Early evaluation of risk stratification and clinical outcomes for patients with advanced breast cancer through combined monitoring of baseline circulating tumor cells and DNA.

PURPOSE: Early evaluation of tumor heterogeneity related to metastasis and outcomes is a major challenge in the management of advanced BCa in the clinic. Here we introduce the value of baseline CTCs and ctDNA to early differentiate clinical stages, tumor heterogeneity, and prognosis. EXPERIMENTAL DESIGN: We enrolled 254 stage IV and 38 stage III BCa patients and examined the baseline levels of CTCs, CTC-clusters, and plasma ctDNA before initiating therapies. Outcome including PFS, and OS were evaluated. RESULTS: The baseline CTCs for stage IV patients were approximately 9.5 times higher than those detected in stage III patients. Baseline CTC counts with a cutoff of 5 were significantly associated with prognosis. Within each stage, patients with <5 CTCs had longer PFS. Stage III patients with no CTCs exhibited the longest survival compared to patients with ≥1 CTC. CTC-clusters were only found in stage IV patients, among whom 15 stage IV patients with ≥5 CTC-clusters had the worst PFS compared to the 239 stage IV patients with <5 CTC-clusters. Similar outcomes were observed in 28 out of 254 stage IV patients who had at least 1 CTC-cluster detected, as these patients had shorter PFS. The major differences in ctDNA mutations between stage III and stage IV BCa were in PIK3CA and ESR1, which were associated with specific organ metastasis and worse outcomes. CONCLUSIONS: Assessing the baseline levels of CTCs, CTC-clusters, and mutational ctDNA profile could reliably aid in differentiation of clinical stage and early prediction of metastasis and outcomes in advanced BCa.

A randomized phase III double-blind placebo-controlled trial of first line chemotherapy and trastuzumab with or without bevacizumab for patients with HER2/neu-positive metastatic breast cancer: a trial of the ECOG-ACRIN Cancer Research Group (E1105).

Background: In 2008, bevacizumab received accelerated Food and Drug Administration (FDA) approval for use in human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC). Based on the preclinical and preliminary clinical activity of the trastuzumab and bevacizumab combination, ECOG-ACRIN E1105 trial was developed to determine if the addition of bevacizumab to a chemotherapy and trastuzumab combination for first-line therapy would improve progression-free survival (PFS) in patients with HER2-positive MBC. Findings: 96 patients were randomized to receive standard first-line chemotherapy and trastuzumab with or without bevacizumab between November 2007 and October 2009, and 93 began protocol therapy. Induction therapy was given for 24 weeks, followed by maintenance trastuzumab with or without bevacizumab. 60% (56/93) began carboplatin and 74% (69/93) completed 6 cycles of induction therapy. Primary endpoint was PFS. Median PFS was 11.1 and 13.8 months for placebo and bevacizumab arms, respectively (hazard ratio [HR] 95%, Confidence Interval [Cl] for bevacizumab vs. placebo: 0.73 [0.43-1.23], p = 0.24), and at a median follow-up of 70.7 months, median survival was 49.1 and 63 months (HR [95% Cl] for OS: 1.09 [0.61-1.97], p = 0.75). The most common toxicities across both arms were neutropenia and hypertension, with left ventricular systolic dysfunction, fatigue, and sensory neuropathy reported more frequently with bevacizumab. Conclusions: In this trial, the addition of bevacizumab did not improve outcomes in patients with metastatic HER2-positive breast cancer. Although the trial was underpowered due to smaller than anticipated sample size, these findings corroborated other clinical trials during this time.

Pharmacological suppression of the OTUD4/CD73 proteolytic axis revives antitumor immunity against immune-suppressive breast cancers.

Despite widespread utilization of immunotherapy, treating immune-cold tumors remains a challenge. Multiomic analyses and experimental validation identified the OTUD4/CD73 proteolytic axis as a promising target in treating immune-suppressive triple negative breast cancer (TNBC). Mechanistically, deubiquitylation of CD73 by OTUD4 counteracted its ubiquitylation by TRIM21, resulting in CD73 stabilization inhibiting tumor immune responses. We further demonstrated the importance of TGF-ß signaling for orchestrating the OTUD4/CD73 proteolytic axis within tumor cells. Spatial transcriptomics profiling discovered spatially resolved features of interacting malignant and immune cells pertaining to expression levels of OTUD4 and CD73. In addition, ST80, a newly developed inhibitor, specifically disrupted proteolytic interaction between CD73 and OTUD4, leading to reinvigoration of cytotoxic CD8+ T cell activities. In preclinical models of TNBC, ST80 treatment sensitized refractory tumors to anti-PD-L1 therapy. Collectively, our findings uncover what we believe to be a novel strategy for targeting the immunosuppressive OTUD4/CD73 proteolytic axis in treating immune-suppressive breast cancers with the inhibitor ST80.

Treatment of residual disease following neoadjuvant therapy in breast cancer.

Substantial advances have been made in the systemic treatment of breast cancer with residual disease following neoadjuvant therapy. We reviewed recent and ongoing studies informing the standard clinical management of residual disease by subtype: HER2+, TNBC, and HR+/HER2-, as well as strategies for BRCA+ disease. We conclude with a discussion of ongoing clinical trials and current controversies regarding the treatment of residual disease in breast cancer.

Interplay between ESR1/PIK3CA codon variants, oncogenic pathway alterations and clinical phenotype in patients with metastatic breast cancer (MBC): comprehensive circulating tumor DNA (ctDNA) analysis.

BACKGROUND: although being central for the biology and druggability of hormone-receptor positive, HER2 negative metastatic breast cancer (MBC), ESR1 and PIK3CA mutations are simplistically dichotomized as mutated or wild type in current clinical practice. METHODS: The study analyzed a multi-institutional cohort comprising 703 patients with luminal-like MBC characterized for circulating tumor DNA through next generation sequencing (NGS). Pathway classification was defined based on previous work (i.e., RTK, RAS, RAF, MEK, NRF2, ER, WNT, MYC, P53, cell cycle, notch, PI3K). Single nucleotide variations (SNVs) were annotated for their oncogenicity through OncoKB. Only pathogenic variants were included in the models. Associations among clinical characteristics, pathway classification, and ESR1/PIK3CA codon variants were explored. RESULTS: The results showed a differential pattern of associations for ESR1 and PIK3CA codon variants in terms of co-occurring pathway alterations patterns of metastatic dissemination, and prognosis. ESR1 537 was associated with SNVs in the ER and RAF pathways, CNVs in the MYC pathway and bone metastases, while ESR1 538 with SNVs in the cell cycle pathway and liver metastases. PIK3CA 1047 and 542 were associated with CNVs in the PI3K pathway and with bone metastases. CONCLUSIONS: The study demonstrated how ESR1 and PIK3CA codon variants, together with alterations in specific oncogenic pathways, can differentially impact the biology and clinical phenotype of luminal-like MBC. As novel endocrine therapy agents such as selective estrogen receptor degraders (SERDS) and PI3K inhibitors are being developed, these results highlight the pivotal role of ctDNA NGS to describe tumor evolution and optimize clinical decision making.

Coping strategies and psychosocial resources among women living with metastatic breast cancer: A qualitative study.

Objective: Despite more women living with metastatic breast cancer (MBC), this population is underrepresented in cancer survivorship research. Few studies have assessed how women with MBC cope with their cancer experience. This qualitative study describes the coping strategies and psychosocial resources utilized by women living with MBC.Methods: Twenty-two women with MBC participated in four focus groups. Transcripts were analyzed using a general inductive approach. Codes derived from participants' responses were subsequently condensed into themes.Results: We identified 12 coping strategies and psychosocial resources and grouped them into five themes: Behavioral Coping Strategies (i.e. stress management, active coping and planning); Cognitive Coping Strategies and Psychological Resources (i.e. cognitive reappraisal, optimism, mindfulness, positive thinking, and religious coping); Existential Approach-Oriented Coping (i.e. acceptance, values-based living, and identity integration); Avoidance (i.e. avoidant coping); and Interpersonal Resources and Seeking Social Support (i.e. social support).Conclusions: Women living with MBC utilize several engagement and disengagement coping strategies, as well as intrapersonal and interpersonal resources. This study provides useful perspectives of women living with MBC that may inform the development of psychosocial interventions. Further research is needed to assess coping strategies and psychosocial resources across different subgroups of MBC patients and determine their impact on cancer outcomes.

Identifying homologous recombination deficiency in breast cancer: genomic instability score distributions differ among breast cancer subtypes.

PURPOSE: A 3-biomarker homologous recombination deficiency (HRD) score is a key component of a currently FDA-approved companion diagnostic assay to identify HRD in patients with ovarian cancer using a threshold score of ≥ 42, though recent studies have explored the utility of a lower threshold (GIS ≥ 33). The present study evaluated whether the ovarian cancer thresholds may also be appropriate for major breast cancer subtypes by comparing the genomic instability score (GIS) distributions of BRCA1/2-deficient estrogen receptor-positive breast cancer (ER + BC) and triple-negative breast cancer (TNBC) to the GIS distribution of BRCA1/2-deficient ovarian cancer. METHODS: Ovarian cancer and breast cancer (ER + BC and TNBC) tumors from ten study cohorts were sequenced to identify pathogenic BRCA1/2 mutations, and GIS was calculated using a previously described algorithm. Pathologic complete response (pCR) to platinum therapy was evaluated in a subset of TNBC samples. For TNBC, a threshold was set and threshold validity was assessed relative to clinical outcomes. RESULTS: A total of 560 ovarian cancer, 805 ER + BC, and 443 TNBC tumors were included. Compared to ovarian cancer, the GIS distribution of BRCA1/2-deficient samples was shifted lower for ER + BC (p = 0.015), but not TNBC (p = 0.35). In the subset of TNBC samples, univariable logistic regression models revealed that GIS status using thresholds of ≥ 42 and ≥ 33 were significant predictors of response to platinum therapy. CONCLUSIONS: This study demonstrated that the GIS thresholds used for ovarian cancer may also be appropriate for TNBC, but not ER + BC. GIS thresholds in TNBC were validated using clinical response data to platinum therapy.

Dose escalation and expansion cohorts in patients with advanced breast cancer in a Phase I study of the CDK7-inhibitor samuraciclib.

Samuraciclib is a selective oral CDK7-inhibitor. A multi-modular, open-label Phase I study to evaluate safety and tolerability of samuraciclib in patients with advanced malignancies was designed (ClinicalTrials.gov: NCT03363893). Here we report results from dose escalation and 2 expansion cohorts: Module 1A dose escalation with paired biopsy cohort in advanced solid tumor patients, Module 1B-1 triple negative breast cancer (TNBC) monotherapy expansion, and Module 2A fulvestrant combination in HR+/HER2- breast cancer patients post-CDK4/6-inhibitor. Core study primary endpoints are safety and tolerability, and secondary endpoints are pharmacokinetics (PK), pharmacodynamic (PD) activity, and anti-tumor activity. Common adverse events are low grade nausea, vomiting, and diarrhea. Maximum tolerated dose is 360 mg once daily. PK demonstrates dose proportionality (120 mg-480 mg), a half-life of approximately 75 hours, and no fulvestrant interaction. In dose escalation, one partial response (PR) is identified with disease control rate of 53% (19/36) and reduction of phosphorylated RNA polymerase II, a substrate of CDK7, in circulating lymphocytes and tumor tissue. In TNBC expansion, one PR (duration 337 days) and clinical benefit rate at 24 weeks (CBR) of 20.0% (4/20) is achieved. In combination with fulvestrant, 3 patients achieve PR with CBR 36.0% (9/25); in patients without detectable TP53-mutation CBR is 47.4% (9/19). In this study, samuraciclib exhibits tolerable safety and PK is supportive of once-daily oral administration. Clinical activity in TNBC and HR+/HER2-breast cancer post-CDK4/6-inhibitor settings warrants further evaluation.

Identification of metabolic pathways contributing to ER+ breast cancer disparities using a machine-learning pipeline.

African American (AA) women in the United States have a 40% higher breast cancer mortality rate than Non-Hispanic White (NHW) women. The survival disparity is particularly striking among (estrogen receptor positive) ER+ breast cancer cases. The purpose of this study is to examine whether there are racial differences in metabolic pathways typically activated in patients with ER+ breast cancer. We collected pretreatment plasma from AA and NHW ER+ breast cancer cases (AA n = 48, NHW n = 54) and cancer-free controls (AA n = 100, NHW n = 48) to conduct an untargeted metabolomics analysis using gas chromatography mass spectrometry (GC-MS) to identify metabolites that may be altered in the different racial groups. Unpaired t-test combined with multiple feature selection and prediction models were employed to identify race-specific altered metabolic signatures. This was followed by the identification of altered metabolic pathways with a focus in AA patients with breast cancer. The clinical relevance of the identified pathways was further examined in PanCancer Atlas breast cancer data set from The Cancer Genome Atlas Program (TCGA). We identified differential metabolic signatures between NHW and AA patients. In AA patients, we observed decreased circulating levels of amino acids compared to healthy controls, while fatty acids were significantly higher in NHW patients. By mapping these metabolites to potential epigenetic regulatory mechanisms, this study identified significant associations with regulators of metabolism such as methionine adenosyltransferase 1A (MAT1A), DNA Methyltransferases and Histone methyltransferases for AA individuals, and Fatty acid Synthase (FASN) and Monoacylglycerol lipase (MGL) for NHW individuals. Specific gene Negative Elongation Factor Complex E (NELFE) with histone methyltransferase activity, was associated with poor survival exclusively for AA individuals. We employed a comprehensive and novel approach that integrates multiple machine learning and statistical methods, coupled with human functional pathway analyses. The metabolic profile of plasma samples identified may help elucidate underlying molecular drivers of disproportionately aggressive ER+ tumor biology in AA women. It may ultimately lead to the identification of novel therapeutic targets. To our knowledge, this is a novel finding that describes a link between metabolic alterations and epigenetic regulation in AA breast cancer and underscores the need for detailed investigations into the biological underpinnings of breast cancer health disparities.

Characterizing unique supportive care needs among women living with metastatic breast cancer: A qualitative study.

Background: Women with metastatic breast cancer face unique challenges as they cope with life-limiting prognoses and arduous treatments. However, the vast majority of research has focused on optimizing quality of life in women with early-stage, non-metastatic breast cancer and little is known about supportive care needs among women living with metastatic cancer. As part of a larger project that sought to inform the development of a psychosocial intervention, the aim of this study was to characterize supportive care needs among women with metastatic breast cancer and elucidate challenges unique to living with a life-limiting prognosis. Methods: Four, two-hour focus groups with 22 women were audio-recorded, transcribed verbatim, and analyzed in Dedoose using a general inductive approach to code categories and extract themes. Results: A total of 16 codes emerged from 201 participant comments regarding supportive care needs. Codes were collapsed into four supportive care need domains: 1. psychosocial, 2. physical and functional, 3. health system and information, and 4. sexuality and fertility needs. The most prevalent needs were breast cancer-related symptom burden (17.4%), lack of social support (14.9%), uncertainty (10.0%), stress management (9.0%), patient-centered care (7.5%), and sexual functioning (7.5%). More than half of needs (56.2%) were in the psychosocial domain and more than two-thirds of needs (76.8%) were in the psychosocial and physical and functional domains. Supportive care needs unique to living with metastatic breast cancer included the cumulative effects of continuously undergoing cancer treatment on symptom burden, worry from scan-to-scan regarding response to cancer treatments, diagnosis-related stigma and social isolation, end-of-life concerns, and misconceptions regarding metastatic breast cancer. Conclusions: Findings suggest that women with metastatic breast cancer have unique supportive care needs compared to women with early-stage breast cancer that are specific to living with a life-limiting prognosis and are not typically captured in existing self-report measures of supportive care needs. Results also highlight the importance of addressing psychosocial concerns and breast cancer-related symptoms. Women with metastatic breast cancer may benefit from early access to evidence-based interventions and resources that specifically address their supportive care needs and optimize quality of life and wellbeing.

Dynamic Glycoprotein Hyposialylation Promotes Chemotherapy Evasion and Metastatic Seeding of Quiescent Circulating Tumor Cell Clusters in Breast Cancer.

Most circulating tumor cells (CTC) are detected as single cells, whereas a small proportion of CTCs in multicellular clusters with stemness properties possess 20- to 100-times higher metastatic propensity than the single cells. Here we report that CTC dynamics in both singles and clusters in response to therapies predict overall survival for breast cancer. Chemotherapy-evasive CTC clusters are relatively quiescent with a specific loss of ST6GAL1-catalyzed α2,6-sialylation in glycoproteins. Dynamic hyposialylation in CTCs or deficiency of ST6GAL1 promotes cluster formation for metastatic seeding and enables cellular quiescence to evade paclitaxel treatment in breast cancer. Glycoproteomic analysis reveals newly identified protein substrates of ST6GAL1, such as adhesion or stemness markers PODXL, ICAM1, ECE1, ALCAM1, CD97, and CD44, contributing to CTC clustering (aggregation) and metastatic seeding. As a proof of concept, neutralizing antibodies against one newly identified contributor, PODXL, inhibit CTC cluster formation and lung metastasis associated with paclitaxel treatment for triple-negative breast cancer. SIGNIFICANCE: This study discovers that dynamic loss of terminal sialylation in glycoproteins of CTC clusters contributes to the fate of cellular dormancy, advantageous evasion to chemotherapy, and enhanced metastatic seeding. It identifies PODXL as a glycoprotein substrate of ST6GAL1 and a candidate target to counter chemoevasion-associated metastasis of quiescent tumor cells. This article is featured in Selected Articles from This Issue, p. 1949.

NCCN Guidelines® Insights: Breast Cancer, Version 4.2023.

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Breast Cancer address all aspects of management for breast cancer. The treatment landscape of metastatic breast cancer is evolving constantly. The therapeutic strategy takes into consideration tumor biology, biomarkers, and other clinical factors. Due to the growing number of treatment options, if one option fails, there is usually another line of therapy available, providing meaningful improvements in survival. This NCCN Guidelines Insights report focuses on recent updates specific to systemic therapy recommendations for patients with stage IV (M1) disease.

Safety and Efficacy of Tucatinib, Letrozole, and Palbociclib in Patients with Previously Treated HR+/HER2+ Breast Cancer.

PURPOSE: To overcome resistance to antihormonal and HER2-targeted agents mediated by cyclin D1-CDK4/6 complex, we proposed an oral combination of the HER2 inhibitor tucatinib, aromatase inhibitor letrozole, and CDK4/6 inhibitor palbociclib (TLP combination) for treatment of HR+/HER2+ metastatic breast cancer (MBC). PATIENTS AND METHODS: Phase Ib/II TLP trial (NCT03054363) enrolled patients with HR+/HER2+ MBC treated with ≥2 HER2-targeted agents. The phase Ib primary endpoint was safety of the regimen evaluated by NCI CTCAE version 4.3. The phase II primary endpoint was efficacy by median progression-free survival (mPFS). RESULTS: Forty-two women ages 22 to 81 years were enrolled. Patients received a median of two lines of therapy in the metastatic setting, 71.4% had visceral disease, 35.7% had CNS disease. The most common treatment-emergent adverse events (AE) of grade ≥3 were neutropenia (64.3%), leukopenia (23.8%), diarrhea (19.0%), and fatigue (14.3%). Tucatinib increased AUC10-19 hours of palbociclib 1.7-fold, requiring palbociclib dose reduction from 125 to 75 mg daily. In 40 response-evaluable patients, mPFS was 8.4 months, with similar mPFS in non-CNS and CNS cohorts (10.0 months vs. 8.2 months; P = 0.9). Overall response rate was 44.5%, median duration of response was 13.9 months, and clinical benefit rate was 70.4%; 60% of patients were on treatment for ≥6 months, 25% for ≥1 year, and 10% for ≥2 years. In the CNS cohort, 26.6% of patients remained on study for ≥1 year. CONCLUSIONS: TLP combination was safe and tolerable. AEs were expected and manageable with supportive therapy and dose reductions. TLP showed excellent efficacy for an all-oral chemotherapy-free regimen warranting further testing. See related commentary by Huppert and Rugo, p. 4993.

Randomized Phase II Trial of Endocrine Therapy With or Without Ribociclib After Progression on Cyclin-Dependent Kinase 4/6 Inhibition in Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer: MAINTAIN Trial.

PURPOSE: Cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) improves progression-free survival (PFS) and overall survival (OS) in hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC). Although preclinical and clinical data demonstrate a benefit in changing ET and continuing a CDK4/6i at progression, no randomized prospective trials have evaluated this approach. METHODS: In this investigator-initiated, phase II, double-blind placebo-controlled trial in patients with HR+/HER2- MBC whose cancer progressed during ET and CDK4/6i, participants switched ET (fulvestrant or exemestane) from ET used pre-random assignment and randomly assigned 1:1 to the CDK4/6i ribociclib versus placebo. PFS was the primary end point, defined as time from random assignment to disease progression or death. Assuming a median PFS of 3.8 months with placebo, we had 80% power to detect a hazard ratio (HR) of 0.58 (corresponding to a median PFS of at least 6.5 months with ribociclib) with 120 patients randomly assigned using a one-sided log-rank test and significance level set at 2.5%. RESULTS: Of the 119 randomly assigned participants, 103 (86.5%) previously received palbociclib and 14 participants received ribociclib (11.7%). There was a statistically significant PFS improvement for patients randomly assigned to switched ET plus ribociclib (median, 5.29 months; 95% CI, 3.02 to 8.12 months) versus switched ET plus placebo (median, 2.76 months; 95% CI, 2.66 to 3.25 months) HR, 0.57 (95% CI, 0.39 to 0.85); P = .006. At 6 and 12 months, the PFS rate was 41.2% and 24.6% with ribociclib, respectively, compared with 23.9% and 7.4% with placebo. CONCLUSION: In this randomized trial, there was a significant PFS benefit for patients with HR+/HER2- MBC who switched ET and received ribociclib compared with placebo after previous CDK4/6i and different ET.

Margetuximab in HER2-positive metastatic breast cancer.

Several anti-HER2 agents are approved for third-line treatment and beyond (after first-line and second-line); however, no specific treatment strategy is recommended for third-line and beyond. Although these agents improve disease outcomes, HER2-positive metastatic breast cancer remains incurable and there is an unmet need for effective therapies in the later line setting. This review focuses on the development of margetuximab-cmkb, a novel, Fc-engineered, anti-HER2 monoclonal antibody, and its role in the systemic treatment of adult patients with metastatic HER2-positive breast cancer who have received two or more prior anti-HER2 regimens, at least one of which was for metastatic disease.

In about 20% of patients with breast cancer, their tumor cells make too many copies of a protein called HER2. We call them HER2-positive breast cancer cells. HER2 is a protein that signals to breast cancer cells to make them grow. Certain drugs, known as antibodies, are able to bind to the HER2 proteins on the surface of the tumor cells. This stops their signaling and slows down the growth of the tumor cells. These antibodies are called anti-HER2 antibodies. In addition to its 'head' region binding to HER2, the 'tail' region of the anti-HER2 antibody can bind to certain other proteins (receptors) found on the surface of immune cells. When the anti-HER2 antibodies bind to the receptors on immune cells, this starts an anticancer immune response against the HER2-positive breast cancer cells and kills them. This review explains how anti-HER2 antibodies may block and destroy HER2-positive breast cancer cells. In particular, we focus on the beneficial and adverse effects of margetuximab, an anti-HER2 antibody. The tail region of margetuximab has been changed to boost the immune responses against HER2-positive cancer cells. Margetuximab is approved in the USA for patients with HER2-positive metastatic breast cancer after they have already received two or more anti-HER2 therapies. The decision to approve this was based on the pivotal clinical trial SOPHIA.

Risk of Recurrence in Patients With HER2+ Early-Stage Breast Cancer: Literature Analysis of Patient and Disease Characteristics.

Human epidermal growth factor receptor 2 (HER2) overexpression occurs in 15% to 20% of patients with early-stage breast cancers (EBCs). Without HER2-targeted therapy, 30% to 50% of patients relapse within 10 years, many developing incurable metastatic disease. This literature review was designed to identify and validate patient- and disease-related factors associated with recurrence in patients with HER2+ EBC. Peer-reviewed primary research articles and congress abstracts were identified by searching MEDLINE. Articles published in English from 2019 to 2022 were included to identify contemporary treatment options. Results were analyzed for the relationship between risk factors and surrogates of HER2+ EBC recurrence to determine how identified risk factors affected HER2+ EBC recurrence. Sixty-one articles and 65 abstracts that assessed age at diagnosis, body mass index (BMI), tumor size at diagnosis, hormone receptor (HR) status, pathologic complete response (pCR) status, and biomarkers were analyzed. We confirmed the results of previously published reviews reporting residual cancer burden >0, non-pCR, and fewer tumor-infiltrating lymphocytes (TILs) as risk factors of recurrence. HR status remained an important risk factor for recurrence, with HER2+/HR+ disease more likely to recur. Two or more positive lymph nodes, higher BMI, larger primary tumor size, and low Ki67 were more commonly associated with HER2+ EBC recurrence. The identification of patient and disease factors frequently associated with HER2+ EBC recurrence in the literature provides insight into potential recurrence risk factors. Further investigation into the risk factors identified in this review could lead to improved treatments for patients at high risk for HER2+ EBC recurrence.

Cyclin-Dependent Kinase 4/6 Inhibitors Beyond Progression in Metastatic Breast Cancer: A Retrospective Real-World Biomarker Analysis.

PURPOSE: As the continuation beyond progression (BP) of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) is becoming increasingly attractive for the treatment of patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC), the definition of resistance factors is crucial. The aim of the study was to investigate the impact of CDK 4/6i BP and to explore potential genomic stratification factors. MATERIALS AND METHODS: We retrospectively analyzed a multi-institutional cohort of patients with HR-positive HER2-negative MBC characterized for circulating tumor DNA through next-generation sequencing before treatment start. Differences across subgroups were analyzed by chi-square test, and survival was tested by univariable and multivariable Cox regression. Further correction was applied by propensity score matching. RESULTS: Among the 214 patients previously exposed to CDK4/6i, 172 were treated with non-CDK4/6i-based treatment (non-CDK) and 42 with CDK4/6i BP. Multivariable analysis showed a significant impact of CDK4/6i BP, TP53 single-nucleotide variants, liver involvement, and treatment line on both progression-free survival (PFS) and overall survival (OS). Propensity score matching confirmed the prognostic role of CDK4/6i BP both for PFS and OS. The favorable impact of CDK4/6i BP was consistent across all subgroups, and a differential benefit was suggested for ESR1-mutated patients. ESR1 and RB1 mutations were more represented in the CDK4/6i BP subgroup with respect to CDK4/6i upfront. CONCLUSION: The study highlighted a significant prognostic impact of the CDK4/6i BP strategy with a potential added benefit in patients with ESR1 mutations suggesting the need for an extensive biomarker characterization.

Computational ranking-assisted identification of Plexin-B2 in homotypic and heterotypic clustering of circulating tumor cells in breast cancer metastasis.

Metastasis is the cause of over 90% of all deaths associated with breast cancer, yet the strategies to predict cancer spreading based on primary tumor profiles and therefore prevent metastasis are egregiously limited. As rare precursor cells to metastasis, circulating tumor cells (CTCs) in multicellular clusters in the blood are 20-50 times more likely to produce viable metastasis than single CTCs. However, the molecular mechanisms underlying various CTC clusters, such as homotypic tumor cell clusters and heterotypic tumor-immune cell clusters, are yet to be fully elucidated. Combining machine learning-assisted computational ranking with experimental demonstration to assess cell adhesion candidates, we identified a transmembrane protein Plexin- B2 (PB2) as a new therapeutic target that drives the formation of both homotypic and heterotypic CTC clusters. High PB2 expression in human primary tumors predicts an unfavorable distant metastasis-free survival and is enriched in CTC clusters compared to single CTCs in advanced breast cancers. Loss of PB2 reduces formation of homotypic tumor cell clusters as well as heterotypic tumor-myeloid cell clusters in triple-negative breast cancer. Interactions between PB2 and its ligand Sema4C on tumor cells promote homotypic cluster formation, and PB2 binding with Sema4A on myeloid cells (monocytes) drives heterotypic CTC cluster formation, suggesting that metastasizing tumor cells hijack the PB2/Sema family axis to promote lung metastasis in breast cancer. Additionally, using a global proteomic analysis, we identified novel downstream effectors of the PB2 pathway associated with cancer stemness, cell cycling, and tumor cell clustering in breast cancer. Thus, PB2 is a novel therapeutic target for preventing new metastasis.