Ado-trastuzumab emtansine (T-DM1) in HER2+ advanced breast cancer patients: does pretreatment with pertuzumab matter?

A clinical systematic literature review of treatments among patients with advanced and/or metastatic human epidermal growth factor receptor 2 positive breast cancer

Aim: This systematic literature review aims to summarize the efficacy/effectiveness of treatments, including eribulin (ERI)-based and anti-human epidermal growth factor receptor 2 (HER2) treatments in advanced/metastatic HER2+ breast cancer. Methods: Three databases from 2016 to September 2021 were searched for clinical trials and observational studies in patients receiving first-line (1L) standard of care (SOC), second-line (2L) SOC or third-line or subsequent lines (3L+). Results: 2692 citations were screened, and 38 studies were included. Eleven studies were randomized-controlled trials (RCTs; 5 in 1L, 6 in 3L+), 6 were single-arm trials (5 in 1L, 1 in 3L+) and 21 were observational studies (13 in 1L, 6 in 2L, 4 in 3L+ [note that studies with subgroups for 1L, 2L, 3L+ are double-counted]). Longer overall survival (OS) was associated with 1L and 2L treatment, and for 3L+ studies that included ERI, ERI or trastuzumab (Tmab) + ERI led to longer OS than treatments of physician's choice (median OS of 11, 10 and 8.9 months, respectively). Progression-free survival was 9 months in Tmab + pertuzumab (Pmab) + ERI, 4 months in Tmab + ERI and 3.3 months in ERI. Conclusion: Available treatments provide a wide range of efficacy. However, later lines lack standardization and conclusions on comparative effectiveness are limited by differing trial designs. Thus, the chance of prolonged survival with new agents warrants further research.

A nationwide real-world study for evaluation of effectiveness and safety of T-DM1 in patients with HER2-positive metastatic breast cancer in Korea (KCSG BR19-15)

Purpose

This study aimed to investigate clinical practices and factors related to the outcomes of T-DM1 use in patients with HER2-positive metastatic breast cancer (mBC).

Methods

We included patients with HER2-positive mBC who received T-DM1 as a palliative therapy between August 2017 and December 2018. The safety and outcomes of T-DM1, including overall response rate (ORR), progression-free survival (PFS), and overall survival (OS), were evaluated. A Cox proportional hazards model was used to estimate the hazard ratio and 95% confidence interval (CI) for mortality or progression to HER2-positive mBC.

Results

In total, 824 patients were enrolled during the study period. The mean age of patients was 58 years, and 516 (62.6%) patients relapsed after curative treatment. Excluding a history of endocrine therapy, 341 (41.4%) patients previously received none or first-line chemotherapy, 179 (21.7%) received second-line therapy, and 303 (36.9%) received third-or later-line chemotherapy before T-DM1 therapy. During a median follow-up of 16.8 months, the ORR was 35%, the median PFS was 6.6 months, and the median OS was not reached. The clinical factors associated with the hazard of progression were age (<65 years), poor performance status (⩾2), advanced line of palliative chemotherapy (⩾2), prior pertuzumab use, and treatment duration of palliative trastuzumab (<10 months). Common grade 3-4 adverse events were thrombocytopenia (n = 107, 13.2%), neutropenia (n = 23, 2.8%), anemia (n = 21, 2.6%), and elevated liver enzyme (n = 20, 2.5%). Hypokalemia (⩽3.0 mmol/L) and any-grade bleeding events occurred in 25 (3.1%) and 94 (22.6%) patients, respectively.

Conclusion

This is the first nationwide real-world study of T-DM1 use in patients with HER2-positive mBC in Korea. The effectiveness and toxicity profiles of T-DM1 in real-world practice were comparable to those in randomized trials. Moreover, patient factors and previous anti-HER2 therapy could predict the outcomes of T-DM1 therapy.

Antibody drug conjugates targeting HER2: Clinical development in metastatic breast cancer

The identification of the HER2 alteration as an actionable oncogenic driver in breast cancer has propelled the development of HER-targeting monoclonal antibodies (mAb) such as trastuzumab and pertuzumab, which led to dramatic improvements in survival outcomes. Lately, the great strides made toward developing antibody-conjugation methods have led to the development of a new class of compelling compounds, the antibody-drug conjugates (ADCs) targeting HER2 which have profoundly transformed the treatment landscape of breast cancer. HER2-targeting ADCs, trastuzumab-emtansine and trastuzumab-deruxtecan, have improved the overall survival in the second and third-line settings with manageable adverse events. Other HER2-targeting ADCs using novel technological advances in the antibody, linker and/or payload conception have shown promising activity in preclinical and clinical studies and some of them are now being evaluated in larger clinical trials. Multiple challenges still impede the success of ADCs in breast cancer namely the lack of a comprehensive understanding of resistance mechanisms as well as the mechanisms of action of ADCs in special subgroups of patients such as those with low or ultra-low HER2 expression and patients with brain or leptomeningeal metastases (BM). In this framework, we review the approved indications and ongoing trials for HER2-targeting ADCs, across patient subgroups, including those with BM and discuss the associated potential mechanisms of action and resistance. Last, we provide an overview of the future perspectives involving HER2-targeting ADCs in breast cancer.

Current challenges and unmet needs in treating patients with human epidermal growth factor receptor 2-positive advanced breast cancer

Human epidermal growth factor receptor 2 oncogene (HER2-positive) overexpression/amplification occurs in less than 20% of breast cancers and has traditionally been associated with poor prognosis. Development of therapies that target HER2 has significantly improved outcomes for patients with HER2-positive advanced breast cancer (ABC). Currently available HER2-targeted agents include the monoclonal antibodies trastuzumab, pertuzumab, and margetuximab, the small-molecule inhibitors lapatinib, tucatinib, neratinib, and pyrotinib, as well as the antibody-drug conjugates trastuzumab emtansine and trastuzumab deruxtecan. Optimal sequencing of these agents in the continuum of the disease is critical to maximize treatment outcomes. The large body of clinical evidence generated over the past 2 decades aids clinicians in treatment decision-making. However, patients with HER2-positive ABC and specific disease characteristics and/or comorbidities, such as leptomeningeal disease, brain metastases, or cardiac dysfunction, are generally excluded from large randomized clinical trials, and elderly or frail patients are often underrepresented. In addition, there is great inequality in the accessibility of approved drugs across countries. This article addresses various challenging clinical situations when treating patients with HER2-positive ABC. The objective is to provide guidance to clinicians on how and when HER2-targeted therapies and additional treatments can be best implemented in routine clinical practice, on the basis of existing clinical evidence and expert opinion where needed.

T-DM1 efficacy in trastuzumab-pertuzumab pre-treated HER2 positive metastatic breast cancer patients: a meta-analysis

Background

Current guidelines consider T-DM1 the standard 2^nd line therapy for HER2 positive metastatic breast cancer (MBC) patients following trastuzumab (T) + pertuzumab (P) and taxane 1^st line treatment. Despite this, there are no prospective studies supporting this sequence.

Methods

We performed a meta-analysis using real world data to determine the efficacy of T-DM1 after 1^st line TP in HER2 positive MBC patients. We used a random-effect model to find differences in the rate of 1-year progression free survival (PFS) between TP pre-treated population and the EMILIA phase III pivotal trial.

Results

Seven studies were eligible. The meta-analysis showed a combined 1-year PFS risk difference for T-DM1 efficacy after TP in 2^nd or more lines of -0.122, with lower and upper limits of -0.253 and 0.010, respectively (p = 0.07), with low heterogeneity among studies (I² 0.01%, p = 0.836). Considering the four studies on T-DM1 in 2^nd line setting, 1-year PFS risk was -0.034 (95% CI -0.207 – 0,139; p = 0.701) (I² 0.01%, p = 0.91).

Conclusion

Overall, the efficacy of T-DM1 after TP seems to be similar to that previously reported in the EMILIA trial. In the second line setting, data are not mature enough to confirm T-DM1 efficacy in TP pre-treated population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09556-7.

T-DM1 after Pertuzumab plus Trastuzumab: Treatment Sequence-Induced Selection Bias in HER2-Positive Metastatic Breast Cancer

Real-world studies have suggested decreased trastuzumab emtansine (T-DM1) effectiveness in patients with metastatic breast cancer (mBC) who received prior trastuzumab plus pertuzumab (H + P). However, these studies may have been biased toward pertuzumab-experienced patients with more aggressive disease. Using an electronic health record-derived database, patients diagnosed with mBC on/after 1 January 2011 who initiated T-DM1 in any treatment line (primary cohort) or who initiated second-line T-DM1 following first-line H ± P (secondary cohort) from 22 February 2013 to 31 December 2019 were included. The primary outcome was time from index date to next treatment or death (TTNT). In the primary cohort (n = 757), the percentage of patients with prior P increased from 37% to 73% across the study period, while population characteristics and treatment effectiveness measures were generally stable. Among P-experienced patients from the secondary cohort (n = 246), median time from mBC diagnosis to T-DM1 initiation increased from 10 to 14 months (2013-2019), and median TTNT increased from 4.4 to 10.2 months (2013-2018). Over time, prior H + P prevalence significantly increased with no observable impact on T-DM1 effectiveness. Drug approval timing should be considered when assessing treatment effectiveness within a sequence.

Targeting HER2+ Breast Cancer Brain Metastases: A Review of Brain-Directed HER2-Directed Therapies

Despite advances in the treatment of metastatic, HER2+ breast cancer, the development of central nervous system metastases remains a therapeutic challenge. The challenge is amplified by the exclusion of patients with active brain metastases from many clinical trials. Initial HER2-targeted therapies, such as trastuzumab and pertuzumab, have shown limited efficacy for patients with brain metastases. In addition, the landscape of systemic therapy for HER2+ metastatic breast cancer is changing rapidly. In recent years, the development of small-molecule inhibitors in combination with chemotherapy has shown promise, though the efficacy is often balanced by key toxicities. Other HER2-targeted therapies, including antibody-drug conjugates, have presented new therapeutic options for this patient population; however, additional data for both small-molecule inhibitors and antibody-drug conjugates with respect to patients with central nervous system metastases is needed. Here, we specifically review the data for the management of HER2+ parenchymal brain metastases. A limited discussion of leptomeningeal disease is included; a more detailed review of this specific subgroup is outside the scope of this article. Key clinical trial data supporting the use of HER2-targeted and non-targeted therapies, including monoclonal antibodies and antibody-drug conjugates, are reviewed, with a specific focus on the use of HER2-targeted small-molecule inhibitors. We also review future directions and provide an overview of ongoing clinical trials which include patients with HER2+ brain metastases. With future focus on inclusive clinical trial design, particularly inclusion of patients with brain metastases, optimal strategies for management will be better elucidated.

Prolonged Responses With Trastuzumab Emtasine Treatment of Human Epidermal Growth Factor Receptor 2-positive Metastatic Breast Cancer Refractory to Trastuzumab and Pertuzumab: Systematic Review of Evidence

Amplification of human epidermal growth factor receptor 2 (HER2) occurs in around 25% of breast cancers and has been associated with aggressive disease. Here, we summarize published evidence on efficacy and prolonged responses with trastuzumab emtansine (T-DM1) after first-line trastuzumab plus pertuzumab and provide possible factors related to prolonged responses to T-DM1. We conducted a literature search using PubMed, and articles that were published in English between July 1, 2012 and December 31, 2019 were included. A review of the bibliography included in the articles found was made. Nine articles were eligible; 2 were case reports, and the remaining 7 were nonexperimental studies, all retrospective. Five were multi-center works. The total number of patients was 796 (276 received pertuzumab). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was used for this systematic review. The population included was heterogeneous among studies according to hormone receptor status, de novo metastatic disease, number of metastatic sites, visceral involvement, brain metastasis, previous neoadjuvant or adjuvant trastuzumab, and line of therapy in which T-DM1 was administered. Less efficacy in terms of responses (overall response rate, 18%-33%) and progression-free survival (4-6 months) with second-line T-DM1, in patients pretreated with pertuzumab, was shown (if compared with the EMILIA trial). The results are more similar to those of the TH3RESA trial (very pretreated population). Prolonged treatments (6 months or more) were observed in at least 17% of cases. The efficacy of T-DM1 after a previous pertuzumab treatment is lower than if pertuzumab is not given, although prolonged responses are observed in this setting.

Clinical benefit of treatment after trastuzumab emtansine for HER2-positive metastatic breast cancer: a real-world multi-centre cohort study in Japan (WJOG12519B)

BACKGROUND

Trastuzumab emtansine (T-DM1) treatment for human epidermal growth factor receptor-2 (HER2)-positive metastatic breast cancer after taxane with trastuzumab and pertuzumab is standard therapy. However, treatment strategies beyond T-DM1 are still in development with insufficient evidence of their effectiveness. Here, we aimed to evaluate real-world treatment choice and efficacy of treatments after T-DM1 for HER2-positive metastatic breast cancer.

METHODS

In this multi-centre retrospective cohort study involving 17 hospitals, 325 female HER2-positive metastatic breast cancer patients whose post-T-DM1 treatment began between April 15, 2014 and December 31, 2018 were enrolled. The primary end point was the objective response rate (ORR) of post-T-DM1 treatments. Secondary end points included disease control rate (DCR), progression-free survival (PFS), time to treatment failure (TTF), and overall survival (OS).

RESULTS

The median number of prior treatments of post-T-DM1 treatment was four. The types of post-T-DM1 treatments included (1) chemotherapy in combination with trastuzumab and pertuzumab (n = 102; 31.4%), (2) chemotherapy concomitant with trastuzumab (n = 78; 24.0%), (3), lapatinib with capecitabine (n = 63; 19.4%), and (4) others (n = 82; 25.2%). ORR was 22.8% [95% confidence interval (CI): 18.1-28.0], DCR = 66.6% (95% CI 60.8-72.0), median PFS = 6.1 months (95% CI 5.3-6.7), median TTF = 5.1 months (95% CI 4.4-5.6), and median OS = 23.7 months (95% CI 20.7-27.4).

CONCLUSION

The benefits of treatments after T-DM1 are limited. Further investigation of new treatment strategies beyond T-DM1 is awaited for HER2-positive metastatic breast cancer patients.

Second line trastuzumab emtansine following horizontal dual blockade in a real-life setting

Despite relevant medical advancements, metastatic breast cancer remains an uncurable disease. HER2 signaling conditions tumor behavior and treatment strategies of HER2 expressing breast cancer. Cancer treatment guidelines uniformly identify dual blockade with pertuzumab and trastuzumab plus a taxane as best first line and trastuzumab emtansine as preferred second line choice. However, there is no prospectively designed available study focusing on the sequence and outcomes of patients treated with T-DM1 following the triplet. In the following report, data concerning a wide series of patients treated in a real-life setting are presented. Results obtained in terms of response and median progression free survival suggests a significant role for T-DM1 in disease control of metastatic HER2 expressing breast cancer.

Pertuzumab and Trastuzumab Emtansine for Human Epidermal Growth Factor Receptor-2-Positive Metastatic Breast Cancer: Contemporary Population-Based Outcomes

Background

Real-world outcomes for patients with human epidermal growth factor receptor-2 (HER2)-positive metastatic breast cancer (MBC) treated with pertuzumab in combination with taxane chemotherapy plus trastuzumab (TaxTP) in the first line setting and trastuzumab emtansine (TE) in any line of treatment are lacking.

Methods

Cohorts of patients treated with (1) TaxTP and (2) TE from January 1, 2013 through December 31, 2016 were retrospectively obtained from a population-based database. Cohorts were described according to age, hormone receptor (HR) status, prior systemic therapies, event-free survival (EFS) defined as time from start of treatment to start of next line of treatment or death, and overall survival (OS).

Results

A total of 122 patients were treated with TaxTP and 104 with TE. In the TaxTP cohort, EFS was significantly longer in the trastuzumab-naïve group compared with the adjuvant trastuzumab group (median EFS = 27.0 vs 12.4 months; P = .002). In the TaxTP cohort, median OS was not reached. In the TE cohort, EFS was significantly longer in the pertuzumab-naïve group compared with pertuzumab-exposed group (median time to treatment failure [TTF] = 18.7 vs 5.5 months; P < .001). Overall survival was also significantly longer in the pertuzumab-naïve group compared with the pertuzumab-exposed group (median OS = 23.2 vs 14.1 months; P = .022). In multivariable analyses, adjuvant trastuzumab and prior pertuzumab exposure in the metastatic setting remained significant predictors of inferior EFS for patients treated with TaxTP and TE, respectively.

Conclusions

New anti-HER2 therapies appear to be clinically relevant in the real-world.

Tucatinib Combined With Ado-Trastuzumab Emtansine in Advanced ERBB2/HER2-Positive Metastatic Breast Cancer: A Phase 1b Clinical Trial

Importance

Treatment options for patients with disease progression after treatment with trastuzumab, pertuzumab, and ado-trastuzumab emtansine (T-DM1) are limited. Tucatinib is an oral, potent, human epidermal growth factor receptor 2 (HER2)-specific tyrosine kinase inhibitor (TKI) being developed as a novel treatment for ERBB2/HER2-positive breast cancer.

Objective

To determine the maximum tolerated dosage of tucatinib in combination with T-DM1 in the treatment of patients with ERBB2/HER2-positive metastatic breast cancer with and without brain metastases.

Design, Setting, and Participants

In this phase 1b open-label, multicenter, clinical trial, 57 participants enrolled between January 22, 2014, and June 22, 2015, were 18 years of age or older with ERBB2/HER2-positive metastatic breast cancer previously treated with trastuzumab and a taxane. Data were analyzed between January and March 2018.

Interventions

Tucatinib 300 mg or 350 mg administered orally twice per day for 21 days and T-DM1 3.6 mg/kg administered intravenously once every 21 days.

Main Outcomes and Measures

Safety assessments, pharmacokinetics, and response were assessed using RECIST 1.1 every 2 cycles for 6 cycles, followed by every 3 cycles.

Results

Fifty-seven T-DM1-naive patients (median [IQR] 51 [44.0-63.0] years of age) who had undergone a median of 2 earlier HER2 therapies (range, 1-3) were treated. The tucatinib maximum tolerated dosage was determined to be 300 mg administered twice per day with dose-limiting toxic reactions seen at 350 mg twice per day. Pharmacokinetic analysis showed that there was no drug-drug interaction with T-DM1. Adverse events seen among the 50 patients treated at the maximum tolerated dosage regardless of causality included nausea (36 patients; 72%), diarrhea (30 patients; 60%), fatigue (28 patients; 56%), epistaxis (22 patients; 44%), headache (22 patients; 44%), vomiting (21 patients; 42%), constipation (21 patients; 42%), and decreased appetite (20 patients; 40%); the majority of adverse events were grade 1 or 2. Tucatinib-related toxic reactions that were grade 3 and above included thrombocytopenia (7 patients; 14%) and hepatic transaminitis (6 patients; 12%).

Conclusions and Relevance

In this study, tucatinib in combination with T-DM1 appeared to have acceptable toxicity and to show preliminary antitumor activity among heavily pretreated patients with ERBB2/HER2-positive metastatic breast cancer with and without brain metastases.

Trial Registration

ClinicalTrials.gov Identifier: NCT01983501.

Comparison of the efficacy of trastuzumab emtansine between patients with metastatic human epidermal growth factor receptor 2-positive breast cancers previously treated with combination trastuzumab and pertuzumab and with trastuzumab only in Japanese population

Background

Trastuzumab emtansine (T-DM1) has been approved since 2013 for patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) who had received trastuzumab (Tmab) and taxane. However, no clinical trial has evaluated the efficacy of T-DM1 in those who have previously received pertuzumab (Pmab). This study aimed to compare the efficacy of T-DM1 between patients who had received Tmab and Pmab and those who had received Tmab only in Japanese population.

Methods

We identified all patients with HER2-positive MBC who received T-DM1 between April 1, 2014 and February 28, 2017 in our institution. The patients were divided into the Tmab group (i.e., those who received only Tmab before T-DM1 treatment) and the Tmab/Pmab group (i.e., those who received Tmab and Pmab before T-DM1 treatment), and progression-free survival (PFS) and best response were compared between the two groups.

Results

A total of 42 patients were enrolled for outcome analysis. The median follow-up period was 4.8 months, and the median number of prior chemotherapy regimens for metastatic disease before T-DM1 was 1 (range 1–2) in the Tmab/Pmab group and 2 (range 0–6) in the Tmab group. The median PFS was 2.8 months in the Tmab/Pmab group (95% confidence interval [CI] 1.7–4.8 months) and 7.8 months in the Tmab group (95% CI 5.5–15.9 months) (p = 0.0030). The best response was lower in the Tmab/Pmab group (11.1% vs. 25.0%).

Conclusions

Patients with HER2-positive MBC who received Tmab and Pmab treatment before T-DM1 have fewer benefits from T-DM1.