TNBC Subtype Research Articles

Impact of Proton Irradiation Depending on Breast Cancer Subtype in Patient-Derived Cell Lines

Research on different types of ionizing radiation’s effects has been ongoing for years, revealing its efficacy in damaging cancer cells. Solid tumors comprise diverse cell types, each being able to respond differently to radiation. This study evaluated the radiobiological response of established (MDA-MB-231 (Triple negative breast cancer, TNBC), MCF-7 (Luminal A)) and patient-derived malignant cell lines, cancer-associated fibroblasts, and skin fibroblasts following proton IRR. All cell line types were irradiated with the proton dose of 2, 4, and 6 Gy. The radiobiological response was assessed using clonogenic assay, γH2AX, and p53 staining. It was noticeable that breast cancer lines of different molecular subtypes displayed no significant variations in their response to proton IRR. In terms of cancer-associated fibroblasts extracted from the tumor tissue, the line derived from a TNBC subtype tumor demonstrated higher resistance to ionizing radiation compared to lines isolated from luminal A tumors. Fibroblasts extracted from patients’ skin responded identically to all doses of proton radiation. This study emphasizes that tumor response is not exclusively determined by the elimination of breast cancer cells, but also takes into account tumor microenvironmental variables and skin reactions.

Risk of locoregional recurrence after breast cancer surgery by molecular subtype-a systematic review and network meta-analysis.

The prevention of locoregional recurrence (LRR) is crucial in breast cancer, as it translates directly into reduced breast cancer-related death. Breast cancer is subclassified into distinct intrinsic biological subtypes with varying clinical outcomes. To perform a systematic review and network meta-analysis (NMA) to determine the rate of LRR by breast cancer molecular subtype. A NMA was performed as per PRISMA-NMA guidelines. Molecular subtypes were classified by St Gallen expert consensus statement (2013). Analysis was performed using R and Shiny. Five studies were included including 6731 patients whose molecular subtypes were available. Overall, 47.3% (3182/6731) were Luminal A (LABC: estrogen receptor (ER) + /human epidermal growth factor receptor-2 (HER2) - /progesterone receptor (PR) + or Ki-67 < 20%), 25.5% (1719/6731) were Luminal B (LBBC: ER + /HER2 - /PR - or Ki-67 ≥ 20%), 11.2% (753/6731) were Luminal B-HER2 + (LBBC-HER2: ER + /HER2 +), 6.9% (466/6731) were HER2 + (HER2 ER - /HER2 +), and finally 9.1% (611/6731) were triple-negative breast cancer (TNBC: ER - /HER2 -). The median follow-up was 74.0months and the overall LRR rate was 4.0% (271/6731). The LRR was 1.7% for LABC (55/3182), 5.1% for LBBC (88/1719), 6.0% for LBBC-HER2 (45/753), 6.0% for HER2 (28/466), and 7.9% for TNBC (48/611). At NMA, patients with TNBC (odds ratio (OR) 3.73, 95% confidence interval (CI) 1.80-7.74), HER2 (OR 3.24, 95% CI 1.50-6.99), LBBC-HER2 (OR 2.38, 95% CI 1.09-5.20), and LBBC (OR 2.20, 95% CI 1.07-4.50) were significantly more likely to develop LRR compared to LABC. TNBC and HER2 subtypes are associated with the highest risk of LRR. Multidisciplinary team discussions should consider these findings to optimize locoregional control following breast cancer surgery.

Optimal management of breast cancer with physical exam negative/radiological abnormal axilla

For breast cancer patients with physical exam node negative but radiological finding node abnormal (cN0/rNa), the NCCN and ASCO guidelines recommend sentinel lymph node biopsy (SLNB) as the first-line axillary staging. However, patients who undergo surgery firstly may be upstaged to pathological II–III status, and these patients happen to be the adaptive population of neoadjuvant therapy (NAT). There is no consensus on the optimal management of cN0/rNa patients. The aim is to explore the optimal management strategy of these patients. We performed a retrospective real-world study of 1414 cN0/rNa patients from June 2014 to October 2022. There were 1003 patients underwent surgery first and 411 patients underwent surgery after NAT. We analyzed the real-world conditions of these patients, compared axilla tumor burden between these two groups. In addition, we compared benefit ratio of axillary surgery and regional nodal irradiation (RNI) de-escalation under the two strategies. Among 1003 patients underwent surgery first, the positive and negative rates of fine needle aspiration (FNA) were 18.5% and 81.5%, respectively. There were 66.1% had ≤ 2 lymph nodes+. There were 40.8% of FNA+ patients could be exempted from ALND underwent surgery first. In 411 patients underwent surgery after NAT, the FNA positive and negative rates were 60.8% and 49.2%, respectively. There were 54.4% of FNA+ patients achieved axilla pathologic complete response (apCR) and could omit ALND after NAT. The apCR was 67.3% in HER2+/TNBC subtypes. According to the NSABP-B51 trial, there were 0 and 54.4% of FNA+ patients could omit RNI among surgery first and after NAT, respectively. Among 1–2 sentinel lymph node (SLN)-positive patients underwent surgery first, with a median follow-up 49 months, there was no difference of survival benefit between SLNB-only and SLNB-ALND. Compared with 1–2 SLN+ patients without RNI, RNI could bring better invasive disease-free survival (97.38% vs. 89.36%, P = 0.046) and breast cancer special survival (100% vs. 94.68%, P = 0.020). It is safe to perform SLNB omitting ALND when detected 1–2 positive SLNs in cN0/rNa patients. Patients with HER2+/TNBC subtypes underwent surgery after NAT had more chance to benefit from dual de-escalation, including axillary surgery and RNI de-escalation.

Direct DNA binding by BRCA1 on β-hCG promoter and its clinical implications

ObjectiveThe role of β-hCG in breast cancer is largely unknown, this study aims to analyse the gene expression and clinical implications of β-hCG and its isoforms in various cancers focussing particularly in Breast Invasive Carcinoma (BRCA). A mechanistic approach deciphering the transcriptional regulation of β-hCG by BRCA1 was also explored. MethodsData from various comprehensive gene expression platforms like UALCAN, GEPIA2, GENT2, TIMER2, LinkedOmics, and STRING were used to analyse the expression of β-hCG and its clinical implications; Immunohistochemistry and ELISA for β-hCG expression analysis from human breast cancer patients; Electrophoretic mobility shift assay (EMSA) to analyse the direct binding of BRCA1 on β-hCG; Immunoblotting and Luciferase assay to understand the regulation of β-hCG by p53 were performed. ResultsResults from UALCAN and GENT2 gene expression cancer database revealed that TNBC subtypes and high-grade metaplastic carcinoma shows elevated expression of β-hCG and infiltration of various immune cells were also identified in BRCA by TIMER2. It was observed that most of the isoforms of β-hCG (CGB) are upregulated in breast cancers irrespective of hormonal status when BRCA1 gene is mutated according to TIMER2. Similar results were observed with Lymphoid neoplasm diffuse large B-cell lymphoma (LGG) and DLBC (Brain lower grade glioma) when BRCA1 is mutated. These results correlate with our earlier reports indicating expression of β-hCG in BRCA1 defective condition. We have also identified direct binding of BRCA1 on β-hCG promoter. ConclusionAll these findings demonstrate the importance of β-hCG as a potential target in BRCA1-deficient carcinomas.

Combination of polymeric micelle formulation of TGFβ receptor inhibitors and paclitaxel produces consistent response across different mouse models of Triple‐negative breast cancer

AbstractTriple‐negative breast cancer (TNBC) is notoriously difficult to treat due to the lack of targetable receptors and sometimes poor response to chemotherapy. The transforming growth factor beta (TGFβ) family of proteins and their receptors (TGFRs) are highly expressed in TNBC and implicated in chemotherapy‐induced cancer stemness. Here, we evaluated combination treatments using experimental TGFR inhibitors (TGFβi), SB525334 (SB), and LY2109761 (LY) with paclitaxel (PTX) chemotherapy. These TGFβi target TGFR‐I (SB) or both TGFR‐I and TGFR‐II (LY). Due to the poor water solubility of these drugs, we incorporated each of them in poly(2‐oxazoline) (POx) high‐capacity polymeric micelles (SB‐POx and LY‐POx). We assessed their anticancer effect as single agents and in combination with micellar PTX (PTX‐POx) using multiple immunocompetent TNBC mouse models that mimic human subtypes (4T1, T11‐Apobec and T11‐UV). While either TGFβi or PTX showed a differential effect in each model as single agents, the combinations were consistently effective against all three models. Genetic profiling of the tumors revealed differences in the expression levels of genes associated with TGFβ, epithelial to mesenchymal transition (EMT), TLR‐4, and Bcl2 signaling, alluding to the susceptibility to specific gene signatures to the treatment. Taken together, our study suggests that TGFβi and PTX combination therapy using high‐capacity POx micelle delivery provides a robust antitumor response in multiple TNBC subtype mouse models.

BECN1 mRNA expression in breast cancer tissue; significant correlation to tumor grade

Breast cancer (BC) is a heterogenous disease with multiple pathways implicated in its development, progression, and drug resistance. Autophagy, a cellular process responsible for self-digestion of damaged organelles, had been recognized as eminent player in cancer progression and chemotherapeutic resistance. The haploinsufficiency of Beclin 1 (BECN1), autophagy protein, is believed to contribute to cancer pathogenesis and progression. In our study, we investigated the expression of BECN1 in a BC female Egyptian patient cohort, as well as its prognostic role through evaluating its association with disease free survival (DFS) after 2 years follow up and association of tumor clinicopathological features. Twenty frozen female BC tissue samples and 17 adjacent normal tissue were included and examined for the expression levels of BECN1. Although the tumor tissues showed lower expression 0.73 (0–8.95) than their corresponding normal tissues 1.02 (0.04–19.59), it was not statistically significant, p: 0.463. BECN1 expression was not associated with stage, nodal metastasis or tumor size, p:0.435, 0.541, 0.296, respectively. However, statistically significant negative correlation was found between grade and BECN1 mRNA expression in the studied cases, p:0.028. BECN1 expression had no statistically significant association with DFS, P = 0.944. However, we observed that triple negative (TNBC) cases had significantly lower DFS rate than luminal BC patients, p: 0.022, with mean DFS 19.0 months, while luminal BC patients had mean DFS of 23.41 months. Our study highlights the potential role of BECN1 in BC pathogenesis, showing that BECN1 expression correlates with poorer differentiation of BC, indicating its probable link with disease aggressiveness. DFS two years follow up showed that TNBC subtype remains associated with less favorable prognosis.

Abstract PO2-15-05: Mesenchymal-like immune-activated: the 4th robust triple-negative breast cancer molecular subtype

Abstract Triple-negative breast cancer (TNBC) accounts for 15-20% of primary BC. This heterogeneous disease is the most aggressive BC subtype. TNBC is characterized by young age at onset, high-grade tumors, high risk of early recurrence and poor prognosis. Until recently, TNBC patients were considered as one group and all patients were treated with conventional chemotherapy. With the emergence of new therapies targeting distinct biological pathways, personalized medicine is now accessible by defining finer TNBC subtypes, e.g. molecular subtypes, and identifying their specific targetable pathways. Several studies based on transcriptomics have identified three to six TNBC molecular subtypes. Today, there is a clear consensus on three TNBC robust subtypes: luminal androgen receptor (LAR), basal-like immune-activated (BLIA) and basal-like immune-suppressed (BLIS). The debate about the robustness of other subtypes is still open, notably mesenchymal-like (M) and mesenchymal stem-like (MSL or MES). The goal of this study was to establish a robust molecular classification of TNBC that allow to determine the best treatment options. To optimize this process, we harvested as much transcriptomic data as possible. Available clinicopathological data linked to these data were also imported. To our knowledge, this is the largest study aimed at subtyping TNBC; it exploits a total of 1942 TNBC patient data collected from 19 datasets: 1243 samples from microarray technology (14 datasets) and 699 from RNAseq technology (five datasets including a new one from our institution [GSE225002]). We performed independent unsupervised analyses on these two large cohorts with consensus k-means clustering including selection of optimal number of clusters and optimal number of variables. Both consensus clustering analyses separated TNBC microarray and RNAseq TNBC cohorts into four optimal clusters. These clusters were then characterized using clinicopathological features, gene ontology enrichment analyses (GOEA), gene set enrichment analysis (GSEA), 70 gene expression signatures (GES) and expression of 47 immune checkpoint genes. We concluded that TNBC are composed of four robust subtypes: LAR, mesenchymal-like immune-activated (MLIA), BLIA and BLIS. Importantly, we propose that MLIA acronym should replace M or MSL, because it highlights the two main biological characteristics of this subtype, i.e. mesenchymal-like features and a high IR comparable to that of BLIA. Furthermore, we showed that each subtype shares common biological characteristics with another one: LAR and MLIA (androgen receptor pathway activation); MLIA and BLIA (immune activation, notably high levels of immune checkpoints); BLIA and BLIS (basal-like features); BLIS and LAR (immune suppression). As regards microarray cohort, LAR included 19.23% (n = 239) of TNBC, MLIA 17.38% (n = 216), BLIA 32.50% (n = 404) and BLIS 30.89% (n = 384). Concerning RNAseq cohort, LAR included 19.60% (n = 137) of TNBC, MLIA 17.31% (n = 121), BLIA 28.47% (n = 199) and BLIS 34.62% (n = 242). Distributions of patients among the four clusters in the two cohorts were similar (p = 0.3583). Distributions were also similar between studies for microarray cohort (p = 0.2479) and RNAseq cohort (p = 0.1775). Pooled data (n = 1942 patients) gave the following distribution: 19.36% for LAR; 17.35% for MLIA; 31.06% for BLIA; 32.23% for BLIS, confirming that TNBC are largely but not exclusively basal-like (63.29%). In brief, according to the TNBC subtype molecular characterisation, anti-androgen therapy could be prescribed for LAR, immune checkpoint inhibitors for MLIA and BLIA, alone or in combination, and TAM-focused and antineurogenic therapies for BLIS. As an extension of this work, TNBC transcriptomic data associated with their clinicopathological features and TNBC subtype annotations were included in bc-GenExMiner v5.0 web tool (http://bcgenex.ico.unicancer.fr). Citation Format: Mario Campone, Pascal Jézéquel, Fadoua Ben Azzouz, Wilfried Gouraud, Agnes Bassevile, Bertrand Michel, Hamza Lasla, Jean Sebastien FRENEL. Mesenchymal-like immune-activated: the 4th robust triple-negative breast cancer molecular subtype [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 PO2-15-05.

Abstract PO2-08-02: Evaluation of predictive and prognostic value of androgen receptorexpression in breast cancer subtypes treated with neoadjuvantchemotherapy

Abstract Background Neoadjuvant chemotherapy is the standard treatment for local advanced breast cancer administered to shrink tumors and destroy undetected metastatic cells, thereby facilitating subsequent surgery. Previous studies have shown that AR may be used as a prognostic predictor in breast cancers, but its role in neoadjuvant therapy and the relationship with prognosis of different molecular subtypes of breast cancer need to be further explored. Methods We retrospectively evaluated 1231 breast cancer patients with complete medical records at Tianjin Medical University Cancer Institute and Hospital who were treated with neoadjuvant chemotherapy between January 2018 to December 2021. All the patients were selected for prognostic analysis. The follow-up time ranged from 12 to 60 months. We first analyzed the AR expression in different subtypes of breast cancer and its correlation with clinicopathological features. Meanwhile, the association of AR expression and pCR of different breast cancer subtypes was investigated. Finally, the effect of AR status on the prognosis of different subtypes of breast cancer after neoadjuvant therapy was analyzed. Results The positive rates of AR expression in HR +/HER2-, HR +/HER2 +, HR-/HER2 + and TNBC subtypes were 82.5%, 86.9%, 72.2% and 34.6%, respectively. Histological grade III (P = 0.014, OR = 1.862, 95% CI 1.137 to 2.562), ER positive expression (P = 0.002, OR = 0.381, 95% CI 0.102 to 0.754) and HER2 positive expression (P = 0.006, OR = 0.542, 95% CI 0.227 to 0.836) were independent related factors for AR positive expression. AR expression status was associated with pCR rate after neoadjuvant therapy only in subtype of TNBC. AR positive expression was independent protective factor for recurrence and metastasis in HR +/HER2- (P = 0.033, HR = 0.653, 95% CI 0.237 to 0.986) and HR +/HER2 + breast cancer (P = 0.012, HR = 0.803, 95% CI 0.167 to 0.959), but was independent risk factors for recurrence and metastasis in TNBC (P = 0.015, HR = 4.551, 95% CI 2.668 to 8.063). AR positive expression is not an independent predictor of HR-/HER2 + breast cancer. Conclusions AR expressed the lowest in TNBC, but it could be a potential marker for the prediction of pCR in neoadjuvant therapy. AR negative patients had a higher pCR rate. AR positive expression was an independent risk factor for pCR in TNBC after neoadjuvant therapy (P = 0.017, OR = 2.758, 95% CI 1.564 to 4.013). In HR +/HER2- subtype and in HR +/HER2 + subtype, the DFS rate in AR positive patients and AR negative patients was 96.2% vs 89.0% (P = 0.001, HR = 0.330, 95% CI 0.106 to 1.034) and was 96.0% vs 85.7% (P= 0.002, HR = 0.278, 95% CI 0.082 to 0.940), respectively. However, in HR-/HER2 + and TNBC subtypes, the DFS rate in AR positive patients and AR negative patients was 89.0% vs 95.9% (P = 0.102, HR = 3.211, 95% CI 1.117 to 9.224) and 75.0% vs 93.4% (P &amp;lt; 0.001, HR = 3.706, 95% CI 1.681 to 8.171), respectively. In HR +/HER2- and HR +/HER2 + breast cancer, AR positive patients had a better prognosis, however in TNBC, AR-positive patients have a poor prognosis Citation Format: Jin Zhang. Evaluation of predictive and prognostic value of androgen receptorexpression in breast cancer subtypes treated with neoadjuvantchemotherapy [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 PO2-08-02.

Abstract PO2-16-10: Characterising HER2-low status in metastatic breast cancer: a real-world retrospective study of patients at a metropolitan cancer centre in Australia

Abstract Background: Traditionally, breast cancer subtyping has described patients as HER2-negative or HER2-positive, with the latter being those in whom HER2-directed therapies are utilised. A proportion of HER2-negative cancers can be classified as “HER2-low” as they express IHC 1+ or 2+ and are non-amplified on in-situ hybridisation (ISH). Until recently, our widely available HER2-targeted therapies have proven to be ineffective in this subtype. The DESTINY-BREAST04 trial (Modi et al, NEJM 2022) showed progression-free and overall survival efficacy of HER2-directed therapy using the antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd) in HER2-low disease, suggesting a need to identify this population for selected therapy. This study evaluated a real-world population of metastatic breast cancer (MBC) patients treated according to traditional breast cancer subtypes to determine the frequency of HER2-low histology, with a focus on selection of first-line therapy. Methods: This retrospective audit identified patients being treated for MBC at a single tertiary hospital (Austin Health in Melbourne, Australia) over a 3.5 year period. Patients were identified from an electronic database, with a date of last follow-up as August 2022. Medical records were interrogated for clinicopathological information including review of pathology reports for breast cancer subtypes. Traditional breast cancer subtypes were defined as (i) ER positive and HER2-negative (HER2 0 or 1+, or 2+ and non-amplified); (ii) HER2-positive (HER2 3+ and/or amplified) and (iii) TNBC (negative for ER and PgR, and HER2 0 or 1+, or 2+ and non-amplified). Selection and duration of first-line treatment for MBC was also recorded. Results: Between March 2018 and August 2022, 202 MBC patients were identified. Based on traditional subtypes, 126 (62%) were ER positive and HER2-negative, 46 (23%) were HER2-positive, 26 (13%) were TNBC and 4 (2%) were unknown. In the total population, 87 (43%) were classified as having HER2-low disease based on retrospective pathology reports. HER2-low represented 61% of ER positive, HER2-non amplified patients and 45% of TNBC patients. Metastatic specimen data was known for 172 cases and of these, 95 patients (55%) were re-biopsied on metastatic progression. This occurred more commonly with HER2-positive (81%) and ER positive HER2-negative (78%) primaries. The most common change in subtype was loss of ER, which occurred in 7 patients (3%). Changes in HER2 status occurred in 29 (14%) of patients, most commonly as either an increase from 1+ to 2+ or decrease from 1+ to 0. HER2-low status remained consistent for 67% of patients who underwent biopsy on recurrence. For patients with ER positive HER2-negative MBC, first-line combination therapy with a CDK4/6 inhibitor + AI was preferred (51%), followed by single agent endocrine therapy (30%) and chemotherapy (17%). The majority (84%) of HER2-positive patients received first-line dual HER2 therapy (trastuzumab and pertuzumab) with taxane chemotherapy. Half of TNBC patients received upfront chemotherapy, with physician preference being capecitabine (45%). There was no significant difference in PFS between the HER2-low vs. HER2-0 cohorts, for either ER positive or TNBC subtypes. No patients in this series were treated based on HER2-low definition due to no funded access to such therapies at the time. Conclusion: HER2-low has emerged as an identifier for patients who may respond to HER2-directed therapies using ADCs such as T-DXd. However, its clinical significance as a discrete clinical subtype remains uncertain. In this retrospective audit, HER2-low patients were identified in both ER positive and TNBC subtypes. Dynamic changes in HER2 staining occurred infrequently. Further evaluation is needed to address whether HER2-low expression provides any prognostic value and whether prospective reporting of HER2-low status may alter how these new HER2-directed therapies are used in future. Citation Format: Michelle Li, Belinda Yeo. Characterising HER2-low status in metastatic breast cancer: a real-world retrospective study of patients at a metropolitan cancer centre in Australia [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 PO2-16-10.

Abstract PO4-05-11: Effects of body mass index on the treatment outcome of patients with metastatic breast cancer in the real world

Abstract Purpose: Metastatic/recurrent breast cancer has a relatively long survival compared to other cancers and depending on the biologic subtype, the treatment outcome is different. In general, obesity or overweight is associated with poor prognosis of breast cancer, but the relationship between body mass index (BMI) and prognosis in metastatic cases is not clear. The aim of this study is investigating the effect of BMI on survival outcome through long-term follow-up in single institution, retrospectively. Method: This study included the patients with metastatic/recurrent breast cancer who has been diagnosed from January 2000 to December 2022 in an institution. BMI was calculated based on weight at diagnosis of metastatic disease, divided into 4 groups according to Asian-Pacific classification, and clinical characteristics including biologic subtype and overall survival (OS) were retrospectively reviewed. The statistical analysis was performed using Kaplan-Meier survival analysis and Cox proportional hazard model. Result: A total of 679 patients were enrolled. Median age was 51 years-old (25~89), 672 patients (99.0%) were female and 425 patients (62.6%) showed pre-menopausal status. The frequencies of HR+, HER2, and TNBC subtype were 335 (50.7%), 191 (28.9%), and 135 (20.4%), respectively and the BMI classification was 33 (5.5%), 251 (41.6%), 124 (20.5%), 196 (32.4%) for underweight, normal, overweight, and obesity, respectively. During a median follow-up of 33.8 months, the median OS in each of the HR+, HER2+, and TNBC subgroups was 54.9 (95% CI 38.7-71.1), 62.8 (95% CI 47.8-77.8), and 20.8 months (95% CI 12.0-29.7). In univariate analysis, there was no statistically significant difference in OS according to BMI in whole patients, however, in the HER2-positive group, the underweight BMI group showed poor OS (p=0.045). In multivariate analysis, the factors affecting OS were age (HR 0.59, 95% CI 0.41-0.87, p=0.008), poor ECOG PS (HR 8.35, 95% CI 2.54-27.49, p&amp;lt; 0.001), TNBC subtype (HR 2.14, 95% CI 1.56-2.94, p&amp;lt; 0.001), visceral metastasis (HR 2.13, 95% CI 1.63-2.79, p&amp;lt; 0.001), 5% or more weight loss during treatment (HR 1.46, 95% CI 1.09-1.97, p=0.012) and obesity BMI group (HR 0.69, 95% CI 0.51-0.94, p=0.019). Conclusion: In the case of patients with metastatic/recurrent breast cancer, there is concern about an increase in body weight, a known risk factor for breast cancer, while receiving palliative aim treatment. For the past 20 years, the mainstay of treatment for metastatic/recurrent breast cancer has been cytotoxic chemotherapy or anti-HER2 agents, and in this case, the higher BMI group patients showed better treatment outcomes compared with normal BMI patients. Citation Format: Kyoung Eun Lee, Ahrong Ham, Sewon Lee, Jungmin Jo, Soo Ji Hong, Ji Eun Lee, Haena Lee, Sungchan Gwark, Jeongshin An, Hyun-Goo Kim, Jun Woo Lee, Joohyun Woo, Woosung Lim, Byung-In Moon, Sei Hyun Ahn, Hye Ah Lee. Effects of body mass index on the treatment outcome of patients with metastatic breast cancer in the real world [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 PO4-05-11.

Abstract PO5-10-07: Risk factors associated with secondary cancers in AYA patients with breast cancer. A SEER database study

Abstract Background Adolescents and young adults (AYA) diagnosed with breast cancer face unique challenges and have distinct characteristics compared to older patients. While primary breast cancer remains a significant concern, the risk of developing secondary cancers in this population is also of great importance. This study aimed to identify these risk factors by analyzing a large cohort of AYA breast cancer patients using SEER (Surveillance Epidemiology and End Result) Database. Methods Patients were identified from SEER Research Data 17, from 2000 to 2019. Patients aged 18-39 years with breast cancer and at least 1 year of survival were identified. Secondary cancers were then identified and included any disease site. Patient demographic and clinical characteristics were summarized by secondary cancer status using Mann-Whitney U and Fisher’s exact tests. Overall survival from the initial breast cancer diagnosis was summarized by secondary cancer status using standard Kaplan-Meier methods, where the median and 3/5-year rates were estimated with 95% confidence intervals. Comparisons were made using the log-rank test. SAS v9.4 (Cary, NC) was used at a significance level of 0.05. Results A total of 47,912 AYA breast cancer patients were identified, of which 2,886 (6.0%) developed a secondary cancer at least 1 year after the initial breast cancer diagnosis. When comparing patients with and without secondary cancers, we observed significant differences with respect to age at initial breast cancer diagnosis, race, stage, nodal status, surgical procedure, ER status, PR status, Her2 status, and sub-type (Table 1). The analysis of overall survival showed that, from the time of breast cancer diagnosis, there was no statistically significant difference between patients with and without secondary cancers. However, this may be due to an immortal time bias. Breast was the most common site of secondary cancer (67%) followed by gynecological (7%), colorectal (3.7%), skin (3.4%) lung and hematologic (2.7%) Compared to other subtypes, TNBC patients were found to have much shorter time to secondary cancer development of 38 months compared to Her2+ and ER/PR+ (40 and 45 months respectively, P&amp;lt; 0.001). Black and Hispanic individuals were found to have higher rates (7.4% and 6.3%) and earlier development of secondary cancer (76 months and 74 months) as compared to whites and Asians (5.9% and 5%, 88 months and 81 months, P&amp;lt; 0.001 and P&amp;lt; 0.002 respectively). Conclusion This study identified several risk factors associated with the development of secondary cancers in AYA breast cancer patients such as age at initial breast cancer diagnosis, race, stage, nodal status, surgical procedure and sub-type. Higher rates and early development of secondary cancer were observed among TNBC subtype and Black and Hispanic races that calls for further investigation and tailored interventions to improve outcomes in specific patient populations. Table 1 showing significant differences in characteristics AYA breast cancer patients who developed secondary breast cancer compared to those who did not Citation Format: Sheeba Ba Aqeel, Alankrita Taneja, Shipra Gandhi. Risk factors associated with secondary cancers in AYA patients with breast cancer. A SEER database 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 PO5-10-07.

Abstract PO3-06-03: Overall Survival and Disease Interval Among Breast Cancer Subtypes in Patients with Brain Metastasis

Abstract Background: Breast cancer brain metastasis (bcbm) is associated with limited survival. There is a paucity of clinical trials and real-world data on the survival and disease interval [primary breast cancer (pbc) to metastatic breast cancer (mbc) or bcbm] of bcbm patients. We performed a retrospective study comparing the overall survival (OS) and disease intervals (INT) between the date of pbc surgery, diagnoses of mbc, and bcbm among 3 subtypes of bc in patients with bcbm. Methods: The informatics team generated a preliminary list of patients with a history of breast cancer and brain metastasis who were treated at the Wilmot Cancer Institute (WCI) of the University of Rochester. Key inclusion criteria were evidence of bcbm, bcbm diagnosed between Jan 1st, 2010 and June 1st, 2021, and adequate medical records available. Patients with de novo mbc were excluded. Final eligible patients were registered for the study. Median OS in bc subtypes was assessed with the Kaplan-Meier method and compared using the log-rank test. Median INTs among bc subtypes were compared using the Kruskal-Wallis test. Registered patients were divided into triple-negative (TNBC), estrogen receptor-positive/HER2 negative (ER+/HER2-), and HER2+ subtypes. Results: Out of 191 patients screened, 83 patients were eligible for the study. The total number of patients enrolled by subtype was 26 (TNBC), 35 (ER+/HER2-), and 22 (HER2+). Disease and patient characteristics are shown in Table 1. Median OS from pbc, mbc, and bcbm among 3 subtypes are shown in Table 2. The differences in the median OS from these 3 different time points were not statistically significant among 3 subtypes. After adjusting for important variables (age, race, tumor grade, stage, and presence of perioperative therapy) in a Cox regression model, there was still no statistical evidence that these 3 subtypes differed in OS. Three different INTs (pbc-mbc, pbc-bcbm, mbc-bcbm) among 3 subtypes are shown in Table 3. INTpbc-mbc and INTpbc-bcbm were significantly different among 3 subtypes of bc. After adjusting for the factors in the model, the subtypes didn’t differ significantly with respect to INTpbc-mbc and INTpbc-bcbm. Stage 3 at pbc was significantly associated with shorter INTpbc-mbc and INTpbc-bcbm. The distribution of INTmbc-bcbm was highly non-normal due to the high % of patients with concurrent diagnoses of mbc and bcbm. Thus an exploratory logistic regression model assessed the association of subtypes and important variables with the odds of having mbc and bcbm concurrently (INTmbc-bcbm&amp;lt; 1 month). It showed that the ER+/HER2- subtype had 4 times lower odds of concurrent mbc and bcbm diagnosis than the HER2+ subtype (p=0.03). In an unadjusted pairwise comparison between the subtypes (Table 3), the ER+/HER2- group had statistically longer INTpbc-mbc and INTpbc-bcbm than TNBC. However, when the subtypes were adjusted for Stage 3 vs 1 or 2, these subtypes were not significantly different for these INT. In our study, a higher proportion of Stage 3 tumors in TNBC subtype is likely associated with the shorter INTs seen with TNBC in unadjusted analysis. Conclusion: Adjusted comparison of OS and disease intervals from pbc between TNBC, ER+/HER2-, and HER2+ subtypes were not statistically different in this cohort of bcbm patients. Interestingly, median OS from mbc were numerically very similar (3.6-3.7 years) among these subtypes. Median OS from pbc and bcbm were numerically longer in HER2+ bc than the other 2 subtypes. Intervals between pbc to mbc and to bcbm and between mbc to bcbm were numerically longer in ER+/HER2- subtypes than the other 2 subtypes. ER+/HER2- subtype was 4 times less likely to have concurrent bcbm at the time of mbc diagnosis than the HER2+ subtype. These results are exploratory and hypotheses generating. Table 1: Disease and Patients Characteristics Table 2: Overall Survival Unadjusted Table 3: Disease Intervals Unadjusted Citation Format: Asis Shrestha, Sugam Gouli, Sujan Niraula, Ramandeep Babbra, Niraj Neupane, Sarah Stanford, Myla Strawderman, Zeni Kharel, Huina Zhang, Sara Hardy, Nimish Mohile, Carey Anders, David Hicks, Ruth O'Regan, Ajay Dhakal. Overall Survival and Disease Interval Among Breast Cancer Subtypes in Patients with Brain Metastasis [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 PO3-06-03.

Abstract PO1-26-01: Leveraging Clinicopathological Factors and Deep Learning-Based Morphometrics for PDX Engraftment Success Prediction in Breast Cancer

Abstract Background: Patient-derived xenografts (PDXs) are pivotal in cancer research. Despite histopathological insights into factors driving PDX success, the role of artificial intelligence (AI) in predicting PDX engraftment remains unexplored. We aimed to bridge this gap by integrating clinicopathological data and AI-based morphometric analysis to predict PDX success in breast cancer. Methods: PDXs were generated from tumor tissues derived from breast cancer patients who had undergone surgical intervention. Clinicopathological information including subtypes, pathological diagnosis, modified Bloom-Richardson system histologic grades, treatment with neoadjuvant chemotherapy (NAC), Miller Payne grade, residual caner burden score, invasive tumor size, lymphovascular invasion status, AJCC 8th T and N stages and the percentage of tumor infiltrating lymphocytes were collected and analyzed. For the image analysis component, whole-slide images (WSIs) of hematoxylin and eosin–stained tissue samples from 64 surgically resected breast cancer patients were used as a training set for an AI model under the supervision of 2 pathologists to extract morphometric features. The model transformed image tiles into patches of morphologically similar patterns, and categorized them into adipose tissue, background, necrosis, invasive carcinoma, carcinoma in situ, stroma, and terminal ductal lobular unit. This trained model was subsequently applied to the WSIs employed in the establishment of PDXs. The classified patches and their relative ratios within the invasive tumor boundary were compiled. The consolidated data from clinicopathological and image analyses were subjected to logistic regression to discern correlates of successful PDX engraftment. Results: Out of the 311 patient tumor samples used for generating PDXs, (131 post-chemotherapy, 180 chemo-naïve), 47 PDXs were successfully established (15.1%). Logistic regression revealed several factors for successful engraftment including NAC treatment with an odds ratio of 6.71 (28.2% vs 5.6%, 95% CI: 2.53 - 17.80, p &amp;lt; 0.001), higher histologic grades (25.3% vs 2.2%, OR = 5.80, 95% CI: 1.49 - 22.63, p = 0.01), triple negative breast cancer compared to hormone receptor-positive cancers (32.0% vs 3.3%, OR = 10.99, 95% CI: 1.26 - 95.89, p = 0.03), and tumors of larger size (OR = 1.34, 95% CI: 1.02 - 1.76, p = 0.03). Interestingly, the percentage of specific tissue patch types within tumor did not significantly impact the likelihood of successful PDX engraftment. However, in our logistic regression analysis based solely on morphometric features, presence of necrosis within the tumor notably enhanced PDX establishment. Specifically, each percent increase in necrosis within tumor boosted the odds of successful PDX creation by 0.01% (OR = 1.0001, 95% CI: 1.00003 - 1.00024, p = 0.01). Conclusions: PDXs are often successfully established from clinically aggressive breast cancers, particularly those with NAC treatment, higher histologic grades, TNBC subtype, and larger tumor size. While morphometric features contribute to the prediction of PDX engraftment success, their importance is surpassed by these clinicopathological factors. However, presence of necrosis emerged as a key morphometric predictor of successful PDX engraftment. Keywords: breast cancer; patient-derived xenograft (PDX); Breast Cancer Morphometrics; Cancer Predictive Modeling. Citation Format: Jongwon Lee, GeonHee Lee, Gyungyub Gong, Hee Jin Lee. Leveraging Clinicopathological Factors and Deep Learning-Based Morphometrics for PDX Engraftment Success Prediction in 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 PO1-26-01.

Abstract PO5-25-01: Treating liver metastases by reversing cell competition between metastatic cancer cells and hepatocytes

Abstract Background: Although breast cancer liver metastases (BCLM) are common events, with 40-50% of patients with metastatic breast cancer developing liver metastases, their development indicates poor prognosis. Patients with BCLM have a 5-year survival rate of 8%. Specific treatments for liver metastases are virtually non-existent, partly because the key events of early liver metastasis formation remain unknown. The liver is a dense organ, and metastatic breast cancer cells (MCC) must clear space among hepatocytes, the primary cell population in the liver, during metastatic formation. Cell competition is a developmentally conserved process that explains how organs or primary tumors form when cells within those tissues have varying fitness and compete with one another. This competition can result in the survival and expansion of one cell population, and the induction of cell death through apoptosis in the other. We hypothesized that MCC use cell competition with hepatocytes to create space and expand within the liver. Objectives: In this study, we tested the hypothesis that MCC use cell competition with hepatocytes to create space and expand within the liver, resulting in hepatocyte apoptosis. Methods: We develop new in-vitro and mouse lineage-traced models to assay cell competition between MCC and hepatocytes, initially using balb/c derived breast cancer (4T1) and hepatocyte (H2.35) cells and syngeneic mouse models of liver metastasis. These models directly capture MCC and hepatocyte interactions, and we can assess modes of cell competition, including apoptosis, through immunostaining. Because prior literature suggests that the developing mammary gland informs both cell competition and metastasis, we next performed a bioinformatics screen to identify potential signals that contribute to cell competition between MCC and hepatocytes. We generated a new single-cell RNA-seq dataset that incorporates information from the developing mammary gland and breast cancer cells. This dataset includes 3264 primary breast cancer cells across 3 models of aggressive breast cancers, encompassing HER2+ and TNBC subtypes, as well as 526 embryonic mammary gland cells. Using this platform, we identify genes enriched in both breast cancer and the developing mammary gland. Next, we validate genes by testing for their high expression in MCC when compared to hepatocytes. Then, we determine the impact of target genes on cell competition in our models. Results/Discussion: Our models demonstrate that MCC use cell competition to create space in the liver by inducing apoptosis in neighboring hepatocytes. MCC induce apoptosis in neighboring hepatocytes through cell competition in in-vitro co-cultures by 11.7-fold compared to MCC apoptosis. Hydrodynamic tail-vein engraftment in NOD-scid-gamma mice livers with MCC also resulted in increased neighboring hepatocyte apoptosis. Using our bioinformatics screen, we identified 5 potential targets that could drive breast cancer metastasis and cell competition. Using our competition models, perturbation of SerpinE2, a protease inhibitor which was one of the top gene targets, successfully modulated competition between MCC and hepatocytes. Knock-out of SerpinE2 in MCC did not affect their viability or growth but resulted in MCC apoptosis adjacent to hepatocyte neighbors by 16.9-fold when compared to wild type conditions. Further, co-culture of MCC that lacked SerpinE2 with hepatocytes resulted in decreased hepatocyte apoptosis by 2.3-fold compared to hepatocytes co-cultured with wild-type (WT) MCC. These findings suggest that hepatocytes cannot outcompete or kill WT MCC, but they can outcompete and kill MCC that lack SerpinE2. Future work focused on the perturbation of SerpinE2 may lead to novel therapies for patients at risk for or with BCLM. Our findings suggest that restoring the competitiveness of the liver parenchyma could be a new treatment modality for treating liver metastases. Citation Format: Katherine Lake, Sakshi Mohta, Clayton Smith, Venkata Repaka, Lily Xu, Kaitlyn Saunders, Vrushali Pandit, Emily Goff, Christine Zhang, Jacob Pena, Christine Hodgdon, Julia Maues, Elizabeth Chen, Isaac Chan. Treating liver metastases by reversing cell competition between metastatic cancer cells and hepatocytes [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 PO5-25-01.

Abstract 4492: Deferiprone optimization for the treatment of triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) is the leading cause of new cancer cases and the second leading cause of cancer deaths in American women disproportionately affecting Black and Hispanic women under 40. Currently, there is no targeted therapy for TNBC and treatment options to manage this lethal disease include surgery, adjuvant chemotherapy and radiotherapy. Among the chemotherapy agents, combination of the PARP inhibitors with DNA-damaging results in a more promising anti-tumor effect. A better understanding of TNBC etiology has aided in unraveling the roles of two additional cellular targets - androgen receptor (AR) and histone lysine demethylase (KDM) - in the viability and survival of TNBC. Interestingly, AR overexpression is the most important driver of prostate cancer (PCa). A class of current medications used to treat PCa act as androgen receptor (AR) antagonists (or antiandrogens). Antiandrogens are under investigation in the clinic as potential therapies for luminal AR (LAR) subtypes of TNBC, a particularly worrisome subtype that frequently metastasizes to regional lymph nodes and bones. Although LAR TNBC constitutes 15-20% of TNBCs, it is characterized by minimal response to chemotherapy and aggressiveness. It is therefore plausible to repurpose and optimize antiandrogens, in the context of designed multiple ligands; to obtain a TNBC-targeting therapy effective against several subtypes of this heterogenous disease, including the basal subtype that is responsible for ~80% of TNBC incidence. The proposed therapeutics are dual-acting antiandrogen-KDM inhibitors. The antiandrogen moiety of these agents will enable TNBC cell-targeting and translocation of the drug into the nucleus where inhibition of KDM will prevent transcription of KDMs that promote tumor growth. The three pharmacophores of these agents are (i) an AR binding group, (ii) a linker, and (iii) an iron-binding group. Two functional classes of these compounds, alkyl- and aryl-derivatives, vary in the design of the AR binding moiety. To optimize these agents, the methylene linker length is varied in each class for in vitro determination of the optimal length for increased drug efficacy. The compounds are tested on TNBC cell lines (MDA-MB-231, low AR+; and MDA-MB-453, high AR+), and ER+ BCa (MCF-7) while PCa cell lines (LNCaP PCa, AR+; and DU 145, PCa, AR-) serve as controls for AR dependency of the compounds. Longer linker length compounds exhibited low micromolar cytotoxicity and selectivity for AR+ TNBC and PCa cell lines. Further analysis of lead compounds in TNBC cells aided in understanding the effects on targets, transcriptomic effects via RNA sequencing analysis and the mechanism of action. Thus far, the designed dual-acting therapeutics have potential to revolutionize the design of anticancer drugs and improve treatment outcome for TNBC patients. Citation Format: Alexis Johnston, Adegboyega K. Oyelere. Deferiprone optimization for the treatment of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4492.

Abstract 6077: Chimeric RNAs are abundantly expressed in precancerous breast tissue of sporadic breast cancer patients

Abstract Background: Immuno-prevention efforts in breast cancer (BC) have been hampered by the lack of known neoantigenic targets that can be used for a cancer prevention vaccine. RNA fusions represent attractive candidates as these are more immunogenic than insertion/deletion mutations and are substantial source of neoantigens. The objective of this study was to characterize chimeric RNAs in precancerous breast tissue. Methodology: Novel RNA fusions were identified by mining the sequence reads from RNA sequencing of 25 Her2 positive, 25 hormone receptor positive (HR) and 25 triple negative (TN) breast tumors and paired histologically normal tissues by Qiagen’s CLC pipeline. Breast samples from women undergoing breast reduction surgery were used as controls to exclude normal tissue associated chimeric mRNAs from analysis. Neoantigen prediction was performed by MHCnuggets. Chimeric mRNAs were validated by PCR. Ribosomal profiling was performed to assess if fusion transcripts are engaged with ribosomes. Results: A median of 36 novel RNA fusions (range 7-877) were identified in the tumor samples. In line with high genomic instability of TNBC subtype of BC, about 1/3 of the TN tumors expressed greater than 300 RNA fusions. In order to identify RNA fusions that are relevant for BC prevention, we investigated the presence of RNA fusions in the paired histologically normal samples as compared to the index tumor. We restricted these analyses to top 20 fusion transcripts that were present across the set of 75 tumor samples and also detected in 1 or more of the TCGA samples. Interestingly, we found that more than 1/3 of the histologically normal samples express at least 1 of the top 20 RNA fusions. When compared to the corresponding tumor, we found up to 50% of the paired normal tissue expressed RNA fusions identified in the tumor, supporting a role for these chimeric mRNA as an early molecular change during breast tumorigenesis. To validate the robustness of the prediction pipeline, PCR validation was performed for the chimeric mRNA with highest prevalence, NSFP1- LRRC37A2 which confirmed the presence of the transcript in 72% (13/18) of the predicted positive patient samples. MHCnuggets pipeline predicted 15 neopeptides from intergenically spliced chimeric NSFP1 [Exon 1-13] - LRRC37A2 [Exon 2-14], ¼ of which we validated to be immunogenic by ELISA. In order to confirm that the translation of the chimeric NSFP1- LRRC37A2 transcript, we investigated their enrichment in polysome enriched fraction obtained from a BC cell line confirmed to express the fusion transcript by PCR. Enrichment of transcripts in the polysomal fraction confirmed that these transcripts are likely to be translated. Conclusions: RNA fusions are frequently present in at risk breast tissue and are the source of substantial number of neoantigens. These RNA fusion- derived neoantigens may provide novel opportunities for developing vaccines for BC prevention. Citation Format: Anjana Bhardwaj, Shiyanth Thevasagayampillai, Sakuni Rankothgedera, Prisha Verma, Micah B. Castillo, Alexander C. Koh, Constance Albarracin, Preethi H. Gunaratne, Isabelle Bedrosian. Chimeric RNAs are abundantly expressed in precancerous breast tissue of sporadic breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6077.

Current therapeutic targets and promising strategies for triple-negative breast cancer

TNBC refers to breast cancer patients with negative estrogen receptor ER, PR and HER-2. It accounts for about 1520% of all breast cancer cases and has a higher rate of disease recurrence and a worse prognosis than other breast cancer subtypes. Chemotherapy is the most effective treatment now available for TNBC, but it has major adverse consequences on human health. Therefore, the development of new TNBC treatment strategies has become an urgent clinical need. This article first starts with the different subtypes of TNBC, analyzes and summarizes the pathogenesis of TNBC and recent research progress. Secondly, the potential targets of TNBC and the development of targeted treatments based on these targets are analyzed. Finally, it is concluded that it is easier to achieve curative effect by using appropriate specific treatments for different subtypes of TNBC. By summarizing existing treatment regimens and their applicable TNBC subtypes, this article aims to provide new insights for follow-up treatment.

The Impact of Chemotherapy on Cardiovascular Mortality across Breast Cancer Subtypes.

This retrospective study used the SEER database of chemotherapy-receiving breast cancer patients (diagnosed in 2013-2020). The study population was categorized by cancer subtype, stage, patient age, and cause of death (COD). The percentage of cardiovascular CODs, odds ratio (ORs), 5-year cumulative crude probability of death, and standardized mortality ratios (SMRs) of each group were analyzed. Among 23,263 nonsurviving breast cancer patients, 5.8% died from cardiovascular disease, whereas the HER2+/HR+ and HER2+/HR- subtypes exhibited the highest ORs of cardiovascular death and percentages of cardiovascular CODs, at 8.21% and 6.55%, respectively. The cardiovascular SMR increased with advancing stages and decreasing patient age. The HER2+/HR- subtype had the highest cardiovascular SMR, at 0.83 (p < 0.05), followed by TNBC, at 0.78 (p < 0.05). The 5-year cumulative probability of cardiovascular CODs also showed the highest risk in the HER2+/HR- subtype (1.02 ± 0.11%) and the TNBC subtype (0.95 ± 0.07%). Breast cancer patients on chemotherapy face an elevated cardiovascular mortality risk, especially with aggressive subtypes (HER2-enriched, TNBC), advanced age, or HER2+/HR+ cancer receiving long-term treatment.

Racial/ethnic differences in the clinical presentation and survival of breast cancer by subtype.

Breast cancer (BC) affects racial and ethnic groups differently, leading to disparities in clinical presentation and outcomes. It is unclear how Hispanic ethnicity affects BC outcomes based on geographic location and proximity to the United States (U.S.)/Mexico border. We hypothesized that the impact of race/ethnicity on BC outcomes depends on geographic location and country of origin within each BC subtype. We analyzed BC data from the Texas Cancer Registry by race/ethnicity/birthplace according to BC subtype (luminal A/luminal B/human epidermal growth factor receptor 2 [HER2]/triple-negative breast cancer[TNBC]). Other covariates included age, geographic location (U.S., Mexico), residency (border, non-border), treatments, and comorbidities. Crude and adjusted effects of race/ethnicity and birthplace on overall survival (OS) were analyzed using Cox regression methods. Our analysis of 76,310 patient records with specific BC subtypes revealed that Hispanic and non-Hispanic Black (NHB) patients were diagnosed at a younger age compared with non-Hispanic White (NHW) patients for all BC subtypes. For the 19,748 BC patients with complete data on race/ethnicity/birthplace/residency, Hispanic patients had a higher mortality risk in the Luminal A subtype, regardless of birthplace, whereas U.S.-born Hispanics had a higher risk of death in the TNBC subtype. In contrast, NHB patients had a higher mortality risk in the Luminal A and HER2 subtypes. Residence along the U.S./Mexico border had little impact on OS, with better outcomes in Luminal A patients and worse outcomes in Luminal B patients aged 60-74 years. Race/ethnicity, geographic birth location, and residency were significant predictors of survival in BC. Migration, acculturation, and reduced healthcare access may contribute to outcome differences.

Abstract B101: Obesity mediates altered triple-negative breast cancer tumor biology in African American women independent of ancestry

Abstract African American (AA) breast cancer (BC) is associated with a higher incidence of aggressive BC phenotypes at younger age, higher grade of tumor as compared to BCs of age-matched patients of European American (EA). For AA women, there is a higher frequency of the more aggressive TNBC subtype and of the PAM50-molecular basal subtype. AA tumors are enriched for inflammatory and immune pathways, implicating inherited susceptibility associated with African ancestry. Obesity induces a state of low-grade inflammation. AA women tend to be more obese than EA and have elevated a inflammatory markers, including CRP, IL6, and IL1. Since inflammation related to obesity is a reflection of dysfunctional adipocyte biology, we used dataset GSE88837 to perform in silico analysis of gene expression changes in visceral adipose tissue for AAs and EAs. AA adipose tissue is more inflamed than EAs at the same level of obesity (BMI&amp;gt;30). There was a high expression of secreted mediators causing systemic inflammation, including heat shock protein 60 (HSPD1), CXCL1, S100A9, and SPP1. VEGFA, S100A9, and SPP, tumor-promoting angiogenic mediators, were higher in obese AAs than EAs. These data indicate that obesity enhances inflammation in visceral adipose tissue of AAs. We performed in silico analysis of dataset GSE78958, of 400 BC patients annotated for race, BMI, and hormone receptor expression. We analyzed BC patients for differential gene expression, PAM50 subtype, tumor stage and grade, based on race and BMI. AA women have a higher BMI (48.9%) than EA women (32.3%) and a higher percentage of poorly differentiated tumors (51.1%) than EAs (40.6%). AA women with BMI &amp;gt;30, had more basal-like tumors (34.8%) than EA women (19.3%). These analyses confirm that excess adiposity promotes the basal BC phenotype. With BMI &amp;gt;30 as a criterion for obesity, the GSE78958 dataset containing BCs for 96 AA and 200 EA patients was analyzed for differences in gene expression. DEGs showed upregulation of T cell exhaustion marker PTPN22 and LAIR2. The metastasis and proliferation promoting chemokines CXCL1, CCL2, CXC12, CXCR4, and S100A9 were higher in the BCs of obese AAs, than BCs of non-obese AAs. Stemness related genes, STAT1, SOX4, and KLF4, were higher in BCs of obese AAs. CD163-expressing M2 macrophages were higher in BCs of obese AAs. Our group showed that there was a considerable overlap of genes among African and AA cases, but there were some non-overlapping genes indicating that ancestry alone cannot explain the genetic diversity in the tumor phenotype of AA patients. The divergence was largely driven by an upregulated gene signature found among AAs and not seen among African patients. GSE78958 (obesity BC dataset) was mapped for ancestral correlation of altered genes in the AA BC dataset. Ancestry mapping showed an inverse correlation of HSPD1 with ancestry. Obesity upregulated HSPD1 in BCs of AAs as well as in AA adipose tissue and decreased the probability of survival for women of AA ethnicity, suggesting delineation of ancestry-specific and race-specific effects. Citation Format: Deepa Bedi, Rachel Martini, Melissa B. Davis, Clayton Yates. Obesity mediates altered triple-negative breast cancer tumor biology in African American women independent of ancestry [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr B101.