Treatment Of Metastatic Breast Cancer Research Articles

Real-world use patterns, effectiveness, and tolerability of sacituzumab govitecan for second-line and later-line treatment of metastatic triple-negative breast cancer in the United States

PurposePatients with metastatic triple-negative breast cancer (mTNBC) have poor prognosis and limited treatment options. Sacituzumab govitecan (SG), a Trop-2–directed antibody–drug conjugate, is approved for patients with mTNBC who have received ≥ 2 systemic therapies (≥ 1 in the metastatic setting) based on the ASCENT study (NCT02574455). The current study describes real-world SG use and outcomes in patients with mTNBC in the United States.MethodsThis retrospective, observational study included adult patients with mTNBC from the ConcertAI Patient360™ database who received SG in the second line (2L) and later from April 2020 to May 2022. SG use patterns, effectiveness, and tolerability are described.ResultsThis analysis included 230 patients (median age 60 years, 26% Black, 17% with ECOG performance status ≥ 2, 66% in community settings; median of 2 prior lines of treatment in the metastatic setting); median follow-up was 7.2 months. Median (95% CI) real-world overall survival was 10.0 (8.3–11.1) months for all patients and 13.9 (9.8-not estimable) months in the 2L subgroup (n = 77). Granulocyte-colony stimulating factor (G-CSF) was administered concomitantly with SG in 134 (58%) patients; 35 (15%) received G-CSF for the first time. Median (IQR) time from SG start to G-CSF use was 8.5 (8.0–29.0) days. Seventeen (7%) patients discontinued SG due to toxicity.ConclusionsUsing a real-world, ethnically diverse population of patients with mTNBC presenting with poor prognosis, these data reinforced the findings from ASCENT. In routine clinical practice, SG is an effective treatment in the 2L setting, consistent with treatment guidelines.

Eribulin in breast cancer: Current insights and therapeutic perspectives.

Eribulin is a non-taxane synthetic analogue approved in many countries as third-line treatment for the treatment of patients with metastatic breast cancer. In addition to its mitotic property, eribulin has non-mitotic properties including but not limited to, its ability to induce phenotypic reversal of epithelial to mesenchymal transition, vascular remodelling, reduction in immunosuppressive tumour microenvironment. Since approval, there has been a surge in studies investigating the application of eribulin as an earlier-line treatment and also in combination with other agents such as immunotherapy and targeted therapy across all breast cancer sub-types, including hormone receptor positive, HER2 positive and triple negative breast cancer, many demonstrating promising activity. This review will focus on the application of eribulin in the treatment of metastatic breast cancer across all subtypes including its role as an earlier-line agent, its toxicity profile, and potential future directions.

Real-world Outcomes of Dual HER2 Blockade Therapy in Metastatic HER2-Positive Breast Cancer: from Induction to Maintenance.

Dual human epidermal growth factor receptor 2 (HER2) blockade with trastuzumab and pertuzumab combined with taxane-based chemotherapy (Cht) has been the standard first-line treatment for HER2-positive metastatic breast cancer (mBC) for years, due to the impressive results of the CLEOPATRA study. Real-world (RW) studies have become critical for assessing treatment effectiveness and safety in real-life circumstances. The aim of this study was to analyze the treatment outcomes of first-line therapy for HER2-positive mBC in RW clinical practice, specifically focusing on the use of maintenance endocrine therapy (ET) in hormone receptor positive (HR-positive) patients. This retrospective analysis included 106 HER2-positive mBC patients treated with trastuzumab and pertuzumab combined with taxane-based Cht from October 2015 to December 2020 at the University Hospital Centre Zagreb. At a median follow-up of 30 months, median progression-free survival (PFS) was 25 months for the total population (95% confidence interval [CI] 16- not analyzed). Patients with de novo mBC had longer median PFS than patients with recurrent disease (not reached vs. 18 months; hazard ratio 1.99; 95% CI 0.69-3.64, p<0.022). Age, hormone receptor positivity, visceral involvement, number of Cht cycles and previous adjuvant trastuzumab did not impact PFS. Most HR-positive patients (N=55, 88.7%) received maintenance ET after induction Cht. This retrospective study provides additional data on patient characteristics, treatment and outcomes of RW HER2-positive mBC patients treated with pertuzumab and trastuzumab as first-line therapy. In our institution, maintenance ET after induction Cht has become standard clinical practice.

Identifying drivers of first-line HR+/HER2- metastatic breast cancer treatment choices.

Aim: Assess factors associated with first-line (1L) treatment for HR+/HER2-metastatic breast cancer.Materials & methods: A cross-sectional survey of 250 US oncologists was conducted. Correlations were calculated between treatment class and demographics, treatment perceptions and other clinical/nonclinical characteristics.Results: Efficacy and safety/tolerability were critical in oncologists' 1L decision-making. CDK4/6i use positively correlated with proportion of Medicare and postmenopausal patients (r=0.54-0.67). Chemotherapy use demonstrated positive correlations with perimenopausal and premenopausal patients and symptom burden (r=0.31-0.42). Aromatase inhibitor (AI) monotherapy correlated positively with anticipated treatment compliance (r=0.42).Conclusion: Efficacy and safety/tolerability were most important to 1L decision-making. Clinical characteristics corresponded with CDK4/6i and chemotherapy use. Anticipated compliance was associated with AI monotherapy use.

Role of microsurgical tumor burden reduction in patients with breast cancer brain metastases considering molecular subtypes: a two-center volumetric survival analysis

BackgroundAdvancements in metastatic breast cancer (BC) treatment have enhanced overall survival (OS), leading to increased rates of brain metastases (BM). This study analyzes the association between microsurgical tumor reduction and OS in patients with BCBM, considering tumor molecular subtypes and perioperative treatment approaches.MethodsRetrospective analysis of surgically treated patients with BCBM from two tertiary brain tumor Swiss centers. The association of extent of resection (EOR), gross-total resection (GTR) achievement, and postoperative residual tumor volume (RV) with OS and intracranial progression-free survival (IC-PFS) was evaluated using Cox proportional hazard model.Results101 patients were included in the final analysis, most patients (38%) exhibited HER2-/HR + BC molecular subtype, followed by HER2 + /HR + (25%), HER2-/HR- (21%), and HER2 + /HR- subtypes (13%). The majority received postoperative systemic treatment (75%) and radiotherapy (84%). Median OS and intracranial PFS were 22 and 8 months, respectively. The mean pre-surgery intracranial tumor volume was 26 cm3, reduced to 3 cm3 post-surgery. EOR, GTR achievement and RV were not significantly associated with OS or IC-PFS, but higher EOR and lower RV correlated with extended OS in patients without extracranial metastases. HER2-positive tumor status was associated with longer OS, extracranial metastases at BM diagnosis and symptomatic lesions with shorter OS and IC-PFS.ConclusionsOur study found that BC molecular subtypes, extracranial disease status, and BM-related symptoms were associated with OS in surgically treated patients with BCBM. Additionally, while extensive resection to minimize residual tumor volume did not significantly affect OS across the entire cohort, it appeared beneficial for patients without extracranial metastases.

Immune checkpoint inhibition for the treatment of metastatic breast cancer with high tumor mutational burden: Real world clinical and genomic correlates of response.

1078 Background: Pembrolizumab has received tumor-agnostic approval for the treatment of unresectable/metastatic solid tumors carrying a tumor mutational burden (TMB) &gt;10 mut/Mb. The registrational KEYNOTE-158 study, however, did not include any patients with metastatic breast cancer (MBC). Here we present a retrospective study of patients with TMB-high MBC treated with immune checkpoint inhibition (ICI) and report real-world efficacy endpoints, including progression free survival as well as clinical and genomic characteristics that may be associated with duration of response. Methods: All patients with MBC treated with an ICI at MSK and with TMB-high tumors (&gt;10 mut/Mb) assessed by tumor-normal targeted sequencing (MSK-IMPACT) were included. Clinicopathological and demographic data were obtained via the MSK Breast Cancer Translational Program. Mutational signatures were determined using the Signature Multivariate Analysis (SigMA) algorithm. Real world progression free survival (PFS) was determined clinically and analyzed using Kaplan-Meier estimates. Univariate and multivariate analyses were performed using Cox-proportional hazards models. Results: Of 688 patients with TMB-high breast cancer at MSKCC, 87 had received ICI-based therapy for estrogen receptor positive (ER+), triple negative breast cancer (TNBC), and HER2+ MBC. Of those, 45 patients were treated with ICI monotherapy (29 ER+, 11 TNBC, 5 HER2), 31 were treated with ICI + chemotherapy (12 ER+, 19 TNBC), and 11 were treated with combinations of ICI and targeted therapy (8 ER+, 1 TNBC, 2 HER2). Median age at time of ICI treatment across all patients was 60. ICI was the median 5th line therapy for all patients (range 1-16). Median PFS of ICI for all patients was 3.17 months (95%CI 2.27-5.5). Multivariable analysis did not show statistically significant differences in PFS based upon treatment regimen (monotherapy vs. chemoIO HR 1.03, 95%CI 0.54-1.96, p= 0.92, monotherapy vs combination IO HR 1.66, 95%CI 0.69-4.02, p=0.26), ER status (ER- vs ER+, HR 1.20, 95%CI 0.63-2.28, p=0.57), or HER2 status (HER2- vs HER2+, HR 1.63, 95%CI 0.51-5.20, p=0.41. However, longer PFS was significantly associated with TMB&gt;30 (HR 0.35, 95%CI 0.13-0.92, p=0.03) and dominant APOBEC signature score (APOBEC- vs APOBEC+, HR 0.49, 95%CI 0.25-0.98, p=0.04). Shorter PFS was significantly associated with later treatment line at the time of ICI exposure (continuous, HR 1.22, 95%CI 1.11-1.36, p=0.0001). Conclusions: In this heavily pretreated real-world cohort, ICI in TMB high MBC shows modest clinical activity. Our analysis suggests that ICI may be more effective in MBC patients that are less heavily pre-treated, have TMB&gt;30, and have a predominantly APOBEC mutational signature. Further translational work is necessary to explore the mechanisms of these findings.

A multicenter real-world study on the efficacy and safety of anlotinib-based treatment for metastatic breast cancer.

e13120 Background: Anlotinib is a multi-targeted small molecule receptor tyrosine kinase (RTK) inhibitor that inhibits angiogenesis. There is only one phase II study on the use of anlotinib in advanced breast cancer (MBC). Therefore, this study aims to analyze its efficacy and safety in the treatment of BC in the real world. It has been approved for the treatment of advanced non-small cell lung cancer and soft tissue sarcoma. There is limited research on the use of anlotinib in advanced breast cancer (MBC). Methods: This study retrospectively analyzed the clinical data of MBC patients who received anlotinib treatment at four domestic centers from January 2021 to December 2023. The primary endpoint was progression-free survival (PFS), and secondary endpoints included overall survival (OS), objective response rate (ORR), disease control rate (DCR), and safety. Kaplan-Meier analysis was used to analyze PFS and OS, and Cox regression model was used to analyze the hazard ratios (HRs) of anlotinib-based treatment on PFS and OS in different subgroups of patients. A p-value &lt;0.05 was considered statistically significant. Results: A total of 153 MBC patients receiving anlotinib-based treatment were included from four centers. The median age was 51 years (range: 22-76), and the median number of prior lines of therapy was 3. The median PFS was 7.7 months (range: 5.2-10.1 months), and the median OS was 28.0 months (range: 21.4-34.9 months). The median ORR and DCR were 19.6% and 60.1%, respectively. The ORR for HR+/HER2- and triple-negative breast cancer patients was 11.6% and 28.8%, respectively, DCR for HR+/HER2- and triple-negative breast cancer (TNBC) patients was 55.8% and 59.6%, respectively. The median PFS was 9.0 months (range: 6.0-11.9 months) for HR+/HER2- patients and 5.3 months (range: 3.5-7.0 months) for TNBC patients, while the median OS was 33.0 months (range: 24.4-41.5 months) and 14.0 months (range: 9.5-18.4 months), respectively. In the subgroup analysis, age &lt;60 years, initial stage IV disease, Ki67≤60%, and treatment with PD-L1 monoclonal antibodies-based regimen were associated with PFS benefit. ECOG &lt;2 and treatment with PD-L1 monoclonal antibodies-based regimen were associated with prolonged OS. Among the 31 patients with brain metastases receiving anlotinib treatment, 11 had active brain metastases and 20 had stable brain metastases. The median PFS was 8.0 months. The intracranial ORR was 12.9%, and the intracranial DCR was 61.3%. No serious adverse events or treatment-related deaths occurred. Grade I/II adverse reactions included hand-foot syndrome (22.2%) and fatigue (19.6%), while grade III/IV adverse reactions included fatigue (6.5%) and decreased neutrophil count (5.2%). Three patients required dose reduction due to intolerable adverse reactions, and nine patients discontinued treatment. Conclusions: Anlotinib demonstrates good antitumor activity and safety in the treatment of MBC. When combined with chemotherapy or immunotherapy, it can improve PFS and OS without significantly increasing toxicity. In particular, it shows promising intracranial ORR and PFS in patients with brain metastases. Clinical trial information: NCT04541420 .

Real world experience of trastuzumab deruxtecan for the treatment of metastatic breast cancer in the UK.

1024 Background: Trastuzumab deruxtecan (TDXd), an antibody drug conjugate, was first approved in the UK for the treatment of human epidermal growth factor receptor 2 positive (HER2+) metastatic breast cancer (mBC) in 2021. We aimed to review the efficacy and tolerability of TDXd in a real-world UK setting. Methods: We collected clinical and demographic data from medical records on HER2+ mBC patients treated with TDXd in the UK from Jan 2021 to Dec 2023 inclusive. This included: radiological response, the frequency of dose reductions and treatment delays, and reasons for discontinuation. Clinical trial patients were excluded. Descriptive statistical techniques were applied. Results: Data was collected from 26 UK cancer centres on 280 patients. The median age at TDXd initiation was 56 years (range 29-85). Median treatment duration was 9 cycles (range 1-40). 239 patients (85%) had visceral disease. 257 and 196 patients (92% and 70%, respectively) had received prior Trastuzumab and Pertuzumab, respectively. 233 patients (83%) had received prior TDM1. The median number of lines of treatment prior to TDXd was 3 (range 1 to 9). 20 patients (7%) were initiated on a reduced dose and 115 further patients (41%) required at least one dose reduction. 151 patients (54%) had at least one dose interruption due to: infection or neutropenia (n=61), other toxicity (n=85), interstitial lung disease (ILD) investigation (n=39), patient request (n=81), other concurrent illness (n=10), and cardiac investigation (n=6). Of these, 55 patients had more than one treatment break. 157 patients (56%) had discontinued TDXd treatment due to: disease progression or death (n=100), drug toxicity (n=39) of which 22 were due to ILD, and patient choice (n=8). 123 patients remained treatment at the time of analysis. The overall response rate of TDXd was 63% overall: stable disease 23%, partial response 56%, complete response 7%. Conclusions: The real-world data set is not directly comparable to either the DB02 or DB03 trials, as it included patients who had received TDXd in both the second line and later line settings. However, the majority (80%) of these patients were treated in the third line and beyond. The rates of drug interruption and reduction were higher in the real-world data set than in DB02, which may impact on efficacy in the real-world setting. Overall response rate is similar between trial data and our real-world data, although the latter was not measured by RECIST. Data collection is ongoing, including an analysis of real-world progression free survival. [Table: see text]

A genetically engineered epothilone analog as a novel oral microtubule inhibitor: A clinical study of utidelone capsule for advanced breast cancer.

e13115 Background: Utidelone, a genetically engineered epothilone analog, is a potential best-in-class novel microtubule stabilizing agent. Utidelone injection was approved for advanced breast cancer in China in 2021. Utidelone is not susceptible to P-glycoprotein, leading to better oral bioavailability and successful development of an oral formulation-Utidelone Capsule (UTD2). As of now, there has been no oral microtubule stabilizing agent approved in China and the United States. UTD2 may benefit patients in various aspects including effectiveness, safety, better compliance, reduced medical cost, and facilitation of combination therapy, especially with other oral anti-cancer drugs. This is the first clinical study in China to investigate the efficacy and safety of UTD2 monotherapy for treatment of advanced breast cancer. Methods: This is an ongoing open-label, multi-center study (NCT05700084) consisting of three parts: dose escalation, bioavailability and food effect, and in combination with capecitabine for treatment of metastatic breast cancer. Here we report the preliminary results from single center for part I with determination of DLT and MTD as the primary objective, and efficacy, PK profile and safety in patients with pretreated metastatic breast cancer as the secondary objectives. Eligible patients are aged 18-70 years with confirmed advanced breast cancer refractory to prior standard therapies, and have an ECOG PS of 0-1, life expectancy ≥12weeks. Patients are treated with UTD2 monotherapy, at starting dose of 50 mg/m2/d-5day for two patients, with planned escalation (3+3) to 75 mg/m2/d-5day and 75 mg/m2/d-7day, then to 85 mg/m2/d-7day or down to 70 mg/m2/d-7day in a 21-day cycle. Results: As of 25th January 2024, 5 advanced breast cancer patients were enrolled, who had received prior treatment in advanced settings. Dose escalation is ongoing, and 75mg/m2/d-7day cohort is under evaluation. Four patients were evaluated for efficacy with an outcome of 2 PR (each for 50 and 75mg/m2/d-5day dose) and 2 SD (75mg/m2/d-5day dose) with treatment durations of 2 to 8 cycles. Most treatment-emergent adverse events (TEAEs) were Grade 1/2, manageable, and included peripheral sensory neuropathy (PN), dizziness and loss of appetite. There were two patients encountered Grade 3 TEAEs including one with PN and one with diarrhea/insomnia, that recovered through dose reduction or supportive treatment. No grade 4/5 adverse events and no treatment discontinuations due to AE were reported. There have been no DLTs and the MTD is not yet reached. Conclusions: These preliminary results suggested promising efficacy with a manageable safety profile of UTD2 in pretreated metastatic breast cancer patients. This study is still actively enrolling; further data will be provided at the time of presentation. Clinical trial information: NCT05700084 .

Real-world experience with CDK4/6 inhibitors in the first-line palliative setting for HR+/HER2- advanced breast cancer.

e13066 Background: CDK4/6 inhibitors paired with aromatase inhibitors (AIs) have redefined the first-line treatment for metastatic breast cancer, as evidenced by several pivotal trials. Although progression-free survival (PFS) has been consistent across these studies, notable differences in overall survival (OS) have been observed. Our study evaluates the real-world efficacy of palbociclib and ribociclib, in combination with AIs, for hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer at our institution. Methods: We retrospectively reviewed charts of adult patients with advanced metastatic breast cancer at a single academic center from January 1, 2015, to December 1, 2022. We extracted relevant clinical data to estimate the median PFS and OS associated with palbociclib and ribociclib. Results: Among 75 patients analyzed, the majority were female (98.7%) and postmenopausal (77.3%). Palbociclib was prescribed to 74.7%, while 52.0% presented with de novo stage IV disease. Those on ribociclib were significantly younger (median age 57.6 vs. 67.5 years; p = 0.013) and more likely premenopausal (42.1% vs. 5.4%; p &lt; 0.001). Median PFS for palbociclib was 20.3 months (95% CI: 14.8-46.0), with an OS of 37.2 months (20.3 months to not reached). Median PFS and OS for ribociclib were not reached. The differences in PFS and OS between the drugs were not statistically significant (PFS log-rank p = 0.1; OS log-rank p = 0.2). Conclusions: Our real-world analysis suggests a non-significant trend towards improved PFS and OS for ribociclib over palbociclib when used with AIs for treating HR+/HER2- advanced breast cancer, potentially influenced by the younger age of patients on ribociclib. Further research with larger cohorts and extended follow-up is warranted to substantiate these observations.

How overall survival is conditioned in the progression to treatment with cyclin inhibitors plus endocrine treatment in metastatic breast cancer with luminal phenotype.

e13079 Background: CDK4/6 inhibitors plus endocrinotherapy (ET) is the standard first-line treatment for metastatic breast cancer with a luminal phenotype. However, the response to this treatment is highly dependent on its previous efficacy. Methods: We analyzed the overall survival in a cohort of 127 patients with metastatic luminal breast cancer in progression after treatment with CDK4/6 inhibitors plus ET. Results: The median age of the group was 67 years (41-96), the interval time between initial diagnosis and first recurrence was 0 in 41 (32%), 1-60 months in 37 (29%) and more than 60 months in 39 (38%). The first line in the metastatic setting was CDK4/6 plus ET in 81 patients (64%), ET in 15 (12%) and 31 (24%) were treated with chemotherapy. The status of HER2 expression was HER2 low in 77% and 43 % had visceral metastases disease. The median progression-free survival for the patients treated with CDK4/6 inhibitors plus ET was 9 months, with a total of deaths of 69 (55%). Overall survival after progression on CDK4/6 plus ET was 38 months (28 – 47) and the most important factor for overall survival was the response time to treatment with CDK4/6 inhibitors plus ET. Conclusions: The most important factor for overall survival is the duration of treatment with CDK4/6 inhibitors plus ET. Patients with a response time of less than 6 months had a median overall survival after progression of 11 months (3 – 19), while the 6- to 12-month group had a median of 39 months (19 – 59) and the group with more than 12 months had the best prognosis with a median overall survival of 53 months (37 – 68). We need to improve the new treatment options for patients who respond for less than 6 months to treatment with CDK4/6 plus ET.

Percutaneous cryoablation of breast cancer metastases: Analysis of long-term single center experience, efficacy and outcomes.

e13105 Background: Percutaneous image-guided cryoablation is a minimally invasive loco-regional treatment modality with wide availability and advantages of minimal sedation, short recovery, and ability to continue concurrent systemic therapy. However, there is a paucity of data about its long-term effects in the treatment of metastatic breast cancer despite evidence suggesting a potential survival advantage with loco-regional therapy for oligo-metastatic disease. Methods: We conducted retrospective analysis of patients who underwent CT-guided percutaneous cryoablation for metastatic breast cancer and had at least 1 follow up post cryoablation. Patient data including demographics, cancer treatment history and outcomes were extracted by chart review after IRB approval. Descriptive analyses of overall survival (OS), progression-free survival (PFS), and time to next-line treatment (TTNL) was performed. Results: The study encompassed 37 metastatic breast cancer patients who underwent cryotherapy between 2004-2021. These ablation procedures targeted various metastatic sites, which included the liver, lung, renal, lymph nodes, subcutaneous nodules, and bone. Their median age at the time of cryoablation was 58 years (range: 34-90). Among them, 46% had triple-negative breast cancer (TNBC), 41% were HR+/HER2-, and 8% were HER2+. Prior to first cryoablation procedure, 59% of patients had received more than one line of systemic therapy, and 73% were actively undergoing systemic treatment. The median size of the metastatic lesions treated with cryoablation was 1.8 cm (range: 0.4-6.5 cm). The most frequent site for cryotherapy was the liver (38%), followed by lymph nodes (30%). For the entire cohort, median PFS, TTNL, and OS were 7.1, 14, and 65.7 months, respectively. Subgroup analysis revealed mPFS of 3.1, 7.4 and 14.2 months for TNBC, Her2+ and HR+/Her2- cohorts respectively. Subgroup analysis for OS was not reported due to the small number of events and premature follow up time. Among the 27 patients who experienced disease progression, the majority (74%) had distant progression, with 22% occurring within the same organ but outside the ablation zone. Local recurrence within the ablation zone was rare, observed in only 4% of cases. Conclusions: Percutaneous image-guided cryoablation of metastatic breast cancer lesions demonstrated durable local response, prolonged PFS, TTNL and OS. Future studies investigating cryoablation as part of a multidisciplinary treatment approach for patients with metastatic breast cancer are worthwhile to confirm disease control rate and improvement in survival.

Efficacy and safety of apatinib combined with nab-paclitaxel for second-line treatment of metastatic triple negative breast cancer (TNBC): An open-label phase II trial.

e13127 Background: Apatinib is an oral, highly potent tyrosine-kinase inhibitor targeting VEGFR2. Preclinical studies have demonstrated that apatinib can enhance the anti-tumor effect of taxanes in TNBC via promoting apoptosis and suppressing migration and invasion of tumor cells. Previous studies have also shown the role of apatinib in combination with chemotherapy for treating TNBC. However, combinational treatment of apatinib and nab-paclitaxel for metastatic TNBC has not been reported. Therefore, the objective of this study was to evaluate the safety and efficacy of apatinib in combination with nab-paclitaxel as a second-line treatment for TNBC. Methods: This is a single-center, single-arm, and open-label prospective study. The patients enrolled in this study had metastatic TNBC, ECOG PS 0-2, at least one measurable lesion, and had previously received one systemic therapy except apatinib and nab-paclitaxel. They were treated with apatinib (250mg, PO, QD) plus nab-paclitaxel (125mg/m2, IV, day 1, 8 and 15) every 3 weeks as second-line treatment until disease progression, unacceptable toxicity, or consent withdrawal. The study utilized RECIST v1.1 to assess efficacy and NCI-CTCAE 5.0 to report adverse events. The study's primary endpoints were tolerability and progressive free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR) and disease control rate (DCR). Results: Twenty patients were enrolled by the cut-off date of December 1st, 2023. The median age was 55 years (range 31-76) and all had an ECOG PS of 0-1. Ninety percent of the sample had a Ki67 of 30% or higher, while 85% tested negative for PD-L1. All patients had distant metastases, with 35.0% having visceral metastasis and 35% having metastatic sites of 3 or more. 70% of patients had undergone surgery on the primary tumor. All patients received apatinib plus nab-paclitaxel treatment, with a median of 9 cycles (range 2-25), were included in the safety dataset. All patients experienced grade 1-2 treatment-related adverse events (TRAEs). Haematological toxicity of grade 3-4 with neutropenia occurred in 25.0% of patients. In addition, non-haematological toxicities were observed in 10% of patients, including abnormal hepatic function (5.0%) and hypertension (5.0%). No treatment-emergent adverse event (TEAE) resulted in death during the study. Out of the 20 evaluated patients, the median progression-free survival (PFS) was 6.7 months (95% CI: 6.0-NR). The objective response rate (ORR) was 65.0% (13/20), and the disease control rate (DCR) was 90.0% (18/20), according to RECIST v1.1. The median overall survival (OS) has not yet been reached. Conclusions: The combination of apatinib and nab-paclitaxel showed promising antitumor activity in patients with metastatic TNBC as a second-line treatment, with a manageable safety profile. Clinical trial information: NCT05019690 .

Real world study of racial disparities associated with toxicities of sacituzumab govitecan.

1572 Background: Sacituzumab govitecan (SG) is approved in the treatment of metastatic hormone receptor positive and triple negative breast cancer (BC). The efficacy of SG across racial subgroups is known but no real-world data compares the racial differences in toxicities. We aim to expand knowledge about racial disparities regarding SG toxicities and any ineffective treatment or drug failure. Methods: We utilized TriNetX, a multi-health care organization electronic health record database, to identify African American (AA) and Caucasian (C) cohort for outcome comparison. Inclusion criteria required a C50 ICD-10-CM diagnosis code and at least one SG treatment. Age, gender, and race-controlled Cox proportional-hazard (CPH) model was used to analyze the time until the first pause or cessation of SG (defined as first deviation from the approved 21-day SG cycle). Several measures of deviation were noted 0, ±1 and ±3 days. Association between race and toxicity outcomes (controlled for age and gender) for anemia, neutropenia, thrombocytopenia, nausea and inpatient encounters were evaluated using multiple logistic regression (MLR). The odds (OR) and hazard (HR) ratios with corrected p-values are reported as an effect size and significance estimation. Results: 823 patients met the inclusion criteria (545 C, 116 AA &amp; 162 unknown). The mean age (in years) at the initiation of 1st SG treatment was 58.22 ± 12.7 for C and 58.19 ± 12.18 for AA. AA had a 1.26 times higher hazard of SG treatment pause/cessation as compared to C. Blacks experienced an 88% increase in the odds of having a delay longer than 7-days between 2 doses of 1st cycle SG. Males were found to have an 80% increase in the pause/cessation rate as compared to females. The median number of SG treatments was 6 (3 cycles) for both AA and C. SG was noted as 4th chemo line (median) among all races. When compared to C, AA had decreased odds for neutropenia, increased odds for anemia and increased odds for hospitalization. Hazard Ratio and corrected p-values for outcomes comparing the AA and C cohorts. Conclusions: Survival analysis indicates that AA and male patients have an increased SG treatment pause/cessation rate. While the result is sensitive to specific conditions used to calculate the deviation, an increased odds of delay in treatment is also found using logistic regression modeling. Additionally, AA experience increased odds for anemia and late-stage hospitalization. These findings highlight the impact of race on BC outcomes, treatment toxicities and the need for further research to enhance treatment outcomes in diverse populations. [Table: see text]

ESG401, a trophoblast cell-surface antigen 2 (TROP2) antibody drug conjugate (ADC), for the treatment of first-line metastatic triple negative breast cancer (mTNBC).

e13132 Background: ESG401, a novel ADC comprising a humanized anti-TROP2 IgG1 monoclonal antibody conjugated to the Topoisomerase I Inhibitor SN-38, with the Drug-Antibody Ratio at 8, by a stable cleavable linker, exhibited preliminary efficacy and tolerability in the Phase Ia trial (Ma, ASCO 2023). This report summarizes current results from the first-line mTNBC cohort of the Phase Ib trial. Methods: Patients (pts) aged ≥18 years with confirmed local advanced/unresectable or metastatic TNBC, without prior metastatic treatment, received ESG401 (16 mg/kg IV on Day 1,8, and 15, with a 28-day cycle) until unacceptable toxicity, progressive disease, or consent withdrawal. Results: As of the cutoff date (Jan 30th, 2024), 23 pts in the cohort received ≥1 dose of ESG401. Median age was 52 years (range: 33-73), 34.8% were ECOG 0, 26.1% were de novo stage IV, 73.9% had visceral disease (8.7% brain, 34.8% liver, 52.2% lung), 43.5% received radiotherapy, and 73.9% received chemotherapy (73.9% Taxanes, 69.6% Anthracycline, 4.3% Platinum)as prior treatments for early-stage disease. Among 14 Efficacy Evaluable (EE) pts, the ORR was 78.6%, including one (7.1%) patient who achieved a complete response. DCR was 100%, and CBR was 85.7%. Eight pts (57.1%) achieved confirmed Partial Response (PR). As of the cutoff date, 14 pts (63.6%) remained on treatment, with the longest on-treatment duration being 8.0 mons. Two (2) pts in this cohort had brain metastases. One pt achieved a complete intracranial response, and the overall response evaluation was PR. The evaluation time for the other pt has not yet been reached. Across the entire Phase Ia/1b trials, including 15 EE pts with brain metastases, the best overall intracranial response rate was 33%, with an intracranial disease control rate of 73%. The response of the intracranial tumor lesion is correlated with the response of the non-CNS lesion. The safety profile of ESG401 remained consistent with previous reports, showing no new or unexpected safety signals. The most common TRAEs were leukopenia (65.2%), neutropenia (69.6%), anemia (43.5%), fatigue (21.7%), nausea (43.5%), and vomiting (34.8%). The most common TRAEs≥ Grade 3 were neutropenia (43.5%). There was no ≥ Grade 3 diarrhea. No interstitial lung disease (ILD) has been reported so far for the entire PhIa/b trials containing 139 pts. Conclusions: ESG401 demonstrates promising antitumor activity in the first-line mTNBC pts, with efficacy comparable to the combination therapy reported by the BEGONIA Study. Additionally, the efficacy of ESG401 in brain metas in the first-line mTNBC pts is in alignment with our previous observations made in the late-line mTNBC and HR+/HER2- BC pts. These results warrant further clinical investigation of ESG401. Clinical trial information: NCT04892342 .

Toxicity differences in CDK 4/6 inhibitors seen in Asian and Pacific Islanders.

e13086 Background: Cyclin-dependent kinases (CDK) 4/6 inhibitors are the standard of care, first line treatment for hormone receptor positive metastatic breast cancer and adjuvant high-risk hormone receptor positive early stage breast cancer along with endocrine therapy. There have been multiple clinical trials validating the effectiveness, along with toxicities of these agents; however, the majority of these trials lack ethnic diversity. This shortcoming limits the ability to apply these findings in diverse patient populations, especially among Asian and Pacific Islanders in Hawaii. Objective: To determine if the toxicity profile of CDK 4/6 inhibitors in women with breast cancer is different among patients at a community oncology practice in Hawaii, in which the majority of patients are Asian, Pacific Islander or a combination of both when compared to three landmark trials. Methods: A retrospective analysis of thirty-two patients with hormone receptor positive, HER2 negative metastatic or high risk breast cancer who started endocrine therapy and CDK 4/6 inhibitor therapy (abemaciclib, ribociclib, or palbociclib) between 2018-2023. Graded toxicities of each individual patient based on CTCAE criteria V. 5, along with demographic data was reviewed and compared to three main registration trials for these agents (MONARCH-3, MONALEESA-2, PALOMA-2). Results: Combined results from the three large randomized trials reported an average of 75% of participants were Caucasian, as compared to 15% in the Hawaii data. While 19% percent of participants from the combined large randomized trials reported being of Asian descent, none of these trials reported a breakdown of Asians versus Pacific Islanders. In the Hawaii sample, 41% were reported as Pacific Islander and 41% reported as Asian, 15% Caucasian, with the final 3% reported as Hispanic. Collective analysis of the FDA registration trials contained 0% Pacific Islander, 19.8% Asian, 74.3% White, 1.5% Black, and 4.4% Other. The majority of all toxicities of all grades were higher in the Hawaii population as compared to the three national trials, except for neutropenia with ribociclib and diarrhea with palbociclib (Table). Conclusions: The Hawaii analysis that was primarily comprised of Asians and Pacific Islanders revealed an increased incidence of toxicities, despite starting at lower doses rates for all CDK 4/6 inhibitors. This data analysis begins to highlight the importance of representative populations in clinical trials for the most effective and safest care of diverse populations. [Table: see text]

Real world outcomes of sequential ADC therapy in metastatic breast cancer: Patients treated with sacituzumab govitecan and trastuzumab deruxtecan.

1085 Background: Sacituzumab govitecan (SG) and trastuzumab deruxtecan (TDXd) are antibody drug conjugates (ADCs) that are approved for the treatment of HER2 low metastatic breast cancer (MBC). Both carry payloads which inhibit topoisomerase 1, and it is unknown whether these ADCs retain clinical activity when used sequentially to each other. Here we present a retrospective study of patients treated with both SG and TDXd at our institution and report real world progression free survival (PFS), clinical factors associated with longer PFS, and whether ADC sequence impacts outcome. Methods: All patients with MBC treated at MSKCC who had received both SG and TDXd (in any order) were eligible for inclusion. Clinicopathological and demographic data were obtained from retrospective chart review. PFS was determined clinically and calculated using Kaplan-Meier survival analysis. Univariate and multivariate associations of survival were assessed using Cox proportional hazards models. Results: Eighty-five patients met eligibility per the criteria above: 54 with estrogen receptor positive (ER+) MBC and 31 with triple negative breast cancer (TNBC). 33 patients received SG followed by TDXd (14 ER+, 19 TNBC), and 52 received TDXd followed by SG (40 ER+, 12 TNBC). Median age at time of second ADC treatment (ADC2) was 59 among all patients, 62 among SG first, and 58 among TDXd first. This cohort was heavily pre-treated, with median 5 prior therapies at the time of first ADC (ADC1) and 7 at the time of ADC2. Both the SG first and TDXd first cohorts had median 1 line of intervening therapy between ADCs. In the SG first group, median ADC2 (TDXd) PFS was 3.5 months (95%CI 2.7-7.7), and in the TDXd first group median ADC2 (SG) was 2.8 months (95%CI 2.6-3.7). On multivariate analysis, neither ADC sequence (SG first vs. TDXd first, HR 1.30, 95%CI 0.71-2.37, p=0.4) nor ER status (TNBC vs. ER+, HR 1.21, 95%CI 0.63-2.32, p=0.6) showed statistically significant differences in ADC2 PFS between these groups. Instead, later treatment line at the time of ADC2 was significantly associated with shorter ADC2 PFS (continuous, HR 1.11, 95%CI 1.01-1.23, p=0.03). To separately evaluate differences in PFS for each ADC depending upon whether it was first or follow-up therapy, median ADC1 vs. ADC2 PFS is summarized by ADC (Table). Conclusions: In this heavily pre-treated patient cohort, the clinical activity of both SG and TDXd appear modest in the ADC2 setting. Further studies are needed to confirm these findings and to determine whether payload cross-resistance may undermine the benefit of sequential ADC therapy. [Table: see text]

Efficacy and safety of inetetamab-containing regimens in patients with HER2-positive metastatic breast cancer in first-line/second-line setting.

e13013 Background: Inetetamab is a novel recombinant humanized anti-human epidermal growth factor receptor-2 (HER-2) monoclonal antibody. This real-world retrospective study assessed the efficacy and safety of inetetamab-based combination regimens in first-line/second-line treatment of HER2-positive metastatic breast cancer (MBC). Methods: This study retrospectively recruited HER2-positive MBC patients who received inetetamab-based combination regimens from June 2020 to May 2023. The outcomes included progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and disease control rate (DCR). Results: A total of 329 patients were enrolled and included in the efficacy analysis. The most frequently used treatment strategy was inetetamab plus pyrotinib-contained regimens (205/329, 62.3%). Patients treated with first-line regimens benefited the most, with a median PFS of 14.5 versus (vs.) 10.0 months (first-line- vs. second-line combination therapy of inetetamab, pyrotinib and chemotherapy, p &lt;0.001), 18.0 vs. 17.0 months (first-line- vs. second-line combination therapy of inetetamab, pertuzumab and chemotherapy, p=0.096), and 14.0 vs. not applicable months (first-line- vs. second-line inetetamab plus chemotherapy, p=0.229). The complete response (CR) was observed in 14 (4.3%) patients. The ORR was 54.4% (95%CI, 49.0%-59.7%), and the DCR was 99.4% (95%CI, 97.8%-99.8%). Diarrhea (39.2%) and white blood cell count decreased (33.0%) were the most common adverse events (AEs). The grade 3 and higher AEs were observed in 29.5% of the whole study cohort. Conclusions: Inetetamab-based combinations therapy demonstrated promising clinical activity and a manageable safety profile in patients with HER2-positive MBC, especially in the first-line setting.

The efficacy and safety of trastuzumab biosimilar HLX02 compared with reference trastuzumab plus pertuzumab in combination with chemotherapy as the first-line treatment for HER2 positive metastatic breast cancer: A real-world study in China.

e13016 Background: Dual-targeted anti-HER2 therapy with trastuzumab (H) and pertuzumab (P) significantly improves outcomes in HER2-positive breast cancer and has become the first-line standard treatment for patients with advanced HER2-positive breast cancer in China in 2019 based on the results of the CLEOPATRA and PUFFIN study. HLX02 (Zercepac) was the first trastuzumab biosimilar manufactured in China. Here, we present the first real-world comparison of HLX02 versus reference trastuzumab (RTZ) and pertuzumab with chemotherapy as the first-line treatment for HER2-positive metastatic China.Between January 2019 and August 2023, 121 patients with HER2-positive MBC patients were enrolled at Beijing Cancer Hospital in China. These patients received HLX02 or RTZ in combination with pertuzumab and various chemotherapies as first-line treatment. We retrospectively analyzed survival outcomes, efficacy, and adverse events. Methods: Between January 2019 and August 2023, 121 patients with HER2-positive MBC patients were enrolled at Beijing Cancer Hospital in China. These patients received HLX02 or RTZ in combination with pertuzumab and various chemotherapies as first-line treatment. We retrospectively analyzed survival outcomes, efficacy, and adverse events. Results: Both groups, 68 received RTZ and 53 received HLX02, showed similar characteristics of age, disease status (de novo or recurrent), metastatic sites (visceral or non-visceral), and treatment history. A total of 118 (97.5%) received trastuzumab plus pertuzumab combined with chemotherapy as the first-line palliative therapy, with a median number of 6 cycles in each group. Taxanes were the most commonly used chemotherapy regimen in both groups (91.2 vs. 92.5%), including nab-paclitaxel (44.1 vs. 45.3%), docetaxel (41.2 vs. 17.0%), paclitaxel (5.9 vs. 30.2%). With a median follow-up of 15.0 months (range 1.0 - 58.0), the results showed no significant difference in PFS between the RTZ and HLX02 arms (median PFS: 22.0 vs. 19.0 months, p=0.900). Additionally, the efficacy outcomes, including objective response rate (ORR), disease control rate (DCR), and safety profiles did not show significant differences between the two groups. Among 121 patients, 20 patients (16.5%) experienced CNS progression. For these patients, the median time from the first-line therapy to the CNS progression was 15.0 months (95% CI 12.8 - 17.2). Conclusions: The real-world data suggest similar efficacy and safety of HLX02 and RTZ plus pertuzumab with different chemotherapy regimens as the first-line treatment for patients with HER2-positive advanced breast cancer patients in China. Overall, the PFS was consistent with the CLEOPATRA trial in both groups, and there was no new safety signal.

PARPi eligibility amongst women with newly diagnosed invasive breast cancer enrolled in the GREAT universal genetic testing study.

531 Background: Poly(ADP-ribose) polymerase inhibitors (PARPi) are approved for the treatment of BRCA-associated metastatic and high-risk early breast cancer. Recent guidelines have endorsed the use of BRCA1/2 testing for all patients with breast cancer who may be eligible for PARPi therapy, however it is unclear what proportion of patients are impacted by these recommendations. Methods: We sought to evaluate pre-test and post-test eligibility for PARPi in women aged &gt;18 years old with a first diagnosis of stage I-IV invasive breast cancer who enrolled in a prospective, multicentered universal genetic testing study between 2019-2022. All enrolled patients underwent pre-test counselling and an obligatory primary panel of BRCA1, BRCA2, and PALB2 at the time of diagnosis. Candidacy for PARPi was determined by biologic subtype, clinical stage, pathologic stage, and/or response to neoadjuvant chemotherapy. Results: Of 1017 patients referred for the study, 805 were eligible and 729 (90.6%) consented to participate. The median age at diagnosis was 53 years (IQR, 45-62 years) and 96.2% had stage I-III disease. Overall, 32 (4.4%) patients had a germline pathogenic variant (GPV) in BRCA1/2, and 7 (1.0%) had a GPV in PALB2. Of 112 (15.4%) patients with triple negative breast cancer (TNBC), 19.6% had a GPV in BRCA1/2 or PALB2, whereas in 487 (66.8%) with ER+HER2- disease, 2.9% had a GPV (p&lt;0.001). Among the 112 patients with TNBC, 64 (57%) were candidates for PARPi pre-genetic testing, and 12 (10.7%) remained eligible due to a GPV in BRCA1/2. Among the 487 patients with ER+HER2- breast cancer, 37 (5.1%) were candidates for PARPi pre-genetic testing, and 1 (0.2%) remained eligible due to a BRCA1 GPV identified on testing. All patients who were PARPi eligible were &lt;65 years of age or &gt;65 years with TNBC. Conclusions: In women with newly diagnosed invasive breast cancer, approximately 14% are candidates for PARPi prior to genetic testing, and 1.8% remain PARPi eligible due to a confirmed pathogenic variant in BRCA1/2. Consequently, genetic testing impacts systemic therapy decisions for PARPi in 10% of TNBC patients and fewer than 1% of women with ER+HER2- breast cancer. [Table: see text]