Real-time assessment of HER2 status in circulating tumor cells of breast cancer patients: Methods of detection and clinical implications

Mapping breast cancer therapy with circulating tumor cells: The expert perspective

Circulating tumor cells (CTCs) have emerged as a key prognostic biomarker for breast cancer, with their role becoming more pronounced in metastatic cases. In metastatic breast cancer, having five or more CTCs per 7.5 mL of blood is linked to poorer survival and more aggressive disease, marking it as stage IVaggressive. Conversely, fewer than five CTCs per 7.5 mL of blood indicates a less aggressive, stage IVindolent disease. Additionally, molecular CTCs characterization provides a real-time snapshot of tumor biology, capturing its temporal and spatial variability and providing insights into tumor behavior. Beyond their role in predicting outcomes, CTCs can help guide treatment intensity as shown in clinical trials like the STIC trial, offering a new way to tailor therapy alongside other liquid biopsy biomarkers such as circulating tumor DNA. The aim of our review is to focus on both enumeration and phenotyping of CTCs and examine how CTC-guided strategies can improve treatment tailoring and patient outcomes. We also explore the potential for integrating CTCs with other biomarkers, such as circulating tumor DNA, and discuss how innovative biomarker-driven clinical trial designs could further advance personalized treatment strategies.

Novel treatment approaches utilizing antibody-drug conjugates in breast cancer

Antibody-drug conjugates (ADCs) are rapidly changing the way we treat patients with breast cancer. Despite this progress, many unanswered questions remain regarding the sequencing of different ADCs with similar payloads, optimal combinations, drug design strategies to limit off-target toxicities, biomarkers to define antigen positivity, and the use of ADCs in the neoadjuvant and adjuvant settings. In this review, we summarize novel ADC approaches in breast cancer treatment, including potential improvements in ADC payloads, linkers, targets, and drug delivery. We also evaluate novel strategies to combine ADCs with other agents, such as targeted drugs and immune checkpoint inhibitors. To improve patient selection, the development of quantitative biomarkers is reviewed, including HER2 mRNA, immunofluorescence-based assays, mass spectrometry, liquid biopsies, digital pathology, and molecular imaging-based approaches. Lastly, we evaluate the potential to incorporate ADCs into the early-stage setting, including evaluating currently published and ongoing clinical trials. This review highlights the potential for ADCs to shift the treatment paradigm in both the advanced and early-stage settings. We further demonstrate the complexity and challenges of improving ADCs to enhance targeting of tumor vulnerabilities while limiting toxicity through rationale drug development strategies to enhance the therapeutic window, linker technology, and payload variability to continue to improve outcomes for patients with breast cancer.

Redefining Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer in the Era of Novel Antibody-Drug Conjugates

The advent of next-generation antibody-drug conjugates (ADCs), particularly trastuzumab deruxtecan (T-DXd), has transformed our understanding of human epidermal growth factor receptor 2 (HER2) targetability for breast cancer (BC) treatment. Historically categorized as HER2-positive or HER2-negative on the basis of trastuzumab eligibility, this classification has evolved significantly over the past 5 years. The DESTINY-Breast04 trial marked the entry of anti-HER2 therapies for patients with HER2-low BC, while DESTINY-Breast06 demonstrated the potential for earlier and broader use of T-DXd. The latter trial revealed that even minimal HER2 expression in tumors previously classified as HER2-0 might be clinically relevant and targetable with T-DXd. This has led to further refinement of HER2 classification, introducing the concepts of HER2-ultralow (HER2-0 with staining) and HER2-null BC (HER2-0 without staining). With these findings, most patients with metastatic BC are currently considered eligible for T-DXd. Accurately identifying candidates for these therapies has highlighted the limitations of current HER2 diagnostic practices, on the basis of immunohistochemistry (IHC)/in situ hybridization assessment. IHC assay, optimized to detect high levels of HER2 protein, faces limitations in discriminating finer variations at the lower end of the HER2 expression spectrum. This is further complicated by the heterogeneity of HER2 expression. To overcome these barriers, new approaches may be required. Quantitative methods for HER2 membrane assessment, genomic and transcriptomic evaluations of HER2, and the integration of artificial intelligence into tissue analysis hold promise and are currently under investigation. Additionally, noninvasive strategies, such as analysis of circulating tumor DNA or circulating tumor cells, may enable real-time HER2 status assessment and better patient selection for ADC. However, these techniques require rigorous validation to ensure their clinical utility. This evolving landscape underscores the need for improvement of diagnostic approaches to support the expanding role of ADCs in BC treatment.

Multi-omic profiling in breast cancer: utility for advancing diagnostics and clinical care

INTRODUCTION

Breast cancer remains a major global health challenge. While advances in precision oncology have contributed to improvements in patient outcomes and provided a deeper understanding of the biological mechanisms that drive the disease, historically, research and patients' allocation to treatment have heavily relied on single-omic approaches, analyzing individual molecular dimensions such as genomics, transcriptomics, or proteomics. While these have provided deep insights into breast cancer biology, they often fail to offer a complete understanding of the disease's complex molecular landscape.

AREAS COVERED

In this review, the authors explore the recent advancements in multi-omic research in the realm of breast cancer and use clinical data to show how multi-omic integration can offer a more holistic understanding of the molecular alterations and their functional consequences underlying breast cancer.

EXPERT OPINION

The overall developments in multi-omic research and AI are expected to complement precision diagnostics through potentially refining prognostic models, and treatment selection. Overcoming challenges such as cost, data complexity, and lack of standardization is crucial for unlocking the full potential of multi-omics and AI in breast cancer patient care to enable the advancement of personalized treatments and improve patient outcomes.

Early Detection, Precision Treatment, Recurrence Monitoring: Liquid Biopsy Transforms Colorectal Cancer Therapy

Colorectal cancer (CRC) is a significant global health concern. We need ways to detect it early and determine the best treatments. One promising method is liquid biopsy, which uses cancer cells and other components in the blood to help diagnose and treat the disease. Liquid biopsies focus on three key elements: circulating tumor DNA (ctDNA), circulating microRNA (miRNA), and circulating tumor cells (CTC). By analyzing these elements, we can identify CRC in its early stages, predict how well a treatment will work, and even spot signs of cancer returning. This study investigates the world of liquid biopsy, a rapidly growing field. We want to understand how it can help us better recognize the molecular aspects of cancer, improve and diagnostics, tailor treatments to individual patients, and keep track of the disease over the long-term. We explored specific components of liquid biopsy, like extracellular vesicles and cell-free DNA, and how they are used to detect CRC. This review sheds light on the current state of knowledge and the many ways a liquid biopsy can be used in treating colorectal cancer. It can transform patient care, disease management, and clinical outcomes by offering non-invasive cancer-targeting solutions.

Modeling the management of patients with human epidermal growth factor receptor 2-positive breast cancer with liquid biopsy: the future of precision medicine

PURPOSE OF REVIEW

In the evolving landscape of human epidermal growth factor receptor 2 (HER2)-positive breast cancer (BC) management, liquid biopsy offers unprecedented opportunities for guiding clinical decisions. Here, we review the most recent findings on liquid biopsy applications in HER2-positive BC and its potential role in addressing challenges specific to this BC subtype.

RECENT FINDINGS

Recent studies have highlighted the significance of liquid biopsy analytes, primarily circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs), in stratifying patients' prognosis, predicting treatment response, and monitoring tumor evolution in both early and advanced stages of BC. Liquid biopsy holds promise in studying minimal residual disease to detect and potentially treat disease recurrence before it manifests clinically. Additionally, liquid biopsy may have significant implication in the management of brain metastasis, a major challenge in HER2-positive BC, and could redefine parameters for determining HER2 positivity. Combining ctDNA and CTCs is crucial for a comprehensive understanding of HER2-positive tumors, as they provide complementary insights.

SUMMARY

Research efforts are needed to address analytical challenges, validate, and broaden the application of liquid biopsy in HER2-positive BC. This effort will ultimately facilitate its integration into clinical practice, optimizing the care of patients with HER2-positive tumors.

Development of 52Mn Labeled Trastuzumab for Extended Time Point PET Imaging of HER2

PURPOSE

Due to their long circulation time in the blood, monoclonal antibodies (mAbs) such as trastuzumab, are usually radiolabeled with long-lived positron emitters for the development of agents for Positron Emission Tomography (PET) imaging. Manganese-52 (52Mn, t1/2 = 5.6 d, β+  = 29.6%, E(βave) = 242 keV) is suitable for imaging at longer time points providing a complementary technique to Zirconium-89 (89Zr, t1/2 = 3.3 d, β+  = 22.7%, E(βave) = 396 keV)) because of its long half-life and low positron energy. To exploit these properties, we aimed to investigate suitable bifunctional chelators that could be readily conjugated to antibodies and labeled with 52Mn under mild conditions using trastuzumab as a proof-of-concept.

PROCEDURES

Trastuzumab was incubated with S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA), 1-Oxa-4,7,10-tetraazacyclododecane-5-S-(4-isothiocyantobenzyl)-4,7,10-triacetic acid (p-SCN-Bn-Oxo-DO3A), and 3,6,9,15-tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene-4-S-(4-isothiocyanatobenzyl)-3,6,9-triacetic acid (p-SCN-Bn-PCTA) at a tenfold molar excess. The immunoconjugates were purified, combined with [52Mn]MnCl2 at different ratios, and the labeling efficiency was assessed by iTLC. The immunoreactive fraction of the radiocomplex was determined through a Lindmo assay. Cell studies were conducted in HER2 + (BT474) and HER2- (MDA-MB-468) cell lines followed by in vivo studies.

RESULTS

Trastuzumab-Oxo-DO3A was labeled within 30 min at 37 °C with a radiochemical yield (RCY) of 90 ± 1.5% and with the highest specific activity of the chelators investigated of 16.64 MBq/nmol. The labeled compound was purified with a resulting radiochemical purity of > 98% and retained a 67 ± 1.2% immunoreactivity. DOTA and PCTA immunoconjugates resulted in < 50 ± 2.5% (RCY) with similar specific activity. Mouse serum stability studies of [52Mn]Mn-Oxo-DO3A-trastuzumab showed 95% intact complex for over 5 days. Cell uptake studies showed higher uptake in HER2 + (12.51 ± 0.83% /mg) cells compared to HER2- (0.85 ± 0.10%/mg) cells. PET images of mice bearing BT474 tumors showed high tumor uptake that was consistent with the biodistribution (42.02 ± 2.16%ID/g, 14 d) compared to MDA-MB-468 tumors (2.20 ± 0.80%ID/g, 14 d). Additionally, both models exhibited low bone uptake of < 1% ID/g.

CONCLUSION

The bifunctional chelator p-SCN-Bn-Oxo-DO3A is promising for the development of 52Mn radiopharmaceuticals as it was easily conjugated, radiolabeled at mild conditions, and illustrated stability for a prolonged duration both in vitro and in vivo. High-quality PET/CT images of [52Mn]Mn-Oxo-DO3A-trastuzumab were obtained 14 d post-injection. This study illustrates the potential of [52Mn]Mn-Oxo-DO3A for the evaluation of antibodies using PET imaging.

Antibody-drug conjugate adverse effects can be understood and addressed based on immune complex clearance mechanisms

ABSTRACT

Numerous antibody-drug conjugates (ADCs) are being developed for cancer immunotherapy. Although several of these agents have demonstrated considerable clinical efficacy and have won Food and Drug Administration (FDA) approval, in many instances, they have been characterized by adverse side effects (ASEs), which can be quite severe in a fraction of treated patients. The key hypothesis in this perspective is that many of the most serious ASEs associated with the use of ADCs in the treatment of cancer can be most readily explained and understood due to the inappropriate processing of these ADCs via pathways normally followed for immune complex clearance, which include phagocytosis and trogocytosis. We review the key published basic science experiments and clinical observations that support this idea. We propose that it is the interaction of the ADC with Fcγ receptors expressed on off-target cells and tissues that can most readily explain ADC-mediated pathologies, which therefore provides a rationale for the design of protocols to minimize ASEs. We describe measurements that should help identify those patients most likely to experience ASE due to ADC, and we propose readily available treatments as well as therapies under development for other indications that should substantially reduce ASE associated with ADC. Our focus will be on the following FDA-approved ADC for which there are substantial literatures: gemtuzumab ozogamicin and inotuzumab ozogamicin; and trastuzumab emtansine and trastuzumab deruxtecan.