Cyclin-dependent kinase 2 (CDK2) inhibitors and others novel CDK inhibitors (CDKi) in breast cancer: clinical trials, current impact, and future directions.

Aberrant cyclin-dependent kinase 2 (CDK2) activation has been identified as a main resistance mechanism to CDK4/6 inhibition in hormone-receptor positive (HR+) breast cancer. Additionally, consistent preclinical evidence states its crucial role in MYC and CCNE1 overexpressed cancer survival, such as triple-negative breast cancers (TNBC), thus representing an appealing and relatively unexplored target treatment opportunity. Despite emerging initial results of novel CDK2 inhibitors (CDK2i) activity, a comprehensive outcomes collection is currently absent from the scientific literature. We aim to provide an overview of ongoing clinical trials involving CDK2i in the context of metastatic breast cancer (mBC), either as monotherapy or in combination with other agents. The review extends beyond CDK2i to encompass novel emerging CDK4 inhibitors, combined CDK2/4/6 inhibitors, and the well-known pan-CDK inhibitors including those specifically directed at CDK2. Delving into the results, we critically appraise the observed clinical efficacy and offer valuable insights into their potential impact and future applications.

Relationship of Ki-67 index in biopsies of metastatic breast cancer tissue and circulating tumor cells (CTCs) at the time of biopsy collection.

BACKGROUND: The proliferation marker Ki-67 is a major pathological feature for the description of the state of disease in breast cancer. It helps to define the molecular subtype and to stratify between therapy regimens in early breast cancer and helps to assess the therapy response. Circulating tumor cells (CTCs) are a negative prognostic biomarker for progression free (PFS) and overall survival (OS) in patients with metastatic breast cancer. Therefore, the CTC count is often described as surrogate for the tumor burden. Both, decrease of Ki-67 and CTC count are considered as evidence for therapy response. The presented work analyzed the correlation between the Ki-67 indices of metastatic tissue biopsies and CTC counts in biopsy time-adjacent peripheral blood samples. PATIENTS AND METHODS: Blood samples from 70 metastatic breast cancer patients were obtained before the start of a new line of systemic therapy. CTCs were enumerated using CellSearch® (Menarini Silicon Biosystems, Bologna, Italy) whereas intact CTCs (iCTCs) and non-intact or apoptotic CTCs (aCTCs) were distinguished using morphologic criteria. The proportion of cells expressing Ki-67 was evaluated using immunohistochemistry on biopsies of metastases obtained concurrently with CTC sampling before the start of a new line of systemic therapy. RESULTS: 65.7% of patients had a Ki-67 index of > 25%. 28.6% of patients had ≥ 5, 47.1% ≥ 1 iCTCs. 37.1% had ≥ 5, 51.4% ≥ 1 aCTCs. No correlation was shown between Ki-67 index and iCTC and aCTC count (r = 0.05 resp. r = 0.05, Spearman's correlation index). High CTC-counts did not coincide with high Ki-67 index. High Ki-67, ≥ 5 iCTCs and aCTCs are associated with poor progression free (PFS) and overall survival (OS). CONCLUSION: CTCs and Ki-67 are independent prognostic markers in metastatic breast cancer. High Ki-67 in metastatic tumor tissue is not correlated to high iCTC or aCTC counts in peripheral blood.

Comparing pyrotinib with trastuzumab and pertuzumab with trastuzumab for HER2-positive metastatic breast cancer: a retrospective, multicenter analysis.

Objective: Pyrotinib and pertuzumab are effective treatment options for HER2-positive metastatic breast cancer (HER2+ MBC). Our study was to directly compare the efficacy and safety of pyrotinib plus trastuzumab (PyroH) and pertuzumab plus trastuzumab (HP) in patients with HER2+ MBC. Methods: We conducted a retrospective examination of HER2+ MBC patients who received PyroH plus chemotherapy or HP plus chemotherapy between 2017 and 2022 at five institutions in China. Our primary endpoint was progression-free survival (PFS). Results: This study involved 333 patients, among which 161 received PyroH and 172 received HP. The utilization of PyroH as a first-line therapy for MBC was more prevalent among older patients, those with a shorter duration of disease-free interval, or those who had previously been treated with trastuzumab. Although in the first-line advanced treatment HP cohort showed numerically longer PFS (median PFS: 14.46 vs. 22.90 months, p=0.057), in the second-line or later treatments, there was no significant difference in PFS between the PyroH and HP groups (median PFS: 8.67 vs. 7.92 months, p=0.286). Despite HP showing a longer PFS in the overall cohort (median PFS: 9.30 vs. 13.01 months, p=0.005), it did not serve as an independent predictor of PFS in the multivariate analysis (HR 1.134, 95% CI 0.710-1.811, p=0.598). Without taxane, PyroH demonstrated a longer PFS than HP (median PFS: 10.12 vs. 8.15 months, p=0.017). PyroH group displayed a numerically longer median PFS in patients with brain metastases compared to the HP group, though not statistically significant (median PFS: 9.03 vs. 8.15 months, p=0.976). PyroH had higher incidence of grade 3/4 diarrhea (34.3% vs. 3.0%) but similar overall adverse events. Conclusion: In conclusion, PyroH is comparable in second-line or later treatment and during brain metastasis, even having superior efficacy without taxane in real-world setting. Toxicities were tolerable in both groups. (ClinicalTrials.gov: NCT05572645).

Anti-HER2 Drugs for the Treatment of Advanced HER2 Positive Breast Cancer.

OPINION STATEMENT: Approximately 15-20% of breast cancers (BC) demonstrate HER2 overexpression/gene amplification. Historically, before the era of HER2-directed therapies, this subtype was associated with poor prognosis. Anti-HER2 agents dramatically changed the natural course of disease and significantly prolonged patients' survival. In recent years, a number of new anti-HER2 therapies have been developed, and their approvals offer new therapeutic options for patients with advanced HER2-positive breast cancer. At present, HER2 pathway blocking drugs used in the treatment of metastatic breast cancer worldwide include trastuzumab and pertuzumab in the first-line treatment; trastuzumab deruxtecan and trastuzumab emtansine in the second line; and tucatinib, neratinib, lapatinib, and margetuximab in further lines of treatment of advanced HER2 positive breast cancer. Additionally, there are many clinical trials underway evaluating drugs blocking the HER2 pathway in advanced disease setting. This article presents new treatment options, discussing the most important findings from clinical trials and real-world reports, clinical benefits and risks of treatment, as well as efficacy of re-treatment with trastuzumab in metastatic breast cancer. New data challenge the current standards, and a number of questions arise regarding the optimal sequence of anti-HER2 targeted therapies, the optimal combination, including endocrine agents in luminal HER2 positive tumors and treatment of special patient population such as patients with brain metastases (BM).

Phase II study of apatinib plus exemestane in estrogen receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer.

PURPOSE: Apatinib is a tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor (VEGFR)-2. This study was conducted to assess the efficacy and safety of apatinib combined with exemestane in patients with estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC). METHODS: This single-center, single-arm phase II study enrolled patients with ER+/HER2- MBC progressed on previous letrozole or anastrozole. Stratified analysis was performed according to the number of chemotherapy regimens for metastatic disease. The primary endpoint was progression free survival (PFS). Secondary endpoints included objective response rate (ORR), disease control rate (DCR), clinical benefit rate (CBR), overall survival (OS) and toxicity. Patients received apatinib at a starting dose of 500 mg/d and exemestane 25 mg/d on days 1-28 of each 4-week cycle. RESULTS: Thirty patients were enrolled with median four prior anticancer therapies. Eighty percent of patients received chemotherapy for metastatic disease. The median PFS (mPFS) and OS were 5.6 (95%CI: 4.3-6.9) months and 15.7 (95% CI: 9.7-21.7) months, respectively. The ORR, DCR, and CBR were 21.4%, 71.4%, and 46.4%, respectively. Patients with 0-1 line chemotherapy for MBC showed a slightly longer mPFS compared to those with ≥2 lines chemotherapy (mPFS: 6.4 months vs 4.8 months, P = .090). Most of the AEs were grade 1/2. One patient (3.3%) who suffered bone marrow metastases experienced grade 4 thrombocytopenia, and 14 experienced grade 3 AEs. Fifty percent of patients were given reduced dose for apatinib. CONCLUSIONS: Apatinib plus exemestane exhibited objective efficacy in patients with ER+/HER2- MBC who have failed multiple lines of treatment. The AEs of apatinib required close monitoring and most of patients were well tolerated.

Sequencing systemic therapy in hormone-receptor positive metastatic breast cancer: a modern paradigm.

Deaths from metastatic breast cancer continue to be a leading cause of global cancer mortality among women. The pace of advances in the treatment of hormone-receptor positive metastatic breast cancer (HR+ MBC) has introduced nuance and complexity in choosing between available agents as patients and physicians explore options across lines of therapy. In this review, we explore the modern paradigm of treatment options and the sequential approach to HR+ MBC, as well as treatment options on the horizon, and the particular impact on survival outcomes and the associated adverse effects of those treatments. We discuss the diagnostic approach, first- and second-line management, as well as management of later-line endocrine-refractory HR+ MBC. Treatments discussed include cyclin-dependent kinase 4/6 inhibitors, antibody drug conjugates, and targeted therapies against phosphatidylinositol-4,5-bisphosphate-3-kinase catalytic subunit alpha (PIK3CA), estrogen receptor 1 (ESR1), and poly[ADP-ribose] polymerase (PARP), among others. Building from the initial diagnostic approach, we describe how to pragmatically layer options by appropriate line of therapy and personalized drivers of disease to aid in treatment decision making step-by-step. Combining sequential treatment options, evolving treatment options, and advanced genetic and genomic testing along with shared decision making between patients and physicians, this review aims to outline the key factors that ultimately drive the decisions for treatment in hormone-positive metastatic breast cancer.

An integrated investigation of structural and pathway alteration caused by PIK3CA and TP53 mutations identified in cfDNA of metastatic breast cancer.

In peripheral blood, cell-free DNA (cfDNA) contains circulating tumor DNA (ctDNA), which indicates molecular abnormalities in metastatic breast tumor tissue. The sequencing of cfDNA of Metastatic Breast Cancer (MBC) patients allows assessment of therapy response and noninvasive treatment. In the proposed study, clinically significant alterations in PIK3CA and TP53 genes associated with MBC resulting in a missense substitution of His1047Arg and Arg282Trp from an next-generation sequencing-based multi-gene panel were reported in a cfDNA of a patient with MBC. To investigate the impact of the reported mutation, we used molecular docking, molecular dynamics simulation, network analysis, and pathway analysis. Molecular Docking analysis determined the distinct binding pattern revealing H1047R-ATP complex has a higher number of Hydrogen bonds (H-bonds) and binding affinity with a slight difference compared to the PIK3CA-ATP complex. Following, molecular dynamics simulation for 200 ns, of which H1047R-ATP complex resulted in the instability of PIK3CA. Similarly, for TP53 mutant R282W, the zinc-free state (apo) and zinc-bounded (holo) complexes were investigated for conformational change between apo and holo complexes, of which the holo complex mutant R282W was unstable. To validate the conformational change of PIK3CA and TP53, 80% mutation of H1047R in the kinase domain of p110α expressed ubiquitously in PIK3CA protein that alters PI3K pathway, while R282W mutation in DNA binding helix (H2) region of P53 protein inhibits the transcription factor in P53 pathway causing MBC. According to our findings, the extrinsic (hypoxia, oxidative stress, and acidosis); intrinsic factors (MYC amplification) in PIK3CA and TP53 mutations will provide potential insights for developing novel therapeutic methods for MBC therapy.

Pyrotinib combined with trastuzumab and chemotherapy for the treatment of human epidermal growth factor receptor 2-positive metastatic breast cancer: a single-arm exploratory phase II trial.

PURPOSE: A substantial need for effective and safe treatment options is still unmet for patients with heavily pre-treated human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). Herein, we assessed the efficacy and safety of pyrotinib plus trastuzumab and chemotherapy in patients with heavily treated HER2-positive MBC. METHODS: In this single-arm exploratory phase II trial, patients with HER2-positive MBC previously treated with trastuzumab plus lapatinib or pertuzumab, received pyrotinib plus trastuzumab and chemotherapy. The primary end point was progression-free survival (PFS) in the total population (TP). Secondary end points included PFS in the subgroup with brain metastases (Sub-BrM), confirmed objective response rate (ORR), clinical benefit rate (CBR), disease control rate (DCR), exploration of predictive factors of PFS, and safety. RESULTS: Between November 1, 2018, and March 31, 2021, 40 patients were eligible for this study. The median PFS reached 7.5 months (95% confidence interval [CI] 4.7 to 9.9 months) and 9.4 months (95% CI 6.6 to 12.1 months) in the TP and Sub-BrM, respectively. ORR was 50.5% (20/40). CBR was 75.5% (30/40) and DCR reached 97.5% (39/40). Cox univariate and multivariate analyses demonstrated that liver or/and lung metastases was the significant adverse prognostic factor for PFS (p = 0.018; p = 0.026; respectively). The most frequent grade 3 or 4 treatment-related adverse events were diarrhea, neutropenia and leukopenia. No new safety signals were observed. CONCLUSION: Pyrotinib plus trastuzumab and chemotherapy offered a promising option with manageable safety profile for heavily pre-treated HER2-positive MBC, especially for those without liver or/and lung metastases.

Primary results of ELAINA: a randomized, multicenter, open-label, phase III study of the efficacy and safety of trastuzumab emtansine vs. lapatinib plus capecitabine in Chinese patients with HER2-positive locally advanced or metastatic breast cancer who have received prior trastuzumab-based therapy.

Background: The antibody-drug conjugate (ADCs) trastuzumab emtansine (T-DM1) is approved for human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (mBC) previously treated with trastuzumab and a taxane. The phase III ELAINA trial aimed to determine the clinical utility of T-DM1 in Chinese patients. Methods: ELAINA was a randomized, multicenter, open-label bridging study of Chinese patients with HER2-positive locally advanced breast cancer (LABC) or mBC previously treated with trastuzumab and a taxane. Using an interactive voice/internet response system, patients were randomized 3:1 to receive T-DM1 or lapatinib plus capecitabine. Patents were stratified by number of prior therapies in this disease setting and by presence of visceral disease using a permuted block randomization scheme. Patients received treatment until disease progression, unmanageable toxicity, or study termination. After that, data on survival and subsequent cancer therapies were collected at approximately 3-month intervals. The primary endpoint was investigator-assessed progression-free survival (PFS). Secondary endpoints were overall response rate, duration of response, overall survival (OS), safety, patient-reported quality of life, and pharmacokinetics (PKs). Results: ELAINA was fully enrolled with 200 patients randomized to T-DM1 (n=151) or lapatinib plus capecitabine (n=49). Median treatment duration was approximately 6 months in each study arm. Median follow-up time was approximately 9 months for all analyses except for OS. T-DM1 was associated with a 15% reduction in risk of disease progression or death compared with lapatinib plus capecitabine [stratified hazard ratio (HR) =0.85; 95% confidence interval (CI): 0.56-1.29] in the intent-to-treat (ITT) population. The objective response rate (ORR) was similar with T-DM1 (50.4%) and lapatinib plus capecitabine (55.8%); median duration of response was 8.4 months for both treatments. At a median follow-up time of approximately 30 months, OS was similar in each treatment arm. Incidence of grade ≥3 adverse events (AEs) was similar with T-DM1 (54.3%) and lapatinib plus capecitabine (57.1%). Grade ≥3 thrombocytopenia was greater with T-DM1 (40.4%) than with lapatinib plus capecitabine (4.1%); there was no grade ≥3 hemorrhage with either treatment. Conclusions: T-DM1 demonstrated an acceptable benefit-risk profile in Chinese patients with HER2-positive LABC/mBC previously treated with trastuzumab and a taxane. T-DM1 therefore provides a chemotherapy-free option in this setting. Trial Registration: ClinicalTrials.gov identifier: NCT03084939.

Construction and validation of a prognostic nomogram in metastatic breast cancer patients of childbearing age: A study based on the SEER database and a Chinese cohort.

Introduction: Cancer in patients of childbearing age continues to become increasingly common. The purpose of this study was to explore the impact of metastatic breast cancer (MBC) on overall survival (OS) and cancer-specifific survival (CSS) in patients of childbearing age and to construct prognostic nomograms to predict OS and CSS. Methods: Data from MBC patients of childbearing age were obtained from the Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2015, and the patients were randomly assigned into the training and validation cohorts. Univariate and multivariate Cox analyses were used to search for independent prognostic factors impacting OS and CSS, and these data were used to construct nomograms. The concordance index (C-index), area under the curve (AUC), and calibration curves were used to determine the predictive accuracy and discriminative ability of the nomograms. Additional data were obtained from patients at the Yunnan Cancer Hospital to further verify the accuracy of the nomograms. Results: A total of 1,700 MBC patients of childbearing age were identifified from the SEER database, and an additional 92 eligible patients were enrolled at the Yunnan Cancer Hospital. Multivariate Cox analyses identifified 10 prognostic factors for OS and CSS that were used to construct the nomograms. The calibration curve for the probabilities of OS and CSS showed good agreement between nomogram prediction and clinical observations. The C-index of the nomogram for OS was 0.735 (95% CI = 0.725-0.744); the AUC at 3 years was 0.806 and 0.794 at 5 years.The nomogram predicted that the C-index of the CSS was 0.740 (95% CI = 0.730- 0.750); the AUC at 3 years was 0.811 and 0.789 at 5 years. The same results were observed in the validation cohort. Kaplan- Meier curves comparing the low-,medium-, and high-risk groups showed strong prediction results for the prognostic nomogram. Conclusion: We identifified several independent prognostic factors and constructed nomograms to predict the OS and CSS for MBC patients of childbearing age.These prognostic models should be considered in clinical practice to individualize treatments for this group of patients.

Efficacy of Metformin as Adjuvant Therapy in Metastatic Breast Cancer Treatment.

BACKGROUND: Metformin has been reported to have an anti-tumorigenic impact against metastatic breast cancer (MBC) cells through several mechanisms. Its effect can be evaluated by using many variables such as the response rate (RR) as well as the progression-free survival (PFS). MATERIALS AND METHODS: A prospective study was conducted to investigate and estimate the metformin effect on MBC. About 107 subjects were included in the study and were divided into two groups: Group A included non-diabetic MBC patients treated with metformin in conjunction with chemotherapy and group B included those treated with chemotherapy alone. Both PFS and RR were used as a criteria to evaluate the treatment outcome. Associated adverse effects of metformin were also assessed. RESULTS: The average age of the participants in group A and group B was 50 vs. 47.5, respectively. No significant differences were detected between both cohorts concerning RR levels (regression disease (RD) 27.8% vs. 12.5%, stationary disease (SD) 44.4% vs. 41.7%, progression disease (PD) 27.8% vs. 45.8%, respectively, p = 0.074). Moreover, PFS showed no significant difference between both groups (p = 0.753). There was no significant correlation between metformin concentration and their adverse effects on the study participants. CONCLUSION: Metformin as an adjuvant therapy to MBC undergoing chemotherapy showed no significant survival benefit as determined by RR and PFS.

The prognostic value of chemotherapy or endocrine therapy choice according to circulating tumor cell count in HR+HER2- metastatic breast cancer: a retrospective study.

Background: Circulating tumor cell (CTC) count have prognostic role for metastatic breast cancer (MBC). No clear biomarkers can guide selection of chemotherapy (CT) or endocrine therapy (ET) in 1st-line setting of hormone-receptor positive and human epidermal growth factor receptor 2 negative (HR+HER2-) MBC. The present study investigated the prognostic role CT or ET according to the CTC count in HR+HER2- MBC. Methods: We consecutively collected the data of 53 HR+HER2- MBC patients who received 1st-line CT or ET, who had CTC count detected by our peptide-based nanomagnetic CTC isolation system (Pep@MNPs) from January 2014 to December 2015. The clinicopathological characteristics according the CTC count and 1st-line ET vs. CT were compared. Follow-up was conducted every 6 months. The primary endpoint was progression-free survival (PFS) and overall survival (OS). A Cox regression analysis was conducted to determine the prognostic roles of CTC and 1st-line therapy of ET vs. CT for PFS and OS. Results: The median CTC count of the 53 patients was 2 (range, 0-18). The clinicopathological characteristics of the patients in the CTC count <2 group and the CTC count ≥2 group were similar. The patients with a CTC count <2 had a significantly longer PFS than those with a CTC count ≥2 (P=0.005, hazard ratio =4.138, 12.1 vs. 7.1 months). The patients who received CT had a significantly longer PFS than those who received ET (P=0.041, hazard ratio =2.721, 9.9 vs. 7.2 months). In the CTC count ≥2 group, the patients who received CT had a significantly longer PFS than those who received ET (P=0.048, hazard ratio =2.475, 8.7 vs. 6.3 months). In the CTC count <2 group, there was no significant difference in PFS between the CT and ET groups (P=0.071). Additionally, the CTC count had no significant effect on OS (P=0.116, hazard ratio =2.391, 54.2 vs. 34.2 months). Conclusions: The present study showed that CTC count determined by the Pep@MNP system confirmed the prognostic value in the HR+HER2- MBC patients. And it might be helpful in choosing a 1st-line treatment of CT or ET for HR+HER2- MBC patients.

Trastuzumab plus pertuzumab in combination with chemotherapy in metastatic HER2-positive breast cancer: a retrospective single-armed cohort study in China.

Background: There are currently few studies on the efficacy and safety of the dual human epidermal growth factor receptor 2 (HER2)-targeted combination of trastuzumab and pertuzumab in second-line or subsequent therapy of metastatic breast cancer (MBC). This study retrospectively demonstrated the clinical efficacy and side effects of trastuzumab plus pertuzumab in combination with chemotherapy in HER2-positive MBC. Methods: Patients with HER2-positive MBC and treated with trastuzumab plus pertuzumab combined with chemotherapy at our hospital between August 2013 and October 2021 were included. The primary endpoint was progression-free survival (PFS), and the secondary endpoints were disease control rate (DCR), objective response rate (ORR), clinical benefit rate (CBR), and side effects. PFS was calculated using the Kaplan-Meier method and side effects were assessed according to Common Terminology Criteria for Adverse Events 5.0. Results: A total of 55 women were included and the median PFS for trastuzumab plus pertuzumab combined with chemotherapy was 10 months. For the different treatment lines, the median PFS was 19, 8, and 5 months in first, second, and third and beyond, respectively. The DCR, ORR, and CBR were 81.8%, 47.3%, and 56.4%, respectively. The median PFS of patients with primary trastuzumab resistance was significantly shorter than trastuzumab-sensitive patients (5 vs. 12 months, P=0.011). The most common adverse reactions were neutropenia (40.0%), leukopenia (34.5%), thrombocytopenia (32.7%), and diarrhea (29.1%). The most common grade 3-4 adverse reactions were leukopenia (12.7%), thrombocytopenia (9.1%), and diarrhea (9.1%). Conclusions: For patients with HER2-positive MBC, treatment with trastuzumab plus pertuzumab combined with chemotherapy appeared efficacious and safe.

The prognosis and risk factors for capecitabine maintenance treatment in metastatic breast cancer: a retrospective comparative cohort study.

Background: Maintenance treatment following efficient chemotherapy can improve the treatment outcomes of patients with metastatic breast cancer (MBC). However, there are no studies for identifying the prognostic factors for patients who could benefit from capecitabine maintenance. Therefore, this study aimed to investigate the prognosis and risk factors of capecitabine maintenance therapy and analysed the circulating tumour DNA (ctDNA) markers that may be related to the treatment response. Methods: This study recruited 482 consecutive patients with MBC who achieved clinical benefit from capecitabine-based chemotherapy from 2011 to 2019. A total of 256 patients received subsequent capecitabine maintenance therapy. The baseline clinical factors included age at diagnosis, menopause, neoadjuvant therapy, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) status and subtypes, prior treatment lines, and prior capecitabine-based treatment response. Treatment outcome (progression-free survival, PFS) was assessed by imaging tools according to RSCIST 1.1 standard during the first two treatment cycles and every 3 weeks thereafter. Univariate and multivariate Cox proportional hazards models were used to analysethe association between capecitabine maintenance treatment and prognosis. Results: The median PFS of patients receiving capecitabine maintenance treatment was 21.7 months [95% confidence interval (CI): 15.1-36.3 months]. Capecitabine maintenance showed similar effects as endocrine maintenance or anti-HER2 therapy in hormone receptor (HR)-positive or HER2-positive patients, with adjusted HR of 1.17 (95% CI: 0.81-1.71, P=0.40). In patients with triple-negative breast cancer (TNBC), capecitabine maintenance showed a marginal benefit in PFS. Compared to late-line (≥2) capecitabine maintenance, first-line capecitabine maintenance significantly prolonged median PFS. Compared to other HR/HER2 subtypes, patients with HR-positive and HER2-positive subtypes significantly benefited from capecitabine maintenance treatment. Analysis of ctDNA revealed that among patients receiving capecitabine maintenance, TP53 aberrations were concentrated in patients with short PFS. Conclusions: Capecitabine maintenance treatment is associated with longer PFS in patients with MBC, especially those receiving first-line capecitabine-based chemotherapy and those with HR positivity/HER2 positivity. TP53 aberrations may be responsible for the poor response to capecitabine maintenance treatment.

Clinical relevance of the combined analysis of circulating tumor cells and anti-tumor T-cell immunity in metastatic breast cancer patients.

Background: Metastatic breast cancer (mBC) is a heterogeneous disease with varying responses to treatments and clinical outcomes, still requiring the identification of reliable predictive biomarkers. In this context, liquid biopsy has emerged as a powerful tool to assess in real-time the evolving landscape of cancer, which is both orchestrated by the metastatic process and immune-surveillance mechanisms. Thus, we investigated circulating tumor cells (CTCs) coupled with peripheral T-cell immunity to uncover their potential clinical relevance in mBC. Methods: A cohort of 20 mBC patients was evaluated, before and one month after starting therapy, through the following liquid biopsy approaches: CTCs enumerated by a metabolism-based assay, T-cell responses against tumor-associated antigens (TAA) characterized by interferon-γ enzyme-linked immunosorbent spot (ELISpot), and the T-cell receptor (TCR) repertoire investigated by a targeted next-generation sequencing technique. TCR repertoire features were characterized by the Morisita's overlap and the Productive Simpson Clonality indexes, and the TCR richness. Differences between groups were calculated by Fisher's, Mann-Whitney or Kruskal-Wallis test, as appropriate. Prognostic data analysis was estimated by Kaplan-Meier method. Results: Stratifying patients for their prognostic level of 6 CTCs before therapy, TAA specific T-cell responses were detected only in patients with a low CTC level. By analyzing the TCR repertoire, the highest TCR clonality was observed in the case of CTCs under the cut-off and a positive ELISpot response (p=0.03). Whereas, at follow-up, patients showing a good clinical response coupled with a low number of CTCs were characterized by the most elevated TCR clonality (p<0.05). The detection of CTCs≥6 in at least one time-point was associated with a lower TCR clonality (p=0.02). Intriguingly, by combining overall survival analysis with TCR repertoire, we highlighted a potential prognostic role of the TCR clonality measured at follow-up (p=0.03). Conclusion: These data, whether validated in a larger cohort of patients, suggest that the combined analysis of CTCs and circulating anti-tumor T-cell immunity could represent a valuable immune-oncological biomarker for the liquid biopsy field. The clinical application of this promising tool could improve the management of mBC patients, especially in the setting of immunotherapy, a rising approach for BC treatment requiring reliable predictive biomarkers.

PIK3CA mutation status, progression and survival in advanced HR + /HER2- breast cancer: a meta-analysis of published clinical trials.

BACKGROUND: Approximately 40% of hormone receptor positive/human epidermal receptor 2 negative (HR + /HER2-) metastatic breast cancer (mBC) patients harbor phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutations. However, associations between PIK3CA mutation status and clinical outcomes among patients with HR + /HER2- mBC have been heterogeneous across clinical trials. This meta-analysis was conducted to survey recently available trial data to assess the prognostic effects of PIK3CA among patients with HR + /HER2- mBC.  METHODS: Randomized clinical trials reporting progression-free survival (PFS) or overall survival (OS) stratified by PIK3CA status in HR + /HER2- mBC were identified via systematic literature review. Trial arms receiving phosphatidylinositol 3-kinase (PI3K)-targeted therapies were excluded. Meta-regression analysis was used to estimate the association between PIK3CA status and PFS and OS among included studies. RESULTS: The analyzed data included 3,219 patients from 33 study arms across 11 trials (PIK3CA mutated: 1,386, wild type: 1,833). PIK3CA mutation was associated with shorter median PFS (difference [95% CI] (months): -1.8 [-3.4, -0.1], I2 = 35%) and shorter median OS (-8.4 [-13.4, -3.5], I2 = 58%, N = 1,545). Findings were similar for PFS rates at 6 months (odds ratio [95% CI]: 0.74 [0.59, 0.94], I2 = 42%, N = 3,160) and 12 months (0.76 [0.59, 0.99], I2 = 42%, N = 2,468) and directionally consistent but not statistically significant at 18 months (N = 1,726). CONCLUSIONS: Pooling evidence across multiple studies, PIK3CA mutation was associated with shorter PFS and OS. These findings suggest a negative prognostic value of PIK3CA mutations in patients with HR + /HER2- mBC.

Chemotherapy modulates CDK4/6 inhibitors resistance in metastatic breast cancer by Rb1 mutations: a case report and literature review.

Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) plays a major role in breast cancer therapeutics acting through preventing the cell cycle from G1 to the S phase. Recently, Endocrine therapy combined with CDK4/6i represented a major milestone in hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer treatment. However, the resistance of CDK4/6i is clinically common, and the mechanism remains to be clarified. Retinoblastoma (Rb) is a negative regulator of cell cycle. It inhibits cell cycle transition by binding to E2F transcription factors, and prevent cells division in this way. Rb is regulated by phosphorylation. The CDK4/6i have been shown to affect cancer by blocking phosphorylation of Rb. In addition, decreasing estrogen signal has been confirmed to reduce cyclin D-CDK4/6 complexing. Currently, FCN-437c is a new CDK4/6i that is in clinical trials. Here, we present the case of an HR-positive and HER2-negative patient whose disease continued to rapidly progress after receiving FCN-437c. To determine why, we did a series of examinations and found that her Rb1 had mutated after using CDK4/6i. To our surprise, the Rb1 mutations recovered after treatment with eribulin, and CDK4/6i was shown to exert a renewed effect. In this way, a hypothesis was made that eribulin may influence the pathway of cyclin D- CDK4/6- Rb- E2F by effecting in Rb. This case provides new insights into strategies for CDK4/6i therapy resistance options and shows the significance of next-generation sequencing in the clinic.

Efficacy and safety of margetuximab plus chemotherapy vs. trastuzumab plus chemotherapy in Chinese patients with pretreated HER2-positive advanced metastatic breast cancer: results from a randomized, open-label, multicenter, phase II bridging study.

Background: Trastuzumab is the recommended first-line treatment for human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) patients in China, but therapeutic resistance to trastuzumab and other early-line treatments is common and late-line treatment options are limited. Derived from the same murine precursor antibody, margetuximab has enhanced anti-tumor activity compared with trastuzumab and may be an effective late-line treatment. However, data regarding the use of margetuximab in pre-treated Chinese patients are scarce. This study aimed to evaluate the efficacy and safety of margetuximab plus chemotherapy vs. trastuzumab plus chemotherapy in Chinese patients, and to determine whether the results are consistent with the clinical benefit of margetuximab observed in the pivotal global phase III study. Methods: In this randomized, open-label, multicenter, phase II bridging study, eligible Chinese patients pretreated with ≥2 lines of anti-HER2 therapies were randomized 1:1 by stratified block randomization to margetuximab (15 mg/kg over at least 120 minutes) or trastuzumab (6 mg/kg over at least 30 minutes), each administered intravenously once every 21-day cycle and plus chemotherapy. Disease assessment was conducted once every two treatment cycles (6 weeks ± 7 days). The primary endpoint was progression-free survival (PFS) by blinded independent central review (BICR). Secondary endpoints included overall survival (OS), investigator-assessed PFS, objective response rate (ORR), duration of response (DoR), clinical benefit rate (CBR), and the incidence and severity of treatment-emergent adverse events (TEAEs). Results: Between February 4, 2020 and February 23, 2021, 123 patients were randomized to the margetuximab (n=62) and trastuzumab (n=61) arms. Among them, 15 and 7 patients, respectively, were still on study treatment as of data cut-off (September 3, 2021). Overall, 99.2% were female, median age was 53 years old. All patients were pretreated with trastuzumab, and 83.7% and 25.2%, respectively, were pretreated with tyrosine kinase inhibitors (TKIs) and pertuzumab. Baseline characteristics were numerically balanced between arms. BICR-assessed median PFS (mPFS) was 5.5 months in the margetuximab arm and 4.1 months in the trastuzumab arm, with a hazard ratio (HR) of 0.69 [95% confidence interval (CI): 0.43-1.12], which met the consistency criterion (HR <0.88) for bridging success. Median investigator-assessed PFS was 5.5 months in the margetuximab arm and 4.0 months in the trastuzumab arm (HR =0.63; 95% CI: 0.41-0.96). Median OS (mOS) was not yet reached. Both ORR and CBR were greater in the margetuximab arm (25.5% vs. 12.5%; 32.7% vs. 14.3%). Safety results were numerically comparable between the two arms. Anti-HER2 treatment-related infusion-related reactions (IRRs) were more common in the margetuximab arm than in the trastuzumab arm (12.9% vs. 1.7%). All IRRs could be resolved. Conclusions: Margetuximab was effective and well-tolerated in this study, supporting its clinical use in pretreated HER2-positive MBC patients in China. Trial Registration: ClinicalTrials.gov Identifier: NCT04262804.