Newly Approved and Emerging Agents in HER2-Positive Metastatic Breast Cancer

Human epidermal growth factor receptor 2-positive breast cancer (HER2+ BC) is an aggressive tumor type, accounting for 15% to 20% of the approximately 300,000 new BC cases in the United States each year. The goal of this review is to discuss the evolving landscape of therapies for HER2+ metastatic BC (mBC). Targeted therapies that have been the standard of care (SOC) for HER2+ mBC for almost a decade have greatly improved patient outcomes. The SOC for the first-line treatment of HER2+ mBC continues to be HER2-targeted monoclonal antibodies (mAbs) + a taxane, but recent updates in the second-line setting favor use of a newer HER2-targeted antibody-drug conjugate (ADC), trastuzumab deruxtecan, versus the prior SOC ADC, trastuzumab emtansine. Numerous options are now available in the third line and beyond, including tyrosine kinase inhibitor (TKI) regimens, newer mAbs, and other ADCs. The optimal course of treatment for individual patients can be guided by location of metastases, prior therapies, concomitant biomarkers, and monitoring and management of adverse events. Ongoing trials will further the evolution of the HER2+ mBC treatment landscape. Furthermore, next-generation ADCs, TKIs, and classes of drugs that have not been approved for the treatment of HER2+ mBC, including immune checkpoint inhibitors and cyclin-dependent kinase 4 and 6 inhibitors, are also being evaluated for their efficacy in the first and second line. Although the influx of new drugs may complicate treatment decisions for physicians, having a multitude of options will undoubtedly further improve patient outcomes and patient-centered care.

Multidisciplinary Management of Brain Metastasis from Breast Cancer

The management of patients with breast cancer and brain metastases (BMs) is exquisitely multidisciplinary. Patients presenting with a symptomatic BM may be offered neurosurgical resection, followed by radiation. Stereotactic radiosurgery (SRS) is preferred over whole-brain radiotherapy (WBRT) in most patients presenting with a limited number of BMs, whereas WBRT with hippocampal-sparing and concomitant memantine is preferred for patients with multiple BMs. There is a growing role for systemic therapy, in some cases in lieu of local therapy, particularly in patients with HER2+ breast cancer.

Assessment of Spinal Metastases Surgery Risk Stratification Tools in Breast Cancer by Molecular Subtype

BACKGROUND

Breast cancer molecular features and modern therapies are not included in spine metastasis prediction algorithms.

OBJECTIVE

To examine molecular differences and the impact of postoperative systemic therapy to improve prognosis prediction for spinal metastases surgery and aid surgical decision making.

METHODS

This is a retrospective multi-institutional study of patients who underwent spine surgery for symptomatic breast cancer spine metastases from 2008 to 2021 at the Massachusetts General Hospital and Brigham and Women's Hospital. We studied overall survival, stratified by breast cancer molecular subtype, and calculated hazard ratios (HRs) adjusting for demographics, tumor characteristics, treatments, and laboratory values. We tested the performance of established models (Tokuhashi, Bauer, Skeletal Oncology Research Group, New England Spinal Metastases Score) to predict and compare all-cause.

RESULTS

A total of 98 patients surgically treated for breast cancer spine metastases were identified (100% female sex; median age, 56 years [IQR, 36-84 years]). The 1-year probabilities of survival for hormone receptor positive, hormone receptor positive/human epidermal growth factor receptor 2+, human epidermal growth factor receptor 2+, and triple-negative breast cancer were 63% (45 of 71), 83% (10 of 12), 0% (0 of 3), and 12% (1 of 8), respectively ( P < .001). Patients with triple-negative breast cancer had a higher proportion of visceral metastases, brain metastases, and poor physical activity at baseline. Postoperative chemotherapy and endocrine therapy were associated with prolonged survival. The Skeletal Oncology Research Group prognostic model had the highest discrimination (area under the receiver operating characteristic, 0.77 [95% CI, 0.73-0.81]). The performance of all prognostic scores improved when preoperative molecular data and postoperative systemic treatment plans was considered.

CONCLUSION

Spine metastases risk tools were able to predict prognosis at a significantly higher degree after accounting for molecular features which guide treatment response.

Targeted Therapeutic Options and Future Perspectives for HER2-Positive Breast Cancer

Simple Summary

The development of several antiHuman Epidermal Growth Factor Receptor 2 (HER2) treatments over the last few years has improved the landscape of HER2-positive breast cancer. Despite this, relapse is still the main issue in HER2-positive breast cancer. The reasons for therapeutic failure lie in the heterogeneity of the disease itself, as well as in the drug resistance mechanisms. In this review, we intended to understand the milestones that have had an impact on this disease up to their implementation in clinical practice. In addition, understanding the underlying molecular biology of HER2-positive disease is essential for the optimization and personalization of the different treatment options. For this reason, we focused on two relevant aspects, which are triple-positive disease and the role that modulation of the immune response might play in treatment and prognosis.

Abstract

Despite the improvement achieved by the introduction of HER2-targeted therapy, up to 25% of early human epidermal growth factor receptor 2-positive (HER2+) breast cancer (BC) patients will relapse. Beyond trastuzumab, other agents approved for early HER2+ BC include the monoclonal antibody pertuzumab, the antibody-drug conjugate (ADC) trastuzumab-emtansine (T-DM1) and the reversible HER2 inhibitor lapatinib. New agents, such as trastuzumab-deruxtecan or tucatinib in combination with capecitabine and trastuzumab, have also shown a significant improvement in the metastatic setting. Other therapeutic strategies to overcome treatment resistance have been explored in HER2+ BC, mainly in HER2+ that also overexpress estrogen receptors (ER+). In ER+ HER2+ patients, target therapies such as phosphoinositide-3-kinase (PI3K) pathway inhibition or cyclin-dependent kinases 4/6 blocking may be effective in controlling downstream of HER2 and many of the cellular pathways associated with resistance to HER2-targeted therapies. Multiple trials have explored these strategies with some promising results, and probably, in the next years conclusive results will succeed. In addition, HER2+ BC is known to be more immunogenic than other BC subgroups, with high variability between tumors. Different immunotherapeutic agents such as HER-2 therapy plus checkpoint inhibitors, or new vaccines approaches have been investigated in this setting, with promising but controversial results obtained to date.

Novel Therapies for the Treatment of HER2-Positive Advanced Breast Cancer: A Canadian Perspective

The advent of anti-HER2 targeted therapies has dramatically improved the outcome of HER2-positive breast cancer; however, resistance to treatment in the metastatic setting remains a challenge, highlighting the need for novel therapies. The arrival of new treatment options and clinical trials examining the efficacy of novel agents may improve outcomes in the metastatic setting, including in patients with brain metastases. In the first-line setting, we can potentially cure a selected number of patients treated with pertuzumab + trastuzumab + taxane. In the second-line setting, clinical trials show that trastuzumab deruxtecan (T-DXd) is a highly effective option, resulting in a shift from trastuzumab emtansine (T-DM1) as the previous standard of care. Moreover, we now have data for patients with brain metastases to show that tucatinib + trastuzumab + capecitabine can improve survival in this higher-risk group and be an effective regimen for all patients in the third-line setting. Finally, we have a number of effective anti-HER2 therapies that can be used in subsequent lines of therapy to improve patient outcomes. This review paper discusses the current treatment options and presents a practical treatment sequencing algorithm in the context of the Canadian landscape.

Current and future landscape of targeted therapy in HER2-positive advanced breast cancer: redrawing the lines

BACKGROUND

Evidence to date supports continued human epidermal growth factor receptor 2 (HER2) suppression beyond progression on HER2-directed therapy for advanced HER2-positive breast cancer. Data from several phase II and III trials evaluating HER2-directed therapy following second-line T-DM1 have recently become available.

METHODS

We performed a systematic search of the published and presented literature to identify phase II and phase III trials assessing novel HER2-targeted agents as third-line therapy or beyond for HER2-positive advanced breast cancer using search terms 'breast cancer' AND 'HER2' AND 'advanced' AND ('phase II' OR 'phase III').

RESULTS

Eight clinical trials reporting efficacy outcomes on third-line or greater HER2-directed therapy for HER2-positive advanced breast cancer were identified. In phase III trials, margetuximab and neratinib combinations demonstrated significant 1.3-month (hazard ratio, HR = 0.71, p < 0.001) and 0.1-month (HR = 0.76, p = 0.006) net improvements in median progression-free survival (PFS), respectively, with no significant improvements in overall survival (OS). Tucatinib added to trastuzumab and capecitabine demonstrated a significant 2.7-month improvement in median PFS (HR = 0.57, p < 0.00001) and a 5.5-month improvement in median OS (HR = 0.73, p = 0.004) in a randomized phase II trial, including significant clinical benefit for patients with brain metastases. Finally, trastuzumab-deruxtecan, zenocutuzumab, and poziotinib demonstrated benefit in phase II trials with the most robust overall response rate (62.0%) and median duration of response (18.2 months) observed for trastuzumab-deruxtecan among heavily pretreated patients.

CONCLUSION

Tucatinib plus trastuzumab and capecitabine significantly prolongs OS, and promising preliminary response outcomes for trastuzumab-deruxtecan suggest that sequencing of these regimens following second-line therapy is reasonable.

How we treat patients with metastatic HER2-positive breast cancer

HER2-positive breast cancer represents 15%-20% of breast malignancies and is characterized by an aggressive behavior and high recurrence rates. Anti-HER2-directed agents represent the mainstay of treatment of patients with HER2-positive metastatic breast cancer (MBC). In this review we propose a treatment algorithm for patients with HER2-positive MBC based on the currently available literature on the topic. The combination of trastuzumab, pertuzumab and a taxane (THP) remains the preferred first-line therapy in most scenarios. Results of trials recently presented at the European Society for Medical Oncology (ESMO) Congress 2021 might have direct clinical impact in the second- and later-line settings. The randomized DESTINY-BREAST03 study compared trastuzumab deruxtecan (T-DXd) with trastuzumab emtansine (T-DM1) in patients previously treated with trastuzumab and a taxane. T-DXd significantly improved progression-free survival and showed a trend towards improved overall survival, establishing this agent as preferred second-line therapy. Treatment with T-DM1, or the combination of tucatinib, trastuzumab and capecitabine, are considered reasonable options after second-line therapy. For subsequent lines, trastuzumab duocarmazine, neratinib plus capecitabine or the continuation of trastuzumab with different chemotherapy partners are valid options. For patients experiencing disease relapse up to 6 months after completion of adjuvant therapy, as well as for those relapsing within 12 months from the completion of pertuzumab-based adjuvant treatment, we recommend T-DXd as preferred first-line option. For those relapsing between 6 and 12 months after non-pertuzumab-based adjuvant treatment, we recommend first-line THP. Finally, for patients with active brain metastasis, tucatinib-based combination represents a suitable second-line option.

The Pharmacokinetics and Safety of Tucatinib in Volunteers with Hepatic Impairment

BACKGROUND AND OBJECTIVE

Tucatinib, a highly selective tyrosine kinase inhibitor of the human epidermal growth factor receptor 2 (HER2) approved for HER2-positive metastatic breast cancer, is cleared by hepatic metabolism and subsequent biliary excretion. Liver disease can alter drug disposition and pharmacokinetics (PK). The objective of this study is to characterize PK and safety of tucatinib in volunteers with hepatic impairment.

METHODS

This Phase 1 study compared the PK and safety of a single 300-mg oral dose of tucatinib in volunteers with mild, moderate, and severe hepatic impairment (Child-Pugh A/B/C) to healthy volunteers matched for sex, age, and body mass index. Pharmacokinetic parameters were determined for tucatinib and its predominant metabolite ONT-993.

RESULTS

Compared with healthy volunteers, tucatinib exposure was similar in volunteers with mild impairment and increased in those with moderate or severe impairment without reaching statistical significance. Respective fold increases in geometric mean ratios for AUC_0-t and AUC_0-∞ were 1.13 and 1.15 in moderate impairment, and 1.43 and 1.61 in severe impairment compared with healthy volunteers. Three treatment-emergent adverse events (nausea, dermatitis, and increased transaminases) were reported in three volunteers and showed no obvious association with hepatic impairment status.

CONCLUSION

The 1.61-fold geometric mean ratio AUC_0-∞ increase in volunteers with severe hepatic impairment supports the recommendation in the tucatinib prescribing information to reduce the dose from 300 mg twice daily to 200 mg twice daily in patients with severe impairment; no dose adjustment is recommended for patients with mild or moderate hepatic impairment. This trial (NCT03722823) was registered on October 29, 2018.