HER2-negative Breast Research Articles

Prognostic factors in non-metastatic HER2 'low' and HER2 'negative' breast cancer: single institute experience.

Comparison of prognosis and survival in human epidermal growth factor receptor 2 (HER2)-low and HER2-negative patients with early stage or locally advanced, hormone receptor-positive breast cancer. In aretrospective single center study, the patients with early stage or locally advanced stage, hormone receptor (HR)-positive [estrogen receptor (ER) ≥ 1% and/or progesterone receptor (PR) ≥ 1%] and HER2 negative or HER2 low invasive breast cancer diagnosis were included. Atotal of 444 patients were included in the study. Patients were divided into two groups: HER2 negative and HER2 low. There were 235 (53%) patients in the HER2 negative group and 209 (47%) patients in the HER2 low group. The HER2 low group had significantly longer 5‑year disease-free survival (DFS) than the HER2 negative group. The patients with lower Ki67 (< 20%) also had a longer 5‑year DFS. Nonmetastatic HR+/HER2 low breast cancer patients had better DFS than HR+/HER2 negative ones. The Ki67 level and HER2 low status were independent prognostic factors. Randomized clinical trials are needed in early stage HER2 low breast cancer patients.

Liver metastasis in estrogen receptor-positive HER 2-negative breast cancer. Ribociclib as prognosis-changing therapy

The life expectancy of patients with metastatic luminal HER 2-negative breast cancer has stagnated at the level of 40 months for many years. The introduction of CDK4/6 inhibitors into practice has changed the standards of therapy, providing not only a significant increase in the time without progression while maintaining a high quality of life, but also significantly increasing overall survival. The presence of liver metastases determines an extremely unfavorable prognosis, with GH+HER 2-mBC reducing life expectancy to a median of 21 months. Endocrine therapy combined with ribociclib significantly increased overall survival rates on average per year, reaching medians of 36.1 and 46.5 months, depending on the line of treatment. This publication is devoted to liver metastases in breast cancer, in particular in the luminal HER 2-negative subtype. Epidemiological aspects are considered, the possibilities of modern systemic therapy are evaluated. A clinical case of successful therapy with ribociclib in a young patient with liver damage is presented.

247P Apatinib combined with chemotherapy versus single chemotherapy in advanced HER-2-negative breast cancer: A randomized, controlled, open-label phase II study

Apatinib is an oral, highly potent tyrosine-kinase inhibitor targeting VEGFR2. Phase II trial of apatinib in triple-negative breast cancer that have failed at least three chemotherapy regimens have demonstrated apatinib dose of 500 mg rather than 750 mg is the recommended starting dose for the heavily pretreated metastatic triple-negative breast cancer (mTNBC) patients with measurable rate of partial response and PFS. This phase II trial aimed to investigate the efficacy and safety of apatinib combined with chemotherapy in patients with HER2-negative advanced breast cancer.

Abstract 3107: Identifying therapeutic vulnerabilities in HR-positive, HER2-negative advanced breast cancer patient-derived xenograft models refractory to CDK4/6 inhibition

Abstract Background: Clinically, the addition of CDK4/6 inhibitors (e.g. palbociclib) to endocrine therapy (ET) significantly delays progression of advanced hormone receptor-positive (HR+), HER2-negative (HER2-) breast cancer patients. However, most patients develop resistance and progress following long-term treatment. Thus, an ongoing clinical challenge has been the identification of biomarkers that predict response to CDK4/6 inhibitors. There is also an unmet need to identify actionable targets for patients who have progressed. Currently, there are no clinically useful biomarkers to predict response and/or resistance to anti-CDK4/6 therapy. Hence, the goal of our study was to identify the therapeutic vulnerabilities of CDK4/6 inhibitor resistant patient derived xenograft (PDX) models and identify key markers that longitudinally correlate with development of resistance and inform new treatment directions. Methods: We obtained 4 different PDX models, two from patients who progressed after 2-4 months on treatment with palbociclib plus ET (i.e. intrinsic resistance) and the other two who developed resistance over time (i.e. acquired resistance) with disease progression between 12-18 months while on palbociclib plus ET. To elucidate mechanisms of resistance, we performed genome-wide expression analysis via RNA-sequencing. Results: The molecular assessment of the PDX models revealed different transcriptomic signatures for intrinsic resistance compared to acquired resistance. We identified 3,386 upregulated and 2,829 downregulated significant differentially expressed genes (DEGs) in the acquired compared to intrinsic resistant PDX models. Further, gene set enrichment analysis (GSEA) revealed enrichment of distinct driver pathways in the acquired-compared to the intrinsic resistant models. Conclusions: Collectively, these results have identified potential unique targets for intrinsic and acquired resistance to guide treatment strategies. Thus, our ongoing studies are geared towards identifying and targeting distinct therapeutic vulnerabilities of intrinsic and acquired resistance to palbociclib. Citation Format: Nicole M. Kettner, Juliana Navarro-Yepes, Tuyen N. Bui, Xiayu Rao, Jing Wang, Funda Meric-Bernstam, Kelly K. Hunt, Debu Tripathy, Khandan Keyomarsi. Identifying therapeutic vulnerabilities in HR-positive, HER2-negative advanced breast cancer patient-derived xenograft models refractory to CDK4/6 inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3107.

Abstract 1774: Circulating IL-6, an early biomarker in HR-positive, HER2-negative metastatic breast cancer patients progressing on CDK4/6 inhibitors

Abstract Background: CDK4/6 inhibitors (CDK4/6i, e.g. palbociclib) in combination with endocrine therapy (ET) have proven successful in delaying progression in hormone receptor-positive (HR+), HER2-negative (HER2-) metastatic breast cancer patients; however, 60-70% will progress within 1-2 years of treatment. Thus, understanding the mechanisms of resistance and identifying novel treatment strategies are needed to improve survival. Our previously published data shows that palbociclib resistance is marked by significant upregulation of the IL6-STAT3 signaling pathway in HR+, HER2- breast cancer cells and treatment with TTI-101, a small-molecule STAT3 inhibitor completing Phase I studies in solid tumor patients, significantly decreased cell viability. Additionally, matched biopsies from advanced HR+, HER2- breast cancer patients who progressed on palbociclib plus ET had an upregulation in activated STAT3 (STAT3 phosphorylated on Y705, pY-STAT3) as compared to their pre-treatment biopsy. Collectively, these data suggest that targeting the IL-6/STAT3 pathway is a viable therapeutic strategy. Our ongoing studies are directed at delineating the role of IL-6 and pY-STAT3 as predictive biomarkers to provide preclinical rationale for targeting STAT3 in patients who develop CDK4/6i resistance. Methods: We downregulated IL-6 using shRNA in MCF7 and T47D palbociclib sensitive and resistant cells. We tested the efficacy of TTI-101 in patient-derived xenograft (PDX) models from patients with metastatic HR+, HER2- breast cancer who progressed on treatment with palbociclib + ET. We also collected plasma samples from patients with metastatic HR+, HER2- breast cancer just prior to CDK4/6i treatment and at disease progression. Results: Downregulation of IL-6 in palbociclib resistant cells reduced pY-STAT3 levels and re-sensitized cells to ET and palbociclib. Induction of IL-6 is an early event by treating sensitive cells with 1uM palbociclib for 21 days during which the cells adapted and eventually developed resistance. Suppression of IL-6 in sensitive cells revealed that it is needed for cells to overcome growth inhibition by palbociclib. Targeting STAT3 in palbociclib resistant PDX mouse models using TTI-101 (50mg/kg twice daily by oral gavage), resulted in significantly reduced tumor volume; a synergistic effect was observed when TTI-101 was combined with palbociclib. Lastly, IL-6 levels in plasma samples from metastatic HR+, HER2- breast cancer patients were significantly higher at disease progression compared to pre-treatment with CDK4/6i. Conclusion: Collectively, these studies suggest that IL-6 signaling through STAT3 is a key mediator of resistance to palbociclib. We provide the rationale for using circulating IL-6 as a biomarker of disease progression and tumor pY-STAT3 as a selection criterion for treatment with TTI-101 to prevent or reverse resistance. Citation Format: Nicole M. Kettner, Tuyen N. Bui, Juliana Navarro-Yepes, T Kris Eckols, Akshara S. Raghavendra, David J. Tweardy, Kelly K. Hunt, Debu Tripathy, Khandan Keyomarsi. Circulating IL-6, an early biomarker in HR-positive, HER2-negative metastatic breast cancer patients progressing on CDK4/6 inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1774.

Abstract 1798: Mechanisms of acquired resistance to palbociclib reveals pathways of response to abemaciclib

Abstract Background: CDK4/6 inhibitors (CDK4/6i) plus endocrine therapy (ET) delay progression and improve survival in patients with hormone receptor positive (HR+), HER2 negative metastatic breast cancer (MBC). However, most patients develop resistance to CDK4/6i leading to disease progression, thus new therapies to overcome resistance are needed. CDK4/6i [palbociclib (palbo), ribociclib (ribo), and abemaciclib (abema)] have the same nominal targets but vary in their target specificity and are pharmacologically distinct. Clinical benefit was observed in patients treated with abema after progression on a prior CDK4/6i suggesting that palbo/ribo refractory tumors retain abema sensitivity. We hypothesize that mechanisms driving acquired resistance to palbo and abema are distinct, and palbo-resistant models may be responsive to abema. Models: 1) MCF-7 and T47D palbo and abema resistant cells, 2) patient derived xenografts (PDX) established from patients who progressed on ET alone (ET-resistant) or palbo + ET (palbo-resistant), 3) organoids derived from the palbo-resistant PDX, and 4) a HR+/HER2- MBC patient cohort who received abema after progression on palbo therapy. Results: RNA-sequencing and proteomic analysis revealed that palbo and abema resistant cells exhibit more than 30 differentially altered pathways. EMT, IL6/STAT3, and CSC pathways were upregulated only in palbo-resistant cells, but not in abema-resistant cells. Palbo-resistant cells also showed upregulation of G2M/Mitotic spindle and downregulation of ER pathways, whereas abema-resistant cells displayed downregulation of G2M/Mitotic spindle and upregulation of ER pathways. Mechanistic analysis revealed that palbo-resistant cells are responsive to abema with a delay in doubling time and a reduction of the proliferation marker pHH3. Further, cells accumulated in the G2M-phase with concomitant high phospho-(Y15)-CDK1 and cyclin B levels. Organoid cultures generated from palbo-resistant PDX were sensitive to abema. Likewise, abema significantly delayed the tumor growth of palbo-resistant PDX, correlating in vivo with ex vivo treatments. Moreover, we assessed response to abema after progression on palbo in the ET-resistant PDX model (CDK4/6 sensitive) demonstrating a continued survival benefit from abema treatment compared to palbo. Clinical outcome analyses of a MBC patient cohort treated with abema following prior CDK4/6i showed a median progression free survival (PFS) of 6.3 months in those treated sequentially vs a PFS of 4.0 months in non-sequential treated patients. Conclusion: Differential mechanism underlying palbo and abema acquired resistance can be exploited to overcome CDK4/6i resistance. These results provide rationale for clinical trials evaluating the benefit of abema treatment following progression on a prior CDK4/6i. Citation Format: Juliana Navarro-Yepes, Nicole M. Kettner, Tuyen Bui, Akshara S. Raghavendra, Xiayu Rao, Jing Wang, Aysegul Sahin, Senthil Damodaran, Debasish Tripathy, Kelly K. Hunt, Khandan Keyomarsi. Mechanisms of acquired resistance to palbociclib reveals pathways of response to abemaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1798.

Abstract 6151: Tumor microenvironment heterogeneity identifies potential biomarkers of response in ER-positive breast cancers treated with palbociclib

Abstract Despite the breast cancer microenvironment being recognized as a critical participant in tumor progression and therapeutic response, current technologies for tumor cell-to-cell interaction analyses are limited to qualitative and descriptive histological methods. Here, we utilized multiplex immunofluorescence (MxIF), RNA sequencing (RNA-seq), and microarray gene expression to quantitatively assess, using the BostonGene automated pipeline, the immune microenvironment composition of clinical stage 2 or 3 primary estrogen receptor-positive (ER+) HER2-negative (HER-) breast tumors (n = 29) from patients treated with neoadjuvant palbociclib in combination with anastrozole. Microenvironment characteristics of pretreatment tumor biopsies were associated with molecular subtype, cytokine signatures, and Ki67 response. MxIF analysis (21 markers, 2-13 ROIs per slide) of the tumor immune composition revealed that while the cellular composition was similar for each tumor region of the same patient, significant cellular heterogeneity was observed in tumor biopsies from different patients. The spatial heterogeneity was found in the distribution of both immune infiltrate cells and stromal components. T cells, CD68+ and CD163+ macrophages, and B cells were the predominant cell populations in the stromal component. Further MxIF analysis showed an increase in Ki67+ tumor cells in nonresponders (NR) versus responders (R). The number of immune cells was similar between Luminal A and B breast cancer molecular subtypes. A lower number of Ki67+ tumor cells was found in Luminal A compared to Luminal B tumors, as expected. MxIF analysis of cell-to-cell interactions revealed that distinct groups of cellular neighborhoods were significantly increased in NR compared with R: the immune inflammation cluster with a high density of CD4 T cells, Tregs, and CD8 T cells in the stromal component (p = 0.03); CD163+ macrophage-enriched cluster (p &amp;lt; 0.001); and tertiary lymphoid structures cluster (p &amp;lt; 0.001). Transcriptomic analysis showed that while CXCL1, CCL17, CCL13, CXCL9, and CCL5 expression correlated with the high density of CD4 and CD8 T cells in the stromal component cluster, VEGFA, IL1B, CXCL16, CCL3, and CCL7 were increased in the CD163+ and CD68+ macrophage-enriched clusters, indicating that differential cytokine expression is associated with the tumor architecture.Comprehensively characterizing, via MxIF, the immune microenvironment of ER+ HER2- breast cancer provided resolution of cellular architecture and elucidated spatial relationships among the immune and stromal cells of the tumor. Quantitatively assessing breast tumor cell-to-cell interactions has the potential to identify imaging markers of response, ultimately leading to the development of effective therapy options. Citation Format: Maria Bruttan, Souzan Sanati, Anna Belozerova, Ilia Galkin, Akshaya Ramachandran, Pavel Ovcharov, Grigory Perelman, Viktor Svekolkin, Ekaterina Postovalova, Alexander Bagaev, Krystle Nomie, Shana Thomas, Jeremy Hoog, Ravshan Ataullakhanov, James Hsieh, Cynthia Ma. Tumor microenvironment heterogeneity identifies potential biomarkers of response in ER-positive breast cancers treated with palbociclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6151.

Abstract 5058: Recurrence risk prediction based on automatic histopathologic analysis of breast cancer using whole slide images

Abstract The RS (Recurrence Score) is the results of a 21-gene test assessing the likelihood of breast cancer recurrence for hormone-positive, HER2-negative, and node-negative breast cancer patients. We conducted an experiment to find out whether there is a correlation between the RS value derived through genetic testing and specific morphological characteristics of breast cancer tissues with the expectation that these morphological features could predict RS values. Deep learning was utilized to assess the morphology of the hematoxylin-eosin (H&amp;E) stained whole slide images (WSIs) of breast cancer. In this study, we used 125 breast cancer cases associated with H&amp;E stained WSIs and RS scores which were divided into 3 risk groups based on the RS values: the low-risk group with 49 cases, the intermediate-risk group with 59 cases, and the high-risk group with 17 cases (low-risk for RS &amp;lt; 18, high-risk for RS &amp;gt; 31, and intermediate-risk for RS in between). On each WSI, an expert pathologist has annotated invasive breast tumor regions. We divided WSIs into 512x512 patches and trained a deep CNN model to classify the patches as benign (including DCIS), low-risk, intermediate-risk, or high-risk. In determining the risk group of each WSI, all patches from the WSI were classified by the model first, and then their majority class was assigned to the WSI. A nested cross validation was adopted to evaluate how well the model generalizes. The performance of the algorithm is shown in Table 1. According to the results, our model was able to distinguish between the low-risk group and the high-risk group to some extent. In particular, there was no case of misclassifying the low-risk group as high-risk. Since these high-risk patients require radiological examination, there is an advantage that the 21-gene test is not required. Although our model has yielded modest results, we believe that future studies through the integration of additional data with other clinical and pathological data will yield better results. Result Table 21-gene test result (*ground truth) Low Intermediate High Prediction Low 42 14 0 Intermediate 5 44 8 High 2 1 9 Accuracy 0.932 0.776 0.912 Sensitivity 0.857 0.746 0.529 Specificity 0.816 0.803 0.972 PPV 0.851 0.772 0.750 Citation Format: Geongyu Lee, Chungyeul Kim, Tae-Yeong Kwak, Sun Woo Kim, Hyeyoon Chang. Recurrence risk prediction based on automatic histopathologic analysis of breast cancer using whole slide images [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5058.

Abstract 216: Expression of DNA damage response proteins modifies the efficacy of CDK4/6 inhibitor-mediated radiosensitization in breast cancer models

Abstract Purpose: CDK4/6 inhibitors (CDK4/6i) are standard of care for the treatment of locally advanced and metastatic estrogen receptor-positive (ER+), HER2-negative metastatic breast cancer (BC). CDK4/6 inhibition + radiation therapy (RT) is synergistic in both ER+ and triple negative breast cancers (TNBC), but the underlying mechanism is not entirely understood. In this study, we evaluated how pre-existing or genetically engineered deficits in DNA damage response genes (BRCA1/2, RAD51, RB1, XRCC6, TP53) influence radiosensitization. We hypothesized that inhibition of homologous recombination (HR) would prevent CDK4/6i-mediated radiosensitization and blocking non-homologous end joining (NHEJ) would be synergistic. Methods: Cellular proliferation assays determined the half-maximal inhibitory concentrations (IC50) of the 3 approved CDK4/6i palbociclib, ribociclib, and abemaciclib. Clonogenic survival assays determined the radiation enhancement ratios (rERs) and evaluated the efficacy of CDK4/6i + RT. Immunofluorescence assays measured RAD51 foci formation and quantified micronuclei formation following RT and/or CDK4/6 inhibition. Immunoprecipitation with myc-RAD51 and GFP-RB assessed potential protein-protein interactions. Results: While ER+ and TNBC cell lines with wild type BRCA1 expression are radiosensitized by CDK4/6i, BRCA1-deficient SUM-149 cells are not radiosensitized by CDK4/6i at concentrations up to 1µM (rER: 0.92-1.01). In an MCF-7 isogenic model of BRCA2 knockout, CDK4/6i-mediated radiosensitization was abolished compared to Cas9 control or parental cell lines. In ER+ BC cell lines (MCF-7-p53 wt, T47D-p53 mutant), transient or genetic knockdown of RAD51 prevented CDK4/6i-induced radiosensitization. The total quantity of RT-induced RAD51 foci increased in vitro following overexpression of RB-a tumor suppressor and downstream target of CDK4/6. RB overexpression also rescued CDK4/6i-mediated radiosensitization in RB-deficient cell lines through changes in HR efficiency but not via NHEJ or altered micronuclei formation. Moreover, immunoprecipitation of RAD51 in ER+ (MCF-7) and TNBC (MDA-MB-231) cells exhibited an interaction with RB. Conversely, loss of the NHEJ-associated protein Ku70 (XRCC6) was synergistic with palbociclib + RT in MCF7 (rER: 1.76-2.44) and T47D (rER: 1.61-3.88) cells. Finally, CRISPR Cas9-mediated loss of the tumor suppressor p53 (TP53) did not affect radiosensitization induced by CDK4/6i in isogenic p53 wt ER+ (MCF-7, rER: 1.19-1.33) and p53 wt TNBC (CAL-51, rER: 1.23-1.52) cell lines with TP53 loss. Conclusions: Taken together, our results in multiple non-overlapping isogenic models of ER+ and TNBC suggest that CDK4/6i-mediated radiosensitization of BC cell lines occurs through impaired HR activity and RB signaling, and not through the actions of p53 or NHEJ-mediated DNA repair. Citation Format: Kassidy M. Jungles, Andrea M. Pesch, Nicole Hirsh, Anna R. Michmerhuizen, Kari Wilder-Romans, Benjamin C. Chandler, Meilan Liu, Lynn Lerner, Lori J. Pierce, James M. Rae, Corey W. Speers. Expression of DNA damage response proteins modifies the efficacy of CDK4/6 inhibitor-mediated radiosensitization in breast cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 216.

Factors associated with CDK 4/6 inhibitor use for patients with advanced, hormone positive, HER-2-negative breast cancer.

e13038 Background: “CDK4/6 inhibitors have emerged as a standard of care for patients with HR-positive, HER2-negative advanced breast cancer.” Wayne Kuznar ASCO Reading Room 10.29.2019. Within an academic institution there were concerns that CDK 4/6 inhibitors were not utilized as indicated. We conducted an analysis of CDK 4/6 inhibitor use for patients with advanced, hormone positive, HER2 negative breast cancer to assess factors associated with CDK 4/6 inhibitor use. Methods: We conducted a retrospective medical records review of patients treated at an academic medical center from 01/1/2015 to 9/30/2020 with stage IV, hormone positive and HER2 negative breast cancer. We compared characteristics for patients that received one or more CDK 4/6 inhibitors to those who did not receive any CDK 4/6 inhibitors. Statistical analysis used Fishers exact 2-sided test via GraphPad QuickCalcs website. Results: 162 patient records met inclusion criteria, 73% (119/162) received one or more CDK 4/6 inhibitors as part of their care. The average age of patients who received CDK 4/6 inhibitors was 59.9, as compared to 66.9 average age in patients who did not receive CDK 4/6 inhibitors. Patients who received CDK 4/6 inhibitors were more likely to have received chemotherapy (Table, p &lt; 0.0001), have a family history of cancer (p &lt; 0.0001) and have a Charlson comorbidity index of 5 or more (p = 0.0005). Patients receiving CDK 4/6 inhibitors trended more likely to have used tobacco at some point (p = 0.09). Patients who did not receive CDK 4/6 were more likely to have refused, moved or be in hospice (p = 0.003). There were no statistically significant differences based on patient status, timing of diagnosis or timing of first hormone receptor positive dose. Further analysis of the 27% (43/162) of patients not receiving CDK 4/6 inhibitors identified that 40% (17/43) died, 28% (12/43) had Charlson comorbidity score of 7 or more, 19% (8/43) refused treatment. The remaining 14% (6/43), 4% (6/162) of entire population, did not have a clear reason for not getting CDK 4/6 inhibitors, of those 4 received hormone therapy, 1 received chemotherapy and 1 received both. Conclusions: In a retrospective analysis of patient records, we found consistent use of CDK 4/6 inhibitors for indicated patients. Patients who did not receive CDK 4/6 inhibitors died, had a high co-morbidity index, or refused treatment. Only 4% of the population analyzed did not have a visible reason to not receive CDK 4/6 inhibitors.[Table: see text]

Treatment sequence for hormone receptor-positive HER2-negative advanced breast cancer: Results of a retrospective analysis of Russian patients diagnosed with aBC in 2014-2021.

e13032 Background: CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) have dramatically changed therapeutic landscape of hormone receptor-positive HER2-negative advanced breast cancer (HR+ HER2- aBC). There are three iCDK4/6 in Russia, which are available and included into the clinical guidelines as a preferred first line treatment option beginning since 2018. The aim of this study was to assess evolution of treatment approaches to HR+ HER2- aBC and identify demographic and disease characteristics in correlation with available groups of therapy (chemotherapy, endocrine therapy ±mTOR inhibitors/ CDK4/6i). Methods: Аdult patients diagnosed with de novo or recurrent HR+ HER2- aBC in 2014-2021 identified in outpatient departments of Moscow state oncology hospitals were included into our non-interventional, descriptive, retrospective cohort study. Primary objective of this real-world study was to describe the rate of CDK4/6i usage in the first line setting. As a secondary objective, we describe patient and disease characteristics in iCDK4/6 group, as well as in the endocrine monotherapy and chemotherapy groups. Results: From the cohort of 1000 patients (full-set analysis population) 874 cases were selected, who received treatment since 2018. 45.9% (95% CI 42.6, 49.2) patients were treated with CDK4/6i in combination with endocrine therapy in the first-line setting. From them in the subgroups of patients with or without visceral metastases 50.5% (95% CI 45.5, 55.5) and 42.1% (95% CI 37.7, 46.5) were treated with CDK4/6i in the first line setting, respectively. Among 874 cases 78.0% (95% CI 75.3, 80.7) patients received endocrine therapy ± targeted therapy; in the subgroups of patients with or without visceral metastases 69.5% (95% CI 64.9, 74.1) and 84.9% (95% CI 81.7, 88.1) were treated with endocrine therapy ± targeted therapy in the first line setting, respectively. Conclusions: Endocrine therapy is a predominant therapeutic option in the first line setting for HR+ HER2- aBC. Clinical trial information: NCT04852081. [Table: see text]

Apatinib combined with chemotherapy versus single chemotherapy in HER-2 negative advanced breast cancer: A randomized, controlled, open-label phase II study.

1072 Background: Apatinib is an oral, highly potent tyrosine-kinase inhibitor targeting VEGFR2. A series of clinical studies have shown that anti-angiogenic drugs combined with chemotherapy enable to improve the efficacy of HER2-negative advanced/metastatic breast cancer(MBC). Methods: Patients with HER2-negative MBC with less than two lines of systemic therapy were enrolled in this open-label, controlled, phase II trial. Patients with measurable disease were randomly assigned, in a 1:1 ratio, to receive oral apatinib (250 mg once daily) combined with chemotherapy(A+CT) or chemotherapy(CT) alone (the physician’s choice) until disease progression or intolerable toxicity. The primary end point was progression-free survival(PFS), which was assessed by investigator and was analyzed on an intention-to-treat basis. Results: Between August 2017 and January 2021, of the 80 patients who underwent randomization, 40 were assigned to receive apatinib plus chemotherapy(A+CT) and 40 were assigned to receive standard therapy(CT). As of January 2022, 10 patient had not undergone response evaluation or dropout, 70 patients(36 patients in A+CT, 34 patients in CT were finally included with PFS events and 72 patients were included in safety set. Median PFS was significantly longer in A+CT than in CT (182 days vs 63 days; P = 0.043);The median PFS of TNBC subgroup (11 in A+CT group, 14 in CT) was longer in the aptinib group than in CT group (167 days vs 63 days; P = 0.637);The median PFS of HR+ subgroup(25 in apatinib group, 20 in chemotherapy group) was longer in the aptinib group than in CT group (259 days vs 56 days; P = 0.054);The median PFS of patients with liver metastases(19 in apatinib group, 17 in chemotherapy group) was longer in the aptinib group than in the CT group (151 days vs 54 days; P = 0.191); The severe adverse reactions (grade 3/4) were neutropenia(22.2% vs 13.9%), hypertension(11.1% vs 0.0%), leukopenia(8.3% vs 8,3%), hypokalemia(8.3% vs 2.8%), anemia(5.6% vs 11.1%), ALT(2.8% vs 8.3%), AST(0.0% vs 5.6%) in the apatinib group and the CT, respectively. Proteinuria did not occur in both groups. Treatment delay or dose reduction owing to adverse event was 16.7% and 11.1%, respectively. Treatment discontinuation owing to adverse event was 23.5% and 8.8%, respectively. Conclusions: Apatinib combined with chemotherapy showed a significant improvements in PFS and a manageable safety profile in HER2 negative MBC.

Phase 2 study of anlotinib combined with taxanes and lobaplatin in the neoadjuvant treatment of triple-negative breast cancer: Efficacy, safety and biomarker analysis.

e12605 Background: Pathological complete response (pCR) is associated with improved prognosis in triple-negative breast cancer (TNBC). Anlotinib, a novel multi-target tyrosine kinase inhibitor that effectively inhibits VEGFR, FGFR, c-KIT, c-MET, and RET, monotherapy has been proven effective in HER-2 negative metastatic breast cancer, but its efficacy in early-stage TNBC is unknown. This phase 2 study aims to evaluate the efficacy and safety of adding anlotinib to neoadjuvant chemotherapy in patients (pts) with primary TNBC. Methods: Pts with clinical stage II/III TNBC were to be treated with 5 cycles of anlotinib (12mg, d1-14, q3w) plus 6 cycles of taxanes (docetaxel 75 mg/m2 or nab-paclitaxel 260 mg/m2, d1, q3w) and lobaplatin (30 mg/m2, d1, q3w), followed by surgery. The primary endpoint was the total pCR (tpCR; ypT0/is ypN0). A Simon’s two-stage optimum design was used, and ＞5 of 11 pts were required to achieve tpCR in the first stage, with a pre-specified tpCR rate of 54.5% before proceeding to the second stage. A total of 31 participants was required for the study. Results: Six out of 11 pts achieved tpCR in the first stage, reaching the threshold for the second stage. From Jan 2021 to Jan 2022, a total of 22 pts were enrolled and 12 received surgery after the completion of neoadjuvant therapy, but a total of 2 pts withdrew from the study due to the COVID-19 pandemic or serious adverse events. Of the 22 eligible pts, the median age was 49 years (range, 29-64), 64% were postmenopausal, and 73% were nodal involved. At the time of surgery, 58.3% (7/12) achieved tpCR. Of the 9 pts with the node-positive disease at diagnosis, 88.9% (8/9) became ypN0. The results of FUSCC TNBC classification (IHC-based) revealed the tpCR rates were 57.1% (4/7), 100% (3/3), and 0% (0/2) for BLIS subtype, IM subtype and LAR/unknown subtypes, respectively. Biomarker analysis showed the tpCR rates were 100% (3/3) and 100% (4/4) in patients with gBRCA1 mutation and MYC amplification, respectively. The most common grade 3 or 4 treatment-related adverse events were leucopenia (6/22, 27%), neutropenia (6/22, 27%), anemia (5/22, 23%), decreased appetite (5/22, 23%), hypertension (2/22, 9%), ALT increased (1/22, 5%) and oral mucositis (1/22, 5%). No treatment-related deaths occurred. The trial is ongoing. Conclusions: The addition of anlotinib to neoadjuvant chemotherapy showed manageable toxicity and promising antitumor activity for patients with early-stage TNBC. Clinical trial information: ChiCTR2100043027.

Cost-effectiveness analysis of Oncotype DX from a Brazilian private medicine perspective: A GBECAM multicenter retrospective study.

e18822 Background: Oncotype DX (ODX) is a validated tool for the prediction of risk of recurrence and benefit of chemotherapy (CH) in both node negative (N0) and positive (N1), hormone receptor positive (HR+), HER2 negative (HER2-) early breast cancer (eBC). Due to limited access to novel genomic assays in Brazil, treatment decisions remain largely driven by traditional clinicopathologic risk factors. ODX has been reported to be cost-effective, but limited data is available considering the reality of middle-income countries such as Brazil. We aim to evaluate the cost-effectiveness of ODX across strata of clinical risk groups using data from a large dataset of patients from various Brazilian institutions. Methods: Clinicopathologic and ODX information were analyzed for patients with T1-T3, N0-N1, HR+/HER2- eBC who had an ODX performed between 2005 and 2020. Projections of CH indication by clinicopathologic criteria were based on binary clinical risk categorization based on the Adjuvant! algorithm, as used in the MINDACT study. The ODX score was correlated with the indication of CH according to TAILORx and RxPONDER data. Two decision-tree models were developed. In the first model, low and high clinical risk patients were included the model. In the second model, only high clinical risk patients were included. The cost for ODX and CH (U$2,846 and U$14,464, respectively) were based on the Brazilian private medicine perspective. Uncertainty was assessed using deterministic and probabilistic sensitivity analyses. Results: Six hundred and forty-five patients were analyzed. 411 patients (63.7%) had low clinical risk and 234 patients (36.3%) had high clinical risk disease. The ODX indicated low (&lt; 11), intermediate (11-25) and high (&gt; 25) risk in 119 (18.4%), 415 (64.3%) and 111 (17.2%) patients, respectively. Among 645 patients analyzed in the first model, 234 (36.2%) had clinical and 198 (30.6%) had genomic indication for CH, respectively. In this model, ODX was modestly effective (5.6% reduction in CH indication) though with an incremental cost of US$ 2,040 per patient. Among 234 patients analyzed in the second model (high clinical risk only), 99 (42.3%) patients had genomic indication of CH. In this model, ODX led to a 57.7% reduction in CH indication and reduced costs by US$5,491 per patient (table). The results remained robust in the 1,000 probabilistic simulations. Conclusions: Our study suggests that ODX is cost-saving for patients with high clinical risk HR+/HER2- eBC in the perspective of the Brazilian private health system. Its incorporation into routine practice should be strongly considered by health care providers.[Table: see text]

Defining resistance mechanisms to CDK4/6 inhibition in hormone receptor-positive HER2-negative metastatic breast cancer (MBC) through a machine learning approach applied to circulating tumor DNA (ctDNA).

3055 Background: Although cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) are a primary treatment for hormone receptor-positive/HER2 negative MBC, data regarding resistance mechanisms are still an unmet need. The aim of the study was to highlight new resistance pathways using machine learning (ML) to detect multiparametric patterns in complex datasets. Methods: The study retrospectively analyzed a cohort of 610 hormone receptor positive HER2 negative MBC patients (pts) at Northwestern University, Massachusetts General Hospital and Washington University in St. Louis between 2015-2020 with baseline ctDNA testing by Guardant360. Pathways were defined based on previous work (Sanchez-Vega F et al, Cell. 2018) (i.e., RTK, RAS, RAF, MEK, NRF2, ER, WNT, MYC, P53, cell cycle, notch, PI3K). Only pathogenic variants according to OncoKB were included in the models. Associations among single nucleotide (SNVs) and copy number (CNVs) variations, pathway classification and previous exposure to CDK4/6i were explored through logistic regression and Gradient boosted machines (GBMs) ML algorithm. Results: at baseline, 322 pts (52.8%) were previously treated with CDK4/6i. The most detected pathway alterations were SNVs in PI3K (37.1%), P53 (31.8%), ER (29.2%) and RTK (22.3%). After stepwise logistic regression, RB1, NF1 and ESR1 SNVs were associated with previous exposure to CDK4/6i (respectively OR: 3.55 P = 0.017; OR: 3.06 P = 0.026 and OR: 1.82 P &lt; 0.001), while SNVs in the ER pathway were associated with CDK4/6i (1.56 P &lt; 0.001). Two GBMs models were designed based on gene variants (training AUC: 0.695, cross validation AUC: 0.631) and oncogenic pathways (training AUC: 0.713, cross validation AUC: 0.619). The highest relative importance (RI) was observed for ESR1 SNVs (RI: 35.35), TP53 SNVs (RI: 11.33), NF1 SNVs (RI: 3.45), SMAD4 SNVs (RI: 3.39) and RB1 SNVs (RI: 3.33). Alterations at a pathway level with the highest RI were ER SNVs (RI: 33.50), P53 SNVs (RI: 14.98), PI3K SNVs (RI: 14.40), RTK SNVs (RI: 10.55), RTK CNVs (RI: 10.26), cell cycle CNVs (RI: 6.99), cell cycle SNVs (RI: 6.77) and RAS SNVs (RI: 6.54). Of the previously highlighted pathway alterations, a significant impact on PFS after ctDNA collection was observed among de novo pts treated with CDK4/6i (165 pts) for ER SNVs (P &lt; 0.0001), RTK SNVs (P = 0.0011), RTK CNVs (P = 0.0006), Cell cycle CNVs (P = 0.0010) and Cell cycle SNVs (P = 0.0143). No impact was observed on PFS for pts who had not received a CDK4/6i-based regimen. Conclusions: The combination of ctDNA-based datasets and machine learning algorithms defined novel resistance pathways for patients treated with CDK4/6i. Although preliminary, these results suggest that alterations of the ER, RTK and Cell cycle pathways might be crucial to optimize treatment strategy and drug development.

Updated FDA pooled analysis of pain medication use in trial participants with HR+, HER2-negative metastatic breast cancer treated with endocrine therapy and a CDK 4/6 inhibitor.

e24101 Background: Pain medications (PMs) are commonly used to treat pain in patients with advanced or metastatic breast cancer (MBC). We previously reported an initial analysis of PM prescribing patterns in clinical trial participants with breast cancer receiving CDK 4/6 inhibitor (CDKI)-based treatment. We present an updated analysis here. Methods: We pooled data from 7 randomized controlled trials of CDKI + endocrine therapy (ET) in patients with HR+, HER2-negative MBC. All analyzed patients received at least 1 dose of CDKI/placebo+ET and a concomitant PM with a documented start date. Medications administered during hospitalizations were not included. We looked at PM use in all patients, patients who took PM only before or after the trial started, and those who took PM both before and during the trial. PMs were categorized as opioid (includes codeine-containing), NSAIDS, or other (i.e. bone-directed, antiepileptic, topical PMs). Results: 4200 patients enrolled across the 7 trials who received at least one dose of CDKI/placebo+ET (n = 2616 CDKI, n = 1548 placebo). Of these, 2881 took a PM at any time (n = 1774 CDKI, n = 1107 placebo). Of the 1774 patients who received CDKI+ET, 487 (27%) took at least one opioid and one NSAID at any time, 782 (44%) took at least one NSAID at any time but no opioids, 244 (14%) took at least one opioid at any time but no NSAIDs, and 261 (15%) took only PM that were not opioids or NSAIDs. Of the 1107 patients who received placebo+ET, 297 (27%) took at least one opioid and one NSAID at any time, 490 (44%) took at least one NSAID at any time but no opioids, 153 (14%) took at least one opioid at any time but no NSAIDS, and 167 (15%) took only PM that were not opioids or NSAIDs. Of the 2881 patients who took a PM at any time, 2038 patients (n = 1222 CDKI, n = 816 placebo) had documented start for their PM. Of these, 544 took PM only before the trial started (n = 334 CDKI, n = 210 placebo), 915 took a PM only during the trial (n = 551 CDKI, n = 364 placebo), and 579 took a PM both before and during the trial (n = 337 CDKI, n = 242 placebo). Overall, more patients took NSAIDs only compared to opioids only. Patient characteristics at baseline were balanced between the two arms. Conclusions: Overall, PM prescribing patterns were similar between the arms. NSAID use was higher than opiates in all groups. These findings are hypothesis generating and additional research is needed to determine the impact of PM on participants’ pain and physical function. Further research should include an understanding of the duration of PM needed in patients with MBC.

Comparison of predicted benefit using RS clin versus observed benefit in a U.S. registry of stage I ER-positive HER2-negative high oncotype DX RS breast cancer.

544 Background: The 21-gene recurrence score assesses the risk of distant breast cancer recurrence and predicts the benefit of adjuvant chemotherapy in ER positive early-stage breast cancer. However, clinicopathologic risk factors continue to impact absolute benefit of adjuvant chemotherapy. Absolute benefit of adjuvant chemotherapy in low clinicopathologic risk Stage I ER positive breast cancer with high Oncotype RS is an important clinical component of shared decision making. The RSClin clinical tool, which integrates the 21-gene recurrence score (RS) and clinicopathologic features, was found to be more prognostic than RS result alone. We assessed RS Clin predicted benefit and compared to absolute benefit in low clinicopathologic risk Stage I ER positive breast cancer with high Oncotype RS as observed in the NCDB. Methods: Using the National Cancer Data Base (NCDB), we identified female patients age 18-75, ER positive and Her 2 negative, 21 gene signature high risk &gt; 25 with negatives surgical margins, &lt;2cm, lymph node negative breast cancers, who had received endocrine therapy with either Tam or AI diagnosed during 2010 - 2017. Clinicopathologic factors and RS were entered into the RSClin calculator, and a predicted benefit of chemotherapy was calculated for each patient. Using NCDB data, Cox proportional hazards regression models were used to project absolute survival benefit at 10 years from diagnosis for those who did vs those who did not receive chemotherapy. NCDB-derived absolute benefit of chemotherapy was compared to estimated absolute benefit as predicted by the RSClin tool. Results: 18,226 patients were identified. Stages T1a = 670(4%), T1b = 4,289(23%), and T1c = 13,267(73%). Median age 59 years (21-75). Race white 84% (15,365), black 10% (1840), and other 1021(6%). AI use 80% (14,711) was greater than Tam use 20% (3515). Chemotherapy was administered in 75% (13,827) of patients. Most patients had high or intermediate grade disease, G3 45% (8225), G2 46% (8328), and G1 9% (1672). Median duration of follow up was 57 months (2-160). Probability of death T1b at 10yrs with chemotherapy was 8.5%, and without chemotherapy was 15.1% with an absolute benefit of 6.6%. Predicted benefit in T1b using RS Clin at 10yrs was 10.8%. Probability of death for T1c at 10yrs with chemotherapy was 15.1%, and without chemotherapy was 23.5% with an absolute benefit of 8.4%. Predicted benefit in T1c using RS Clin at 10yrs was 14%. Conclusions: Patients with stage IB and IC hormone receptor positive HER2 negative breast cancers with high RS had a lower absolute benefit than predicted by RS Clin. The RSClin tool overestimated benefit of therapy in both IB and IC stages requiring caution when using this tool in patients with the lowest clinicopathologic risks.

Survival outcomes in metastatic HR-positive, HER2-negative invasive ductal carcinoma compared to invasive lobular carcinoma and mixed ductal/lobular treated with endocrine therapy in combination with CDK4/6 inhibitors, mTOR inhibitor, or PI3K inhibitor.

1067 Background: The majority of invasive lobular breast cancers (ILC) are hormone receptor (HR)-positive, HER2-negative and are clinically treated similarly to HR+ HER2-negative invasive ductal cancers (IDC). However, ILC differs distinctly from IDC in its clinicopathologic characteristics and molecular alterations. ILC also differs in response to systemic therapy, with studies showing ILC as less sensitive to chemotherapy. It is currently unknown if patients with ILC or mixed ductal/lobular (MDL) histologies derive similar benefits as IDC from endocrine therapy (ET) in combination with cyclin-dependent kinase 4/6 inhibitors (CDK4/6is), mTOR inhibitor everolimus or PI3K inhibitor alpelisib. Methods: We retrospectively searched for patients treated at MD Anderson Cancer Center with a diagnosis of HR+, HER2-negative metastatic breast cancer (MBC) with ET in combination with CDK4/6is, everolimus or alpelisib. Patients were divided into 3 groups based on their histology: ILC, IDC and mixed. We obtained data on demographics, estrogen (ER) and progesterone (PR) receptor status, menopausal status, treatment duration and survival status. The Kaplan-Meier product-limit method was used to compare progression-free survival (PFS) and overall survival (OS) between the three different groups stratified by the treatment received. Results: We identified 2,971 patients (2,432 IDC [82%], 427 ILC [14%], 112 Mixed [4%]) with HR+ HER2-negative MBC treated with ET in combination with CDK4/6is, everolimus and/or alpelisib between 2010 and 2021. Median age was around 50 years in all groups. Around 80% of patients were white, 10% Hispanic and 5% black. Around 55% of patients were post-menopausal, 99% had ER+ and 88% PR+ tumors; 1,895 patients (81% IDC, 15% ILC, 4% mixed) received CDK4/6is, 1,027 (82% IDC, 14% ILC, 4% mixed) received everolimus and 49 (81% IDC, 19% ILC) received alpelisib. PFS and OS were not statistically different between the 3 groups (Table). Conclusions: HR+ HER2-negative MBC patients with IDC, ILC and MDL benefited from ET in combination with CDK4/6is, everolimus or alpelisib similarly with no significant differences in PFS and OS. [Table: see text]

Single center experience with alpelisib-fulvestrant in heavily pretreated women with HR(+), HER-2 (−) metastatic breast cancer.

e13034 Background: HR-positive, Her2-negative metastatic breast cancer patients harboring PIK3CA mutations are associated with resistance to endocrine therapy and worse prognosis. Results from the phase III SOLAR-1 trial demonstrate improved PFS for patients treated with Alpelisib-Fulvestrant after failure on first or second line treatment with aromatase inhibitor. Methods: Within an early access program for Alpelisib in a single oncology center, patients diagnosed with metastatic HR-positive, Her2 -negative breast cancer were screened for PIK3CA mutations. New generation sequencing (NGS) was the preferred technique to identify carriers with PIK3CA mutations on soft tissue or liquid biopsy. Patients who progressed and carried PIK3CA mutations received Alpelisib and fulvestrant as subsequent line of therapy. Results: Among 32 patients (pts) screened, 13 (40,6%) had a PIK3CA mutation. In total, 11 pts received alpelisib. Median age at diagnosis was 57.5 years (range, 39-69). Eight pts (72.7%) had been operated for early-stage breast cancer, 6 (54.5%) had received adjuvant chemotherapy and 5 (45.5%) had received adjuvant radiotherapy. Of 11 pts with evaluable histology, 3 pts (27.3%) had high grade tumors at diagnosis. Ten pts (90.9%) had PR positive tumors. Median Ki67 was 20% (range, 2-80). Eight pts (72.7%) had PIK3CA exon 20 and 3 (27.3%) had exon 9 mutations. Six pts (54.5%) had received prior chemotherapy in the metastatic setting and 10 (90.9%) prior CDK4/6 inhibitor. Three pts (27.3%) received Alpelisib as 2nd line and all remaining patients received alpelisib beyond 3rd line treatment. All pts (100%) had metastasis to the bones, 8 pts (72.7%) to the liver, 6 pts (54.5%) to the lungs and 2 pts (18.2%) to the brain. Until the date of last assessment, Alpelisib was administered for a median of 5.1 months (range, 0.4-21.3). Ten pts were evaluable for response to treatment with Alpelisib. One (10%) had CR, 5 (50%) SD and 4 (40%) PD as best response. Median duration of disease control was not reached. Baseline characteristics were not associated with disease control. Adverse events noticed were thrombocytopenia grade II (1/11), diarrhea grade II (2/11), skin rash grade I &amp;II (4/11), weakness grade III (1/11) and hyperglycemia (3/11). Conclusions: Prevalence of PIK3CA mutations is consistent with published data. Furthermore, combination of Alpelisib-Fulvestrant is a highly active line of therapy even in heavily pretreated patients.

Serum thymidine kinase 1 and its kinetics in HER2-positive breast cancer: Results from the Swedish phase II PREDIX HER2 trial.

e12598 Background: Thymidine kinase 1 (TK1) plays a pivotal role in DNA synthesis and cellular proliferation. TK1 has been studied as a prognostic marker and as an early indicator of treatment response in HER2-negative early and metastatic breast cancer (BC). Here we present the first report of TK1 in HER2-postitive BC. Methods: In the PREDIX HER2 trial, 202 patients with HER2-positive BC were randomized to 6 cycles of neoadjuvant trastuzumab, pertuzumab and docetaxel or trastuzumab emtansine every three weeks followed by surgery and adjuvant epirubicin and cyclophosphamide. Serum was prospectively collected from all participants at multiple timepoints: At baseline, after cycles 2, 4 and 6, at end of adjuvant therapy and then annually for 5 years and in case of recurrence. TK1 activity was measured by DiviTum assay (Biovica, Sweden), blinded to treatment allocation, patient characteristics and outcome. TK1 activity was correlated with baseline characteristics, pathologic complete response (pCR) and event-free survival (EFS). Results: Baseline TK1 activity as categorical variable was not associated with tumor size or hormone receptor expression. An increase of TK1 activity was seen in the majority of cases after treatment (mean TK1 at baseline = 111.7, after cycle 2 = 1257.0, after cycle 4 = 1157.0, after cycle 6 = 1178.0). Neither baseline TK1, on-treatment TK1 nor its change from baseline to cycle 2 were significantly associated with pCR in multivariable logistic regression analysis (Table). Baseline TK1 activity was not predictive for differential benefit to the study treatments ( pinteraction = 0.19). After a median follow-up of 52.5 months, 21 patients had EFS events. There was no significant correlation between baseline TK1 activity and EFS in multivariable Cox regression analysis. Conclusions: Serum TK1 activity in HER2-positive BC increased following treatment with neoadjuvant therapy but was not correlated to pCR rates or EFS. [Table: see text]