HER2-negative Breast Cancer Patients Research Articles

Abstract PO5-04-13: Liquid Biopsy Testing in a Greek Cohort of ER-positive, HER2-negative metastatic breast cancer patients

Abstract AIM Endocrine therapy (ET) represents the first line treatment for patients with ER+, HER2- breast cancer, however disease progression is observed in many cases. PIK3CA and ESR1 are the most encountered mutated genes that have been associated with targeted molecular treatment, as well as with resistance to Endocrine Therapy. Liquid biopsy is a non-invasive procedure, that can provide “real-time” monitoring of disease progression and response to treatment. The aim of this study is to determine the mutation rate of ESR1 and PIK3CA genes in a selected cohort of 200 Greek breast cancer patients, using liquid biopsies and NGS technology. PATIENTS AND METHODS Liquid biopsies were collected from 200 ER-positive, HER2-negative metastatic breast cancer patients who have received at least one previous line of endocrine treatment. cfDNA was extracted using the QIAamp Circulating Nucleic Acid Kit (Qiagen). Library preparation was performed using Oncomine™ Breast cfDNA Research Assay (Thermofisher Scientific) and sequencing was carried out using Ion GeneStudio™ S5 System (Thermofisher Scientific). Ion Torrent Oncomine Knowledgebase Reporter was used in sequence analysis and interpretation of Copy number variations, SNPs, and indels. RESULTS Preliminary data of the first 49 examined samples demonstrated the prevalence of ESR1 and PIK3CA mutations in 20.4% (10/49) and 38.7% (19/49) of the cases respectively. The most frequently mutated codon in the ESR1 gene is the Y537, while in the PIK3CA gene, the H1047 codon is mainly altered. ESR1 and PIK3CA genes were co-mutated in 10.2% of the cases. Mutations in KRAS (6.1%) and TP53 (24%) were also detected. CONCLUSION More than 20% of the ER-positive, HER2-negative breast cancer patients with metastatic disease are eligible for targeted treatment with elacestrant. In addition, the high prevalence of mutations detected in our cohort indicates that liquid biopsy NGS panel testing can be used to monitor treatment response, track the development of resistance, and identify emerging genetic alterations that may guide treatment adjustments or the selection of alternative targeted therapies in breast cancer patients. REFERENCES Demir Cetinkaya B, Biray Avci C. Molecular perspective on targeted therapy in breast cancer: a review of current status. Med Oncol. 2022 Jul 14;39(10):149. doi: 10.1007/s12032-022-01749-1. PMID: 35834030; PMCID: PMC9281252. Liao H, Huang W, Pei W, Li H. Detection of ESR1 Mutations Based on Liquid Biopsy in Estrogen Receptor-Positive Metastatic Breast Cancer: Clinical Impacts and Prospects. Front Oncol. 2020 Dec 15;10:587671. doi: 10.3389/fonc.2020.587671. PMID: 33384956; PMCID: PMC7770162. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-elacestrant-er-positive-her2-negative-esr1-mutated-advanced-or-metastatic-breast-cancer Citation Format: Nikolaos Tsoulos, Angeliki Meintani, Georgios Kapetsis, Chrysiis Chatzigiannidou-Florou, Aikaterini Tsantikidi, Stella Maxouri, Eleni Thanou, Kalliopi Aggelaina, Vasiliki Metaxa-Mariatou, Georgios Tsaousis, Ioannis Natsiopoulos, Vasileios Venizelos, Christos Markopoulos, Flora Zagouri, Eleftherios Kampletsas, Eirini Karyda, Dimitrios Tryfonopoulos, Konstantinos Papazisis, Dimitrios Ziogas, Ilias Athanasiadis, Eirini Papadopoulou, Georgios Nasioulas. Liquid Biopsy Testing in a Greek Cohort of ER-positive, HER2-negative metastatic breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-04-13.

Abstract PO1-14-02: Real world application of a 21-gene recurrence score in a Swiss single center breast cancer population. A comparative analysis of treatment administration before and after TAILORx

Abstract PO1-14-02: Real world application of a 21-gene recurrence score in a Swiss single center breast cancer population. A comparative analysis of treatment administration before and after TAILORx

Abstract PO5-09-04: Oncotype DX Breast Recurrence Score® analysis in early-stage breast cancer associated with CHEK2, ATM and PALB2 germline pathogenic variants

Abstract Background: The 21-gene assay (Oncotype DX Recurrence Score, RS) is the only clinically validated assay to determine the prognosis in hormone-positive, HER2-negative breast cancer (BC) patients treated with endocrine therapy alone by predicting locoregional and distant recurrence. Outcomes of Oncotype RS in BRCA-associated BC has been studied previously, but the results of RS analysis in BC patients with the other BC susceptibility genes have not been documented. This study evaluates the clinical and pathological characteristics of BC patients with ATM, CHEK2 and PALB2 germline pathogenic variants (PV). Methods: Patients with invasive hormone-positive, HER2-negative BC who have had Oncotype DX Breast Recurrence Score® testing and who underwent genetic testing in the Breast Medical Oncology and the Breast Clinical Cancer Genetics Clinic at the University of Texas MD Anderson Cancer Center (MDACC) were identified from the prospectively maintained research database. Clinical and tumor characteristics were analyzed using descriptive statistics. Results: Between 1996 and June 2023, 5652 patients with Oncotype RS were included in this analysis. Amongst those 828 BC patients had genetic testing and 81 patients were found to have a pathogenic variant: 17 patients with a CHEK2 mutation, 10 patients with an ATM mutation, and 18 patients with a PALB2 mutation. Among patients with CHEK2 PV, median Oncotype RS was 17 (5–32) overall, 21 (13–32) for patients age < 50, and 14.5 (5–28) for patients age ≥50 (p= 0.2). Among patients with ATM PV, median RS was 16.5 (3–54) overall, 25 (10–54) for patients age < 50, and 14.5 (3–29) for patients age ≥50 (p= 0.19). Among patients with PALB2 PV, median RS was 26.5 (15–40) overall, 20 (15–40) for patients age < 50, and 31 (26–37) for patients age ≥50 (p= 0.012). Further patient and tumor characteristics are shown in Table 1. Conclusion: This is a single-institutional cohort of hormone-positive, HER2-negative BC patients who had Oncotype RS and who underwent genetic testing. Further analysis on clinical and tumor pathological characteristics and long-term outcome is ongoing. Table1. Patient and tumor characteristics Citation Format: Fatma Akkoc Mustafayev, Angelica Gutierrez Barrera, Diane Liu, Banu Arun. Oncotype DX Breast Recurrence Score® analysis in early-stage breast cancer associated with CHEK2, ATM and PALB2 germline pathogenic variants [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-09-04.

Abstract PO5-04-14: Quality of Life (QoL) among metastatic hormone receptor positive, HER2 negative breast cancer patients during first line systemic treatment

Abstract Background Current international guidelines recommend endocrine therapy combined with a CDK4/6 inhibitor as the preferred first line systemic treatment in patients diagnosed with metastatic hormone receptor positive (HR), HER2 negative breast cancer (BC). Randomized controlled trials that led to the approval of these agents in the first line disease setting are derived from controlled environments and selected patients. We aimed to assess real-world patients’ characteristics, safety and health related quality of life in a non-select cohort of patients being managed in a Brazilian private Cancer Center. Methods: We performed a cross sectional study at Beneficencia Portuguesa de Sao Paulo evaluating quality of life among patients with metastatic HR+/HER2 negative treated in the first line disease setting. Inclusion criteria included patients that received the combination of a CDK4/6i with any endocrine therapy (ET) between January 2018 and April 2023. Primary endpoint was quality of life assessed using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) and EORTC QLQ-BR23, it is baseline, there is only one measurement for each patient. Results: We analyzed 72 patients who meet the inclusion criteria. Median age at diagnosis was 49 years old (ranging from 31 to 91). Approximately half of the population was premenopausal (51%). Palbociclib and abemaciclib were the most commonly used CDK4/6i, with 42 and 35% of patients, respectively. ECOG performance status was zero or one in almost the entire patient population analyzed (97%). 53% of the patients were diagnosed as de novo metastatic BC. Table 1 and 2 summarize the patients characteristics. Mean global health status was 75.4, with social and cognitive functioning scoring the highest (Mean 78.6 and 79.1, respectively). The most distressing symptom among the symptom scale was fatigue (Mean 27.2). Most symptoms and functioning scales did not meet the threshold for clinically meaningful differences between the different CDK4/6 inhibitors. Conclusion: Real-world data from our study is consistent with the historical expected health related quality of life among patients diagnosed with HR+/HER2 negative metastatic BC in the first line disease setting. Table. Citation Format: Débora Gagliato, Julio Antonio Araujo, Bianca Milena Verboski, Guilherme William Marcelino, Fabiana Nogueira Momberg, Gilmara Silveira da Silva, Rozana Mesquita Ciconelli, Antônio Buzaid. Quality of Life (QoL) among metastatic hormone receptor positive, HER2 negative breast cancer patients during first line systemic treatment [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-04-14.

Abstract PO5-14-02: Diagnostic leukapheresis to increase CTC detection rate in breast cancer patients after 5 years of adjuvant endocrine treatment

Abstract Purpose: Patients with early hormone receptor positive, HER2 negative breast cancer have a risk of recurrence for up to 20 years after the initial diagnosis and is therefore treated with adjuvant endocrine treatment (ET) for 5 to 10 years. As a result there is a large proportion of patients that overtreated, hence, an urgent need for better biomarkers to guide treatment decisions. In previous research, it was shown that circulating tumor cells (CTCs) are detected in 5% of patient after 5 years of adjuvant treatment and that this indicated a 13-fold higher risk of recurrence, with a median lead time of 2.8 years. However, the sensitivity and specificity of the test were moderate. This could be caused by stochastic variation, given the low numbers of CTCs detected in 7.5 ml peripheral blood. We hypothesized that increasing the screening volume, increases the test statistics. Methods: In this study, we investigated whether increasing the screening volume by diagnostic leukapheresis (DLA) can increase the detection rate of CTCs (CellSearch platform). With DLA, 5 liters of peripheral blood was screened, which in previous studies had shown to increase the CTC-yield per ml by 25-fold. To this end, we included early hormone receptor positive, HER2 negative breast cancer patients that were treated with ET for 4.5-5.5 years with no signs of disease recurrence. We compared the number of detected CTCs in the standard fraction of 7,5 mL peripheral blood (PB), to buffy coat (30 ml), to DLA sample (200 × 109 white blood cells (WBC), equal to 25-50 mL PB) and to DLA after WBC depletion. Results: Thirty two hormone receptor positive/HER2 negative breast cancer patients were included in this study after a median duration of ET of 60 months, of which 3 (9%) patients completed ET according to clinical guidelines and the remaining patients were still on treatment. Twenty eight patients (88%) had 1-3 positive lymph nodes at diagnosis, and 3 patients had 4-9 positive lymph nodes. The Clinical Treatment Score at 5 years (CTS5 score) was intermediate or high in 75%, and unknown in 19%, indicating a recurrence risk of >5% at years 5-10 after diagnosis. In none of the included patients, CTCs were detected in 7,5 ml PB, nor in any of the other tested blood volumes. To date, 2 patients have been diagnosed with overt metastatic disease during follow-up. DLA was well tolerated and did not cause adverse events. Conclusions: We conclude that DLA was unable to increase the detection rate of CTCs in hormone receptor positive, HER2 negative patients with early breast cancer being on treatment for a median duration of 5 years. Additional circulating tumor DNA analyses are planned. Citation Format: Noortje Verschoor, Jaco Kraan, Johanna Zuetenhorst, Mijntje Vastbinder, Jan Drooger, Stefan Sleijfer, Saskia M Wilting, John WM Martens, Agnes Jager. Diagnostic leukapheresis to increase CTC detection rate in breast cancer patients after 5 years of adjuvant endocrine treatment [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-14-02.

Abstract PO2-01-02: Clinicopathologic features and prognosis of breast cancer with low HER2 expression evaluated by fluorescence in situ hybridization

Abstract Background Although trastuzumab deruxtecan has been found to improve progression-free survival and overall survival of HER2-low breast cancer patients in DESTINY Breast04 trial, the characteristics and prognostic value of low HER2 expression remains to be elucidated. In this study, we retrospectively examined the clinicopathologic characteristics and prognosis of HER2-low expressing breast cancer. Methods A prospective database of 1026 clinical stage I to Ⅲ, HER2 negative breast cancer patients who underwent surgery from September 2012 to October 2022 at Teikyo University Hospital was analyzed. HER2 was evaluated by fluorescence in situ hybridization assay, and HER2-low and HER2-negative was defined as HER2/CEP17 ratio ≧1.0, and < 1.0, respectively. The chi-squared test was performed to estimate correlations between HER2-low status and clinicopathological factors. Distant-disease survival (DDFS) was calculated using the Kaplan-Meier curves and log-rank test. Multivariate logistic regression analyses were used to identify the independent prognostic factors. Results Median age, tumor size and ki67 of the entire 1026 patients was 56.0 years (range=23.0-93.0), 2.0 cm (range=0.3-15.0 cm), and 15.0 % (range=0.5-99.0 %), respectively. 155 (15.1 %) patients had lymph node metastasis. 904 (88.1 %) patients revealed hormone receptor positive (estrogen receptor [ER] positive; 904 patients, progesterone receptor [PgR] positive; 810 patients). Neoadjuvant and adjuvant chemotherapy was performed in 197 (19.2 %) and 160 (15.6 %) patients, respectively. Among all patients, 904 (88.1 %) patients had HER2-low tumors and 122 (11.9 %) patients had HER2-negative tumors. Positive rate of ER and PgR was significantly higher in HER2-low compared to HER2-negative patients (ER: 804 [88.9 %] patients vs 100 [82.0 %] patients; p=0.026 , PgR: 723 [80.0 %] patients vs 87 [71.3 %] patients; p=0.028). The median ki67 was significantly lower in HER2-low compared to HER2-negative patients (14.5 % vs 18.5 %, p=0.013). Pathologic complete response rates were not significantly different between HER2-low and HER2-negative patients (16.1 % [27/168 patients] vs 17.2 % [5/24 patients], p=0.528). With a median follow-up time of 39.7 months, DDFS was significantly better in HER2-low compared to HER2-negative patients (96.6 % vs 90.7 %, p=0.027). Multivariate logistic regression analyses showed that HER2-low expression was not independently related factors for DDFS. Conclusion These data suggested that HER2-low expression might not have significant association with prognosis despite significant correlation with ki67 and hormone receptor expression. Citation Format: Ayana Sato, Saki Naruse, Yuka Isono, Yuka Maeda, Miki Yamada, Akiko Matsumoto, Tatsuhiko Ikeda, Hiromitsu Jinno. Clinicopathologic features and prognosis of breast cancer with low HER2 expression evaluated by fluorescence in situ hybridization [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-01-02.

Abstract PO3-01-12: Clinicopathologic Factors affecting response in patients with Estrogen receptor-positive and Human Epidermal Growth Factor Receptor-negative breast cancer receiving neoadjuvant chemotherapy

Abstract Background: The evolution of Neoadjuvant chemotherapy(NAC) regimen has enabled the down-staging of locally advanced breast cancer, allowing patients to undergo breast conserving surgery. NAC is known to be effective in triple-negative breast cancer (TNBC) and HER2-positive breast cancer. However, the role of NAC in hormone receptor-positive and HER2-negative (HR+HER2-) breast cancer patients remains unclear. In this study, we aimed to explore the utility of NAC for estrogen receptor-positive and HER2-negative (ER+HER2-) breast cancer patients. Methods: Clinical data were collected from 120 patients who were diagnosed with estrogen receptor (ER)-positive and HER2-negative breast cancer and received neoadjuvant chemotherapy between July, 2017 and April, 2023 at Seoul St Mary’s Hospital (Seoul, Korea). We analyzed the factors that affect clinical response subgroups, including pathologic complete response (pCR), partial response (PR), stable disease(SD), and progressive disease (PD), following neoadjuvant chemotherapy. The median follow-up period was 17 months. < Results: Among 120 patients after NAC, 5.8% achieved pCR, while 67.5% had a partial response. The median age at the time of surgery was 55 years at pCR group, 49 years at PR group, 47 years at SD group, and 49 years at PD group. Although the age of patients achieving pathological complete response was higher, this differences was not statistically significant. Patients achieving pCR had a higher incidence of progesterone receptor (PR) negativity (pCR 71.4% vs PR 30.9%, p=0.011) and higher levels of Ki-67 expression than those who did not achieve pCR (71.7% vs 35.6%, p=0.003). Also, there was no significant difference in Androgen receptor (AR) and HER-2 expression between the groups. Tumor size was also significantly associated with clinical response (p=0.003). However, no differences in clinical response was observed between patients with lymph node metastasis (p=0.221). Our analysis of 107 patients who were clinically N positive before NAC showed that the Ki-67 index level was the only factor found to affect nodal pCR. In addition, in the non-pCR group, patients with a Ki-67 index of less than 20% after neoadjuvant had a significantly better disease-free survival (5yr DFS, 79.8% vs 65.9%, p=0.039) Conclusion: Our analysis revealed that patients with higher levels of Ki-67 and lower level of PR expression were more likely to achieve pCR or PR. Also, decrease in Ki-67 index was confirmed to be an important prognostic factor of ER+ HER2- breast cancer. A combination of clinical and molecular factors, such as tumor size, progesterone receptor expression, and Ki-67 expression, can be used to optimize treatment plans and improve outcomes for the patient population. Citation Format: Jin Ah Lee, Young Joo Lee, Dooreh Kim, Chang Ik Yoon, Woo-Chan Park, Soo Youn Bae. Clinicopathologic Factors affecting response in patients with Estrogen receptor-positive and Human Epidermal Growth Factor Receptor-negative breast cancer receiving neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-01-12.

Abstract PS15-04: A Phase 1b/2 study of palazestrant (OP-1250), an oral complete estrogen receptor antagonist (CERAN) and selective ER degrader (SERD), with palbociclib in ER-positive, HER2-negative, advanced or metastatic breast cancer patients

Abstract Background: Palazestrant (OP-1250) is a small molecule oral complete estrogen receptor (ER) antagonist (CERAN) and selective ER degrader (SERD) that binds the ligand binding domain of ER and completely blocks ER-driven transcriptional activity in both wild-type (ESR1-wt) and mutant (ESR1-mut) forms of ER. In preclinical studies, palazestrant demonstrated improved tumor growth inhibition and shrinkage when combined with a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. In a Phase 1/2 monotherapy clinical study in patients with ER-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer, palazestrant was well tolerated with demonstrated antitumor efficacy and favorable pharmacokinetics (PK) supporting once a day (qd) dosing at the recommended Phase 2 dose of 120 mg. In this study, pts received palazestrant at escalating doses of 30, 60, 90, and 120 mg qd in combination with palbociclib (125 mg qd) and no dose-limiting toxicities were observed. Palazestrant did not affect palbociclib PK and no drug–drug interactions (DDIs) occurred. Here we report updates on safety, efficacy, and PK from the ongoing study of palazestrant in combination with palbociclib. Methods: Patients with advanced or metastatic breast cancer with progression on or after ≤1 line of endocrine therapy (prior CDK4/6 inhibitor therapy and ≤1 chemotherapy allowed) were enrolled to receive oral palazestrant 120 mg qd with oral palbociclib 125 mg qd for 21 of 28 days (NCT0526610). Results: As of May 12, 2023, 33 patients have been treated with palazestrant in combination with palbociclib; 12 pts were dosed in the dose-escalation phase and 21 patients were dosed in the dose-expansion phase of the study. Twenty-two patients (67%) received prior CDK4/6 inhibitor therapy; 15 patients received prior palbociclib. Thirteen of 25 patients (52%) with available baseline ctDNA had an ESR1 mutation. The most common (≥20%) treatment-emergent adverse events (TEAEs) were neutropenia, nausea, vomiting, constipation, and diarrhea. Most of these events were grade 1 or 2. The most common grade 3 or 4 related AE was neutropenia (18/33 [55%] were grade 3; 3/33 [9%] were grade 4). The steady-state exposure of palazestrant when dosed with 125 mg palbociclib was consistent with the monotherapy study. Palbociclib exposure at steady-state was comparable to published monotherapy data when combined with palazestrant at all dose levels tested. As of the data cut-off, there were 4 partial responses (2 confirmed) out of 19 response-evaluable patients, with a clinical benefit rate (CBR) of 42% (8/19) across all patients and 67% (6/9) in patients with ESR1 mutations. Conclusions: Palazestrant and palbociclib dosed in combination were well tolerated with a safety profile consistent with the individual profiles of each drug as monotherapy, and there were no DDIs. Tumor responses and clinical benefit were observed in this population of patients, including those who received prior CDK4/6 inhibitors. Expanding on our previous report, these data provide the rationale to continue advancing the clinical development of palazestrant with the approved dose of palbociclib. Updated data will be presented. Citation Format: Arlene Chan, Daphne Day, Phuong Dinh, Michael Slancar, Janine Lombard, Vinod Ganju, Nicole McCarthy, Rosalind Wilson, Demiana Faltaos, Gurpreet Mathauda-Sahota, Caitlin Murphy. A Phase 1b/2 study of palazestrant (OP-1250), an oral complete estrogen receptor antagonist (CERAN) and selective ER degrader (SERD), with palbociclib in ER-positive, HER2-negative, advanced or metastatic breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS15-04.

Abstract PO2-02-09: Pathological complete response to neoadjuvant systemic therapy and its predictive factors among early breast cancer subtypes: the emerging role of HER2

Abstract Purpose Pathological complete response (pCR) after neoadjuvant chemotherapy (NACT) for breast cancer (BC) is a prognostic factor for relapse-free and overall survival (OS). Despite recent therapeutic developments for early BC, there are still a significant proportion of patients who do not achieve pCR. In this study we established pCR rates in routine care and investigated possible predictive factors of pCR, including HER2 status. Methods We evaluated 980 stage I-III BC patients receiving NACT between 2013 and 2022. Patient characteristics, rates of pCR (ypT0-is ypN0), toxicities, treatment modifications and survival outcomes were recorded. Standard histopathological variables were recorded [with HER2-low status, defined as HER2 1+ on immunohistochemistry (IHC) or 2+ on IHC without in situ hybridization (ISH) gene amplification]. Overall survival (OS) and relapse-free survival (RFS) were calculated. Median follow-up time was 60.3 months (interquartile range 19.7-78.7). Results The mean age of the study population was 49.6 ± 11.2 years. 64% had stage II disease, 70.5% had grade 3 disease, and 90.5% had ductal histopathology. 34.6% had estrogen receptor (ER)-positive/HER2-negative, 27.1% had triple-negative (TN), and 38.3% had HER2-positive BC. 233 patients (23.8%) had HER2-low disease. pCR rate was 35.8% in the overall population, 16.8% in ER-positive/HER2 negative BC, 32.7% in TNBC and 55.2% in HER2-positive BC. pCR rate differed according to grade, histology, HER2 status, radiological and clinical response of disease (p < 0.001) and early discontinuation of NACT (p = 0.001), but not according to age, menopausal status, BRCA status, platinum use, NACT dose reduction or delays, neutrophils-to-lymphocytes, platelets-to-lymphocytes, or lymphocytes-to-monocytes ratios. OS and RFS were better following pCR [HR 0.23 (95% CI, 0.14-0.38, p < 0.001) and HR 0.27 (95% CI, 0.18-0.40, p < 0.001), respectively]. Among HER2-negative BC patients (605, 61.7% of the entire cohort), there was a trend to lower pCR rate in HER2-low compared to HER2-negative (IHC 0) BC (19.7% vs 26.3% respectively, p = 0.06). pCR rate was significantly lower in ER-positive/HER2-low compared to ER-positive/HER2-negative (IHC 0) BC (12.1% vs 20.9% respectively, p = 0.031), while no difference in pCR rates was observed in TNBC patients by HER2 status. Despite a lower rate of pCR, Kaplan-Meyer curve showed that OS was significantly better in the HER2-low BC compared to HER2-negative (IHC 0) population at 100-months follow up. Multivariable Cox-regression model in the HER2-negative BC cohort demonstrated that HER2-low status was an independent predictor of OS (HR 0.59, 95% CI, 0.39-0.89 p = 0.012). Conclusions In our real-world analysis, pCR rates are consistent with the published data. Many patients still have residual disease following NACT, predicting worse outcomes, and may benefit from further adjuvant systemic therapies. Consistent with other studies, our findings suggest a possible prognostic and predictive role of HER2-low status especially among patients with ER-positive BC. This could lay the foundations for novel therapies targeting HER2 among HER2-low cancer subtypes. Citation Format: Matilde Corianò, Nicolo M.L. Battisti, Hala Aziz, Nalinie Joharatnam Hogan, Antonino Musolino, Alistair Ring. Pathological complete response to neoadjuvant systemic therapy and its predictive factors among early breast cancer subtypes: the emerging role of HER2 [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-02-09.

Abstract PO1-23-08: Exosome-based delivery of microRNAs confers adriamycin-resistance to sensitive cells through modulating the immune and metabolism-related gene PTEN in HER2-negative breast cancer

Abstract Background: Anthracycline-based chemotherapy is widely used to treat breast cancer. However, acquired drug resistance remains a challenge to successful treatment. Recently, increasing evidence has shown that changes in the tumour immune microenvironment (TIME), in addition to increasing drug resistance of tumour cells, consistently contribute to the development of chemoresistance. Methods: TIME scores and tumor-infiltrating immune cells (TICs) scores were used to investigate the prognosis, clinicopathological characteristics and gene transcriptome profiling of HER2-negative breast cancer patients who received anthracycline-based chemotherapy. Exosomes isolated from MCF/7-ADR (ADR-exos) and MCF/7-S (S-exos) cell lines were characterized. We identified dysregulated miRNAs using miRNA microarray analysis on MCF/7-ADR cells and their exosomes compared to MCF/7-S cells and their exosomes. Protein profiling was performed to identify differentially expressed proteins in up- and down-regulated miR-222 cells. The ability of ADR-exos to transfer drug-resistance mediated by miR-222 was assessed by immunofluorescence assay, flow cytometry and qRT-PCR. We optimized the conditions to load miR-222 mimic (or inhibitor) into exosomes produced by HBL-100 cells (H-exos). The influence of miR-222 inhibitor-containing exosomes (inhibitor-exos) on the downstream pathway of miR-222 and the potential therapeutic effects both in vitro and in vivo were evaluated. We also evaluated the relationship between miR-222/PTEN and drug resistance in circulating exosomes from mice after adriamycin-based chemotherapy. Results: Firstly, we discovered the complicated and heterogenous TICs subtypes and their unique biological behaviors in HER2-negative breast cancer. Then, we identified 85 differentially expressed immunologic signature gene sets and 7202 corresponding immune-related genes in three subtypes quantified by gene set variation analysis (GSVA). We identified 12 up-regulated and 13 down-regulated genes using miRNA microarray analysis in adriamycin-resistant cells and their exosomes. The TMT mass spectrometry found 45 differentially expressed proteins affected by the miR-222 level. Moreover, we successfully established miRNA mimic/inhibitor-containing exosomes to explore the solo function of exosomal miR-222 in adriamycin-resistance both in vitro and in vivo. More importantly, for the first time, we detected the levels of miR-222 and its target gene PTEN in circulating exosomes from mice after adriamycin-based chemotherapy and explored the potential clinical implications of miR-222/PTEN-containing exosomes in chemotherapy and immune suppression of breast cancer patients. Conclusions: HER2-negative breast cancer patients own unique TIME subtypes, leading to different outcomes of chemotherapy. We exhibit the potential applications of miR-222-mimic/inhibitor-containing exosomes for reversing chemo-resistance. Adriamycin-resistant cells can transmit drug-resistance to sensitive cells via delivering miR-222 by modulating the immune- and metabolism-related target gene PTEN both in vitro and in vivo without interference from other relevant drug-resistance factors in exosomes. Therefore, miR-222-containing exosomes as well as their target gene PTEN may be a promising biomarker for predicting the efficacy of chemo-resistance and tumor immunity regulation in breast cancer patients receiving anthracycline-based chemotherapy. Keywords: exosomes, breast cancer, tumor immune microenvironment, chemo-resistance, microRNAs Citation Format: Sujin Yang, Tian-cheng Cheng, Jia-hao Wu, Wei-xian Chen. Exosome-based delivery of microRNAs confers adriamycin-resistance to sensitive cells through modulating the immune and metabolism-related gene PTEN in HER2-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-23-08.

Abstract PO5-02-14: Clinical-pathological determinant factors to choose between four or six cycles of adjuvant chemotherapy with docetaxel/cyclophosphamide (TC) in a retrospective real-world cohort of HER2-negative breast cancer patients

Abstract Introduction: The long-term severe adverse events associated with anthracyclines, including irreversible cardiotoxicity, myelodysplastic syndromes, and therapy-related leukemias, led researchers to question the risk-benefit of anthracycline-based chemotherapy regimens, especially for patients without axillary lymph node involvement, leading to an increasing trend to omit anthracyclines in adjuvant treatment. Docetaxel plus cyclophosphamide (TC) has replaced doxorubicin plus cyclophosphamide (AC) for lower-risk patients that need adjuvant chemotherapy. However, the optimal number of cycles of adjuvant in patients with node-positive or node-negative breast cancer is currently unknown. Methods: We performed a retrospective cohort study of patients with HER2-negative breast cancer, stage I to III, that received adjuvant docetaxel and cyclophosphamide (TC) for four or six cycles, treated from January 2010 to December 2021. Patients were included from four cancer institutions, both private and public, located in the South, Southeast, and Northeast of Brazil. Objectives: To investigate the clinical-pathological characteristics and survival of earlystage HER2-negative breast cancer patients who received four (TC4) or six cycles (TC6) of adjuvant docetaxel and cyclophosphamide (TC). Results: We collected data from six hundred and ninety-eight patients, 98.7% were female with an average age of 52 years, 51.9% were postmenopausal, 14.6% BRCA gene mutation, 66% had some comorbidity, and only 8.4% were not candidates for anthracyclines. Two hundred and twenty-five patients had public and 473 private health insurance. About 13.2% of the patients were hormone receptor negative (HR-) and 86.8% hormone receptor positive (HR+), 57.4% breast-conserving surgery and 77.7% sentinel lymph node (SL). Five hundred sixty-four (80.8%) patients received TC4 and 134 (19.2%) TC6. We observed that patients who received TC 6 had unfavorable prognostic factors such as: (TC4 vs TC6) previous breast cancer (8.7% vs 16.3%) (p=0.002), invasive ductal carcinoma (IDC) (73.4 vs 86.7%) (p=0.009), histological grade 3 (HG3) (34.9 vs 42.9%) (p= 0,085) conservative surgery (59.4% vs 53%) (p=0144), SL (80.9% vs 62.2%) (p =0.001), Lymph node positive (15% vs 42.3%) (p=0.001), pathological stage II (37.5% vs 50%) (p=0.001).Treatment completion rates were 96.5% and 84.3% for TC4 and TC6, respectively (p=0,02). The incidence of grade 3 or higher toxicity with TC6 (14% vs 21.1%; p= 0,043). Febrile neutropenia was observed in 6.7% of both groups. Grade 3 or higher neuropathy was most common with TC6 (2.2% vs 10.3%; p=0,163). Permanent treatment discontinuation was more frequent in the TC6 group (3.4% vs. 9.8%; p=0,004), as well as late toxicity (3.4% vs. 9.2%; p=0,004). Ninety-four percent of the patients completed the proposed cycles of chemotherapy, 72% received adjuvant radiotherapy and 85.4% received adjuvant hormone therapy, with 42% of these receiving an aromatase inhibitor for 5 years. The median follow-up of the entire cohort was 61 months. There was no difference in the 5-year DFS (77.5% vs. 64.7%; p=0.159) or the 5-year OS (89.5% vs. 70.5%; p= 0,06) between patients treated with TC4 and TC6. Conclusion: TC6 was commonly used for patients with unfavorable prognostic factors as history of previous breast cancer, (IDC), HG III, lymph node positive and stage II. Patients who received TC6 had less chance of completing the treatment and more severe toxicity, especially late peripheral neuropathy. There was no difference in DFS or OS. Citation Format: Mila Kraychete, Marcelle Cesca, Guilherme Almeida, Leonardo Santana, Luciana Leite, Solange M. Sanches, Vladmir Cordeiro de Lima, Rafaela Pirolli, Rafael Manea, Felipe Kaneta, Jean Coutinho, Lucas Vian, Waires Zeviani, Marcio Reis, Luciana Landeiro, Clarissa Mathias, Geila Nunez, Tamara Santana, Monique Tavares. Clinical-pathological determinant factors to choose between four or six cycles of adjuvant chemotherapy with docetaxel/cyclophosphamide (TC) in a retrospective real-world cohort of HER2-negative breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-02-14.

Abstract PO2-02-03: Clinical and pathological factors associated with Oncotype DX® 21-Gene recurrence score in patients diagnosed with early stage breast cancer in a low-middle income country

Abstract INTRODUCTION: Oncotype DX® recurrence score (ODX RS) is a 21-gene assay warranted to determine the the prognosis in patients with hormone receptor positive, HER-2 negative early stage breast cancer. In this context, the test is also predictive of benefit of adjuvant chemotherapy.1,2,3 OBJECTIVES: We aimed to correlate the clinical and pathological factors associated with Oncotype DX® 21-Gene in patients diagnosed with early stage Breast Cancer. Additionally, description of adjuvant treatment patterns and survival outcomes were described according to the Oncotype DX® 21-Gene result. METHODS: Data from medical records from a single center in Brazil were collected retrospectively from women over 18 years diagnosed with early breast cancer between 2012 and 2022. Included patients were diagnosed with stage T1-T2 breast cancer, hormone receptor positive, HER-2 negative, with up to three positive lymph nodes. All included patients had an Oncotype DX® test performed after definitive breast surgery. The ODX RS has been categorized into two levels according to menopausal status. Correlation between breast cancer recurrence and clinicopathological characteristics was done. The software SPSS was used for statistical analyzes with the significance of 0.05. RESULTS: From 197 patients, 20 have had breast cancer recurrence (10.15%) whom 10 were premenopausal and 10 were postmenopausal. The median ODX RS in these 20 patients was 15 (ranged from 9 to 31). The most common site of recurrence was breast and regional recurrence in 18 patients (90%). Adjuvant chemotherapy was omitted in 16 patients (80%) who have had breast cancer recurrence. Among premenopausal patients whose ODX RS was >20, 33 patients (91.66%) received adjuvant chemotherapy. Among postmenopausal patients whose ODX RS was >25, 19 (86.36%) received adjuvant chemotherapy. The probability of recurrence free survival was worse in premenopausal patients > 44-years-old compared to those with < =44 years-old (p = 0.036) and also worse in histological grade 3 tumors compared to grade 1 (p=0.0048). Tumor size >14 millimeters (mm) was correlated to worse recurrence free survival in premenopausal patients (p=0.017). Low estrogen and progesterone receptor was associated with a higher ODX RS (p=0.0035 and p< 0.0001, respectively) in premenopausal patients, but not associated with recurrence free survival. Clinicopathological characteristics and recurrence free survival correlation in postmenopausal patients were not significant. CONCLUSION: This retrospective analysis suggests that factors other than the Oncotype DX® score, such as age and grade contributed to worse survival outcomes among our patients population. Of note, age older than 44 years-old, histological grade 3 and tumor size >14 mm were associated with a higher probability of recurrence in premenopausal patients, despite the Oncotype DX® score. REFERENCES: 1. Paik S, Shak S, Tang G, Kim C, Baker J, Cronin M, et al. A multigene assay to predict recurrence of tamoxifen-treated, node-negative breast cancer. N Engl J Med [Internet]. 2004;351(27):2817–26. Available from: http://dx.doi.org/10.1056/NEJMoa041588. 2. Sparano JA, Gray RJ, Makower DF, Pritchard KI, Albain KS, Hayes DF, et al. Adjuvant chemotherapy guided by a 21-gene expression assay in breast cancer. N Engl J Med [Internet]. 2018;379(2):111–21. Available from: http://dx.doi.org/10.1056/NEJMoa1804710. 3. Kalinsky K, Barlow WE, Gralow JR, Meric-Bernstam F, Albain KS, Hayes DF, et al. 21-gene assay to inform chemotherapy benefit in node-positive breast cancer. N Engl J Med [Internet]. 2021;385(25):2336–47. Available from: http://dx.doi.org/10.1056/NEJMoa2108873. Table 1 – Clinical and pathological characteristics of 197 hormone receptor positive, HER-2 negative early breast cancer patients who did the Oncotype DX® 21-Gene Recurrence Score assay. Data from medical records collected retrospectively of women diagnosed with early breast cancer between 2012 and 2022 from a single center in Brazil. Figure 1 – Probability of recurrence free survival in premenopausal patients according to age <=44 (blue line) or > 44-years-old (pink line). Data from medical records collected retrospectively of women with hormone receptor positive, HER-2 negative early breast cancer who did the Oncotype DX® 21-gene assay diagnosed between 2012 and 2022 from a single center in Brazil. Figure 2 – Probability of recurrence free survival in premenopausal patients according to histological grade. Tumor with histological grade 1 (blue line) or histological grade 3 (pink line). Data from medical records collected retrospectively of women with hormone receptor positive, HER-2 negative early breast cancer who did the Oncotype DX® 21-gene assay diagnosed between 2012 and 2022 from a single center in Brazil. Citation Format: Carolina Cavalcanti Gonçalves Ferreira, Julio Araujo, Shermann Brandão Rodrigues Moreira, Antônio Buzaid, Débora Gagliato. Clinical and pathological factors associated with Oncotype DX® 21-Gene recurrence score in patients diagnosed with early stage breast cancer in a low-middle income country [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-02-03.

Abstract PO1-01-07: Cryoablation and endocrine therapy for clinical stage I/II, ER+ breast cancer in patients with omission of surgical axillary staging. A retrospective study

Abstract OBJECTIVE To evaluate the efficacy of combined treatment with ultrasound-guided cryoablation and endocrine therapy (ET) in hormone receptor-positive (ER+), HER2-negative (HER-) invasive breast cancer (BC) patients with clinical stage I/II who are not candidates for axillary surgery. PATIENTS AND METHODS Patients with ER+, HER- invasive BC in clinical stage I/II who did not undergo sentinel lymph node biopsy (SLNB) or target axillary dissection (TAD) were included. They received treatment consisting of ultrasound-guided cryoablation combined with daily letrozole 2.5 mg orally. Cryoablation was performed as the initial treatment for BC < 15mm, followed by adjuvant ET, while neoadjuvant ET was administered for 6-12 months before cryoablation for BC ≥ 15mm. Cryoablation was performed using the ICEfx Galil argon gas system (Boston Scientific, USA) and the ProSense liquid nitrogen system (IceCure Medical Ltd, Caesarea, Israel). Follow-up breast ultrasound examinations were conducted every six months. Patients with a minimum follow-up of 12 months after cryoablation were included in the study. Core needle biopsies were performed if recurrence was suspected, and rescue cryoablation was considered for confirmed relapse. The tolerance and safety of the procedures were recorded. RESULTS From March 2019 to July 2023, a total of 96 patients with 105 ER+, HER2- invasive BC in clinical stage I/II who did not undergo SLNB or TAD were treated with ultrasound-guided cryoablation and ET. Among them, 58 patients (aged 58-96 years, mean 83, SD ±7.64) with 64 BC lesions (ranging from 5 to 60mm, mean 17, SD ±13.75) were followed up for a minimum of 12 months, with a mean follow-up period of 24 months (ranging from 12 to 50 months). The invasive carcinomas included 40 ductal, 16 lobular, 5 colloid, and 3 papillary cases. The ipsilateral breast tumor recurrence rate was 1,72% (1/58 patients). One patient with lobular carcinoma experienced a relapse at 17 months. Rescue cryoablation was performed, and after 25 months, she remains free of recurrence. Therefore, local control was achieved in all patients. Six patients died from causes unrelated to BC during the follow-up period. All procedures were well-tolerated with local anesthesia, and no serious complications were reported. CONCLUSION Ultrasound-guided cryoablation with ET constitutes an effective combined treatment for the local control of ER+, HER2- BC in patients with clinical stage I/II and omission for surgical axillary staging. Cryoablation is a very well tolerated procedure without morbidity. Citation Format: José María Oliver Goldaracena, Pilar Zamora, Covadonga Marti, Vicenta Córdoba Chicote, Maria José Roca Navarro, Diego Garrido Alonso, Ylenia Navarro Monforte, Teresa Diaz de Bustamante Durban, Fernando García Martínez, Jose Ignacio Sanchez-Mendez, Elisa York Pineda, Laura Yebenes Gregorio, Adolfo Loayza, Laura Frías Aldeguer, Elisa Moreno Palacios, Marcos Melendez Gisper, Joaquin Gomez Ramirez, Luis Asensio Gómez, Virginia Martínez Marín, David Hardisson Hernáez, Alberto Berjón García. Cryoablation and endocrine therapy for clinical stage I/II, ER+ breast cancer in patients with omission of surgical axillary staging. A retrospective study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-01-07.

Abstract PO3-16-06: Perceptions and experiences of patients and healthcare providers on genetic testing and treatment of early breast cancer: qualitative findings

Abstract Background: Olaparib is approved as adjuvant therapy for high-risk HER2-negative early breast cancer (eBC) patients with germline BRCA mutations (BRCAm). Understanding patients’ preferences for genetic testing and treatment in the context of shared decision-making is needed to support optimal care in eBC. This study elicited the perspectives of patients with eBC and healthcare providers (HCP) treating eBC regarding treatment decision-making, and drivers and barriers to BRCA testing. Methods: Semi-structured interviews were conducted in the United States from Jan-Feb 2023 with women (n=12) diagnosed with eBC from 2017-2021. Community and academic oncologists treating eBC (n=12) and genetic counselors (GCs; n=8) were also interviewed. Patients who were tested (n=7) and untested (n=5) for BRCAm were included. A content and thematic analysis was performed which identified key factors from the data; these analyses provided both a range and common responses that may influence BRCA testing and treatment decisions. Results: BRCA-tested patients considered testing beneficial. In choosing to receive testing, >50% of patients reported HCP recommendation (n=7) and the opportunity to have “all of the information” about their eBC (n=7) as strong influencers. Patients declined genetic testing noting fear around negative impact to their insurance coverage (n=2) or mental health (n=3), or if they did not have family who would benefit from the information. Cost did not strongly influence testing choice. In choosing a treatment, patients sought to maintain their quality of life (QoL) with fewer side effects while minimizing chance of recurrence. They expressed the dual goals of normalcy during treatment, including curtailing side effects that impact QoL, and returning to normalcy after treatment (n=7). Patients were willing to accept unpleasant side effects to have a more effective treatment if those side effects do not severely impact their QoL and the treatment is highly effective (n=9). Side effects that may lead to hospitalization were the least accepted as they disrupt normalcy. HCPs reported that patients eagerly accept testing and face minimal familial or access barriers to testing. HCPs observed that among their non-Medicare patients, testing is usually covered by insurance with minimal out-of-pocket costs, thus alleviating financial constraints observed in previous years. HCPs believe BRCA testing is driven by updated hereditary cancer testing guidelines (e.g., NCCN), lower testing costs, closer collaborations of physicians and genetic counselors, and greater awareness among patients. HCPs reported that they embrace patient-led decision-making in eBC, especially as it relates to patients with BRCAm considering additional prophylactic surgery, and GCs further emphasized patient autonomy. Oncologists mentioned that they discuss risk status starting at diagnosis and these conversations evolve over the patient journey as new information emerges. In HR+ eBC, oncologists offered most patients with BRCAm adjuvant olaparib, which they perceive as well tolerated. In triple-negative eBC, oncologists opted for neoadjuvant Keytruda regimen prior to considering adjuvant olaparib for gBRCAm patients. Conclusions: Patients value information that empowers them to achieve their goals of normalcy and remission that can be achieved by addressing QoL, side effects, and patients' goals of living “normally”. Though prior research highlighted insurance coverage and costs as significant barriers to BRCA testing, results from this study suggest that cost was not a major factor in testing decisions. Prior barriers to testing access have been mitigated making it more available and affordable than in the past, which could be broadly communicated to patients and HCPs to minimize misperception. Citation Format: Jagadeswara Earla, Emily Mulvihill, Josh Lankin, Lauren Howell, Alex Kissling, Weiyan Li, Jaime Mejia. Perceptions and experiences of patients and healthcare providers on genetic testing and treatment of early breast cancer: qualitative findings [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-16-06.

Abstract PO3-16-02: Trastuzumab and taxane chemotherapy in the first-line in MBC patients with a HER2-negative primary tumor and HER2-positive circulating tumor cells: a phase II trial

Abstract Purpose: HER2 overexpressing circulating tumor cells (CTCs) are observed in up to 20% of HER2-negative metastatic breast cancer patients. Since targeted anti-HER2 therapy has drastically increased the outcome of patients with HER2 positive breast cancer, we hypothesized that patients with HER2 overexpressing CTCs might benefit from the addition of trastuzumab to chemotherapy. Methods: In this single-arm, phase II trial, HER2 negative patients with HER2-positive CTCs received trastuzumab as addition to first-line treatment with taxane chemotherapy (trastuzumab group). Patients with detectable CTCs but without HER2 overexpression and that received taxane chemotherapy only, were used as internal control group (taxane monotherapy group). The primary outcome measure was progression-free rate at 6 months (PFR6). The study was powered to reach a PFR6 of 80%; in this case this strategy was considered worth further investigation. In November 2022, the study was terminated early due to slow patient accrual. Results: 63 HER2 negative patients with metastatic disease were screened, of which 8 patients had HER2-positive CTCs and were treated in the first line with trastuzumab in addition a taxane. Patients receiving taxane monotherapy were used as a control group (n = 27). The median number of CTCs was 15 (range 1 – 131) in patients with HER2-positive CTCs, compared to median 5 (range 1-1047) in the control group. PFR6 was 50% in the trastuzumab group and 64% in the taxane monotherapy group, with no significant difference in median PFS (8 versus 9 months, p=0.51). Excluding the patients that had no measurable CTCs, there was a borderline significant difference between median CTC count in the patients that did and that did not have HER2 positive CTCs (p=0.05). We confirmed a significant higher CTC-count in samples that had at least one HER2-postive CTC in an independent patient set (n=233, p< 0.001). Conclusions: Although this study was performed in a limited number of patients, no clinical benefit of trastuzumab was observed. Firstly, we conclude that our strategy was not feasible for clinical implementation due to high numbers needed to screen. And, second, due to the strong correlation between CTC numbers and detected CTC HER2 positivity, the prognostic value of the CTC numbers precludes judgement of any predictive value of the HER2 status of CTCs. Citation Format: Noortje Verschoor, Manouk Bos, Inge de Kruijff, Ngoc M Van, Jaco Kraan, Jan Drooger, Johanna Zuetenhorst, Saskia M Wilting, Stefan Sleijfer, Agnes Jager, John WM Martens. Trastuzumab and taxane chemotherapy in the first-line in MBC patients with a HER2-negative primary tumor and HER2-positive circulating tumor cells: a phase II trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-16-02.

Abstract PO3-08-11: Association between Histologic Variants and the Results of Multigene Testing in Patients with Hormone Receptor-positive, HER2-negative Invasive Lobular Cancer

Abstract Invasive lobular carcinoma (ILC), which accounts for approximately 5-15% of all breast cancers, can be divided into classic type and various other variants. Multigene testing (MGT) has prognostic value in hormone receptor (HR)-positive, HER2-negative breast cancer. We aimed to investigate the association between the results of MGT and histological variation of ILC. 1582 HR-positive, HER2-negative breast cancer patients treated between January 2014 and December 2022 were reviewed. Patients were divided into three groups; ILC-favorable group, ILC-unfavorable group and invasive ductal carcinoma (IDC) group. The ILC-favorable group consisted of classic and tubulolobular types, while the ILC-unfavorable group included pleomorphic, solid, signet ring cell, florid, and alveolar types according to the reported prognosis of each ILC variant. Among the various types of MGT, the 21-gene assay (OncotypeDX), the 70-gene assay (Mammaprint), and the 12-gene assay (Endopredict) assay were used in clinical setting. The median age of patients was 50 years (range 20-85 years). 75.5% of patients received the 21-gene assay, 12.8% received the 70-gene assay, and 11.6% received the 12-gene assay. The high-risk results in MGT were showed in 7.7% of 155 patients in ILC-favorable group, 26.1% of 23 patients in ILC-unfavorable group, and 20.9% of 1404 patients in IDC group (p-value < 0.001). In the multivariate logistic regression analysis, ILC-favorable group showed significantly lower odds of high-risk results compared to IDC group (OR=0.284, 95% CI; 0.147-0.548), while ILC-unfavorable group did not show any significant difference compared to IDC group (OR=0.797, 95% CI; 0.263-2.411). In comparison to IDC, the variants of ILC with favorable prognosis show lower rates of high-risk results in MGT, while the variants of ILC with poor prognosis do not differ significantly from IDC. For patients who diagnosed the variants of ILC with poor prognosis, MGT could be useful for prognosis prediction or treatment decision-making. Citation Format: Jee Hyun Ahn, Suk Jun Lee, Seung Hye Yang, Jee Ye Kim, Hyung Seok Park, Seung Il Kim, Byeong Woo Park, Seho Park. Association between Histologic Variants and the Results of Multigene Testing in Patients with Hormone Receptor-positive, HER2-negative Invasive Lobular Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-08-11.

Prognostic value of EndoPredict test in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative primary breast cancer screened for the randomized, double-blind, phase III UNIRAD trial

The purpose of this study was to evaluate the prognostic value of the multigene EndoPredict test in prospectively collected data of patients screened for the randomized, double-blind, phase III UNIRAD trial, which evaluated the addition of everolimus to adjuvant endocrine therapy in high-risk, hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative early breast cancer. Patients were classified into low or high risk according to the EPclin score, consisting of a 12-gene molecular score combined with tumor size and nodal status. Association of the EPclin score with disease-free survival (DFS) and distant metastasis-free survival (DMFS) was evaluated using Kaplan-Meier estimates. The independent prognostic added value of EPclin score was tested in a multivariate Cox model after adjusting on tumor characteristics. EndoPredict test results were available for 768 patients: 663 patients classified as EPclin high risk (EPCH) and 105 patients as EPclin low risk (EPCL). Median follow-up was 70 months (range 1-172 months). For the 429 EPCH randomized patients, there was no significant difference in DFS between treatment arms. The 60-month relapse rate for patients in the EPCL and EPCH groups was 0% and 7%, respectively. Hazard ratio (HR) supposing continuous EPclin score was 1.87 [95% confidence interval (CI) 1.4-2.5, P < 0.0001]. This prognostic effect remained significant when assessed in a Cox model adjusting on tumor size, number of positive nodes and tumor grade (HR 1.52, 95% CI 1.09-2.13, P= 0.0141). The 60-month DMFS for patients in the EPCL and EPCH groups was 100% and 94%, respectively (adjusted HR 8.10, 95% CI 1.1-59.1, P < 0.0001). The results confirm the value of EPclin score as an independent prognostic parameter in node-positive, hormone receptor-positive, HER2-negative early breast cancer patients receiving standard adjuvant treatment. EPclin score can be used to identify patients at higher risk of recurrence who may warrant additional systemic treatments.

Changes in blood metabolomes as potential markers for severity and prognosis in doxorubicin-induced cardiotoxicity: a study in HER2-positive and HER2-negative breast cancer patients.

We aimed to compare the changes in blood metabolomes and cardiac parameters following doxorubicin treatment in HER2-positive and HER2-negative breast cancer patients. Additionally, the potential roles of changes in blood metabolomes as severity and prognostic markers of doxorubicin-induced cardiotoxicity were determined. HER2-positive (n = 37) and HER2-negative (n = 37) breast cancer patients were enrolled. Cardiac function assessment and blood collection were performed at baseline and 2weeks after completion of doxorubicin treatment in all patients, as well as at three months after completion of doxorubicin treatment in HER2-negative breast cancer patients. Blood obtained at all three-time points was processed for measuring cardiac injury biomarkers. Blood obtained at baseline and 2weeks after completion of doxorubicin treatment were also processed for measuring systemic oxidative stress and 85 metabolome levels. Cardiac injury and systolic dysfunction 2weeks after completion of doxorubicin treatment were comparable between these two groups of patients. However, only HER2-negative breast cancer patients exhibited increased systemic oxidative stress and cardiac autonomic dysfunction at this time point. Moreover, 33 and 29 blood metabolomes were altered at 2weeks after completion of doxorubicin treatment in HER2-positive and HER2-negative breast cancer patients, respectively. The changes in most of these metabolomes were correlated with the changes in cardiac parameters, both at 2weeks and 3months after completion of doxorubicin treatment. The changes in blood metabolomes following doxorubicin treatment were dependent on HER2 status, and these changes might serve as severity and prognostic markers of doxorubicin-induced cardiotoxicity. The study was conducted under ethical approval from the Institutional Review Board of the Faculty of Medicine, Chiang Mai University (Registration number: MED-2563-07001; Date: April 28, 2020). The study also complied with the Declaration of Helsinki.

Real-world data of HER2-negative early breast cancer patients treated with anthracycline and/or taxane regimens in Japan.

Anthracycline- and taxane-based chemotherapy regimens are established treatments for human epidermal growth factor receptor (HER)2-negative early-stage breast cancer with high risk of recurrence. This study examined the prevalence of these chemotherapy regimens as perioperative therapy, the patterns of retreatment, and factors influencing prescription choices in Japan. This observational cohort study focused on high-risk early-stage breast cancer patients not undergoing anti-HER2 therapy, utilizing data from a hospital-based claims database in Japan spanning from April 2008 to September 2021. Of 42,636 high-risk patients who underwent breast cancer surgery, 32,133 (75.4%) were categorized as having luminal-type (received endocrine therapy) and 10,503 (24.6%) as having triple-negative cancer (not receiving any endocrine therapies). Most patients (98.7%) with luminal-type breast cancer received perioperative therapy, and 40.3% of those received anthracycline/taxane. In the triple-negative group, 57.0% of all patients received perioperative therapy and of those, 93.4% received anthracycline/taxane. Being over 40years old, having an early stage (clinical stage ≤ II), and receiving treatment in non-specialized facilities were associated with less use of anthracycline/taxane in the luminal-type group. For the triple-negative group, associated factors with less use of anthracycline/taxane included being over 60years old, treatment in small hospital (capacity < 200 beds), and treatment in non-specialized facilities. Approximately half the patients in both the luminal-type and triple-negative groups were prescribed anthracycline and/or taxane for perioperative chemotherapy. The choice was associated with patient age, cancer stage, and the scale and specialization of the treatment facilities. This study sheds light on the current state of breast cancer treatment practices in Japan.

Abstract LB242: Prediction of patient response to neoadjuvant chemotherapy in breast cancer from their deconvolved tumor microenvironment transcriptome

Abstract Introduction: The tumor microenvironment (TME) is a complex and dynamic ecosystem that plays critical roles in tumor development and clinical outcome. While the multifarious cellular interactions within the TME have been extensively studied with a significant emphasis on immunotherapy, understanding its role in chemotherapy outcome remains less explored. To this end, we present a novel generic computational framework named DECODEM (DEcoupling Cell-type-specific Outcomes using DEconvolution and Machine learning). DECODEM facilitates the exploration of the association of cell-type-specific gene expression profiles with the effectiveness of neoadjuvant chemotherapy (NAC) in treating breast cancer (BC). This approach holds promise for elucidating the nuanced ways in which the TME can modulate therapeutic efficacy, potentially paving the way for more personalized and effective cancer treatments. Methods: DECODEM employs cellular deconvolution of bulk transcriptomics to extract cell-type-specific gene expression profiles within the TME, and subsequently harnesses machine learning to construct cell-type-specific predictors of clinical outcomes. Utilizing DECODEM, we analyzed three publicly available cohorts of HER2-negative BC patients who received NAC. We assessed the predictive capabilities of the individual cell types as well as their collective influence, benchmarking against a state-of-the-art predictor that employs both clinical and transcriptomic features. We corroborated our findings in a single-cell (SC) transcriptomics cohort of patients with triple negative breast cancer (TNBC) undergoing chemotherapy. Further, we expanded DECODEM to DECODEMi, which accounts for cell-cell interactions (CCIs) among the predominant cell types, offering potential insights into the mechanistic processes governing clinical responses. Results: Our analysis indicated that the heterogeneous composition of the TME is crucial for chemotherapy response prediction in HER2-negative BC, beyond the influence of malignant cells alone. The key insights from our study are as follows:1. Gene expression of immune cells (myeloid, plasmablasts, B-cells) and stromal cells (endothelial, normal epithelial, cancer-associated fibroblasts) displayed comparable-to-superior predictive powers over both bulk expression and the state-of-the-art predictor.2. The predictive accuracy is further augmented by multi-cell-type ensembles, with a triad ensemble comprising endothelial, myeloid, and plasmablast cells achieving the highest predictive accuracy across multiple cohorts.3. DECODEMi can effectively capture the regulatory impact of CCIs (validated in a SC dataset sourced from the SC-TNBC cohort) and has identified novel CCIs likely to influence chemotherapy response in HER2-negative BC. Conclusion: We provide an unprecedented computational methodology to quantitatively assess the cell-type-specific influences of the TME on clinical outcome. Our analysis offers insights into the complex interactions among TME cells and their correlation with chemotherapy efficacy in HER2-negative BC, thereby enriching the knowledge base of BC treatment effectiveness. Citation Format: Saugato Rahman Dhruba, Sahil Sahni, Binbin Wang, Di Wu, Yael Schmidt, Eldad Shulman, Sanju Sinha, Stephen-John Sammut, Carlos Caldas, Kun Wang, Eytan Ruppin. Prediction of patient response to neoadjuvant chemotherapy in breast cancer from their deconvolved tumor microenvironment transcriptome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB242.