Dual anti-HER2 Blockade Research Articles

De-escalation of breast cancer surgery using vacuum-assisted biopsy (VAB): Interim results.

e12590 Background: Currently, there is a point of view according to which, in patients diagnosed with breast cancer (BC), surgical intervention when achieving a complete pathological response (pCR) after neoadjuvant systemic therapy (NST) is diagnostic, not therapeutic, and does not affect long-term treatment outcomes. Vacuum-assisted biopsy (VAB) of the tumor bed in breast cancer has shown promising results as a minimally invasive method for diagnosing pCR. This work presents a prospective analysis of treatment of patients with triple-negative and HER2-positive breast cancer who achieved pCR after NST and who underwent VAB alone without subsequent breast surgery. Methods: Women aged 18 years old and older with unicentric (cT1-2N0-1M0) triple-negative or HER2-positive breast cancer were included. Primary lesions were marked with a single clip before NST. In cases with nodal involvement (cN1) the affected lymph nodes were also clipped. Patients with TNBC received 4 cycles of AC q21d followed by 12 cycles of weekly paclitaxel and carboplatin AUC 2.0. HER2+ patients received dual anti-HER2 blockade with chemotherapy (TCHP or AC-DHP regimen). Breast US, mammography and mammolymphoscintigraphy were used at baseline and at response evaluation. Patients with complete clinical response after NST underwent VAB with 7G needle and US-guidance simultaneously with the sentinel lymph node biopsy and/or targeted axillary dissection. In case if no invasive or in situ residual tumor cells were detected (ypT0N0), no further breast surgery was performed and patients underwent subsequent radiation therapy. Primary endpoint was 2-year ipsilateral breast tumour recurrence-free survival [IBTR-FS]. Secondary endpoints included 2-year disease-free survival (DFS) and complication rates. The study is registered on сlinicaltrials.gov, NCT04293796. Results: 35 patients with a mean age of 48.3 (31–67) years were included in the trial. Examination of VAB samples showed that 11 (31.4%) patients had a residual tumor, and in 24 (68.6%) patients no tumor cells were detected (ypT0N0). This 24 patients were included in the analysis. Median follow-up was 26 months. Median survival was not reached for any endpoint. 2-year IBTR-FS was 91.7% in the VAB group. 2-year DFS was 83.3% in the VAB group. We registered 4 events: in 2 patients biopsy-proven de novo breast cancer occurred in contralateral breast, in 1 patient recurrence occurred in the postoperative zone and in 1 patient recurrence occurred in another quadrant of the ipsilateral breast. Conclusions: Additional observation and large randomized prospective studies are needed to determine the safety of VAB use. Clinical trial information: NCT04293796 .

Prognostic significance of HER2 loss after HER2-targeted neoadjuvant treatment in patients with HER2-positive locally advanced breast cancer

Loss of human epidermal growth factor receptor 2 (HER2) expression can be seen in almost 25–30 % patients after HER2 receptor directed neoadjuvant treatment. These patients have unclear clinical outcomes in previous studies. We aimed to investigate the importance of HER2 loss, additionally with predictive factors for the loss of HER2. This was a retrospective and multicenter study that included 272 HER2-positive BC patients with no pathological complete response who received neoadjuvant chemotherapy plus HER2-targeted treatments. The factors that may affect the loss of HER2 detected by immunohistochemistry(IHC) and the association with survival were analyzed.The rate of HER2 loss after neoadjuvant treatments(NAT) was 27.9 % (n = 76). Disease recurrence was observed in 18(23.7 %) patients with HER2 loss, while it was detected in 62 (31.7 %) patients without HER2 loss(p = 0.23). Pre and post-NAT ER status, and post-NAT ki-67 status had a significant impact on disease-free survival(DFS) (p = 0.0012, p = 0.004, and p = 0.04, respectively).There were no significant association between DFS and loss of HER2 (p = 0.64) and dual anti-HER2 blockade (p = 0.21). Pre-NAT clinical stage (HR:1.65 p = 0.013), post-NAT LN status (HR:3.18, p = 0.02) and pre-NAT ER status (HR:0.24, p = 0.041) were significant independent prognostic factors for DFS while post-NAT residual disease in axillar tissue was an independent prognostic factor for OS (HR:1.54 p = 0.019). Moreover, age (<40 years vs ≥40 years) (p = 0.031) and tumor grade (p = 0.004) were predictive factors for HER2 loss. Our results showed that HER2 loss did not affect survivals. However, young age and being high grade tumor may predict HER2 loss.

The Impact of Initial Tumor Response on Survival Outcomes of Patients With HER2-Positive Advanced Breast Cancer Treated With Docetaxel, Trastuzumab, and Pertuzumab: An Exploratory Analysis of the CLEOPATRA Trial

IntroductionThe CLEOPATRA trial (NCT00567190) established a dual anti-HER2 blockade in combination with docetaxel as the first-line standard of care for patients with metastatic HER2-positive breast cancer. While this treatment is overall associated with significant improvement in progression-free survival (PFS) and overall survival (OS), not all patients respond equally. We hypothesized that a radiological complete response (CR) at week 9 (i.e., first disease re-evaluation) is associated with prolonged OS and PFS compared to radiological partial response (PR) or stable disease (SD). MethodsWe performed an exploratory analysis of the CLEOPATRA study to address this question. ResultsOut of 362 patients treated with docetaxel, trastuzumab, and pertuzumab eligible for our analysis, 46 (12.7%) had radiological CR at week 9, 243 (67.1%) PR, and 73 (20.2%) SD per central RECIST v1.0. Radiological CR at first tumor re-evaluation was associated with a 60% risk reduction for death compared to SD (adjusted HR = 0.40 95% confidence interval (CI) 0.23-0.70), whereas no significant impact on survival was observed for PR (adjusted HR = 0.85 95% CI 0.60-1.20). The same was observed for PFS with adjusted HR = 0.30 (95% CI 0.18-0.48) for the CR subgroup and adjusted HR = 0.81 (95% CI 0.60-1.09) for the PR subgroup. In multivariate analysis, no variables were associated with radiological CR. ConclusionsOur findings suggest that radiological CR at first disease re-evaluation is associated with more prolonged survival; this might result from stronger dependence on HER2 pathway addiction, supporting the need for further translational research.

Immune microenvironment dynamics of HER2 overexpressing breast cancer under dual anti-HER2 blockade.

The clinical prognosis of the HER2-overexpressing (HER2-OE) subtype of breast cancer (BC) is influenced by the immune infiltrate of the tumor. Specifically, monocytic cells, which are promoters of pro-tumoral immunosuppression, and NK cells, whose basal cytotoxic function may be enhanced with therapeutic antibodies. One of the standards of care for HER2+ BC patients includes the combination of the anti-HER2 antibodies trastuzumab and pertuzumab. This dual combination was a breakthrough against trastuzumab resistance; however, this regimen does not yield complete clinical benefit for a large fraction of patients. Further therapy refinement is still hampered by the lack of knowledge on the immune mechanism of action of this antibody-based dual HER2 blockade. To explore how the dual antibody challenge influences the phenotype and function of immune cells infiltrating the HER2-OE BC microenvironment, we developed in vitro 3D heterotypic cell models of this subtype. The models comprised aggregates of HER2+ BC cell lines and human peripheral blood mononuclear cells. Cells were co-encapsulated in a chemically inert alginate hydrogel and maintained in agitation-based culture system for up to 7 days. The 3D models of the HER2-OE immune microenvironment retained original BC molecular features; the preservation of the NK cell compartment was achieved upon optimization of culture time and cytokine supplementation. Challenging the models with the standard-of-care combination of trastuzumab and pertuzumab resulted in enhanced immune cytotoxicity compared with trastuzumab alone. Features of the response to therapy within the immune tumor microenvironment were recapitulated, including induction of an immune effector state with NK cell activation, enhanced cell apoptosis and decline of immunosuppressive PD-L1+ immune cells. This work presents a unique human 3D model for the study of immune effects of anti-HER2 biologicals, which can be used to test novel therapy regimens and improve anti-tumor immune function.

The effect of the alpha-specific PI3K inhibitor alpelisib combined with anti-HER2 therapy in HER2+/PIK3CA mutant breast cancer.

HER2 is amplified or overexpressed in around 20% of breast cancers (BC). HER2-targeted therapies have significantly improved the prognosis of patients with HER2+ BC, however, de novo and acquired resistance to anti-HER2 treatment is common. Activating mutations in the PIK3CA gene are reported in ∼30% of HER2+ BC and are associated with resistance to anti-HER2 therapies and a poor prognosis. Here, we investigated the in vitro and in vivo antitumor efficacy of the alpha-specific PI3K inhibitor alpelisib alone or in combination with anti-HER2 therapy using a panel of HER2+ BC cell lines. We also generated models of acquired resistance to alpelisib to investigate the mechanisms underlying resistance to alpha-specific PI3K inhibition. PIK3CA mutant (HCC1954, KPL4 and JMT1) and wild-type (BT474 and SKBR3) HER2+ BC cell lines were used. The HCC1954 and KPL4 cells were chronically exposed to increasing concentrations of alpelisib or to alpelisib + trastuzumab in order to generate derivatives with acquired resistance to alpelisib (AR) and to alpelisib + trastuzumab (ATR). The transcriptomic profiles of HCC1954, KPL4 and their AR and ATR derivatives were determined by RNA sequencing. Cell growth was assessed by MTT assay. Changes in the protein levels of key PI3K pathway components were assessed by Western blotting. Gene expression, cellular and patients' data from the Cancer Dependency Map (DepMap) and KMPlot datasets were interrogated. HER2+ BC cell lines harboring activating mutations in PIK3CA were less sensitive to single or dual anti-HER2 blockade compared to PIK3CA wild-type cells. Alpelisib treatment resulted in dose-dependent inhibition of the growth of cells with or without PIK3CA mutations and enhanced the antitumor efficacy of anti-HER2 therapies in vitro. In addition, alpelisib greatly delayed tumor growth of HCC1954 xenografts in vivo. Functional annotation of the significantly differentially expressed genes suggested the common activation of biological processes associated with oxidation reduction, cell proliferation, immune response and RNA synthesis in alpelisib-resistant models compared with native cells. Eight commonly upregulated genes (log2 fold-change >1, False Discovery Rate [FDR] <0.05) in models with acquired resistance to alpelisib or alpelisib + trastuzumab were identified. Among these, AKR1C1 was associated with alpelisib-resistance in vitro and with a poor prognosis in patients with HER2+ BC. Our findings support the use of an alpha-selective PI3K inhibitor to overcome the therapeutic limitations associated with single or dual HER2 blockade in PIK3CA-mutant HER2+ breast cancer. Future studies are warranted to confirm the potential role of candidate genes/pathways in resistance to alpelisib.

Gene expression signatures, stromal tumor infiltrating lymphocytes (sTILs), and change in tumor cellularity to predict pathological complete response (pCR) after 12 week de-escalated neoadjuvant endocrine therapy (ET) vs paclitaxel + dual HER2 blockade in the WSG-TP-II trial.

519 Background: There are limited data on predictive biomarkers for de-escalated ET or chemotherapy with dual anti-HER2 blockade in HR+/HER2+ early breast cancer (BC). In this translational pre-planned project of the WSG-TP-II phase II-trial (NCT03272477), we aimed to identify associations of gene expression signatures and sTILs with pCR. Methods: Patients with cT1c-cT4c, cN0-3 centrally confirmed HR+/HER2+ BC were randomized to 12 weeks of standard ET (n = 100) or paclitaxel (Pac; n = 107). All patients received trastuzumab + pertuzumab (T+P) q3w as neoadjuvant and adjuvant treatment. Gene expression signatures were analyzed using NanoString BC360 panel in baseline biopsies (T+P+ET: n = 72; T+P+Pac: n = 78). sTILs were analyzed in 93 (T+P+ET) and 97 patients (T+P+Pac) at baseline and in 65 (T+P+ET) and 57 patients (T+P+Pac) at week 3. Impacts of standardized BC360 gene expression signatures and sTILs on pCR (ypT0/is ypN0; primary endpoint) expressed in odds ratios (OR) were estimated by logistic regression analysis. Results: pCR rate in patients with BC360 analysis was 39.3% (T+P+ET: 23.6%; T+P+Pac: 53.9%). Overall, ERBB2 (OR 2.37; 95%CI 1.55, 3.62) and cytotoxic cells signature (OR 1.42; 95%CI 1.02, 1.99) were favorable for pCR, while apoptosis (OR 0.64; 95%CI 0.44, 0.92), estrogen receptor 1 (OR 0.60; 95%CI 0.42, 0.85), estrogen receptor signaling (OR 0.64; 95%CI 0.45, 0.91), and progesterone receptor (OR 0.67; 95%CI 0.47, 0.94) signatures were unfavorable. Analyzing by treatment arm, a similar pattern was observed in the T+P+Pac arm (ERBB2: OR 2.01; apoptosis: OR 0.59; estrogen- and progesterone-related signatures: OR 0.41-0.58), but not in the T+P+ET arm where only ERBB2 was prognostic for pCR (OR 7.24; 95%CI 2.12, 24.05). Baseline ≥30% sTIL levels (vs &lt; 30% sTILs; n = 16 vs n = 174) were associated with pCR (OR 5.16; 95%CI 1.60, 16.66); significance was not achieved in either trial arm. Compared to &lt; 30% sTILs (n = 90), low tumor cellularity at week 3 precluding sTILs analysis ( &lt; 500 invasive tumor cells, n = 22), but not ≥30% sTILs (n = 10), was prognostic for pCR in all patients (OR 9.47; 95%CI 2.94, 30.50) and in individual trial arms (OR 6.00-11.79). Conclusions: This hypothesis-generating translational results suggest that gene expression signatures (particularly ERBB2), baseline sTILs, and low tumor cellularity at week 3 predict pCR after ET + double HER2 blockade. Future neoadjuvant trials are needed to prospectively test the use of baseline gene expression and sTILs analysis, and early on-treatment cellularity measurement to select patients with HR+/HER2+ tumors for de-escalated endocrine-therapy-based approaches. Clinical trial information: NCT03272477 .

HER2 ‘neu’ promise for mCRC

Following the staggering impact of anti-HER2 treatment in improving the outcomes for breast and gastric cancers, human epidermal growth factor receptor 2 (HER2 neu) has emerged as a promising new oncogenic target for metastatic colorectal carcinoma (mCRC) also. Through this article, we review the role of HER2 in mCRC as a prognostic biormarker as well as a poor predictive factor and mechanism of resistance against anti-EGFR therapy. We discuss the emergence of dual anti-HER2 blockade as effective therapeutic intervention for HER2 amplified mCRC and the advantageous role of ct-DNA in appropriate clinical setting. Furthermore, we explore the encouraging future paradigms for effectively targeting HER2 in mCRC.

Cardiac safety of dual anti-HER2 blockade with pertuzumab plus trastuzumab in early HER2-positive breast cancer in the APHINITY trial

Trastuzumab increases the incidence of cardiac events (CEs) in patients with breast cancer (BC). Dual blockade with pertuzumab (P) and trastuzumab (T) improves BC outcomes and is the standard of care for high-risk human epidermal growth factor receptor 2 (HER2)-positive early BC patients. We analyzed the cardiac safety of P and T in the phase III APHINITY trial. Left ventricular ejection fraction (LVEF) ≥ 55% was required at study entry. LVEF assessment was carried out every 3 months during treatment, every 6 months up to month 36, and yearly up to 10 years. Primary CE was defined as heart failure class III/IV and a significant decrease in LVEF (defined as ≥10% from baseline and to <50%), or cardiac death. Secondary CE was defined as a confirmed significant decrease in LVEF, or CEs confirmed by the cardiac advisory board. The safety analysis population consisted of 4769 patients. With 74 months of median follow-up, CEs were observed in 159 patients (3.3%): 83 (3.5%) in P+ T and 76 (3.2%) in T arms, respectively. Most CEs occurred during anti-HER2 therapy (123; 77.4%) and were asymptomatic or mildly symptomatic decreases in LVEF (133; 83.6%). There were two cardiac deaths in each arm (0.1%). Cardiac risk factors indicated were age > 65 years, body mass index ≥ 25 kg/m2, baseline LVEF between 55% and <60%, and use of an anthracycline-containing chemotherapy regimen. Acute recovery from a CE based on subsequent LVEF values was observed in 127/155 patients (81.9%). Dual blockade with P+ T does not increase the risk of CEs compared with T alone. The use of anthracycline-based chemotherapy increases the risk of a CE; hence, non-anthracycline chemotherapy may be considered, particularly in patients with cardiovascular risk factors.

Efficacy and Safety of Dual Anti-HER2 Blockade and Docetaxel With or Without Carboplatin as Neoadjuvant Regimen for Treatment of HER2-Positive Breast Cancer.

Introduction: This study aimed to compare the efficacy and safety of docetaxel + trastuzumab + pertuzumab and docetaxel + carboplatin + trastuzumab + pertuzumab for treating HER2-positive breast cancer. Method: HER2-positive breast cancer from patients diagnosed between January 2020 and September 2022 were included in this retrospective study. Docetaxel + trastuzumab + pertuzumab or docetaxel + carboplatin + trastuzumab + pertuzumab was selected as the neoadjuvant regimen. The primary endpoint was a complete pathological remission rate. Secondary endpoints were toxicity during neoadjuvant treatment, adjustment of the neoadjuvant therapy scheme, and adjuvant medication. Result: A total of 81 patients were included in this study (38 in the docetaxel + carboplatin + trastuzumab + pertuzumab treatment group and 43 in the docetaxel + trastuzumab + pertuzumab group). The complete pathological remission rates in the docetaxel + carboplatin + trastuzumab + pertuzumab and docetaxel + trastuzumab + pertuzumab groups were 44.7% (95% confidence interval: 30.2%-60.3%) and 51.2% (95% confidence interval: 36.8%-65.4%), respectively. The incidence of grade 3 or higher toxicity in the docetaxel + carboplatin + trastuzumab + pertuzumab group was significantly higher than that in the docetaxel + trastuzumab + pertuzumab group (68.4% vs 39.5%, P = .009). Neutropenia and asthenia were the most common grade 3 or higher toxicities. The incidence of neoadjuvant scheme adjustment was significantly higher in the docetaxel + carboplatin + trastuzumab + pertuzumab group than in the docetaxel + trastuzumab + pertuzumab group (26.3% vs 7.0%, P = .039). The proportion of patients who received <6 cycles of neoadjuvant therapy was significantly higher in the docetaxel + carboplatin + trastuzumab + pertuzumab group than in the docetaxel + trastuzumab + pertuzumab group (31.6% vs 4.7%, P = .004). Patients in the docetaxel + carboplatin + trastuzumab + pertuzumab group received higher doses of granulocyte-macrophage colony-stimulating factor. Conclusion: In the neoadjuvant treatment of HER2-positive breast cancer, the docetaxel + trastuzumab + pertuzumab regimen might be more tolerated than the docetaxel + carboplatin + trastuzumab + pertuzumab regimen and did not show a lower complete pathological remission rate. However, our findings require further validation through prospective studies.

Dual neoadjuvant blockade plus chemotherapy versus monotherapy for the treatment of women with non-metastatic HER2-positive breast cancer: a systematic review and meta-analysis.

We aimed to determine the effect of dual anti-HER2 blockade compared to monotherapy on clinically important outcomes. We carried out a systematic review updated until July 2022. The outcomes included pathological complete response (pCR), clinical response, event-free survival, and overall survival. We identified eleven randomized clinical trials (2836 patients). When comparing paclitaxel plus dual treatment versus paclitaxel plus trastuzumab or lapatinib, dual treatment was associated with a higher probability of achieving a pathological complete response (OR 2.88, 95% CI 2.02-4.10). Addition of a taxane to an anthracycline plus cyclophosphamide and fluorouracil, plus lapatinib or trastuzumab, showed that the dual treatment was better than lapatinib alone (OR 2.47, 95% CI 1.41-4.34), or trastuzumab alone (OR 1.89, 95% CI 1.13-3.16). Dual treatment may result in an increase in survival outcomes and tumour clinical response, although such benefits are not consistent for all the combinations studied. The use of dual blockade with combinations of trastuzumab and pertuzumab can be recommended for the neoadjuvant treatment of women with HER2-positive breast cancer. PROSPERO Registration number: CRD42018110273.

DECRESCENDO: De-escalation of adjuvant chemotherapy in patients with HER2+/HR-/node-negative early breast cancer who achieve pCR after neoadjuvant taxane and subcutaneous dual anti-HER2 blockade.

TPS621 Background: Human Epidermal growth factor Receptor-2 positive (HER2+) breast cancer (BC) heterogeneity can be captured at the mRNA level by the PAM50 classification. The HER2 “Enriched” (HER2-E) intrinsic subtype is encountered more often in HER2+ Hormone Receptor negative (HR-) tumors compared to HER2+ HR+ tumors and is particularly sensitive to HER2 blockade. HER2+ HR- and HER2-E achieve high pathological complete response (pCR) rates with neoadjuvant chemotherapy (CT) and dual anti-HER2 blockade with trastuzumab and pertuzumab. Additionally, the patients with pCR have improved outcomes. However, standard CT with common drugs such as anthracyclines has significant short and long-term toxicities, including cardiac events and secondary leukemias. Thus, tailoring the neoadjuvant treatment among carefully selected patients in order to reduce toxicity while preserving efficacy is a priority in early HER2-positive BC. Methods: DECRESCENDO is a large, multicentric, single-arm, phase 2 de-escalation study evaluating the efficacy of neoadjuvant CT with paclitaxel 80mg/m2 weekly or docetaxel 75mg/m2 every 3 weeks (Q3W) with pertuzumab and trastuzumab (P+T) 600/600mg fixed-dose combination (FDC) for subcutaneous (SC) injection Q3W for patients with early HER2+, HR- (ER&lt;1% and PR&lt;1%) BC. After surgery, the patients with pCR (defined as Residual Cancer Burden (RCB)=0, per local assessment) will receive 14 additional cycles of P+T FDC SC. Patients with RCB≥1 will receive adjuvant T-DM1 (preceded by anthracycline-based CT if RCB≥2). Eligible patients must be candidates for neoadjuvant treatment, with a tumor between 15 and 50mm, N0, ECOG PS 0-1, with LVEF ≥55%. 1,065 patients will be enrolled in 12 countries. A baseline tumor sample is required to retrospectively assess the intrinsic tumor subtype. The primary objective is to evaluate 3-year recurrence-free survival (RFS) in patients with HER2-E tumors who achieve pCR after neoadjuvant treatment. The key secondary objective is to evaluate 3-year RFS in all patients with pCR. If a 3-year RFS ≥94% with the lower boundary of a 1-sided 95% CI ≥92% is observed in the target group, the study treatment will be considered an acceptable alternative to strategies that include the addition of other chemotherapies such as anthracyclines, alkylating agents and platinum salts. A flexible care sub-study will enroll 121 patients with pCR in Belgium, France, Ireland, Israel and Italy to receive adjuvant P+T FDC SC in a location outside the hospital, such as at home or workplace. The aim is to compare patient preference for administration of P+T FDC SC outside the hospital vs in the hospital. The first patient was enrolled in January 2022. The trial is co-led by the Breast International Group (BIG) and Institut Jules Bordet. Clinical trial information: NCT04675827.

Computed tomography based analyses of body mass composition in HER2 positive metastatic breast cancer patients undergoing first line treatment with pertuzumab and trastuzumab

Body composition parameters (BCp) have been associated with outcome in different tumor types. However, their prognostic value in patients with HER2-positive metastatic breast cancer (BC) receiving first line treatment with dual anti-HER2 antibody blockade is unknown. Preclinical evidences suggest that adipocytes adjacent to BC cells can influence response to anti-HER2 treatments. We retrospectively analyzed Computed Tomography (CT)-based BCp from 43 patients with HER2-positive metastatic BC who received first line pertuzumab/trastuzumab-based treatment between May 2009 and March 2020. The impact of baseline CT-based BCp on progression-free survival (PFS) was tested using Kaplan–Meier estimates and univariate and multivariate Cox regression models. We found a significantly worse PFS for patients with high baseline subcutaneous fat index (median 7.9 vs 16.1 months, p = 0.047, HR = 2.04, 95%CI 1–4.17) and for those with high total abdominal fat index (8.1 vs 18.8 months, p = 0.030, HR = 2.17, 95%CI 1.06–4.46). Patients with baseline sarcopenia did not show shorter PFS compared to those without sarcopenia (10.4 vs 9.2 months, p = 0.960, HR = 0.98, 95%CI 0.47–2.03). Total abdominal fat index remained a significant predictor of PFS at multivariate analysis. Our findings suggest that a high quantity of total abdominal fat tissue is a poor prognostic factor in patients receiving trastuzumab/pertuzumab-based first-line treatment for HER2-positive metastatic BC.

Abstract P1-15-04: Features of HER2+ metastasic patients (pts) from a prospective registry of advanced breast cancer (ABC), GEICAM/2014-03 (RegistEM)

Abstract Background: The RegistEM study is a non-interventional study that is providing prospective data from around 1900 ABC pts (females and males) diagnosed with advanced disease between 01/Jan/2016 and 31/Dec/2019, either after recurrence or at 1st diagnosis, in 38 Spanish sites representative of the national territory and whose investigators are GEICAM members. Methods: In the current analysis (cut-off date 10/May/2021, ongoing database), we describe the features of 279 pts included in the RegistEM study, with HER2+ (immunohistochemistry [IHQ] 3+, IHQ 2+ and in situ hybridization [ISH]+) tumors at any time of their ABC (5% after the 1st-line therapy). This subgroup has been evaluated because of the interest from a clinical perspective. Multivariate Cox analysis aiming to identify factors associated with overall survival (OS) were built. Results: 279 pts were identified, representing the 15% pts available in the database at the cut-off date. At first ABC diagnosis, 48% pts had recurrent BC (&amp;gt;12 months [mo] from initial BC diagnosis in 93%), 51% de novo metastatic BC and 1% unresectable locally advanced BC (ULABC). The median age was 59 years, 98% were white , 71% postmenopausal and only 1 male was part of this subset. Considering the BC subtype assessed in the most recent tumor lesion before the 1st-line therapy, 264 pts wereHER2 positive (67% with hormone receptor [HR]+). Family history of BC and/or ovarian cancer was reported in 31% pts, and an hereditary-risk genetic test was performed in 25% (66/267 pts). BRCA1/2 and TP53 mutations were reported in 4/20 and 4/19 pts, respectively, and p53 overexpression in 20/46 pts. Lymph nodes (56%), bone (49%), liver (34%), lung (33%), soft tissue (10%) and brain (8%) were the main metastatic sites. Additional data according to HR status and type of ABC are detailed in the table below. In HR- pts, bone metastases were less frequent and lymph nodes metastases more frequent compared to HR+ pts. Visceral disease was present in 68% pts and ≈75% had ≤3 (47% ≤2) locations involved. The most common therapies by line were: 1) 1st-line: CT + dual anti-HER2 blockade (3%), chemotherapy (CT) (almost in all pts taxane-based)+dual anti-HER2 blockade + endocrine therapy (ET) (mainly aromatase inhibitors) (35%), and ET + anti-HER2 blockade or ET + cyclin-dependent kinases 4/6 inhibitors (11%); 2) 2nd-line: anti-HER2 blockade (56%) [mostly an antibody-drug conjugate (90%)], CT + anti-HER2 blockade (18%) and ET + anti-HER2 blockade (14%); 3) 3rd-line: CT + anti-HER2 blockade (55%) and anti-HER2 blockade (22%). The median time-to-progressions to 1st-, 2nd- and 3rd-line were 14, 5, and 4 mo, respectively. A 4th-line therapy was reported in 52% of pts who received a 3rd-line. At database cut-off date, death was reported in 34% of pts. The median OS of this subset of pts was 41 mo (36-49). In a multivariate Cox regression analysis, the following variables were significantly related with worse survival (from ABC diagnosis): Brain (HR=2.62; 95% CI, 1.02-6.73) and Visceral no Brain involvement (HR=2.15; 95% CI, 1.02-4.53) compare to only soft tissue lesions; early stage at first diagnosis (HR=1.77; 95% CI, 1.15-2.73); HR- (HR=1.70; 95% CI, 1.11-2.60) and age (HR=1.04; 95% CI, 1.02-1.07). Conclusions: In this cohort of HER2+ pts with advanced disease, half of them had de novo ABC which was associated with better OS. The median PFS in 1st- and 3rd-line were slightly better in HR+ pts, and in 2nd-line was similar between HR+ and HR- cohorts. HR+181 (67%)HR- 91 (33%)Recurrent EBC134 (48%)ULABC or de novo M1 145 (52%)Time to recurrence &amp;gt;12 mo in EBC pts., n8435125NALocation of metastaticsites, nBoneBrainLiverLungLymph nodesSoft tissue104 10 62 57 90 1829 9 3232 64 1059 15 36 47 51 2278 6 59 46 1056Líne123123123123n180935690492613385521446333Deaths, n211112111161715141584Therapies by line, nET/BT261922101910212100ET12441011022323CT/BT/ET935031038305830CT/BT4017307581552182366924CT3572353711211BT6431373651145143385The most frequent therapies, nCT + dual anti-HER2 blockade + ET8623331551CT + single-agent HER2 blockade + ET522CT + dual anti-HER2 blockade3493644391016252CT + single-agent HER2 blockade4825641588211521CT5573354711411ET*22105212162644ET + HER2 blockade1213411662782Anti-HER2 blockade6431073651145143382Median duration of treatment, mo125585310441064TTP (mo), median (range)15(1-47)5(1-32)5(0-18)11(2-38)5(1-27)4(2-12)12 (1-47)5(1-26)4(0-17)17(2-45)7(1-32)4(1-18)Median PFS, mo14561154------HR: hormone receptor; EBC: early breast cancer; ULABC: unresectable locally advanced breast cancer; M1: metastatic; mo: month; ET: endrocrine therapy; BT: biological therapy; CT: chemotherapy; TTP: time-to-progression; PFS: progression-free survival. *ET includes aromatase inhibitors or selective estrogen receptor degraders, as single-agents or combined with cyclin-dependent kinases 4/6 inhibitors. Citation Format: Isabel Álvarez, Ángel Guerrero-Zotano, Josefina Cruz, Purificación Martínez, María Hernández, César A Rodríguez, Álvaro Rodríguez-Lescure, Silvia Antolín, Encarna Adrover, Raquel Andrés, Catalina Falo, Jose Ignacio Chacón, Ana Miguel, Sonia Servitja, Maria Galán Gramaje, Mireia Margelí Vila, César Gómez Raposo, María Jose Echarri, Rafael Villanueva, Ariadna TIbau Martorell, Silvia Varela Ferreiro, Ruth Campo, Juan Jose Miralles, Susana Bezares, Federico Rojo, Sara López-Tarruella. Features of HER2+ metastasic patients (pts) from a prospective registry of advanced breast cancer (ABC), GEICAM/2014-03 (RegistEM) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-15-04.

Abstract PD10-11: Keyriched-1- A prospective, multicenter, open label, neoadjuvant phase ii single arm study with pembrolizumab in combination with dual anti-HER2 blockade with trastuzumab and pertuzumab in early breast cancer patients with molecular HER2-enriched intrinsic subtype

Abstract Background: De-escalating strategies seem promising in HER2-positive early breast cancer (EBC) and chemo-free regimens are thus of key interest. Recent data have underlined the role of tumor immunogenicity in response to de-escalated neoadjuvant anti-HER2 therapy. Therefore, the prospective single arm hypothesis-generating phase II KEYRICHED-1 trial (NCT03988036) investigates the pCR-rate in patients with HER2-enriched EBC receiving four cycles of the dual anti-HER2 blockade in combination with the checkpoint inhibitor pembrolizumab. Initial studies with dual antibody-based HER2 blockade alone were able to achieve pCR-rates of 20-40%, which did not quite match the pCR-rates obtained with concurrent chemotherapy. KEYRICHED-1 aims at achieving pCR-rates comparable to standard chemotherapy-containing regimens by incorporating appropriate molecular selection and immune oncology.. Methods: A total of 48 pre- and postmenopausal patients with newly diagnosed HER2 2+ or 3+ EBC (stage I-III) and HER2-enriched (HER2-E) subtype by PAM50 were enrolled in this single-arm study. All patients received four cycles of study treatment with pembrolizumab (200mg), trastuzumab biosimilar (Trazimera®, loading dose 8mg/kg bodyweight (BW), maintenance dose 6mg/kg BW), and pertuzumab (loading dose 840mg/kg BW, maintenance dose 420mg/kg BW) q21d. Primary endpoint was centrally confirmed pCR (ypT0/is, ypN0). The trial was planned as a Simon's two-stage design (null and alternative pCR were 40% and 60%); interim analysis after 16 patients had to show a pCR rate of at least 50% to continue recruitment.. Results: Between 05/2020 and 03/2021, 98 patients were screened. N=52 (55%) had HER2-E subtype, of whom 48 patients entered the treatment phase. Median patient age was 57 years (28-83). 65% had tumors &amp;gt; 2 cm and 30% positive lymph node status. Centrally confirmed pCR-rate in surgical specimens was 46% (95% CI 0.31-0.62) in the 43 patients of the per-protocol-population, and 52% (95%CI 0.37-0.67) in all 46 evaluable patients (local assessment; two pCRs verified only by core biopsy) (p=0.22 and p=0.06 for null hypothesis, respectively). Despite HER2-E subtype, no pCR was observed in the four patients with immunohistochemical (IHC) HER2 2+/ISH-positive status in contrast to 20/39 (51.2%) pCR in IHC HER2 3+ tumors. Centrally confirmed pCR-rate in HR+/HER2+ tumors was 38.5% compared to 58.5% in HR-/HER2+ tumors. No new safety signals were observed.. Conclusions: These are the first results of a neoadjuvant chemotherapy-free 12-week de-escalation anti-HER2-regimen with trastuzumab and pertuzumab in combination with the PD-1 inhibitor pembrolizumab in patients with a HER2-E EBC. In the context of the WSG ADAPT HER2+ de-escalation trials the observed pCR-rates compare favorably in HR+ as well as HR- HER2+ EBC. Moreover, KEYRICHED-1 demonstrates that with appropriate molecular patient selection clinically meaningful pCR-rates in the range of those obtained with longer, more toxic chemotherapy-containing regimens can be achieved. Citation Format: Sherko Kuemmel, Oleg Gluz, Mattea Reinisch, Athina Kostara, Iris Scheffen, Monika Graeser, Rachel Wuerstlein, Ulrike Nitz, Kerstin Luedtke-Heckenkamp, Andreas Hartkopf, Felix Hilpert, Angela Kentsch, Carsten Ziske, Reinhard Depenbusch, Michael Braun, Jens Blohmer, Christine zu Eulenburg, Matthias Christgen, Stephan Bartels, Hans Kreipe, Enrico Pelz, Peter Schmid, Nadia Harbeck. Keyriched-1- A prospective, multicenter, open label, neoadjuvant phase ii single arm study with pembrolizumab in combination with dual anti-HER2 blockade with trastuzumab and pertuzumab in early breast cancer patients with molecular HER2-enriched intrinsic subtype [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD10-11.

Abstract P2-13-03: KEYRICHED-1 - A prospective, multicenter, open label, neoadjuvant phase II single arm study with pembrolizumab in combination with dual anti-HER2 blockade with trastuzumab and pertuzumab in early breast cancer patients with molecular HER2-enriched intrinsic subtype

Abstract Background: De-escalating strategies seem promising inHER2-positive early breast cancer (EBC) and chemo-free regimens are thus of keyinterest. Recent data have underlined the role of tumor immunogenicity inresponse to de-escalated neoadjuvant anti-HER2 therapy. Therefore, theprospective single arm hypothesis-generating phase II KEYRICHED-1 trial (NCT03988036)investigates the pCR rate in patients with HER2-enriched EBC receiving fourcycles of the dual anti-HER2 blockade in combination with the checkpointinhibitor pembrolizumab. Initial studies with dual antibody-based HER2 blockadealone were able to achieve pCR-rates of 20-40%, which did not quite match the pCRrates obtained with concurrent chemotherapy. KEYRICHED-1 aims at achieving pCR-ratescomparable to standard chemotherapy-containing regimens by incorporating appropriatemolecular selection and immune oncology. Methods: A total of 48 pre- and postmenopausal patients with newly diagnosed HER22+ or 3+ EBC (stage I-III) and HER2-enriched (HER2-E) subtype by PAM50 wereenrolled in this single-arm study. All patients received four cycles of studytreatment with pembrolizumab (200mg), trastuzumab biosimilar (Trazimera®,loading dose 8mg/kg bodyweight (BW), maintenance dose 6mg/kg BW), and pertuzumab(loading dose 840mg/kg BW, maintenance dose 420mg/kg BW) q21d . Primaryendpoint was centrally confirmed pCR (ypT0/is, ypN0). The trial was planned asa Simon's two-Stage design (null and alternative pCR were 40% and 60%); interimanalysis after 16 patients had to show a pCR rate of at least 50% to continuerecruitment. Results: Between 05/2020 and 03/2021, 98 patients werescreened. N=52 (55%) had HER2-E subtype,of whom 48 patients entered thetreatment phase. Median patient age was 57 years (28-83). 65% had tumors &amp;gt; 2cm and 30% positive lymph node status. Centrally confirmed pCR rate in surgicalspecimens was 46% (95% CI 0.31-0.62) in the 43 patients of the per protocolpopulation, and 52% (95%CI 0.37-0.67) in all 46 evaluable patients (localassessment; two pCRs verified only by core biopsy) (p=0.22 and p=0.06 for nullhypothesis, respectively). Despite HER2-E subtype, no pCR was observed in the 4patients with immunohistochemical (IHC) HER2 2+/ISH-positive status in contrastto 20/39 (51.2%) pCRs in IHC HER2 3+ tumors. Centrally confirmed pCR rate in HR+/HER2+tumors was38.5% compared to 58.5% in HR-/HER2+ tumors. No new safety signals wereobserved. Conclusions: These are the first results of a neoadjuvant chemotherapy-free12-week de-escalation anti-HER2-regimen with trastuzumab and pertuzumab incombination with the PD-1 inhibitor pembrolizumab in patients with a HER2-E EBC.In the context of the WSG ADAPT HER2+ de-escalation trials the observed pCRrates compare favourably in HR+ as well as HR- HER2 EBC. Moreover, KEYRICHED-1demonstrates that with appropriate molecular patient selection clinicallymeaningful pCR rates in the range of those obtained with longer, more toxicchemotherapy-containing regimens can be achieved. Citation Format: Sherko Kuemmel, Oleg Gluz, Mattea Reinisch, Athina Kostara, Iris Scheffen, Monika Graeser, Kerstin Luedtke-Heckenkamp, Andreas Hartkopf, Felix Hilpert, Angela Kentsch, Carsten Ziske, Reinhard Depenbusch, Michael Braun, Jens Blohmer, Christine zu Eulenburg, Matthias Christgen, Stephan Bartels, Hans Kreipe, Enrico Pelz, Peter Schmid, Nadia Harbeck. KEYRICHED-1 - A prospective, multicenter, open label, neoadjuvant phase II single arm study with pembrolizumab in combination with dual anti-HER2 blockade with trastuzumab and pertuzumab in early breast cancer patients with molecular HER2-enriched intrinsic subtype [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-03.

Abstract ES10-3: IO beyond TNBC

Abstract Hormone receptor-positive breast cancer is not considered an immunogenic tumor, since characterized by lower level of programmed death-ligand 1 (PD-L1) expression and tumor infiltrating lymphocytes. Despite being a cold tumor some studies are addressing the question on potential role of immune-checkpoint inhibitors in the adjuvant or metastatic setting. The phase II Checkmate7A8 trial (NCT04075604) is investigating the combination of nivolumab, anastrozole, and palbociclib versus anastrozole with palbociclib as neoadjuvant therapy for postmenopausal women with luminal BC. The phase II ImmunoADAPT trial (NCT03573648) is studying the combination of tamoxifen, palbociclib, and avelumab versus tamoxifen with avelumab for patients with early-stage luminal BC, expecting to show an improvement in the radiological complete response rates assessed after four cycles of treatment. A phase I safety study is also investigating the combination of durvalumab, abemaciclib, and anastrozole in a similar population (NCT04088032). The Phase 3 CA209-7FL trial is a randomized, multicenter, placebo-controlled phase 3 study of nivolumab versus placebo in combination with neoadjuvant chemotherapy and adjuvant endocrine therapy in patients with high-risk, estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) primary breast cancer. In the HER2 positive metastatic breast cancer the combination of pembrolizumab and trastuzumab administered upon progression on a trastuzumab-based regimen was investigated in the PANACEA study, which reported a response rate of 15%, restricted to PD-L1 positive tumors with a PFS benefit in the PD-L1 population. In the KATE2 trial, the addition of atezolizumab to trastuzumab emtansine in patients previously treated with trastuzumab demonstrated no significant benefit in PFS, although numerically higher PFS and response rates were observed in the PD-L1-positive population. A subsequent underpowered analysis (due to the small number of events) of the same trial suggested a possible OS benefit for patients with PD-L1-positive tumors. The combination of trastuzumab, pertuzumab, taxane, and atezolizumab is under investigation in the first-line setting (NCT03199885). The phase III IMpassion050 (NCT03726879) trial compares atezolizumab or placebo combined with neoadjuvant chemotherapy and dual anti-HER2 blockade for early-stage HER2-positive BC. This trial includes patients with PD-L1-positive and PD-L1-negative tumors and is considering pCR rates in the PD-L1-positive and ITT population as primary endpoints. In patients who do not achieve a pCR, TDM-1 is added in the adjuvant phase. The addition of atezolizumab to an anthracycline-free regimen of neoadjuvant chemotherapy and dual anti-HER2 blockade is the objective of the phase III APTneo trial (NCT035955592). In my presentation I will cover biological rational for IO studies beyond triple negative breast cancer in the attempt to provide an ideal immunogram for this population of patients. Citation Format: G Curigliano. IO beyond TNBC [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES10-3.

Features of response to modern neoadjuvant chemotherapy with dual anti-HER2 blockade (trastuzumab and pertuzumab) in the patients with HER2-positive breast cancer stage II–III

Background. Neoadjuvant chemotherapy (NACT) with dual anti-HER2 blockade has become a priority in the treatment of patients with HER2+ breast cancer (BC) stages IIIII. However, the question of the accordance of various systems for assessing tumor response to NACT, as well as identifying predictor factors for achieving a complete pathomorphological response (pCR) in HER2+ BC remains open.&#x0D; Aim. To assess the accordance of various systems for assessing tumor response to neoadjuvant chemotherapy (NACT) in patients with HER2+ BC and to identify predictor factors for achieving pCR and residual cancer burden.&#x0D; Materials and methods. The study included 49 women with HER2+ BC stage IIIII, who underwent NACT with anti-HER2 blockade, followed by surgical treatment and morphological analysis of the results. The median age of the patients was 47 years; 91.8% had tumor size T2, N+ status 71.4%; tumor grade G3 73.5%, luminal and non-luminal HER2+ subtype 44.9 and 55.1% of patients, respectively. Ki6730% was observed in 93.9% of cases, the level of TILs in the tumor was 10%, 1020% and 20% in 38.1, 9.5 and 52.4% of cases, respectively. The patients received combinations of anthracyclines and taxanes or the anthracycline-free regimen of docetaxel + carboplatin; 87.8% of patients received a dual blockade of trastuzumab + pertuzumab, and 12.2% trastuzumab. After the end of NACT, all patients underwent a radical surgery (mastectomy or breast-conserving) with an assessment of the pathomorphological response, the pathomorphological stage of ypTN, and the residual cancer burden according to the RCB system.&#x0D; Results. The rate of complete pathomorphological response (tpCR/RCB-0/ypT0N0) in HER2+ BC was 61.2%; significant predictors of achieving tpCR were only 3 factors: primary operable BC stages (T13N01) the rate of tpCR was 71.4%, the level of TILs20% the proportion of tpCR reached 95.5%, and the dual anti-HER2 therapy (trastuzumab + pertuzumab) tpCR was 65.1%. Residual tumor was presented by classes RCB-I, RCB-II, RCB-III in 10.2, 24.5, 4.1%. The RCB-I class included of patients with a residual tumor less than 1.0 cm in the absence of regional lymph node involvement (80% of cases); class RCB-II was represented by the presence of a residual tumor less than 2.0 cm in combination with the absence or presence of residual metastases in 13 lymph nodes (83.4%), and class RCB-III was presented the residual tumors 2.0 cm and N12 status in 100% of cases (p0.0001).&#x0D; Conclusion. Modern NACT with dual anti-HER2 blockade (trastuzumab + pertuzumab) are highly effective the rate of tpCR is 61.2%, and in the presence of high TILs20% reaches 95.5%. Residual tumor in most cases was presented by class RCB-I or RCB-II, only 4% of patients had massive residual tumor load (class RCB-III).

Dual anti-HER2 blockade in late-line treatment of metastatic HER2-positive breast cancer

In recent years, there has been a wide range of treatment options for patients with metastatic HER2-positive breast cancer, resulting in the highest life expectancy for these patients among all subtypes. The addition of pertuzumab to trastuzumab and docetaxel has been shown to increase overall survival and is therefore recognized as the standard first-line treatment. The most optimal second-line treatment option is trastuzumab emtansine. In addition, various combinations of cytostatics and anti HER2 targeting agents can be used. The choice of treatment options in heavily pretreated patients is of great interest. If they have not previously received pertuzumab, is it worth to use it and which combination is the best? One possible option is the combination of eribulin with the dual anti-HER2 blockade with trastuzumab and pertuzumab. Eribulin is an anti-microtubule agent that irreversibly blocks mitosis. In addition, it has non-mitotic effects – in vivo and in vitro experiments demonstrated its ability to restore normal tumor vascularization, reduce the area of hypoxia and, as a consequence, decrease tumor cells migration and invasion. This article represents a clinical case of the use of eribulin with double anti-HER2 blockade in the 6th line of treatment in a patient with metastatic HER2-positive breast cancer. Long-term control of the disease (within 2 years) with a satisfactory quality of life has been demonstrated.

Role of Post-Neoadjuvant therapy with trastuzumab emtansine in HER2-positive breast cancer

The widespread introduction of anti-HER2 agents has changed the natural course of Her2-positive breast cancer. The use of trastuzumab, and later dual anti-HER2 blockade with pertuzumab, in neoadjuvant regimens significantly increased the chances of complete cure. However, among patients with early and locally advanced forms of Her2-positive cancer, there is a cohort with an extremely unfavorable prognosis – tumors that have not achieved complete pathomorphological regression after neoadjuvant chemotherapy.The presence of a residual tumor in Her2-positive breast cancer has long been only a prognostically unfavorable factor without the potential to influence disease outcome. The results of the international phase III study KATHERINE, which demonstrated the high efficacy of post-adjuvant therapy with trastuzumab emtansine (T-DM1) in this patient cohort, have established a new standard of care. Due to T-DM1 adjuvant therapy, the possibility to significantly improve long-term results determined the predictive characteristics of the morphological response to the choice of treatment tactics, which became an important argument in favor of neoadjuvant therapy in patients with not only locally advanced but also primarily resectable Her2-positive breast cancer, followed by personalization of therapy.This article presents our own experience with post-neoadjuvant therapy with trastuzumab emtansine in a young patient with a residual tumor. The data of the main studies in early Her2-positive breast cancer are summarized.

Neoadjuvant chemotherapy for HER2-positive breast cancer using dose-consolidated regimens and dual anti-HER2 blockade with pertuzumab and trastuzumab (preliminary results)

The main goal of neoadjuvant chemotherapy (NACT) in aggressive breast cancer (BC) subtypes (triple-negative, HER2-positive) is to achieve complete pathological response (pCR), since it is associated with a significant decrease in the likelihood of recurrence and death. Currently, the standard approach for HER2+ BC stage II–III is NACT with the inclusion of a double anti-HER2 blockade, since this significantly increases the frequency of pCR. To date, it remains unclear whether the intensification of modern anthracycline-taxane-containing regimens of NACT affects the incidence of pCR in different BC subtypes, including HER2-positive, provided that a double anti-HER2 blockade is used.The aim of our prospective observational study from daily clinical practice was to assess the efficacy (according to the RCB system and the frequency of pCR) and tolerability of dose-dense NACT in stage II–III HER2-positive BC.Materials and methods. The study included 86 patients, mean age 45 years (26–74 years), in 96.5% of cases, the tumor was represented morphologically by invasive cancer of a nonspecific type, in 53.5% of the tumors had a positive luminal B HER2 phenotype, in 46.5% – non-luminal HER2+. The majority of patients (67.4%) had locally advanced inoperable breast cancer; in 80.2% of cases, metastatic lesions of regional lymph nodes were determined. NACT included anthracyclines and taxanes: four cycles of AC in a dose-dense regimen (once every 2 weeks), then four cycles of docetaxel 75 mg/m2 once every 3 weeks + trastuzumab + pertuzumab.Results. The frequency of pCR = RCB0 in the entire group was 54.7% (47/86), in locally advanced breast cancer – 55.9%, in operable breast cancer – 51.9%. In the luminal HER2+ subtype, the frequency of pCR was lower than in the non-luminal HER2+ subtype – 43.5% vs 67.5%, however, the differences were statistically insignificant (p = 0.09). The frequency of RCB0–I in ER+ HER2+ subtype was 60.9%, as in ER-HER2+ – 80%. Conclusions. In our study, for the first time, the efficacy of dose-dense NACT in HER2+ breast cancer was assessed; it was shown that the frequency of pCR and RCB0–I correspond to those in standard anthracycline-taxane-containing regimens. In the context of the use of double anti-HER2 blockade, the anthracycline stage, most likely, does not need to be escalated, since this does not lead to an increase in the frequency of complete pathomorphological regressions.