Activity of T-DM1 in Her2-positive breast cancer brain metastases

Real-world data on trastuzumab emtansine (TDM1) efficacy and safety: Results of a single-centre retrospective study of HER2-positive metastatic breast cancer patients

HER2-positive metastatic breast cancer (MBC) represents a challenging subtype of breast cancer, characterized by aggressive disease and poor clinical outcomes. Trastuzumab emtansine (TDM1), an antibody-drug conjugate combining trastuzumab and emtansine, has demonstrated efficacy in clinical trials as a second-line treatment for patients progressing after prior therapies. This study aims to provide real-world evidence on the efficacy and safety of TDM1 in HER2-positive MBC patients. A retrospective analysis was conducted on 70 HER2-positive MBC patients treated with TDM1 at our centre between January 2020 and December 2022. Clinical characteristics, progression-free survival (PFS), overall survival (OS), response rates, and toxicity were evaluated using hospital records. PFS and OS were calculated using Kaplan-Meier methods, and survival curves were compared with log-rank tests. The median age of patients was 47 years, with a majority presenting with advanced disease and prior treatment lines. The median PFS was 6.1 months (95% CI, 4.5-7.6), and the median OS was 14.4 months (95% CI, 10.2-18.0). The objective response rate was 75.7%, with 12.8% achieving a complete response and 62.8% a partial response. PFS was significantly longer in hormone receptor-positive patients compared to hormone receptor-negative patients (8.1 vs. 4.1 months, p = 0.035). Toxicity was manageable, with grade 3-4 adverse events including elevated transaminases (8.5%), thrombocytopenia (5.7%), and anemia (4.2%). The efficacy of TDM1 in this real-world cohort aligns with clinical trial data, though PFS and OS were somewhat lower compared to trials, likely due to the inclusion of patients with more extensive disease and prior treatments. Notably, TDM1 demonstrated activity against CNS metastases and a manageable safety profile, with higher incidence of hepatic and hematologic toxicities. Our study supports the use of TDM1 as a viable option for treating HER2-positive MBC in routine clinical practice, confirming its effectiveness and safety profile observed in clinical trials.

Prognostic relevance of the neurological symptom burden in brain metastases from breast cancer

BACKGROUND

Existing prognostic models for breast cancer (BC) brain metastases (BM) overlook neurological symptoms. Thus, we explored the incidence and prognostic relevance of neurological symptoms in a real-world cohort of BC patients with BM.

METHODS

The Vienna Brain Metastasis Registry identified BC patients with BM between 1992 and 2020, categorised by subtype: hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-), HER2 overexpressing (HER2+), and triple-negative (TN).

RESULTS

A total of 716 patients with BM from BC were included. In total, 80% (573/716) of the patients presented with neurological symptoms at BM diagnosis. Across all BC subtypes, asymptomatic patients presented with a significantly longer median OS from diagnosis of BM compared to symptomatic patients (p < 0.05; log-rank test; HR+ BC 29 vs. 9 months; HER2+ BC 24 vs. 12 months; TN 12 vs. 6 months). In multivariate analysis with the BC-specific Graded Prognostic Assessment (Breast-GPA: HR:1.4; 95% CI:1.3-1.5; p < 0.001), the presence of neurological symptoms at diagnosis (HR:1.6; 95% CI: 1.4-1.9; p < 0.001) presented as independently associated with OS from time of BM diagnosis, respectively.

CONCLUSIONS

Neurological burden at BM diagnosis independently predicts survival in BC patients. Our findings emphasise incorporating the symptom status in the prognostic evaluation and reassessing BM screening in high-risk patients during prospective clinical trials.

Factors associated with local failure after stereotactic radiation to the surgical bed of patients with a single breast cancer metastasis

INTRODUCTION

Breast cancer brain metastases (BCBM) are increasingly common due to improved systemic therapies prolonging survival. This study evaluates local control and factors influencing outcomes in patients with resected BCBM treated with postoperative stereotactic radiotherapy (SRT).

METHODS

A retrospective review included single resected BCBM treated with postoperative SRT from 2010 to 2022. The median follow-up was 28 months (range, 14-43). Variables analyzed included tumor size, biology, surgical corridor inclusion, radiation dose, and timing of SRT. Multivariable analysis was conducted using Cox regression.

RESULTS

62 patients were analyzed in multivariable analysis, HER2-positive status was associated with improved local control (HR: 0.76, 95% CI: 0.36-0.88, p = 0.032), as was a higher biologically effective dose (BED > 40 Gy, HR: 0.65, 95% CI: 0.45-0.89, p = 0.028). In contrast, tumor size > 5 cm (HR: 2.1, 95% CI: 1.7-4.6, p = 0.021) and delayed initiation of SRT beyond 28 days post-surgery (HR: 2.7, 95% CI: 1.9-4.7, p = 0.015) were associated with worse outcomes. Age, cystic metastases, inclusion of surgical corridor, and tumor location were not significantly related to local control. Radiation necrosis occurred in 13% of patients, predominantly asymptomatic.

CONCLUSION

Postoperative SRT provides effective local control in resected BCBM. In multivariable analysis, HER2 positivity, higher BED, and timely SRT significantly influenced outcomes, while larger tumor size and delayed treatment were negative prognostic factors. Future research should optimize dosimetric strategies and integrate systemic therapy to improve local and intracranial control.

Real life outcome analysis of breast cancer brain metastases treated with Trastuzumab Deruxtecan

Tumor dissemination to the central nervous system (CNS) is almost a rule in the treatment journey of advanced HER2+ breast cancer (BC). Recent results demonstrated high intracranial efficacy with Trastuzumab Deruxtecan (T-DXd). However, a real-world evidence is lacking in literature. We conducted a multicenter, observational, retrospective real-world analysis on 39 cases collected at 12 Italian Oncological Units. Patients with brain metastases (BMs) from HER2 + BC treated with T-DXd in various treatment lines were enrolled. Primary endpoint was the intracranial overall response rate (iORR). Secondary endpoints were intra- and global progression free survival (iPFS - gPFS); other secondary objectives were the intracranial disease control rate (iDCR), duration of response (iDoR), clinical benefit rate at 6 and 12 months (iCBr), overall survival, and safety. iORR was 59%, iPFS was 15.6 months, gPFS was 11.8 months. iDCR was 94.9%, iDoR was 11.9 months, and iCBr at 6 and 12 months were 69.2% and 59%, respectively. OS was not reached, with an overall rate of 77.9% of patients alive at 12 months. This study confirmed the high intracranial efficacy and manageable safety profile of T-DXd in this first-ever real world analysis.

Results of a patient-level pooled analysis of three studies of trastuzumab deruxtecan in HER2-positive breast cancer with active brain metastasis

BACKGROUND

Brain metastases (BMs) are common in human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer, increasing morbidity and mortality. Systemic therapy for BMs can be effective, with the triple combination of trastuzumab, capecitabine, and tucatinib being a potential standard. More recently, intracranial activity of antibody-drug conjugates has been reported, but the size of individual studies has been small. Therefore, this patient-level pooled analysis was conducted.

PATIENTS AND METHODS

This is a patient-level pooled analysis of the prospective phase II DEBBRAH and TUXEDO-1 trials and the retrospective DFCI/Duke/MDACC cohort. Patients with evaluable active BMs (defined as newly diagnosed and untreated or progressing with measurable tumor-related size after previous local therapy) from HER2-positive breast cancer (BC) and treated with trastuzumab deruxtecan (T-DXd) included in these studies were eligible. The primary endpoint was intracranial objective response rate (ORR-IC) by Response Assessment in Neuro-Oncology (RANO)-BM criteria.

RESULTS

Overall, 37 patients were assessable for intracranial response assessment. BMs progressing after prior local therapy were present in 64.9% of patients. The median patient age was 49.1 years. All patients had received prior trastuzumab and the median number of prior systemic treatment lines was 3 (0-13). The pooled ORR-IC by RANO-BM criteria was 64.9% [95% confidence interval (CI) 47.5% to 79.8%] with low heterogeneity observed between the studies included. The clinical benefit rate by RANO-BM was 81.1% (95% CI 64.8% to 92.0%). The median progression-free survival was 13.3 months (95% CI 8.4-22.6 months) and the median overall survival was 22.5 months (95% CI 14.9 months-not achieved) with high heterogeneity between studies and numerically longer in patients with few prior treatment lines. Quality of life remained stable throughout treatment, with no new safety concerns.

CONCLUSIONS

This patient-level pooled analysis of DEBBRAH, TUXEDO-1, and the DFCI/Duke/MDACC cohort indicates clinically relevant intracranial activity of T-DXd in patients with active HER2-positive BC, BMs, and extensive systemic pretreatment. The results therefore support the use of T-DXd when clinically indicated irrespective of BMs.

Real-world application of disitamab vedotin (RC48-ADC) in patients with breast cancer with different HER2 expression levels: efficacy and safety analysis

BACKGROUND

Disitamab vedotin (RC48-ADC), an antibody-drug conjugate (ADC), combines specific antibody disitamab with cytotoxicity monomethyl auristatin E to effectively target the human epidermal growth factor receptor 2 (HER2) protein on tumor cells for precise elimination. Recent studies have demonstrated that RC48-ADC offers therapeutic benefits for patients with HER2-positive and HER2-low-expression breast cancer (BC). However, a thorough exploration of its efficacy and safety in real-world settings for patients with metastatic breast cancer (mBC) is currently lacking.

METHODS

This retrospective, multicenter, real-world study included patients with mBC who received RC48-ADC from September 2021 to March 2024. These patients include HER2-positive BC and HER2-low-expression BC. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), restricted mean survival time, objective response rate (ORR), and disease control rate (DCR). Factors affecting efficacy and the occurrence of treatment-related adverse events (TRAE) were evaluated.

RESULTS

The study included a cohort of 89 patients with mBC, with 48 of those being identified as HER2-positive. As of March 2024, 22 deaths were recorded, with an immature median OS. Total PFS varied from 1.0 to 31.2 months, with a median of 5.5 months (95% CI, 4.368-6.632). HER2-positive patients exhibited prolonged PFS compared with HER2-low-expression patients (6.6 months vs 4.1 months, P = .023). The overall ORR stood at 25.8% (95% CI, 0.178-0.358), with higher rates observed in HER2-positive patients compared with HER2-low-expression patients (31.3% vs 19.5%). Similarly, the overall DCR was 78.7% (95% CI, 0.691-0.859), with HER2-positive patients demonstrating superior DCR compared with HER2-low-expression patients (83.3% vs 73.2%). Notably, HER2 expression emerged as the primary determinant of RC48-ADC efficacy. The most prevalent TRAE among all patients included leukopenia (21.3%) and alopecia (20.2%).

CONCLUSION

RC48-ADC showcases promising efficacy and manageable safety in patients with both HER2-positive and HER2-low-expression mBC.

Neratinib and ado-trastuzumab emtansine for pretreated and untreated human epidermal growth factor receptor 2 (HER2)-positive breast cancer brain metastases: Translational Breast Cancer Research Consortium trial 022

BACKGROUND

Treatment options for human epidermal growth factor receptor 2 (HER2)-positive breast cancer brain metastases (BCBMs) remain limited. We previously reported central nervous system (CNS) activity for neratinib and neratinib-capecitabine. Preclinical data suggest that neratinib may overcome resistance to ado-trastuzumab emtansine (T-DM1) when given in combination. In Translational Breast Cancer Research Consortium (TBCRC) 022's cohort 4, we examined the efficacy of neratinib plus T-DM1 in patients with HER2-positive BCBM.

PATIENTS AND METHODS

In this multicenter, phase II study, patients with measurable HER2-positive BCBM received neratinib 160 mg daily plus T-DM1 3.6 mg/kg intravenously every 21 days in three parallel-enrolling cohorts [cohort 4A-previously untreated BCBM, cohorts 4B and 4C-BCBM progressing after local CNS-directed therapy without (4B) and with (4C) prior exposure to T-DM1]. Cycle 1 diarrheal prophylaxis was required. The primary endpoint was the Response Assessment in Neuro-Oncology-Brain Metastases (RANO-BM) by cohort. The overall survival (OS) and toxicity were also assessed.

RESULTS

Between 2018 and 2021, 6, 17, and 21 patients enrolled in cohorts 4A, 4B, and 4C. Enrollment was stopped prematurely for slow accrual. The CNS objective response rate in cohorts 4A, 4B, and 4C was 33.3% [95% confidence interval (CI) 4.3% to 77.7%], 35.3% (95% CI 14.2% to 61.7%), and 28.6% (95% CI 11.3% to 52.2%), respectively; 38.1%-50% experienced stable disease for ≥6 months or response. Diarrhea was the most common grade 3 toxicity (22.7%). The median OS was 30.2 [cohort 4A; 95% CI 21.9-not reached (NR)], 23.3 (cohort 4B; 95% CI 17.6-NR), and 20.9 (cohort 4C; 95% CI 14.9-NR) months.

CONCLUSIONS

We observed intracranial activity for neratinib plus T-DM1, including those with prior T-DM1 exposure, suggesting synergistic effects with neratinib. Our data provide additional evidence for neratinib-based combinations in patients with HER2-positive BCBM, even those who are heavily pretreated.

Delayed neurotoxicity in HER2-positive breast cancer: a case series on combined SRS and T-DM1 treatment

This case series presents four instances of late neurotoxicity observed in HER2-positive breast cancer patients with brain metastases following treatment with stereotactic radiosurgery (SRS) and subsequent trastuzumab emtansine (T-DM1) therapy. Despite initial control of intracranial disease, patients experienced neurological deterioration months to years post-treatment. Radiological assessments revealed distinct patterns consistent with radiation necrosis, particularly in areas previously treated with SRS and subsequent T-DM1 administration. These changes, characterized by enlarging cystic masses with hemorrhagic components, emphasize the importance of vigilant monitoring in patients undergoing combined SRS and T-DM1 therapy for brain metastatic breast cancer. This report underscores the need for further investigation into the long-term effects of combining SRS with novel systemic therapies, particularly in HER2-positive breast cancer patients with brain metastases. Understanding and mitigating late neurotoxicity are critical for optimizing treatment strategies and improving patient outcomes.

Breast Cancer Brain Metastasis: A Comprehensive Review

The mechanisms underlying breast cancer brain metastasis (BCBM) development are complex, and its clinical presentation varies depending on the number, location, and size of brain metastases. Common symptoms include headache, neurologic deficits, and seizures. Diagnosis of BCBM typically relies on neuroimaging techniques, such as magnetic resonance imaging and computed tomography scans. Local therapies, such as surgery and stereotactic radiosurgery, can be used to control tumor growth and relieve symptoms. Whole-brain radiotherapy has been a mainstay of treatment for BCBM, but its use has been associated with cognitive decline. Systemic therapy with chemotherapy and targeted agents plays an increasingly important role in the management of BCBM. Novel agents, such as human epidermal growth factor receptor 2 (HER2)-targeted therapies and tyrosine kinase inhibitors, have shown promising results in improving survival for patients with HER2-positive and triple-negative BCBM. This comprehensive review synthesizes current knowledge, clinical insights, and evolving paradigms to provide a robust understanding and roadmap for optimizing the diagnosis and management of BCBM.

Pyrotinib and trastuzumab plus palbociclib and fulvestrant in HR+/HER2+ breast cancer patients with brain metastasis

Human epidermal growth factor receptor 2-positive (HER2+) breast cancer (BC) patients are at a high risk of developing metastases in the brain. However, research focusing on treatment strategies for hormonal receptor positive (HR+), HER2+ BC patients with brain metastases (BM) remains limited. Thus, a multi-center, prospective trial was conducted in China. Women over the age of 18 who were naive to whole brain radiotherapy and had estrogen receptor (ER)/progesterone-receptor (PgR) positive, HER2+ BM were treated with palbociclib, fulvestrant, trastuzumab and pyrotinib, until disease progression or the development of intolerable side effects. The primary endpoint was objective response rate (ORR) in the central nervous system (CNS). This ongoing study is still recruiting participants and is registered with ClinicalTrials.gov (NCT04334330). This report presents the findings from an interim analysis. From December 4, 2020, to November 2, 2022, 15 patients were enrolled. Among the 14 patients who were evaluable for clinical response, the ORR was 35.7% (95% CI: 12.8-64.9%), with a CNS-ORR of 28.6% (95% CI: 8.4-58.1%). The median follow-up period was 6.3 months (range, 2.1-14.3 months), during which the median progression-free survival (PFS) was 10.6 months (95% CI: 4.3-16.9 months), and the median time to CNS progression was 8.5 months (95% CI: 5.9-11.1 months). The most common adverse event was diarrhea (93%), with 33% having grade 3 and 6.7% having grade 4. The study suggests that the combination of palbociclib, trastuzumab, pyrotinib and fulvestrant offers a promising chemo-free treatment strategy for HR+, HER2+ BC patients with BM.

Trastuzumab deruxtecan versus trastuzumab emtansine in HER2-positive metastatic breast cancer patients with brain metastases from the randomized DESTINY-Breast03 trial

BACKGROUND

DESTINY-Breast03 is a randomized, multicenter, open-label, phase III study of trastuzumab deruxtecan (T-DXd) versus trastuzumab emtansine (T-DM1) in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (mBC) previously treated with trastuzumab and a taxane. A statistically significant improvement in progression-free survival (PFS) versus T-DM1 was reported in the primary analysis. Here, we report exploratory efficacy data in patients with and without brain metastases (BMs) at baseline.

PATIENTS AND METHODS

Patients were randomly assigned 1 : 1 to receive T-DXd 5.4 mg/kg or T-DM1 3.6 mg/kg. Patients with clinically inactive/asymptomatic BMs were eligible. Lesions were measured as per modified RECIST, version 1.1. Outcomes included PFS by blinded independent central review (BICR), objective response rate (ORR), and intracranial ORR as per BICR.

RESULTS

As of 21 May 2021, 43/261 patients randomized to T-DXd and 39/263 patients randomized to T-DM1 had BMs at baseline, as per investigator assessment. Among patients with baseline BMs, 20/43 in the T-DXd arm and 19/39 in the T-DM1 arm had not received prior local BM treatment. For patients with BMs, median PFS was 15.0 months [95% confidence interval (CI) 12.5-22.2 months] for T-DXd versus 3.0 months (95% CI 2.8-5.8 months) for T-DM1; hazard ratio (HR) 0.25 (95% CI 0.13-0.45). For patients without BMs, median PFS was not reached (95% CI 22.4 months-not estimable) for T-DXd versus 7.1 months (95% CI 5.6-9.7 months) for T-DM1; HR 0.30 (95% CI 0.22-0.40). Confirmed systemic ORR was 67.4% for T-DXd versus 20.5% for T-DM1 and 82.1% for T-DXd versus 36.6% for T-DM1 for patients with and without BMs, respectively. Intracranial ORR was 65.7% with T-DXd versus 34.3% with T-DM1.

CONCLUSIONS

Patients with HER2-positive mBC whose disease progressed after trastuzumab and a taxane achieved a substantial benefit from treatment with T-DXd compared with T-DM1, including those with baseline BMs.

Current indications and future perspectives for antibody-drug conjugates in brain metastases of breast cancer

Breast cancer is one of the main cause of cerebral and leptomeningeal metastases, the prognosis of which remains poor to this day. Most studies excluded patients with active brain metastases (BM) and particularly with leptomeningeal metastases (LM) explaining the lack of therapeutic innovation in this area. Currently, the standard management of patients with BM of breast cancer is based on the combination of surgery, radiotherapy and systemic treatments. Recently, third-generation of Antibody-Drug Conjugates (ADCs), have revolutionized the management of metastatic breast cancer. Trastuzumab deruxtecan and Sacituzumab govitecan have indeed shown significant improvements of survival outcomes and can now be used in a wide range of breast cancer subtypes. However, few data are available on the efficacy of third-generation ADCs on BM and LM of breast cancer. As the field of ADCs is rapidly evolving, with new constructs entering the late clinical development, in this review we describe the efficacy of approved and novel promising conjugates on patients with BM and LM of breast cancer.

Understanding the activity of antibody-drug conjugates in primary and secondary brain tumours

Antibody-drug conjugates (ADCs), a class of targeted cancer therapeutics combining monoclonal antibodies with a cytotoxic payload via a chemical linker, have already been approved for the treatment of several cancer types, with extensive clinical development of novel constructs ongoing. Primary and secondary brain tumours are associated with high mortality and morbidity, necessitating novel treatment approaches. Pharmacotherapy of brain tumours can be limited by restricted drug delivery across the blood-brain or blood-tumour barrier, although data from phase II studies of the HER2-targeted ADC trastuzumab deruxtecan indicate clinically relevant intracranial activity in patients with brain metastases from HER2⁺ breast cancer. However, depatuxizumab mafodotin, an ADC targeting wild-type EGFR and EGFR variant III, did not provide a definitive overall survival benefit in patients with newly diagnosed or recurrent EGFR-amplified glioblastoma in phase II and III trials, despite objective radiological responses in some patients. In this Review, we summarize the available data on the central nervous system activity of ADCs from trials involving patients with primary and secondary brain tumours and discuss their clinical implications. Furthermore, we explore pharmacological determinants of intracranial activity and discuss the optimal design of clinical trials to facilitate development of ADCs for the treatment of gliomas and brain metastases.

Trastuzumab emtansine vs lapatinib and capecitabine in HER2-positive metastatic breast cancer brain metastases: A real-world study

BACKGROUND

Trastuzumab emtansine (T-DM1) has demonstrated improvements in survival and neurological symptoms in patients with breast cancer with brain metastases (BCBM). This real-world study investigated the effectiveness of T-DM1 versus lapatinib plus capecitabine (LC) in patients with BCBM.

METHODS

This retrospective, observational study evaluated patients with HER2-positive BCBM using a real-world database. Eligible patients had initiated T-DM1 or LC with a prior diagnosis of brain metastasis and ≥1 prior metastatic breast cancer treatment. The primary endpoint was overall survival (OS); secondary endpoints were time to next relevant treatment or death (TTNT) and real-world progression-free survival (rwPFS). An inverse probability of treatment weighting (IPTW) approach was used to account for differences in potential baseline characteristics between treatment groups. Outcomes were described using the Kaplan-Meier method, and the average treatment effect of initiating T-DM1 versus LC was estimated using weighted Cox proportional hazard models and hazard ratio (HR).

RESULTS

A total of 214 patients were available for analysis (T-DM1, n = 161; LC, n = 53). Demographics and baseline characteristics were generally well-balanced between treatment groups after weighting. After weighting, median OS was 17.7 (T-DM1) versus 9.6 (LC) months (HR, 0.55 [95% CI, 0.34-0.89]; P=0.013). Median TTNT was 9.0 (T-DM1) versus 6.0 (LC) months (HR, 0.55 [95% CI, 0.36-0.85]; P = 0.005). After weighting, median rwPFS was 6.0 (T-DM1) versus 4.0 (LC) months (HR, 0.50 [95% CI, 0.36-0.69]; P < 0.001).

CONCLUSIONS

These results support the superior effectiveness and clinical relevance of T-DM1 versus LC in patients with HER2-positive BCBM in the real world.

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.

Systemic Therapy for Patients with HER2-Positive Breast Cancer and Brain Metastases: A Systematic Review and Meta-Analysis

AIM

Patients with HER2-positive (HER2+) metastatic breast cancer (mBC) develop brain metastases (BM) in up to 30% of cases. Treatment of patients with BM can consist of local treatment (surgery and/or radiotherapy) and/or systemic treatment. We undertook a systematic review and meta-analysis to determine the effect of different systemic therapies in patients with HER2+ mBC and BM.

METHODS

A systematic search was performed in the databases PubMed, Embase.com, Clarivate Analytics/Web of Science Core Collection and the Wiley/Cochrane Library. Eligible articles included prospective or retrospective studies reporting on the effect of systemic therapy on objective response rate (ORR) and/or median progression free survival (mPFS) in patients with HER2+ mBC and BM. The timeframe within the databases was from inception to 19 January 2022. Fixed-effects meta-analyses were used. Quality appraisal was performed using the ROBINS-I tool.

RESULTS

Fifty-one studies were included, involving 3118 patients. Most studies, which contained the largest patient numbers, but also often carried a moderate-serious risk of bias, investigated lapatinib and capecitabine (LC), trastuzumab-emtansine (T-DM1) or pyrotinib. The best quality data and/or highest ORR were described with tucatinib (combined with trastuzumab and capecitabine, TTC) and trastuzumab-deruxtecan (T-DXd). TTC demonstrated an ORR of 47.3% in patients with asymptomatic and/or active BM. T-DXd achieved a pooled ORR of 64% (95% CI 43-85%, I² 0%) in a heavily pretreated population with asymptomatic BM (3 studies, n = 96).

CONCLUSIONS

Though our meta-analysis should be interpreted with caution due to the heterogeneity of included studies and a related serious risk of bias, this review provides a comprehensive overview of all currently available systemic treatment options. T-Dxd and TTC that appear to constitute the most effective systemic therapy in patients with HER2+ mBC and BM, while pyrotinib might be an option in Asian patients.

An Insight into Molecular Targets of Breast Cancer Brain Metastasis

Brain metastasis is one of the major reasons of death in breast cancer (BC) patients, significantly affecting the quality of life, physical activity, and interdependence on several individuals. There is no clear evidence in scientific literature that depicts an exact mechanism relating to brain metastasis in BC patients. The tendency to develop breast cancer brain metastases (BCBMs) differs by the BC subtype, varying from almost half with triple-negative breast cancer (TNBC) (HER2^- ER^- PR^-), one-third with HER2⁺ (human epidermal growth factor receptor 2-positive, and around one-tenth with luminal subclass (ER⁺ (estrogen positive) or PR⁺ (progesterone positive)) breast cancer. This review focuses on the molecular pathways as possible therapeutic targets of BCBMs and their potent drugs under different stages of clinical trial. In view of increased numbers of clinical trials and systemic studies, the scientific community is hopeful of unraveling the underlying mechanisms of BCBMs that will help in designing an effective treatment regimen with multiple molecular targets.

Treatment of Brain Metastases: The Synergy of Radiotherapy and Immune Checkpoint Inhibitors

Brain metastases are a devastating sequela of common primary cancers (e.g., lung, breast, and skin) and have limited effective therapeutic options. Previously, systemic chemotherapy failed to demonstrate significant benefit in patients with brain metastases, but in recent decades, targeted therapies and more recently immune checkpoint inhibitors (ICIs) have yielded promising results in preclinical and clinical studies. Furthermore, there is significant interest in harnessing the immunomodulatory effects of radiotherapy (RT) to synergize with ICIs. Herein, we discuss studies evaluating the impact of RT dose and fractionation on the immune response, early studies supporting the synergistic interaction between RT and ICIs, and ongoing clinical trials assessing the benefit of combination therapy in patients with brain metastases.

Trastuzumab deruxtecan in HER2-positive breast cancer with brain metastases: a single-arm, phase 2 trial

Trastuzumab deruxtecan is an antibody–drug conjugate with high extracranial activity in human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. We conducted the prospective, open-label, single-arm, phase 2 TUXEDO-1 trial. We enrolled patients aged ≥18 years with HER2-positive breast cancer and newly diagnosed untreated brain metastases or brain metastases progressing after previous local therapy, previous exposure to trastuzumab and pertuzumab and no indication for immediate local therapy. Patients received trastuzumab deruxtecan intravenously at the standard dose of 5.4 mg per kg bodyweight once every 3 weeks. The primary endpoint was intracranial response rate measured according to the response assessment in neuro-oncology brain metastases criteria. A Simon two-stage design was used to compare a null hypothesis of <26% response rate against an alternative of 61%. Fifteen patients were enrolled in the intention-to-treat population of patients who received at least one dose of study drug. Two patients (13.3%) had a complete intracranial response, nine (60%) had a partial intracranial response and three (20%) had stable disease as the best intracranial response, with a best overall intracranial response rate of 73.3% (95% confidential interval 48.1–89.1%), thus meeting the predefined primary outcome. No new safety signals were observed and global quality-of-life and cognitive functioning were maintained over the treatment duration. In the TUXEDO-1 trial (NCT04752059, EudraCT 2020-000981-41), trastuzumab deruxtecan showed a high intracranial response rate in patients with active brain metastases from HER2-positive breast cancer and should be considered as a treatment option in this setting.

Findings from the TUXEDO-1 trial demonstrate efficacy of the antibody–drug conjugate trastuzumab deruxtecan for treatment of brain metastases in patients with HER2-positive breast cancer.

Trastuzumab emtansine increases the risk of stereotactic radiosurgery-induced radionecrosis in HER2 + breast cancer

INTRODUCTION

In this study, we investigate factors associated with radionecrosis (RN) in HER2 + (human epidermal growth factor receptor 2) patients with brain metastases (BrM) treated with stereotactic radiosurgery (SRS).

METHODS

Patients with HER2 + breast cancer BrM treated with SRS (2010-2020) were identified from an institutional database. The incidence of RN was determined per treated BrM according to serial imaging and/or histology. Factors associated with RN such as age, RT dose, BrM volume, and initiation of Trastuzumab Emtansine (T-DM1) were investigated with univariate and multivariable analyses (MVA).

RESULTS

67 HER2 + patients with 223 BrM were identified. 21 patients (31.3%) were treated with T-DM1 post-SRS, including 14 patients (20.9%) who received T-DM1 within 12 months of SRS. The median follow-up was 15.6 (interquartile range (IQR) 5.4-35.3) months. The overall probability of RN post-SRS was 21.6% (95% confidence interval (CI) 2.7-10.7), and the 1 and 2 year risk was 6.7% (95% CI 2.7-10.7) and 15.2% (95% CI 9.2-21.3). MVA identified T-DM1 treatment post-SRS (hazard ratio (HR) 2.5, 95% CI 1.2-5.3, p = 0.02) and equivalent dose in 2 Gy fractions (EQD2) > 90 Gy₂ (HR 2.4, 95% CI 1.1-5.1, p = 0.02) as predictors of RN. Patients treated with T-DM1 and SRS had a 29.9% (95% CI 15.3-44.6%) probability of RN, with a 25.2% (95% CI 12.8-37.6%) risk at 1- and 2 years post-T-DM1. The majority of RN were symptomatic (71%), with a median time to RN of 4.8 months.

CONCLUSION

T-DM1 exposure post-SRS was associated with a higher risk of RN among patients with HER2 + BrM.

Trastuzumab deruxtecan in patients with central nervous system involvement from HER2-positive breast cancer: The DEBBRAH trial

BACKGROUND

Trastuzumab deruxtecan (T-DXd) has shown durable antitumor activity in pretreated patients with HER2-positive advanced breast cancer (ABC), but its efficacy has not yet been evaluated in patients with active brain metastases (BMs). DEBBRAH aims to assess T-DXd in patients with HER2-positive or HER2-low ABC and central nervous system involvement.

METHODS

This ongoing, five-cohort, phase II study (NCT04420598) enrolled patients with pretreated HER2-positive or HER2-low ABC with stable, untreated, or progressing BMs, and/or leptomeningeal carcinomatosis. Here, we report findings from HER2-positive ABC patients with non-progressing BMs after local therapy (n = 8; cohort 1), asymptomatic untreated BMs (n = 4; cohort 2), or progressing BMs after local therapy (n = 9; cohort 3). Patients received 5.4 mg/kg T-DXd intravenously once every 21 days. The primary endpoint was 16-week progression-free survival (PFS) for cohort 1 and intracranial objective response rate (ORR-IC) for cohorts 2 and 3.

RESULTS

As of October 20, 2021, 21 patients received T-DXd. In cohort 1, 16-week PFS rate was 87.5% (95%CI, 47.3-99.7; P < .001). ORR-IC was 50.0% (95%CI, 6.7-93.2) in cohort 2 and 44.4% (95%CI, 13.7-78.8; P < .001) in cohort 3. Overall, the ORR-IC in patients with active BMs was 46.2% (95%CI, 19.2-74.9). Among patients with measurable intracranial or extracranial lesions at baseline, the ORR was 66.7% (12 out of 18 patients; 95%CI, 41.0-86.7), 80.0% (95%CI, 28.4-99.5) in cohort 1, 50.0% (95%CI, 6.7-93.2) in cohort 2, and 66.7% (95%CI, 29.9-92.5) in cohort 3. All responders had partial responses. The most common adverse events included fatigue (52.4%; 4.8% grade ≥3), nausea (42.9%; 0% grade ≥3), neutropenia (28.6%; 19% grade ≥3), and constipation (28.6%; 0% grade ≥3). Two (9.5%) patients suffered grade 1 interstitial lung disease/pneumonitis.

CONCLUSIONS

T-DXd showed intracranial activity with manageable toxicity and maintained the quality of life in pretreated HER2-positive ABC patients with stable, untreated, or progressing BMs. Further studies are needed to validate these results in larger cohorts.

Intracranial Metastatic Disease: Present Challenges, Future Opportunities

Intracranial metastatic disease (IMD) is a prevalent complication of cancer that significantly limits patient survival and quality of life. Over the past half-century, our understanding of the epidemiology and pathogenesis of IMD has improved and enabled the development of surveillance and treatment algorithms based on prognostic factors and tumor biomolecular characteristics. In addition to advances in surgical resection and radiation therapy, the treatment of IMD has evolved to include monoclonal antibodies and small molecule antagonists of tumor-promoting proteins or endogenous immune checkpoint inhibitors. Moreover, improvements in the sensitivity and specificity of imaging as well as the development of new serological assays to detect brain metastases promise to revolutionize IMD diagnosis. In this review, we will explore current treatment principles in patients with IMD, including the emerging role of targeted and immunotherapy in select primary cancers, and discuss potential areas for further investigation.

Pyrotinib plus capecitabine for patients with human epidermal growth factor receptor 2-positive breast cancer and brain metastases (PERMEATE): a multicentre, single-arm, two-cohort, phase 2 trial

BACKGROUND

Patients with HER2-positive metastatic breast cancer have a high risk of developing brain metastases. Efficacious treatment options are scarce. We investigated the activity and safety of pyrotinib plus capecitabine in patients with HER2-positive metastatic breast cancer and brain metastases.

METHODS

We did a multicentre, single-arm, two-cohort, phase 2 trial in eight tertiary hospitals in China. Patients aged 18 years or older who had radiotherapy-naive HER2-positive brain metastases (cohort A) or progressive disease after radiotherapy (cohort B), with an Eastern Cooperative Oncology Group performance status of 0-2, received pyrotinib 400 mg orally once daily, and capecitabine 1000 mg/m2 orally twice daily for 14 days, followed by 7 days off every 3 weeks until disease progression or unacceptable toxicity. The primary endpoint was confirmed intracranial objective response rate by investigator assessment according to the Response Evaluation Criteria In Solid Tumours (version 1.1). Activity and safety were analysed in patients with at least one dose of study drug. The study is ongoing, but recruitment is complete. The study is registered with ClinicalTrials.gov, NCT03691051.

FINDINGS

Between Jan 29, 2019, and July 10, 2020, we enrolled 78 women: 51 (86%) of 59 patients in cohort A and 18 (95%) of 19 patients in cohort B had previous exposure to trastuzumab. Median follow-up duration was 15·7 months (IQR 9·7-19·0). The intracranial objective response rate was 74·6% (95% CI 61·6-85·0; 44 of 59 patients) in cohort A and 42·1% (20·3-66·5; eight of 19 patients) in cohort B. The most common grade 3 or worse treatment-emergent adverse event was diarrhoea (14 [24%] in cohort A and four [21%] in cohort B). Two (3%) patients in cohort A and three (16%) in cohort B had treatment-related serious adverse events. No treatment-related deaths occurred.

INTERPRETATION

To our knowledge, this is the first prospective study showing the activity and safety of pyrotinib plus capecitabine in patients with HER2-positive breast cancer and brain metastases, especially in radiotherapy-naive population. This combination deserves further validation in a randomised, controlled trial.

FUNDING

National Cancer Centre Climbing Foundation Key Project of China, Jiangsu Hengrui Pharmaceuticals.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Intracranial Response Rate in Patients with Breast Cancer Brain Metastases after Systemic Therapy

Simple Summary

For many years, patients with breast cancer and brain metastases were excluded from participation in clinical trials. It was believed that anticancer drugs could not cross the blood–brain barrier. However, recent evidence strongly suggests that some drugs can act against brain metastases, with the greatest intracranial response rate reported in the case of capecitabine, neratinib plus capecitabine, trastuzumab deruxtecan and tucatinib plus trastuzumab and capecitabine. In this article, we discuss the achievements in systemic therapy of breast cancer patients with brain metastases. We stress on the newest clinical trial results which indicate tremendous progress in HER2-positive breast cancer. On the other hand, in patients with triple-negative breast cancer or hormone-receptor-positive brain metastases, much fewer compounds were discovered. Based on the presented results, patients with active brain metastases should be routinely included in clinical trials with novel agents.

Abstract

Brain metastases are detected in 5% of patients with breast cancer at diagnosis. The rate of brain metastases is higher in HER2-positive and triple-negative breast cancer patients (TNBC). In patients with metastatic breast cancer, the risk of brain metastases is much higher, with up to 50% of the patients having two aggressive biological breast cancer subtypes. The prognosis for such patients is poor. Until recently, little was known about the response to systemic therapy in brain metastases. The number of trials dedicated to breast cancer with brain metastases was scarce. Our review summarizes the current knowledge on this topic including very significant results of clinical trials which have been presented very recently. We focus on the intracranial response rate of modern drugs, including new antibody–drug conjugates, HER2- targeted tyrosine kinase inhibitors and other targeted therapies. We highlight the most effective and promising drugs. On the other hand, we also suggest that further efforts are needed to improve the prognosis, especially patients with TNBC and brain metastases. The information contained in this article can help oncologists make treatment-related decisions.

CXCR2 Mediates Distinct Neutrophil Behavior in Brain Metastatic Breast Tumor

Brain metastasis is one of the main causes of mortality among breast cancer patients, but the origins and the mechanisms that drive this process remain poorly understood. Here, we report that the upregulation of certain CXCR2-associated ligands in the brain metastatic variants of the breast cancer cells (BrM) dynamically activate the corresponding CXCR2 receptors on the neutrophils, thereby resulting in the modulation of certain key functional neutrophil responses towards the BrM. Using established neutrophil-tumor biomimetic co-culture models, we show that the upregulation of CXCR2 increases the recruitment of Tumor-Associated Neutrophils (TANs) towards the BrM, to enable location-favored formation of Neutrophil Extracellular Traps (NETs). Inhibition of CXCR2 using small molecule antagonist AZD5069 reversed this behavior, limiting the neutrophil responses to the BrM and retarding the reciprocal tumor development. We further demonstrate that abrogation of NETs formation using Neutrophil Elastase Inhibitor (NEI) significantly decreases the influx of neutrophils towards BrM but not to their parental tumor, suggesting that CXCR2 activation could be used by the brain metastatic tumors as a mechanism to program the tumor-infiltrating TANs into a pro-NETotic state, so as to assume a unique spatial distribution that assists in the subsequent migration and invasion of the metastatic tumor cells. This new perspective indicates that CXCR2 is a critical target for suppressing neutrophilic inflammation in brain metastasis.

Targeting brain metastases in breast cancer

Brain metastases (BMs) are an important source of morbidity and mortality in patients with metastatic breast cancer (BC). As survival of patients with advanced BC considerably improved thanks to research advancements and new therapeutic approaches, the apparent incidence of BMs is increasing. Local interventions, in the form of either surgical resection or radiation therapy, remain the mainstay in the management of BMs. Systemic treatments are typically used to complement local strategies to further improve and maintain control of central nervous system (CNS) disease. Although high-level evidence data about the impact of the blood-brain barrier (BBB), as well as the efficacy of anti-cancer agents on BMs and differentials between the systemic compartment and CNS are still scant, our understanding of the activity of systemic treatments with impact on BMs is rapidly evolving. Novel anti-HER2 agents, such as tucatinib, ado-trastuzumab emtansine, trastuzumab deruxtecan and neratinib, have shown intracranial efficacy. Current research efforts are ongoing not only to clarify the activity of existing treatments on the CNS, as well as to develop new drugs and innovative multi-modality approaches. This review will encompass the current treatment landscape of BMs arising from BC, with a focus on recent advancements in the field and investigational approaches.

Focal Radiotherapy of Brain Metastases in Combination With Immunotherapy and Targeted Drug Therapy

BACKGROUND

Advances in systemic treatment and in brain imaging have led to a higher incidence of diagnosed brain metastases. In the treatment of brain metastases, stereotactic radiotherapy and radiosurgery, systemic immunotherapy, and targeted drug therapy are important evidence-based options. In this review, we summarize the available evidence on the treatment of brain metastases of the three main types of cancer that give rise to them: non-small-cell lung cancer, breast cancer, and malignant melanoma.

METHODS

This narrative review is based on pertinent original articles, meta-analyses, and systematic reviews that were retrieved by a selective search in PubMed. These publications were evaluated and discussed by an expert panel including radiation oncologists, neurosurgeons, and oncologists.

RESULTS

There have not yet been any prospective randomized trials concerning the optimal combination of local stereotactic radiotherapy/radiosurgery and systemic immunotherapy or targeted therapy. Retrospective studies have consistently shown a benefit from early combined treatment with systemic therapy and (in particular) focal radiotherapy, compared to sequential treatment. Two metaanalyses of retrospective data from cohorts consisting mainly of patients with non-small-cell lung cancer and melanoma revealed longer overall survival after combined treatment with focal radiotherapy and checkpoint inhibitor therapy (rate of 12-month overall survival for combined versus non-combined treatment: 64.6% vs. 51.6%, p <0.001). In selected patients with small, asymptomatic brain metastases in non-critical locations, systemic therapy without focal radiotherapy can be considered, as long as follow-up with cranial magnetic resonance imaging can be performed at close intervals.

CONCLUSION

Brain metastases should be treated by a multidisciplinary team, so that the optimal sequence of local and systemic therapies can be determined for each individual patient.

Precision medicine biomarkers in brain metastases: applications, discordances, and obstacles

Brain metastases (BM) present a common cause of mortality and morbidity in several metastatic cancer entities. New therapeutic developments during the last decades, including targeted and immune-related therapies, have shown considerable extra- and intracranial response rates in specific subgroups of BM patients. However, differences in the molecular alteration in the BM tumor tissue compared to extracranial tumors leads to heterogeneous therapeutic responses. Therefore, an accurate molecular analyzation of BM tissue, if possible, has become an essential part in therapeutic decision making in BM patients. The concordance of predictive molecular biomarkers between multiple sites including extracranial and intracranial tumor tissue have been analyzed for some but not all biomarkers routinely applied in modern precision medicine approaches. In the present review, we summarize the current evidence of predictive biomarkers for personalized therapy approaches in the treatment of parenchymal BM.

Human induced pluripotent stem cell-derived platelets loaded with lapatinib effectively target HER2+ breast cancer metastasis to the brain

Prognosis of patients with HER2+ breast-to-brain-metastasis (BBM) is dismal even after current standard-of-care treatments, including surgical resection, whole-brain radiation, and systemic chemotherapy. Radiation and systemic chemotherapies can also induce cytotoxicity, leading to significant side effects. Studies indicate that donor-derived platelets can serve as immune-compatible drug carriers that interact with and deliver drugs to cancer cells with fewer side effects, making them a promising therapeutic option with enhanced antitumor activity. Moreover, human induced pluripotent stem cells (hiPSCs) provide a potentially renewable source of clinical-grade transfusable platelets that can be drug-loaded to complement the supply of donor-derived platelets. Here, we describe methods for ex vivo generation of megakaryocytes (MKs) and functional platelets from hiPSCs (hiPSC-platelets) in a scalable fashion. We then loaded hiPSC-platelets with lapatinib and infused them into BBM tumor-bearing NOD/SCID mouse models. Such treatment significantly increased intracellular lapatinib accumulation in BBMs in vivo, potentially via tumor cell-induced activation/aggregation. Lapatinib-loaded hiPSC-platelets exhibited normal morphology and function and released lapatinib pH-dependently. Importantly, lapatinib delivery to BBM cells via hiPSC-platelets inhibited tumor growth and prolonged survival of tumor-bearing mice. Overall, use of lapatinib-loaded hiPSC-platelets effectively reduced adverse effects of free lapatinib and enhanced its therapeutic efficacy, suggesting that they represent a novel means to deliver chemotherapeutic drugs as treatment for BBM.

Assessment of racial differences in the incidence of thrombocytopenia induced by trastuzumab emtansine: a systematic review and meta-analysis

Background

Trastuzumab emtansine (T-DM1) has been proved to have value and efficacy in the treatment of advanced metastatic cancer, including in the adjuvant setting. However, there is increasing concern about T-DM1-induced thrombocytopenia (TCP), which shows racial differences in incidence. This meta-analysis aimed to evaluate differences in the incidence of T-DM1-related TCP between Asian and non-Asian patients by combining accessible information from all single-agent T-DM1 clinical trials published to date.

Methods

We conducted systematic searches of the PubMed, Embase, and the Cochrane Library databases to identify relevant clinical studies of T-DM1 that reported on safety, including the incidence of TCP, which were published between January 1980 and March 2020. Two reviewers were responsible for the screening and extraction of data. The pooled-effect estimate calculated with a fixed-effects or random-effects model was represented as incidence with 95% confidence intervals (CIs).

Results

A total of 29 studies involving 6,188 patients were included. The incidence of all-grade TCP in Asian patients and non-Asian patients was 0.39 (95% CI: 0.11–0.67) and 0.29 (95% CI: 0.23–0.35), respectively. The incidence of TCP of grade 3 or higher in Asians was 0.20 (95% CI: 0.10–0.29), compared with 0.02 (95% CI: 0.01–0.03) in non-Asians. Gastrointestinal cancer type and a T-DM1 treatment dose of 2.4 mg/kg Q3W were related to grade 3 or higher TCP events.

Discussion

Asian patients have a higher risk of developing TCP after receiving T-DM1 than non-Asian patients. Clinicians should be aware of the importance of careful observation of platelet count in patients receiving T-DM1 therapy.

Is Molecular Tailored-Therapy Changing the Paradigm for CNS Metastases in Breast Cancer?

Breast cancer (BC) is the second most common tumour spreading to the central nervous system (CNS). The prognosis of patients with CNS metastases depends on several parameters including the molecular assessment of the disease. Although loco-regional treatment remains the best approach, systemic therapies are acquiring a role leading to remarkable long-lasting responses. The efficacy of these compounds diverges between tumours with different molecular assessments. Promising agents under investigation are drugs targeting the HER2 pathways such as tucatinib, neratinib, pyrotinib, trastuzumab deruxtecan. In addition, there are several promising agents under investigation for patients with triple-negative brain metastases (third-generation taxane, etirinotecan, sacituzumab, immune-checkpoint inhibitors) and hormone receptor-positive brain metastases (CDK 4/5, phosphoinositide-3-kinase-mammalian target of rapamycin [PI3K/mTOR] inhibitors). Also, the systemic treatment of leptomeningeal metastases, which represents a very negative prognostic site of metastases, is likely to change as several compounds are under investigation, some with interesting preliminary results. Here we performed a comprehensive review focusing on the current management of CNS metastases according to molecular subtypes, site of metastases (leptomeningeal vs brain), and systemic treatments under investigation.

Brain Metastases in HER2-Positive Breast Cancer: Current and Novel Treatment Strategies

Development of brain metastases can occur in up to 30-50% of patients with breast cancer, representing a significant impact on an individual patient in terms of survival and quality of life. Patients with HER2-positive breast cancer have an increased risk of developing brain metastases; however, screening for brain metastases is not currently recommended due to the lack of robust evidence to support survival benefit. In recent years, several novel anti-HER2 agents have led to significant improvements in the outcomes of HER2-positive metastatic breast cancer. Despite these advances, brain and leptomeningeal metastases from HER2-positive breast cancer remain a significant cause of morbidity and mortality, and their optimal management remains an unmet need. This review presents an update on the current and novel treatment strategies for patients with brain metastases from HER2-positive breast cancer and discusses the open questions in the field.

Glembatumumab vedotin for patients with metastatic, gpNMB overexpressing, triple-negative breast cancer ("METRIC"): a randomized multicenter study

The METRIC study (NCT#0199733) explored a novel antibody–drug conjugate, glembatumumab vedotin (GV), targeting gpNMB that is overexpressed in ~40% of patients with triple-negative breast cancer (TNBC) and associated with poor prognosis. The study was a randomized, open-label, phase 2b study that evaluated progression-free survival (PFS) of GV compared with capecitabine in gpNMB-overexpressing TNBC. Patients who had previously received anthracycline and taxane-based therapy were randomized 2:1 to receive, GV (1.88 mg/kg IV q21 days) or capecitabine (2500 mg/m² PO daily d1–14 q21 days). The primary endpoint was RECIST 1.1 PFS per independent, blinded central review. In all, 327 patients were randomized to GV (213 treated) or capecitabine (92 treated). Median PFS was 2.9 months for GV vs. 2.8 months for capecitabine. The most common grade ≥3 toxicities for GV were neutropenia, rash, and leukopenia, and for capecitabine were fatigue, diarrhea, and palmar-plantar erythrodysesthesia. The study did not meet the primary endpoint of improved PFS over capecitabine or demonstrate a relative risk/benefit improvement over capecitabine.

Current treatment options for HER2-positive breast cancer patients with brain metastases

Brain metastases (BMs) are frequently associated with HER2+ breast cancer (BC). Their management is based on a multi-modal strategy including both local treatment and systemic therapy. Despite therapeutic advance, BMs still have an adverse impact on survival and quality of life and the development of effective systemic therapy to prevent and treat BMs from HER2 + BC represents an unmet clinical need. Trastuzumab-based therapy has long been the mainstay of systemic therapy and over the last two decades other HER2-targeted agents including lapatinib, pertuzumab and trastuzumab emtansine, have been introduced in the clinical practice. More recently, novel agents such as neratinib, tucatinib and trastuzumab deruxtecan have been developed, with interesting activity against BMs. Further research is needed to better elucidate the best sequence of these agents and their combination with local treatment.

Breast Cancer Brain Metastasis-Overview of Disease State, Treatment Options and Future Perspectives

Simple Summary

In this review, we present the latest information on the pathophysiology, diagnosis, and local and systemic treatment of brain metastases from breast cancer, with a focus on recent publications. Improving the local treatment and subtype-specific systemic therapies through advancements in basic and translational research will contribute to better clinical outcomes for patients with breast cancer brain metastasis.

Abstract

Breast cancer is the second most common origin of brain metastasis after lung cancer. Brain metastasis in breast cancer is commonly found in patients with advanced course disease and has a poor prognosis because the blood–brain barrier is thought to be a major obstacle to the delivery of many drugs in the central nervous system. Therefore, local treatments including surgery, stereotactic radiation therapy, and whole-brain radiation therapy are currently considered the gold standard treatments. Meanwhile, new targeted therapies based on subtype have recently been developed. Some drugs can exceed the blood–brain barrier and enter the central nervous system. New technology for early detection and personalized medicine for metastasis are warranted. In this review, we summarize the historical overview of treatment with a focus on local treatment, the latest drug treatment strategies, and future perspectives using novel therapeutic agents for breast cancer patients with brain metastasis, including ongoing clinical trials.

Dose-reduced trastuzumab deruxtecan can be safely used in liver failure and active leptomeningeal metastases

Trastuzumab deruxtecan has been shown to have responses in heavily pretreated patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. However, the safety of this medication in patients with severe liver dysfunction and untreated or symptomatic central nervous system metastases is unknown. We describe a patient with metastatic HER2-positive breast cancer with liver failure and leptomeningeal metastases who was treated with dose-reduced trastuzumab deruxtecan. With treatment, the patient’s hyperbilirubinemia resolved and she demonstrated a response on imaging. She was dose-escalated to full dose with minimal adverse events.

Treatment strategies for breast cancer brain metastases

Brain metastases from breast cancer (BCBM) constitute the second most common cause of brain metastasis (BM), and the incidence of these frequently lethal lesions is currently increasing, following better systemic treatment. Patients with ER-negative and HER2-positive metastatic breast cancer (BC) are the most likely to develop BM, but if this diagnosis remains associated with a worse prognosis, long survival is now common for patients with HER2-positive BC. BCBM represents a therapeutic challenge that needs a coordinated treatment strategy along international guidelines. Surgery has always to be considered when feasible. It is now well established that stereotaxic radiosurgery allows for equivalent control and less-cognitive toxicities than whole-brain radiation therapy, which should be delayed as much as possible. Medical treatment for BCBM is currently a rapidly evolving field. It has been shown that the blood-brain barrier (BBB) is often impaired in macroscopic BM, and several chemotherapy regimens, antibody-drug conjugates and tyrosine-kinase inhibitors have been shown to be active on BCBM and can be part of the global treatment strategy. This paper provides an overview of the therapeutic option for BCBM that is currently available and outlines potential new approaches for tackling these deadly secondary tumours.

Brain metastases in metastatic cancer: a review of recent advances in systemic therapies

Introduction: Brain metastases (BM) are a frequent complication of metastatic cancer. Due to the wider availability and application of screening procedures, an increasing fraction of patients are diagnosed at the asymptomatic stage. The introduction of immune checkpoint inhibitors and targeted therapies has revolutionized treatment in several frequently BM-causing entities like metastatic lung cancer, melanoma and breast cancer. However, registered trials of new targeted and immunotherapy mostly excluded patients with BM resulting in limited knowledge of the intracranial efficacy of new systemic agents.Areas covered: The present review highlights recent advances in systemic therapies for the treatment and prophylaxis of the three leading BM causing tumors: NSCLC, melanoma and breast cancer.Expert opinion: High intracranial efficacy was observed for several next-generation tyrosine kinase inhibitors as well as immune checkpoint inhibitors, especially in patients with asymptomatic disease. Ongoing discussions addressed the need for local therapies in patients with asymptomatic BM and the availability of systemic therapy with high intracranial efficacy. Further BM-specific studies as well as BM-specific endpoints in registered trials are needed to define the role of systemic monotherapies in patients with BM.

HER2 antibody-drug conjugate controls growth of breast cancer brain metastases in hematogenous xenograft models, with heterogeneous blood-tumor barrier penetration unlinked to a passive marker

BACKGROUND

Brain metastases of HER2+ breast cancer persist as a clinical challenge. Many therapeutics directed at human epidermal growth factor receptor 2 (HER2) are antibodies or antibody-drug conjugates (ADCs), and their permeability through the blood-tumor barrier (BTB) is poorly understood. We investigated the efficacy of a biparatopic anti-HER2 antibody-tubulysin conjugate (bHER2-ATC) in preclinical models of brain metastases.

METHODS

The compound was evaluated in 2 hematogenous HER2+ brain metastasis mouse models, SUM190-BR and JIMT-1-BR. Endpoints included metastasis count, compound brain penetration, cancer cell proliferation, and apoptosis.

RESULTS

Biparatopic HER2-ATC 3 mg/kg prevented metastasis outgrowth in the JIMT-1-BR model. At 1 mg/kg bHER2-ATC, a 70% and 92% reduction in large and micrometastases was observed. For the SUM190-BR model, an 85% and 53% reduction, respectively, in large and micrometastases was observed at 3 mg/kg, without statistical significance. Proliferation was reduced in both models at the highest dose. At the endpoint, bHER2-ATC uptake covered a median of 4-6% and 7-17% of metastasis area in the JIMT-1-BR and SUM190-BR models, respectively. Maximal compound uptake in the models was 19% and 86% in JIMT-1-BR and SUM190-BR, respectively. Multiple lesions in both models demonstrated ADC uptake in the absence or low diffusion of Texas Red Dextran, a marker of paracellular permeability. Using in vitro BTB assays, the ADC was endocytosed into brain endothelial cells, identifying a potentially new mechanism of antibody permeability.

CONCLUSIONS

Biparatopic HER2-ATC significantly prevented JIMT-1-BR brain metastasis outgrowth and showed activity in the SUM190-BR model. The bHER2-ATC penetration into metastases that are impermeable to fluorescent dye suggested an endocytic mechanism of brain penetration.

Management of Brain and Leptomeningeal Metastases from Breast Cancer

The management of breast cancer (BC) has rapidly evolved in the last 20 years. The improvement of systemic therapy allows a remarkable control of extracranial disease. However, brain (BM) and leptomeningeal metastases (LM) are frequent complications of advanced BC and represent a challenging issue for clinicians. Some prognostic scales designed for metastatic BC have been employed to select fit patients for adequate therapy and enrollment in clinical trials. Different systemic drugs, such as targeted therapies with either monoclonal antibodies or small tyrosine kinase molecules, or modified chemotherapeutic agents are under investigation. Major aims are to improve the penetration of active drugs through the blood-brain barrier (BBB) or brain-tumor barrier (BTB), and establish the best sequence and timing of radiotherapy and systemic therapy to avoid neurocognitive impairment. Moreover, pharmacologic prevention is a new concept driven by the efficacy of targeted agents on macrometastases from specific molecular subgroups. This review aims to provide an overview of the clinical and molecular factors involved in the selection of patients for local and/or systemic therapy, as well as the results of clinical trials on advanced BC. Moreover, insight on promising therapeutic options and potential directions of future therapeutic targets against BBB and microenvironment are discussed.

Local and systemic treatment for HER2-positive breast cancer with brain metastases: a comprehensive review

The management of human epidermal growth factor receptor (HER2)-positive breast cancer has improved over the past decade. However, despite improvements in systemic control, a substantial proportion of patients with advanced HER2-positive breast cancer suffer from central nervous system metastases and even intracranial progression after aggressive local treatment. There is paucity of data and no consensus on the systemic therapies for patients with intracranial progression. This review discusses both local and systemic treatments for HER2-positive breast cancer with brain metastases with a special focus on the response of central nervous system metastases. A recommended practical treatment algorithm to guide physicians in selecting the most appropriate anti-HER2 therapy for their patients is suggested.

HER2‐positive breast cancer brain metastasis: A new and exciting landscape

Background

Brain metastases (BrM) incidence is 25% to 50% in women with advanced human epidermal growth factor receptor 2 (HER2)‐positive breast cancer. Radiation and surgery are currently the main local treatment approaches for central nervous system (CNS) metastases. Systemic anti‐HER2 therapy following a diagnosis of BrM improves outcomes. Previous preclinical data has helped elucidate HER2 brain trophism, the blood‐brain/blood‐tumor barrier(s), and the brain tumor microenvironment, all of which can lead to development of novel therapeutic options.

Recent findings

Several anti‐HER2 agents are currently available and reviewed here, some of which have recently shown promising effects in BrM patients, specifically. New strategies driven by and focusing on brain metastasis‐specific genomics, immunotherapy, and preventive strategies have shown promising results and are under development.

Conclusions

The field of HER2+ breast cancer, particularly for BrM, continues to evolve as new therapeutic strategies show promising results in recent clinical trials. Increasing inclusion of patients with BrM in clinical studies, and a focus on assessing their outcomes both intracranially and extracranially, is changing the landscape for patients with HER2+ CNS metastases by demonstrating the ability of newer agents to improve outcomes.

Management of brain metastases according to molecular subtypes

The incidence of brain metastases has markedly increased in the past 20 years owing to progress in the treatment of malignant solid tumours, earlier diagnosis by MRI and an ageing population. Although local therapies remain the mainstay of treatment for many patients with brain metastases, a growing number of systemic options are now available and/or are under active investigation. HER2-targeted therapies (lapatinib, neratinib, tucatinib and trastuzumab emtansine), alone or in combination, yield a number of intracranial responses in patients with HER2-positive breast cancer brain metastases. New inhibitors are being investigated in brain metastases from ER-positive or triple-negative breast cancer. Several generations of EGFR and ALK inhibitors have shown activity on brain metastases from EGFR and ALK mutant non-small-cell lung cancer. Immune-checkpoint inhibitors (ICIs) hold promise in patients with non-small-cell lung cancer without druggable mutations and in patients with triple-negative breast cancer. The survival of patients with brain metastases from melanoma has substantially improved after the advent of BRAF inhibitors and ICIs (ipilimumab, nivolumab and pembrolizumab). The combination of targeted agents or ICIs with stereotactic radiosurgery could further improve the response rates and survival but the risk of radiation necrosis should be monitored. Advanced neuroimaging and liquid biopsy will hopefully improve response evaluation.

Trastuzumab-deruxtecan: an investigational agent for the treatment of HER2-positive breast cancer

INTRODUCTION

The prognosis of patients with HER2-positive breast cancer was dramatically changed by the introduction of targeted therapies. With trastuzumab, pertuzumab, and T-DM1 widely used as (neo)adjuvant therapy today, novel treatment options are required to optimize treatment of HER2-positive metastatic disease. Trastuzumab-deruxtecan is an antibody-drug conjugate (ADC) consisting of a monoclonal humanized immunoglobulin G1 antibody, a linker molecule, and the exatecan derivative DXd. T-DXd has a higher drug to antibody ratio compared with T-DM1; in addition, membrane permeability of DXd is high, resulting in an increased bystander effect. Results from early clinical development suggest a clinically relevant activity of T-DXd in heavily pretreated patients with HER2-positive metastatic breast cancer progressing on T-DM1. Interstitial lung disease was a side-effect requiring special attention and was observed in approximately 13% of patients.

AREAS COVERED

This article reviews preclinical and clinical data on T-DXd. A systematic literature search was performed to identify relevant publications. The search included original research articles, abstracts from major conferences, and reviews and was limited to English-language publications.

EXPERT OPINION

T-DXd is an efficacious and tolerable drug and harbors promise as a key addition to the therapeutic field in HER2-positive breast cancer.

Tumor Primary Site and Histology Subtypes Role in Radiotherapeutic Management of Brain Metastases

Randomized controlled trials have failed to report any survival advantage for WBRT combined with SRS in the management of brain metastases, despite the enhanced local and distant control in comparison to each treatment alone. Literature review have revealed important role of primary histology of the tumor when dealing with brain metastases. NSCLC responds better to combined approach even when there was only single brain metastasis present while breast cancer has registered better survival with SRS alone probably due to better response of primary tumor to advancement in surgical and chemotherapeutic agents. Furthermore, mutation status (EGFR/ALK) in lung cancer and receptor status (ER/PR/HER2) in breast cancer also exhibit diversity in their response to radiotherapy. Radioresistant tumors like renal cell carcinoma and melanoma brain metastases have achieved better results when treated with SRS alone. Secondly, single brain metastasis may benefit from local and distant brain control achieved with combined treatment. These diverse outcomes suggest a primary histology-based analysis of the radiotherapy regimens (WBRT, SRS, or their combination) would more ideally establish the role of radiotherapy in the management of brain metastases. Molecularly targeted therapeutic and immunotherapeutic agents have revealed synergism with radiation therapy particularly SRS in treating cancer patients with brain metastases. Clinical updates in this regard have also been reviewed.