quantity/(ESR1 expression quantity + 1). Secondly, we performed multiplex immunofluorescence (mIF) to evaluate HER2 and estrogen receptor (ER) expression simultaneously in the third cohort, enrolling 43 cases of early HR+/HER2+ breast cancer from Cancer Hospital, Chinese Academy of Medical Sciences (CAMS). When using mIF, rH/E was adjusted to prH/E, which was calculated as HER2-positive cells%/(ER-positive cells + 1)%.

RESULTS

All four main intrinsic subtypes were identified in HR+/HER2+ breast cancer, of which the luminal B subtype was the most common, followed by the HER2-enriched and luminal A subtypes. Significantly increased TP53 and ERBB3 and decreased PIK3CA somatic mutation frequency were observed in the HER2-enriched subtype compared with the non-HER2-enriched subtype. In addition, the HER2-enriched subtype was characterized by significantly higher ERBB2 and lower ESR1 expression. We then constructed a marker termed rH/E to reflect the relative expression of ERBB2 to ESR1 in each patient. rH/E discriminates the HER2-enriched subtype from the better than the expression of ERBB2 or ESR1 alone. In the CAMS cohort, we observed four subtypes of tumor cells: ER+/HER2-, ER+/HER2+, ER-/HER2+, and ER-/HER2-. Tumor cell diversity was common, with 86% of patients having all four subtypes of tumor cells. Moreover, prH/E showed a significant prognostic association in the CAMS cohort.

CONCLUSIONS

This study furthers our understanding of the complexity of tumor heterogeneity in HR+/HER2+ breast cancer, and suggests that the combined analysis of ERBB2 and ESR1 expression may contribute to identifying patients with specific subtypes in this population.

Developments in the Management of Metastatic HER2-Positive Breast Cancer: A Review

Approximately 20% of breast cancers overexpress human epidermal growth factor receptor 2 (HER2), providing an actionable target for many different therapies. In the metastatic setting, prognosis has improved greatly with the use of anti-HER2 drugs such as trastuzumab, pertuzumab, and trastuzumab-emtansine. In the third line setting and beyond, several emerging treatments have shown benefits, including novel small molecule targeted agents and antibody-drug conjugates. Systemic treatment of brain metastases in HER2-positive patients and the role of endocrine-based treatment for patients with hormone receptor (HR) positive disease remain areas of research interest. This article will review the current approach to systemic management of metastatic HER2-positive breast cancer in Canada, and present novel treatments that may be available in the near future.

Trastuzumab Plus Endocrine Therapy or Chemotherapy as First-line Treatment for Patients with Hormone Receptor-Positive and HER2-Positive Metastatic Breast Cancer (SYSUCC-002)

PURPOSE

There is no research evidence demonstrate which is the better partner strategy, endocrine therapy or chemotherapy, to combine with anti-HER2 therapy as the first-line management of hormone receptor (HR)-positive (HR+) and HER2-positive (HER2+) metastatic breast cancer (MBC). We wished to ascertain if trastuzumab plus endocrine therapy is noninferior to trastuzumab plus chemotherapy.

PATIENTS AND METHODS

We conducted an open-label, noninferiority, phase III, randomized, controlled trial (NCT01950182) at nine hospitals in China. Participants, stratified by previous adjuvant endocrine therapy and disease status (recurrent disease vs. de novo metastasis), were assigned randomly (1:1) to receive trastuzumab plus endocrine therapy (per investigator's choice of oestrogen-receptor modulators or aromatase inhibitor, with/without concurrent ovarian suppression) or chemotherapy (per investigator's choice of taxanes, capecitabine, or vinorelbine). The primary endpoint was progression-free survival (PFS) with a noninferiority upper margin of 1.35 for the HR. The intention-to-treat population was used in primary and safety analyses.

RESULTS

A total of 392 patients were enrolled and assigned randomly to receive trastuzumab plus endocrine therapy (ET group, n = 196) or trastuzumab plus chemotherapy (CT group, n = 196). After a median follow-up of 30.2 months [interquartile range (IQR) 15.0-44.7], the median PFS was 19.2 months [95% confidence interval (CI), 16.7-21.7)] in the ET group and 14.8 months (12.8-16.8) in the CT group (hazard ratio, 0.88; 95% CI, 0.71-1.09; Pnoninferiority < 0.0001). A significantly higher prevalence of toxicity was observed in the CT group compared with the ET group.

CONCLUSIONS

Trastuzumab plus endocrine therapy was noninferior to trastuzumab plus chemotherapy in patients with HR+HER2+ MBC.

Trastuzumab and fulvestrant combination therapy for women with advanced breast cancer positive for hormone receptor and human epidermal growth factor receptor 2: a retrospective single-center study

BACKGROUND

Trastuzumab and fulvestrant combination therapy is one of the treatment options for patients with hormone receptor- and human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer; however, there are limited studies evaluating the efficacy of this combination therapy.

METHODS

We retrospectively reviewed the data of women with hormone receptor- and HER2-positive metastatic breast cancer who received trastuzumab and fulvestrant combination therapy between August 1997 and August 2020 at the Cancer Institute Hospital. The primary endpoint of this study was progression-free survival, and the secondary endpoints were response rate, overall survival and safety.

RESULTS

We reviewed the data of 1612 patients with recurrent or metastatic breast cancer, of which 118 patients were diagnosed with hormone receptor- and HER2-positive breast cancer. Of these, 28 patients who received trastuzumab and fulvestrant combination therapy were eligible for this study. The median treatment line for advanced breast cancer was 6 (range, 1-14), the median progression-free survival was 6.4 months (95% confidence interval [CI], 3.46-8.17), and the median overall survival was 35.3 months (95% CI, 20.0-46.7). Of the 28 patients, partial response was observed in 1 (4%), stable disease in 17 (61%), and progressive disease in 10 (36%) patients. The disease control rate was 64%. Adverse events of grade ≥ 3 were not observed.

CONCLUSIONS

Trastuzumab and fulvestrant combination therapy showed moderate clinical efficacy and no severe toxicity after standard anti-HER2 treatment, which is a reasonable treatment option for patients with hormone receptor- and HER2-positive metastatic breast cancer. These data contribute to understanding the efficacy of trastuzumab and fulvestrant combination therapy as control data for further development of anti-HER2 agents plus hormone therapy.

Comparative review of pharmacological therapies in individuals with HER2-positive advanced breast cancer with focus on hormone receptor subgroups

Breast cancer is the fifth leading cause of cancer-related deaths worldwide. The randomized controlled trials (RCTs) of targeted therapies in human epidermal receptor 2 (HER2)-positive advanced breast cancer (ABC) have provided an evidence base for regulatory and reimbursement agencies to appraise the use of cancer therapies in clinical practice. However, a subset of these patients harbor additional biomarkers, for example, a positive hormone receptor status that may be more amenable to therapy and improve overall survival (OS). This review seeks to explore the reporting of evidence for treatment effects by the hormone receptor status using the RCT evidence of targeted therapies for HER2-positive ABC patients. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were followed to identify published RCTs. Extracted data were synthesized using network meta-analysis to obtain the relative effects of HER2-positive-targeted therapies. We identified a gap in the reporting of the effectiveness of therapies by the hormone receptor status as only 15 out of 42 identified RCTs reported hormone receptor subgroup analyses; the majority of which reported progression-free survival but not OS or the overall response rate. In conclusion, we recommend that future trials in ABC should report the effect of cancer therapies in hormone receptor subgroups for all outcomes.

Complete response to pyrotinib combined with letrozole as first-line treatment of HER2-positive/HR-positive breast cancer: a case report

Approximately 15–20% of breast cancer patients are epidermal growth factor receptor 2 (HER2)-positive, and about half of these are also hormone receptor (HR)-positive. The mainstay treatment for HER2-positive/HR-positive patients is anti-HER2 treatment combined with chemotherapy. However, many patients are not suitable for this treatment regimen due to their poor physical health and inability to tolerate chemotherapy. Pyrotinib is a novel, irreversible tyrosine kinase inhibitor (TKI) with activity against EGFR/HER1, HER2, and HER4. Several studies have shown pyrotinib’s anti-tumor activity and safety profile in treating HER-2 positive breast cancer patients, but its effect on metastatic breast cancer (MBC) when combined with letrozole as a first-line treatment remains to be verified. Here, we present a case of a 50-year-old postmenopausal HER2-positive/HR-positive breast cancer patient who received pyrotinib plus letrozole as a first-line treatment following a diagnosis of left axillary lymph node and double lung metastases after modified radical mastectomy for left breast cancer. Two months after administration of combined pyrotinib and letrozole, a complete response (CR) was confirmed by CT scan. The patient experienced only mild and tolerable adverse events. At the time of writing, the patient was still alive without any recurrence. Our case indicates that the combined therapy of pyrotinib plus letrozole may/can be a promising treatment option for patients with HER2-positive/HR-positive MBC. Nevertheless, further evidence is needed to verify this conclusion.

Targeting HER2 in Breast Cancer: Latest Developments on Treatment Sequencing and the Introduction of Biosimilars

Approximately 20% of all breast cancers overexpress the human epidermal growth factor receptor 2 (HER2). Targeting breast cancer through this vital oncogenic protein has been a major step towards improved patient outcomes. Today, several anti-HER2 agents are in clinical use including: the monoclonal antibodies trastuzumab and pertuzumab; the small molecule inhibitors lapatinib, neratinib, and tucatinib; and the antibody-drug conjugates ado-trastuzumab emtansine and trastuzumab deruxtecan, in some jurisdictions. In addition, several trastuzumab biosimilars have recently been granted regulatory approval in North America and the EU, and are enhancing patient access to HER2-directed therapy. The various agents differ greatly in their side-effect profiles and approved indications, from neoadjuvant and adjuvant use in early disease, to first- and later-line use in metastatic disease. This review discusses the current treatment recommendations for the use of anti-HER2 agents alone and in combination, examines the latest advances in HER2-targeted drugs and how they may be best applied in clinical practice, and provides guidance on optimal sequencing of the growing array of therapeutic options for HER2-positive breast cancer.

Current and Future Management of HER2-Positive Metastatic Breast Cancer

Human epidermal growth factor receptor 2 (HER2) is overexpressed and/or amplified in approximately 20% of breast cancers, conferring an aggressive tumor behavior but also an opportunity for targeted therapies. In the advanced setting, the prognosis of patients suffering from this disease has greatly improved after the introduction of new anti-HER2 drugs beyond trastuzumab. For most patients, a taxane combined with trastuzumab and pertuzumab in the first-line setting, followed by trastuzumab-emtansine in second line, should be considered the standard of care today. However, chemo-free anti-HER2 strategies in hormone receptor-positive, HER2-positive breast cancer could also be considered in selected patients. In the third-line setting and beyond, several emerging anti-HER2 therapies are becoming available, including tucatinib, fam-trastuzumab deruxtecan-nxki (DS-8201a), neratinib, and margetuximab-cmkb. In addition, new compounds and combinations are showing promising results in the late-line setting. The treatment landscape of HER2-positive advanced disease is evolving constantly, active drugs such as pertuzumab and trastuzumab-emtansine are moving to early-stage, many biomarkers, including quantification of HER2 itself, are being explored to improve patient selection, and patient populations with specific needs are emerging, such as those with brain metastasis. Here, we provide an overview of the current and future management of HER2-positive advanced breast cancer.

Recent advances in the treatment of hormone receptor-positive/human epidermal growth factor 2-positive advanced breast cancer

Hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-positive (HR+/HER2+) advanced breast cancer is a special subtype of cancer with unique features. Major guidelines recommend that combination therapy containing anti-HER2 therapy (e.g., trastuzumab and pertuzumab) should be applied as the first-line treatment for HER2+ advanced breast cancer, regardless of HR status. Endocrine therapy could be relegated to patients who cannot tolerate chemotherapy or as a post-chemotherapy empirical maintenance strategy. Previous studies have shown that the HR pathway interacts with the HER2 pathway, and the HR and HER2 pathways of endocrine therapy combined with targeted therapy can effectively avoid tumor resistance. Therefore, the combination of endocrine and targeted therapies is the preferred treatment plan for HR+/HER2+ patients to replace chemotherapy. In this review, we will discuss research progress regarding endocrine therapy combined with anti-HER2 therapy in patients with advanced breast cancer, to provide more evidence for clinical practice and broader perspectives for related research. In the future, we hope there will be more studies on HR+/HER2+ advanced breast cancer to elucidate the optimal and appropriate treatment for these patients.

Current trends in the treatment of HR+/HER2+ breast cancer

Treatment for HR+/HER2+ patients has been debated, as some tumors within this luminal HER2+ subtype behave like luminal A cancers, whereas others behave like non-luminal HER2+ breast cancers. Recent research and clinical trials have revealed that a combination of hormone and targeted anti-HER2 approaches without chemotherapy provides long-term disease control for at least some HR+/HER2+ patients. Novel anti-HER2 therapies, including neratinib and trastuzumab emtansine, and new agents that are effective in HR+ cancers, including the next generation of oral selective estrogen receptor downregulators/degraders and CDK4/6 inhibitors such as palbociclib, are now being evaluated in combination. This review discusses current trials and results from previous studies that will provide the basis for current recommendations on how to treat newly diagnosed patients with HR+/HER2+ disease.

The changing treatment of metastatic her2-positive breast cancer

Human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer has been historically associated with an aggressive disease course with common distant metastasis and poor prognosis. HER2-targeting therapies have significantly changed treatment and drastically improved outcomes for this group of patients. However, primary or acquired resistance to anti-HER2 regimens leads almost universally to disease progression, often with difficult to treat central nervous system (CNS) metastases. The current review summarized the existing therapeutic options for HER2-positive metastatic disease in the first, second and further line setting. Furthermore, novel agents currently under development were presented, which have demonstrated encouraging results in heavily pretreated patients or specific subgroups, such as HR-positive/HER2-positive tumors and CNS disease.

Aromatase and CDK4/6 Inhibitor-Induced Musculoskeletal Symptoms: A Systematic Review

BACKGROUND

Treatment with aromatase inhibitors (AIs) is fundamental in women with hormone receptor-positive breast cancer in the adjuvant as well as the metastatic setting. Even though it is considered to be a well-tolerated therapy, aromatase inhibitor-associated musculoskeletal syndrome (AIMSS) is the most common adverse event encountered by breast cancer patients. CDK4/6 inhibitors have emerged as a new treatment strategy in metastatic hormone receptor-positive breast cancer. However, the impact of CDK4/6 inhibitors on musculoskeletal symptoms caused by AIs is not well-defined.

OBJECTIVES

This systematic review aims to identify the frequency of joint symptoms induced by treatment with AIs and CDK4/6 inhibitors in the metastatic setting.

SEARCH STRATEGY

Eligible articles were identified by a search of existing literature for the period 2005/01/01-2021/01/01; The algorithm consisted of a predefined combination of the following keywords "breast", "cancer", "aromatase inhibitors", "CDK4/6", "phase III".

SELECTION CRITERIA

This study was performed in accordance with PRISMA guidelines. All randomized controlled Phase III trials (RCTs) evaluating the administration of third-generation aromatase inhibitors (AIs) and CDK4/6 inhibitors in postmenopausal women in the metastatic setting were considered eligible for this review.

DATA COLLECTION

Overall, 16 randomized control trials (RCTs) were retrieved, of which nine studies explored the administration of AIs in the metastatic setting and seven studies investigated the combination of CDK4/6 inhibitors and AIs. Arthralgia was reported in 1-47% of patients treated with AIs and 5.8-33.3% of patients treated with CDK4/6 inhibitors. Myalgias occurred in 2-23.7% of patients receiving AIs compared with 4.8-11.9% of patients treated with CDK4/6 inhibitors. The incidence of back pain was 7-32.9% vs. 2.9-8.5% in postmenopausal women with metastatic disease treated with AIs and CDK4/6 inhibitors, respectively. Bone pain was reported in 7-32.9% of postmenopausal women treated with AIs and 2.9-8.5% of women treated with CDK4/6 inhibitors.

CONCLUSIONS

AI treatment-induced musculoskeletal syndrome is an adverse event affecting over one-third (20-47%) of postmenopausal patients treated with AIs that often leads to treatment discontinuation. Data from RCTs provide evidence that the incidence of musculoskeletal symptoms is relatively decreased upon CDK4/6 inhibitor administration. CDK4/6 inhibitors may provide a protective role against AIMSS development.

The efficacy and safety of pertuzumab plus trastuzumab and docetaxel as a first-line therapy in Japanese patients with inoperable or recurrent HER2-positive breast cancer: the COMACHI study

PURPOSE

In the CLEOPATRA study of patients with human epidermal growth factor receptor 2 (HER2)-positive recurrent or metastatic breast cancer, the Japanese patient subgroup did not demonstrate the improved progression-free survival (PFS) of pertuzumab plus trastuzumab and docetaxel vs. placebo that was seen in the overall population. Therefore, COMACHI was conducted to confirm the efficacy and safety of this treatment regimen in this patient subgroup.

METHODS

This was a phase IV study of pertuzumab plus trastuzumab and docetaxel in Japanese patients with histologically/cytologically confirmed inoperable or recurrent HER2-positive breast cancer. All patients received pertuzumab, trastuzumab, and docetaxel intravenously every 3 weeks until disease progression/unacceptable toxicity. The primary endpoint was investigator-assessed PFS. Secondary endpoints were overall survival (OS), investigator-assessed objective response rate, and duration of response (DoR). Safety was also assessed.

RESULTS

At final analysis, median investigator-assessed PFS was 22.8 months (95% CI 16.9-37.5). From first dose, OS rate at 1 year was 97.7%; and at 2 and 3 years were 88.5% and 79.1%, respectively. Of the 118 patients with measurable disease at baseline, response rate was 83.9% (95% CI 77.3-90.5) and median investigator-assessed DoR was 26.3 months (95% CI 17.1-not evaluable). Treatment was well tolerated, with no new safety signals detected.

CONCLUSIONS

Our results suggest similar efficacy and safety for pertuzumab plus trastuzumab and docetaxel in Japanese patients compared with the overall population of CLEOPATRA, providing further support for this combination therapy as standard of care for Japanese patients with inoperable or recurrent HER2-positive breast cancer.

Therapeutic Strategies for the Management of Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Positive (HR+/HER2+) Breast Cancer: A Review of the Current Literature

Enormous advances have been made in the understanding and treatment of human epidermal growth factor receptor 2-positive breast cancer (HER2+ BC) in the last 30 years that have resulted in survival gains for affected patients. A growing body of evidence suggests that hormone receptor-positive (HR+)/HER2+ BC and HR-negative (HR-)/HER2+ BC are biologically different, with complex molecular bidirectional crosstalk between the estrogen receptor and HER2 pathway potentially affecting sensitivity to both HER2-targeted and endocrine therapy in patients with HR+/HER2+ BC. Subgroup analyses from trials enrolling patients with HER2+ BC and the results of clinical trials specifically designed to evaluate therapy in patients with HR+/HER2+ BC are helping to guide treatment decisions. In this context, encouraging results with strategies aimed at delaying or reversing drug resistance, including extended adjuvant therapy and the addition of drugs targeting alternative pathways, such as cyclin-dependent kinase (CDK) 4 and 6 inhibitors, have recently emerged. We have reached the point where tailoring the treatment according to risk and biology has become the paradigm in early BC. However, further clinical trials are needed that integrate translational research principles and identify and consider specific patient subgroups and biomarkers.

Treatment Landscape and Prognosis After Treatment with Trastuzumab Emtansine

Purpose Pertuzumab and T-DM1 are two efficient anti-HER2 treatments for patients with HER2-positive advanced breast cancer. While pertuzumab is usually given in first-line treatment and T-DM1 in second-line treatment, standard therapy options seem to be exhausted up to now after the treatment of patients with these two therapy options. Therefore, it is important to have data that describes the therapy situation and prognosis after T-DM1 treatment. Methods The PRAEGNANT metastatic breast cancer registry (NCT02338167) is a prospective registry for breast cancer patients with a focus on molecular biomarkers. Patients of all therapy lines with any kind of treatment are eligible. Collected data comprises therapies, adverse events, quality of life and other patient reported outcomes. Here we report on the patient characteristics and descriptive prognostic data for HER2-positive patients who have completed a treatment with T-DM1. Therapy patterns after T-DM1 and progression-free survival are reported as well as overall survival. Results A total of 85 patients were identified for the study who were prospectively observed during therapy after the termination of T-DM1. The main reason for T-DM1 termination was progress. Following T-DM1, lapatinib, trastuzumab and chemotherapy were the main therapy choices. Median progression-free survival was 4.8 months (95% CI: 3.2 - 6.3) and median overall survival was 18.4 months (95% CI: 15.5 - 21.3). Conclusions Therapy options after T-DM1 in a real-world setting seem to exhibit a relevant clinical efficacy, supporting the concept of continuous anti-HER2 treatments in the advanced therapy setting for breast cancer patients. Novel therapies are needed to improve the rather short median progression-free survival.

Systemic therapy for metastatic HER2-positive breast cancer

The human epidermal growth factor receptor 2 (HER2), is amplified and/or overexpressed in approximately 15%-20% of breast cancers. Targeting of the HER2 receptor with the humanized monoclonal antibody trastuzumab in combination with chemotherapy has become the backbone of treatment for both early stage and metastatic breast cancer for the last 2 decades. Relapsed or de novo metastatic HER2-positive breast cancer essentially remains an incurable disease. Nonetheless, with advances in therapeutics, survival rates in this group continue to increase with median survival now in excess of 57 months. First line systemic therapy for HER2-positive metastatic breast cancer using taxane chemotherapy combined with trastuzumab and pertuzumab, and second line therapy with trastuzumab emtansine, are well established. Recent studies of small molecule oral tyrosine kinase inhibitors such as tucatinib and neratinib, and antibody drug conjugates such as trastuzumab deruxtecan further improve outcomes. Major treatment challenges remain in the areas of brain metastases and development of drug resistance. This review details an up to date analysis of current and emerging treatments of metastatic HER2-positive breast cancer.

Pyrotinib with trastuzumab and aromatase inhibitors as first-line treatment for HER2 positive and hormone receptor positive metastatic or locally advanced breast cancer: study protocol of a randomized controlled trial

Background

HER2 dual-blockade combined with aromatase inhibitors (AI) is a promising strategy to improve progression-free survival (PFS) in hormone receptor (HR) positive, metastatic breast cancer (MBC). Pyrotinib is a novel irreversible epidermal growth factor receptor/HER2 dual tyrosine kinase inhibitor. However, there is scarcity of data on the effectiveness and safety of pyrotinib combined with trastuzumab and AI as first-line treatment in a metastatic setting.

Methods/design

The present study is a prospective, randomized, open-label trial. 198 patients with HER2+/HR+ MBC will be recruited. Eligible patients will be allocated (2:1) to either an experimental group (pyrotinib + trastuzumab + AI) or a control group (trastuzumab + AI). Allocation will be stratified by 1) time since adjuvant hormone therapy (≤ 12 months/> 12 months/no prior hormone therapy); 2) lesion sites (visceral / non-visceral). The primary endpoint is PFS.

Discussion

To our knowledge, this is the first prospective randomized controlled trial to assess dual HER2-blockade with pyrotinib in the metastatic setting. This study will provide valuable evidence regarding the efficacy and safety of pyrotinib when combined with trastuzumab and an AI as first-line treatment for MBC. Moreover, it will also evaluate the feasibility of endocrine therapy as an alternative to chemotherapy in providing de-escalation therapy with less toxicity for advanced HR+/HER2+ patients.

Trial registration

ClinicalTrials.gov, ID: NCT03910712. Registered on 10 Apr. 2019.

Biomarkers for HER2-positive metastatic breast cancer: Beyond hormone receptors

The overexpression of human epidermal growth factor receptor-2 (HER2) results in a biologically and clinically aggressive breast cancer (BC) subtype. Since the introduction of anti-HER2 targeted agents, survival rates of patients with HER2-positive metastatic BC have dramatically improved. Currently, although the treatment decision process in metastatic BC is primarily based on HER2 and hormone-receptor (HR) status, a rapidly growing body of data suggests that several other sources of biological heterogeneity may characterize HER2-positive metastatic BC. Moreover, pivotal clinical trials of new anti-HER2 antibody-drug conjugates showed encouraging results in HER2-low metastatic BC, thus leading to the possibility, in the near future, to expand the pool of patients suitable for HER2-targeted treatments. The present review summarizes and puts in perspective available evidence on biomarkers that hold the greatest promise to become potentially useful tools for optimizing HER2-positive metastatic BC patients' prognostic stratification and treatment in the next future. These biomarkers include HER2 levels and heterogeneity, HER3, intrinsic molecular subtypes by PAM50 analysis, DNA mutations, and immune-related factors. Molecular discordance between primary and metastatic tumors is also discussed.

ABC4 Consensus: First Latin American Meeting-Assessment, Comments, and Application of Its Recommendations

Breast cancer accounts for a high burden among all the neoplasms in Latin America, with more-advanced stages at presentation, which could result in high mortality rates. The 4th International Consensus Conference for Advanced Breast Cancer (ABC4) is focused on standardizing therapy for advanced breast cancer (ABC) and has held 5 meetings so far. ABC4 took place in Lisbon, Portugal, from November 2 to 4, 2017; however, the first Latin American ABC conference was held in Lima, Peru, from 18 to 19 May, 2018, chaired by Fatima Cardoso, MD, PhD. During these 2 days, the ABC4 consensus recommendations for advanced and locally advanced breast cancer were presented. Local treatment and systemic therapy were discussed with local experts, mainly focusing on anti-human epidermal growth factor receptor 2 therapy and newly approved drugs for hormone receptor-positive breast cancer, such as as CDK4/6, mammalian target of rapamycin, and poly (ADP-ribose) polymerase inhibitors for triple-negative breast cancer. The discussion focused additionally on access to drugs and ABC4 consensus recommendations as regards Latin American patients.

Evaluating Trastuzumab in the treatment of HER2 positive breast cancer

The transmembrane oncoprotein HER2 is encoded by ERBB2 gene and overexpressed in around 20% of invasive breast cancers. It can be specifically targeted by Trastuzumab (Herceptin®), a humanised IgG1 antibody. Trastuzumab has been regarded as one of the most effective therapeutic drugs targeted to HER2 positive cancers. However, there are drawbacks, notably cardiotoxicity and resistance, which have raised awareness in clinical use. Therefore, understanding the mechanism of action is vital to establish improved therapeutic strategies. Here we evaluate Trastuzumab application in the treatment of HER2 positive breast cancer, focusing on its mechanistic actions and clinical effectiveness. Alternative therapies targeting the HER2 receptor and its downstream anomalies will also be discussed, as these could highlight further targets that could be key to improving clinical outcomes.

Breast Cancer, Version 3.2020, NCCN Clinical Practice Guidelines in Oncology

Several new systemic therapy options have become available for patients with metastatic breast cancer, which have led to improvements in survival. In addition to patient and clinical factors, the treatment selection primarily depends on the tumor biology (hormone-receptor status and HER2-status). The NCCN Guidelines specific to the workup and treatment of patients with recurrent/stage IV breast cancer are discussed in this article.

Review of concepts in therapeutic decision-making in HER2-negative luminal metastatic breast cancer

Purpose

Hormone receptor (HR)-positive, Human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) requires a therapeutic approach that takes into account multiple factors, with treatment being based on anti-estrogen hormone therapy (HT). As consensus documents are valuable tools that assist in the decision-making process for establishing clinical strategies and optimize the delivery of health services, this consensus document has been created with the aim of developing recommendations on cretiera for hormone sensitivity and resistance in HER2-negative luminal MBC and facilitating clinical decision-making.

Methods

This consensus document was generated using a modification of the RAND/UCLA methodology, which included the definition of the project and identification of issues of interest, a non-exhaustive systematic review of the literature, an analysis and synthesis of the scientific evidence, preparation of recommendations, and external evaluation with a panel of 64 medical oncologists specializing in breast cancer.

Results

A Spanish panel of experts reached consensus on 32 of the 32 recommendations/conclusions presented in the first round and were accepted with an approval rate of 100% about definition of metastatic disease not susceptible to local curative treatment, definition of hormone sensitivity and hormone resistance in metastatic luminal disease and therapeutic decision-making.

Conclusion

We have developed a consensus document with recommendations on the treatment of patients with HER2-negative luminal MBC that will help to improve therapeutic benefits.

Hormonal treatment combined with targeted therapies in endocrine-responsive and HER2-positive metastatic breast cancer

Approximately 50% of HER2 positive breast cancer cases are also estrogen receptor (ER) positive. Data supports a role for close cross-talk between the ER and HER2 signaling pathways as an important contributor to the development of de novo or acquired resistance to hormone therapies. Therefore a strategy that simultaneously blocks both signaling pathways is a reasonable approach to prevent or overcome either endocrine or anti-HER2 therapy resistance. Moreover, preclinical data support the idea that PI3K inhibitors and CDK4/6 could be an attractive target that functions downstream of both ER and HER2 pathways. We conducted a literature review of the results of phase II and III studies testing targeted therapies in metastatic breast cancer with HER2-positive and hormonal-receptor-positive disease. The analyses included efficacy and toxicity data from earlier studies with a single anti-HER2 drug combined with hormonal therapy up to more recent studies testing new molecules targeting these signaling pathways. The aims of this review are to summarize current knowledge and to discuss research development including the possibility to spare chemotherapy in this subgroup of HER2-positive breast cancer patients.

An RB-1 loss of function gene signature as a tool to predict response to neoadjuvant chemotherapy plus anti-HER2 agents: a substudy of the NeoALTTO trial (BIG 1-06)

BACKGROUND

Chemotherapy added to anti-HER2 agents (H) is the treatment of choice in patients with HER2+ early breast cancer. However, HER2+ tumours are clinically and biologically heterogeneous, and treatment response varies significantly by hormone receptor (HR) status and molecular subtype. Predictive biomarkers are needed in this context. This study assessed whether an RB-1 loss of function gene signature (RBsig) is predictive of response to neoadjuvant chemotherapy in combination with trastuzumab, lapatinib or both, within the NeoALTTO trial.

METHODS

We collected RNA-sequencing data from pretreatment biopsies derived from the NeoALTTO trial. RBsig expression was computed retrospectively and correlated with pathological complete response (pCR) using receiver-operating characteristic (ROC) curves. The RBsig was dichotomised as High/Low in correspondence to the 25th percentile. Reported p values resulted from Fisher's exact test.

RESULTS

Of 455 NeoALTTO patients, 244 were eligible for this substudy (HR+ n = 129; HR- n = 115). Overall, pCR rate was significantly higher in patients with RBsig High tumours than those with RBsig Low (35% versus 18% respectively; p = 0.01). The area under the ROC curve (AUC) was 0.60 (95% CI 0.52-0.67). A remarkably low pCR rate of 11% was seen in HR+/RBsig Low patients versus 28% in HR+/RBsig High.

CONCLUSIONS

These results indicate RBsig may add valuable information to HER2 and HR expression, which may in turn inform treatment choices. HR+/HER2+/RBsig Low breast cancers exhibited the poorest pathological response following chemotherapy plus H. Accordingly, in such patients, endocrine therapy in combination with H and, possibly, a CDK4/6 inhibitor, may potentially prove to be a more effective treatment.