Triple-negative Breast Cancer Cases Research Articles

A Rare Case of Triple-Negative Breast Cancer with RAD51D Gene Mutation

Background: The heterogeneity of breast cancer (BC) subtypes poses a significant challenge, with carcinogenesis involving multiple stages and genes, including proto-oncogenes, tumor suppressor genes, and DNA repair genes. Next-generation sequencing has expanded access to multigene panels, such as RAD51 paralogs, which increase the risk of ovarian cancer and possibly triple-negative (TN) BC. Case presentation: We present a rare case of a 45-year-old woman with TNBC and a RAD51D gene mutation. Mammography and breast ultrasonography revealed an irregular, 30 mm hypoechoic area and dystrophic calcifications in the right breast. Immunohistochemistry showed a lack of expression of ER, RP, HER-2, and P53, with 50% of neoplastic cell nuclei positive for Ki-67. Next-generation sequencing revealed a mutation in RAD51D and MUYTH genes. The patient underwent partial mastectomy, chemotherapy, and prophylactic mastectomy. Conclusion: Genetic analysis is crucial for identifying specific mutations contributing to TNBC development. Current preventive interventions primarily address BRCA1 and BRCA2 mutations, following established guidelines.

A Comprehensive Review of TRPS1 as a Diagnostic Immunohistochemical Marker for Primary Breast Carcinoma: Latest Insights and Diagnostic Pitfalls

Background/Objectives: Immunohistochemical expression of TRPS1 (trichorhinophalangeal syndrome type 1) protein is usually used by pathologists to confirm breast origin for triple-negative breast cancers (TNBC) or metastatic carcinomas of unknown primary. However, recent studies have reported TRPS1 expression in a variety of non-breast lesions. This review aims to provide a comprehensive evaluation of TRPS1 expression across various tumor types, highlighting both its diagnostic utility and potential pitfalls that may arise in clinical practice. Methods: A thorough search of the PubMed database on TRPS1 immunoexpression in tumor pathology was conducted. While the gene itself has been known for several decades, most studies regarding its use in immunohistochemistry emerged in the late 2010s. Particular emphasis was placed on case reports and cohort studies that examined the implications of TRPS1 expression in non-breast tissues, as well as variations in the results between commercially available TRPS1 clones, which may influence the staining intensity and specificity. Results: TRPS1 demonstrated a strong diagnostic utility in identifying primary breast lesions, particularly in TNBC cases. However, its expression in a growing number of non-breast cancers, such as lung adenocarcinoma, prostate adenocarcinoma, urothelial carcinoma, ovarian high-grade serous carcinoma, and endometrial adenocarcinoma, as well as up to 96% of synovial sarcomas with SS18-SSX fusion, emphasizes the need for caution when interpreting TRPS1 positivity and suggests a multi-marker approach in order to increase the diagnostic accuracy. Conclusions: While TRPS1 remains a highly sensible immunohistochemical marker for confirming breast primary lesions, pathologists should be aware of its low specificity and incorporate complementary diagnostic methods in order to ensure accurate clinical management. Further research should focus on elucidating the molecular pathways regulating TRPS1 expression in various tumor types, which may better define its clinical utility.

Prognostic Significance of Combining Cytokeratin-19, E-Cadherin and Ki-67 Analysis in Triple-Negative Breast Cancer with Basal-Like and Non-Basal-Like Phenotype.

Triple-negative breast cancer (TNBC) is known to have the worst outcome compared to the other forms of breast cancer. Moreover, molecular markers identified basal-like breast cancer (BLBC) phenotypes to be also related to a worse prognosis. In this study, we evaluated by immunohistochemistry (IHC) the prognostic significance of combining Cytokeratin-19 (CK19), E-cadherin, and Ki-67 tissue expression in triple-negative breast cancer (TNBC) cases presenting a basal-like (BLBC) or a non-basal-like (n-BLBC) phenotype to improve the selection and the monitoring of BC patients with a more aggressive outcome. Herein, when compared to n-BLBC, patients with BLBC showed a positive correlation with lymph node metastasis occurrence and lower survival rates. Immunohistochemistry analysis revealed significantly lower E-cadherin prevalence and higher prevalence of both CK19 and Ki-67 in BLBC when compared to n-BLBC. Spearman correlation showed that E-cadherin is negatively and significantly correlated to CK19 and Ki-67 expressions. Moreover, in BLBC, expressing both CK19 and Ki-67 combined with E-cadherin loss was associated with the worst relapse-free and overall survival. In conclusion, TNBC/BLBC phenotypes simultaneously losing E-cadherin and overexpressing CK19 and Ki-67 markers are the most aggressive forms. This combined analysis could be a predictive marker of poor prognosis.

Pregnancy-associated triple-negative breast cancer: A case report and literature review.

The incidence of pregnancy-associated breast cancer (PABC) is relatively low, but it has been increasing in recent years. The onset of PABC causes serious harm to the fetus and the mother due to the unique physiological characteristics of pregnancy, which poses a particular challenge to clinicians. This article reports a case of pregnancy-associated triple-negative breast cancer and describes the patient characteristics and systematic treatment of this type of breast cancer. A 33-year-old woman was admitted to hospital with a left breast mass that had appeared more than a year earlier. She was a second-time pregnant woman with a single live intrauterine fetus at 23 + 4 weeks of gestation. During the examination of the left breast, a 6 by 8 cm sized mass can be observed on the upper outer quadrant. Pregnancy-associated triple-negative breast cancer. The patient underwent a breast ultrasound which showed a left breast mass and the diagnosis was confirmed by a puncture biopsy of the left breast mass. The pregnancy was terminated after multidisciplinary discussion, taking into account the wishes of the patient and her family. After termination of the pregnancy, all treatments were given according to the standard triple-negative breast cancer (TNBC) treatment protocol. The patient was treated with neoadjuvant chemotherapy with epirubicin in combination with docetaxel (TE) in cycles of 21 days. After 3 cycles of TE, a modified radical mastectomy for left breast cancer was performed, and the appropriate radiotherapy and chemotherapy treatments were carried out in sequence. After the surgery, the disease-free survival for the patient was 3 months until local metastases were diagnosed. Thus the radiotherapy and chemotherapy were carried out, and then the patient was in good general condition with no recurrence or metastases. Clinicians need more research into the diagnosis, treatment and prognosis of PABC. Improving the rate of early diagnosis and using standardized and individualized comprehensive treatment plans will minimize fetal damage and improve survival and quality of life for patients.

TRPS1, a sensitive marker for different histological and molecular types of breast cancer

ObjectivesWe explored Trichorhinophalangeal syndrome type 1 (TRPS1) expression in special types of breast carcinoma, and analyzed the correlation between TRPS1 and androgen receptor (AR) expression in triple-negative breast cancer (TNBC).MethodsTRPS1 expression was analyzed in 801 patients with special types of breast carcinoma. A total of 969 TNBC were used to analyze the correlation between the expression of TRPS1 and AR. TRPS1 expression was evaluated in 1975 cases of breast cancer with different molecular types.ResultsA total of 801 special types of breast cancers were stained with TRPS1.TRPS1 was positive in 100% (63/63) of mucinous carcinoma, 100% (7/7) adenoid cystic carcinomas (4 classic adenoid cystic carcinomas and 3 solid-basaloid adenoid cystic carcinomas), 100% (4/4) tubular carcinomas, 100% (2/2) secretory carcinomas, and 99.59% (243/244) invasive lobular carcinomas, 99.26% (267/269) invasive micropapillary carcinomas, 97.44% (38/39) ER-positive neuroendocrine tumors, 94.44% (34/36) metaplastic breast carcinomas (MBCs), 63.73% (65/102) apocrine carcinomas. TRPS1 was negative in all triple-negative neuroendocrine carcinomas (0/7).TRPS1 was positive in 92.86% (26/28) of metastatic special types of breast cancer. TRPS1 and AR expression were analyzed in 969 cases of TNBC. 90.40% were positive for TRPS1, and 42.41% were positive for AR. A significant inverse correlation between TRPS1 and AR expression was shown in TNBC (p < .001). TRPS1 showed a higher positive rate (93.13%) in TNBC compared to GATA binding protein 3 (GATA3), gross cystic disease fluid protein 15 (GCDFP-15) and forkhead box transcription Factor C 1 (FOXC1).ConclusionsIn conclusion, our study demonstrated that TRPS1 is a highly sensitive marker for most special types of breast carcinoma. TRPS1 was positive in 63.73% of apocrine carcinomas. TRPS1 and AR expression was inversely correlated in TNBC.

Impacts of Matrix Metalloproteinase-2 Promoter Genotypes on Breast Cancer Risk.

Matrix metalloproteinase-2 (MMP-2) has been implicated in the pathogenesis of breast cancer (BC). However, there is limited research on the role of MMP-2 genotypes in BC risk. This study aimed to investigate the associations between two MMP-2 promoter polymorphisms, rs243865 and rs2285053, and BC risk. MMP-2 genotypes were analyzed using PCR-based RFLP methodology in a cohort comprising 1,232 BC cases and 1,232 controls. Genotypic frequencies of MMP-2 rs243865 and rs2285053 in controls were consistent with Hardy-Weinberg equilibrium (p=0.3702 and 0.2036, respectively). There were no significant differences in the distribution of rs243865 and rs2285053 genotypes between BC cases and controls (p for trend=0.1602 and 0.2170, respectively). Variant genotypes at rs243865 and rs2285053 appeared to confer a protective effect, although not statistically significant (all p>0.05). Similarly, the variant T allele at rs243865 and rs2285053 showed a non-significant trend towards decreased BC risk (OR=0.84 and 0.89, 95%CI=0.69-1.02 and 0.78-1.02, p=0.0811 and 0.1043, respectively). There was no interaction observed between MMP-2 rs243865 or rs2285053 genotypes and age. Stratified analysis did not reveal significant associations between MMP-2 rs243865 or rs2285053 genotypes and triple-negative breast cancer (TNBC) (p=0.6458 and 0.8745, respectively). Among both TNBC and non-TNBC cases, none of the variant genotypes at rs243865 or rs2285053 showed significant associations with TNBC (all p>0.05). MMP-2 rs243865 and rs2285053 genotypes appear to have a minimal impact on individual susceptibility to BC or TNBC.

Triple-Negative Breast Cancer: Molecular Particularities Still a Challenge.

Worldwide, breast cancer (BC) is one of the most common cancers in women and is responsible for the highest number of cancer-related deaths among women, with a special clinical behavior and therapy response. Triple-negative breast cancer (TNBC) is seen as a highly invasive BC, characterized by a short survival, higher mortality, recurrence, and metastasis when it is compared to the other BC subtypes. The molecular subtyping of TNBC based on mRNA expression levels does not accurately reflect protein expression levels, which impacts targeted therapy effectiveness and prognostic predictions. Most TNBC cases exhibit a high frequency of homologous recombination (HR) DNA repair deficiency (HRD) signatures and are associated with a complex genomic profile. Biomarker research in TNBC includes investigating genetic mutations, gene expression patterns, immune system-related markers, and other factors that can provide valuable information for diagnosis, treatment selection, and patient outcomes. Additionally, these biomarkers are often crucial in the development of personalized and precision medicine approaches, where treatments are customized to each patient's unique characteristics. This ongoing research is essential for improving the management and outcomes of TNBC, which is a challenging and heterogeneous form of breast cancer. The findings of this research have practical implications for refining treatment strategies, particularly in selecting appropriate systemic therapies and integrating traditional treatment modalities like surgery and radiotherapy into comprehensive care plans for TNBC patients.

Stromal CD73 Expression in Breast Cancer: Subtype-specific Expression and its Prognostic Significance.

Invasive ductal carcinoma (IDC) is classified into distinct subtypes with varying prognoses and treatment sensitivities. For instance, triple-negative breast cancer (TNBC) is associated with poorer outcomes than other subtypes. We have previously reported the role of interstitial CD73 in tumor invasion and its correlation with prognosis in other cancers. This study aimed to investigate the expression of stromal CD73 (sCD73) in IDC and its potential prognostic significance. We analyzed 61 cases of human epidermal growth factor receptor 2-negative IDC, including TNBC and hormone receptor-positive (luminal-type) cases, treated surgically at our institution from 2005 to 2010. Cases that received preoperative drug therapy were excluded. CD73 expression was evaluated by immunostaining of the tumor stroma. sCD73 expression was observed in 70% of all cases, with a significantly higher rate in TNBC (93%) compared with luminal breast cancer (48%). High sCD73 expression was associated with poor prognosis in terms of overall survival (OS) and disease-free survival (DFS) across all cases. In patients with luminal breast cancer, high sCD73 expression was also indicative of poor prognosis with respect to both OS and DFS. High expression of sCD73 is associated with poor prognosis in IDC, particularly in luminal breast cancer. Further research is needed to establish sCD73 as an independent prognostic factor.

Neoadjuvant Chemotherapy Response in Triple-Negative Apocrine Carcinoma: Comparing Apocrine Morphology, Androgen Receptor, and Immune Phenotypes.

Apocrine differentiation and androgen receptor (AR) positivity represent a specific subset of triple-negative breast cancer (TNBC) and are often considered potential prognostic or predictive factors. To evaluate the response of TNBC to neoadjuvant chemotherapy (NAC) and to assess the impact of apocrine morphology, AR status, Ki-67 labeling index (Ki-67LI), and tumor-infiltrating lymphocytes (TILs). A total of 232 TNBC patients who underwent NAC followed by surgical resection in a single institute were analyzed. The study evaluated apocrine morphology and AR and Ki-67LI expression via immunohistochemistry from pre-NAC biopsy samples. Additionally, pre-NAC intratumoral TILs and stromal TILs (sTILs) were quantified from biopsies using a deep learning model. The response to NAC after surgery was assessed based on residual cancer burden. Both apocrine morphology and high AR expression correlated with lower Ki-67LI (P < .001 for both). Apocrine morphology was associated with lower postoperative pathologic complete response (pCR) rates after NAC (P = .02), but the difference in TILs between TNBC cases with and without apocrine morphology was not statistically significant (P = .09 for sTILs). In contrast, AR expression did not significantly affect pCR (P = .13). Pre-NAC TILs strongly correlated with postoperative pCR in TNBCs without apocrine morphology (P < .001 for sTILs), whereas TNBC with apocrine morphology demonstrated an indeterminate trend (P = .82 for sTILs). Although TIL counts did not vary significantly based on apocrine morphology, apocrine morphology itself was a more reliable predictor of NAC response than AR expression. Consequently, although apocrine morphology is a rare subtype of TNBC, its identification is clinically important.

Potential target and mechanism exploration from α-mangostin against triple-negative breast cancer: An in silico study.

Triple-negative breast cancer (TNBC) is one of the most common types of serious breast cancer. Due to the absence of therapeutic hormone receptors, TNBC treatment generally involves chemotherapy which results in various side effects and resistance development. Herbal compounds, including α-mangostin, have shown potential anticancer effects against TNBC. However, rigorous screening is needed to uncover its mechanisms and characteristics. The aim of this study was to understand the molecular mechanism of α-mangostin against TNBC and its possible limitations. The study design used is an in si lico study. The study involved database mining and compound characteristic analysis. Network pharmacology and molecular docking were also done to explore potential target and molecular mechanisms against TNBC. There was no statistical analysis conducted as this study relies on predefined algorithms and simulation models. Instead, a parameter threshold was used for each analysis to ensure its reliability. Prediction of Activity Spectra for Substances prediction and Gene Ontology-Kyoto Encyclopedia of Genes and Genomes enrichment predicted potential anticancer effects of α-mangostin through the regulation of enzyme activity and apoptotic pathway. Compound property predictions showed α-mangostin to have promising drug-likeness with sufficient bioavailability and low biodegradability. However, α-mangostin still has some potential limitations in water solubility and toxicity risks. Through network pharmacology, 75 potential target proteins of α-mangostin in TNBC cases were found. The top three most significant of which (AKT1, CTNNB1, and HSPAA91) were proven to bind with α-mangostin through molecular docking. Study results suggested α-mangostin to have a promising anticancer and chemopreventive activity with great drug-likeness and pharmacokinetic properties. It was revealed that α-mangostin can bind to key components in TNBC-related pathways, including AKT1, CTNNB1, and HSP90AA1 proteins. However, further experimental studies may be needed to verify its effectiveness as well as possible solubility and toxicity limitations.

Population attributable fraction of reproductive factors in triple negative breast cancer by race.

10522 Background: Age-adjusted incidence rates of triple negative breast cancer (TNBC) are higher in African American (AA) women than in non-Hispanic White (White) women. The disproportionate incidence of TNBC in AA women partially drives the 40% higher mortality rate from breast cancer in AA women compared to White women. Several studies have identified lack of breastfeeding and younger age at first birth as risk factors for TNBC. There are large differences in breastfeeding uptake and duration in the US: only 44% of AA women breastfeed for 6 months or longer, compared to 60% of White women. To quantify the contribution of differences in breastfeeding patterns and younger age at first birth to disparities in incidence of TNBC, we calculate the population-attributable fraction (PAF), which is the proportion of the incidence of a disease that may be attributable to a particular exposure. Methods: A systematic review was performed to identify relevant case-control studies. Pooled odds ratios (ORs) for breastfeeding for &lt; 6 months and age at first birth &lt; 25 years were calculated from data extracted from studies using a common effect model. PAF was calculated using the Levin formula. Risk factor population prevalences were extracted from national surveys. Pooled ORs were used as estimates of relative risk (RR). A combined PAF was calculated using the polychoric correlation coefficient between breastfeeding duration and age at first birth to account for contributions of multiple risk factors. Results: Using race specific ORs, the PAF of breastfeeding for &lt; 6 months was 12% (95% confidence interval (CI) 5-20%) among White women and 15% (95% CI 3-26%) among AA women. The PAF of having a child before age 25 was not significantly different from zero for White women (2% (CI -6-11%)) but was significantly different from zero for AA women (21% (CI 5-25%)). The combined PAF was 27% for AA women and 17% for all women in the US. Extrapolating to the US population, we estimated that 4,850 annual cases of TNBC (2,421 among White women and 1,533 among AA women) could be attributed to breastfeeding for &lt; 6 months and age at first birth &lt; 25 years. Conclusions: Given the protective role of breastfeeding against TNBC, policy changes aimed at supporting breastfeeding, addressing structural barriers, and promoting a culture shift could reduce racial disparities in TNBC incidence in the US. [Table: see text]

A systematic review of racial disparity in pivotal poly (ADP-ribose) polymerase (PARP) inhibitor trials.

e13737 Background: Breast cancer is the most common cancer diagnosed worldwide. Breast cancer related mortality has decreased in the US, however this did not extend equally to African American women (AAW). According to CDC mortality rate from breast cancer in AAW is 20% higher than other ethnic groups. Younger age at diagnosis in AAW, higher incidence of triple negative breast cancer (TNBC), and higher incidence of AA males with breast cancer suggest genetic predisposition plays an important role in the disparate outcomes based on race. In an unbiased analysis of TNBC cases, the prevalence of pathogenic germline BRCA 1 &amp; 2 mutations are twice as high as in breast cancer overall. Poly (ADP-ribose) polymerase (PARP) inhibitors have proven to be effective in germline BRCA 1 and BRCA 2 mutation associated breast cancer. However, data regarding the enrollment of racial and ethnic minorities in these pivotal trials that lead to the approval of these drugs is limited. Methods: We examined the demographic data reporting in Phase II/ III clinical trials of PARP inhibitors in breast cancer from 2016 to 2023. In order to highlight the disparities in the enrollment of minority groups we calculated an enrollment percentage of various racial groups in these trials. We conducted a systematic review of Phase II/III clinical trials of PARP inhibitors in BRCA 1 &amp; 2 mutated breast cancer reported studies with sources from PubMed, Embase, Scopus, Clinicaltrials.gov, CENTRAL and Cochrane. 56 full text studies were identified, out of which 14 met inclusion criteria. The total number of patients included was N=5,067. Five trials did not include racial data. Results: Among trials that reported race and ethnicity (N=4004), the enrollment percentage was lowest for racial and ethnic minorities. AA: 3.4%, N=136. Non- Hispanic Whites were the most common to be enrolled: 71.05%, N=2845, Asians were 16.53% N= 662, Hispanics 2.03 %; N=83 and other 6.17%, N=247. Conclusions: Racial minorities are consistently underrepresented in all the pivotal PARP inhibitor trials and contributing to the race-based disparities in breast cancer. [Table: see text]

Clinical and histological profiling of triple-negative breast cancer at Chihuahua´s state cancer center: An observational study.

e22529 Background: Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by the absence of estrogen receptor, progesterone receptor, and HER2 expression. This subtype is associated with a poorer prognosis and higher recurrence rates compared to other breast cancer subtypes. Understanding the histopathological and clinical characteristics of TNBC is crucial for improving early detection, clinical management, and treatment outcomes. In this context, a descriptive analysis was conducted to explore the association between TNBC and histological grade, histopathological type, and clinical stage at the State Cancer Center. Methods: A retrospective, single-center study was conducted at Chihuahua's State Cancer Center, where medical records of patients aged ≥ 18 years old diagnosed with TNBC between January 2018 and December 2022 were retrospectively reviewed. Data related to weight, histological grade, histopathological type, and clinical stage at TNBC diagnosis were collected. Frequency analysis was performed to determine the distribution of these characteristics in the TNBC patient population. Additionally, the association between histological grade and clinical stage at diagnosis was examined using appropriate statistical tests. Results: During the study period, 753 patients were diagnosed with breast cancer. Of these, 84 (11%) were diagnosed with triple-negative breast cancer and were included in the study. The mean age was 49 ± 13 years, with a mean BMI of 28 ± 5. The most common histologic subtype in this group was invasive ductal carcinoma, accounting for 78 (93%) of the TNBC cases. At the time of diagnosis, 19 (23%) were diagnosed with stage IIA, 17 (20%) with stage IIIA, 9 (11%) with stage IV, and 4 (5%) were detected in situ. Overall, the majority were identified as grade 3 tumors (44; 52%). Finally, within the stage IIA group, the majority were grade 3 tumors (58%). Conclusions: As seen in other cohorts, we found a similar frequency of TNBC among patients with breast cancer in our facility in the northwest of Mexico. The distribution of clinical stages highlights the varying degrees of disease progression at the time of diagnosis, with a considerable portion presenting at advanced stages. Moreover, these insights underscore the urgent need for improved screening strategies and early detection methods.

Immunohistochemical Profile of Triple-Negative Breast Cancers: SOX10 and AR Dual Negative Tumors Have Worse Outcomes

Triple-negative breast cancer (TNBC) refers to an estrogen receptor–negative, progesterone receptor–negative, and HER2-negative breast cancer. Although accepted as a clinically valid category, TNBCs are heterogeneous at the histologic, immunohistochemical, and molecular levels. Gene expression profiling studies have molecularly classified TNBCs into multiple groups, but the prognostic significance is unclear except for a relatively good prognosis for the luminal androgen receptor subtype. Immunohistochemistry (IHC) has been used as a surrogate for basal and luminal subtypes within TNBC, but prognostication of TNBC using IHC is not routinely performed. We aimed to study immunophenotypic correlations in a well-annotated cohort of consecutive TNBCs, excluding postneoadjuvant chemotherapy cases. Tissue microarrays were constructed from a total of 245 TNBC cases. IHC stains were performed and consisted of luminal (AR and INPP4B), basal (SOX10, nestin, CK5, and EGFR), and diagnostic (GCDFP15, mammaglobin, GATA3, and TRPS1) markers. Survival analysis was performed to assess the significance of clinical-pathologic variables including age, histology, grade, lymphovascular invasion, Nottingham prognostic index category, American Joint Committee on Cancer (AJCC) stage, stromal tumor-infiltrating lymphocytes at 10% increment, CD8+ T-cell count, Ki-67 index, PD-L1 status, and chemotherapy along with the results of IHC markers. Apocrine tumors show prominent reactivity for luminal markers and GCDFP15, whereas no special-type carcinomas are often positive for basal markers. TRPS1 is a sensitive marker of breast carcinoma but shows low or no expression in apocrine tumors. High AJCC stage, lack of chemotherapy, and dual SOX10/AR negativity are associated with worse outcomes on both univariable and multivariable analyses. Lymphovascular invasion and higher Nottingham prognostic index category were associated with worse outcomes on univariable but not multivariable analysis. The staining for IHC markers varies based on tumor histology, which may be considered in determining breast origin. Notably, we report that SOX10/AR dual negative status in TNBC is associated with a worse prognosis along with AJCC stage and chemotherapy status.

The Effects of National Insurance Coverage Expansion and Genetic Counseling's Role on BRCA1/2 Mutation Tests in Breast Cancer Patients.

This study aims to evaluate the impact of South Korea's national insurance coverage (NIC) expansion and the addition of genetic counselors on BRCA1/2 mutation testing rates in breast cancer patients. A retrospective review was conducted at the Samsung Medical Center (SMC), dividing patients into three groups: pre-NIC expansion, post-NIC expansion, and post-extra genetic counselor involvement. The number of BRCA1/2 tests performed and the detection rates among newly diagnosed and follow-up patients, particularly focusing on triple-negative breast cancer (TNBC) cases, were analyzed. Post-NIC expansion, there was a significant increase in BRCA1/2 testing rates, with a gradual rise in detection rates while maintaining statistical significance. TNBC patients under 60 experienced substantial increases in testing rates. The number of follow-up patients recalled for testing also rose significantly after the extra genetic counselor involvement. Additionally, NIC expansion increased insurance coverage for TNBC patients, enhancing accessibility to testing. The study highlights the positive impact of NIC expansion and genetic counselor involvement on BRCA1/2 mutation testing rates and subsequent patient management. Addressing financial barriers to testing and incorporating genetic counseling significantly improve patient outcomes. This model provides a potential strategy for enhancing early detection and personalized treatment for breast cancer patients with BRCA1/2 mutations, contributing to global cancer management efforts.

Abstract PO5-06-09: Metastatic triple negative breast cancer has distinct tumor immune landscape

Abstract Background: Triple negative breast cancer (TNBC) is considered the most immunogenic breast cancer subtype due to higher levels of tumor infiltrating immune cells (TILS), elevated tumor mutational burden and PD-L1 expression, providing a rationale for immunotherapy. Here we aimed to investigate the differences in the immune microenvironment of primary vs. metastatic sites in TNBC vs. non-TNBC and their impact on survival. Methods: Comprehensive immune profiling, including PD-L1 IHC and the expression of 395 immune genes, was performed on 147 real-world FFPE breast cancer samples (32 primary, 115 metastatic). 37 samples were, by definition, triple negative for ER, PR, and HER2 overexpression. PD-L1 (CPS positive ≥1% and CPS positive ≥10%) was determined using immunohistochemistry (22C3). mRNA expression signatures of tumor inflammation (TIGS, weak/moderate/strong) and cell proliferation (CP, poor/moderate/high) were determined by RNA-sequencing. Demographic and clinicopathologic variables were collected. Statistical comparisons of biomarkers between groups were calculated using the Wilcoxon Rank-Sum test for continuous variables and the proportions test for categorical variables (p≤0.05 for significance). Survival differences were quantified by Cox proportional hazards analysis (p≤0.05 for significance). Results: Triple negative status was associated with current use of alcohol [p=0.03]. Black patients were also more likely to have TNBC, constituting 24% of TNBC patients while only making up 14% of the total cohort [p=0.04]. Conversely, white patients were less likely to have TNBC, constituting 73% of TNBC patients while making up 84% of the total cohort [p=0.04]. Comparing TNBC and non-TNBC cases, TNBC cases were observed to have significantly higher TIGS [p=0.014] and PD-L1 expression [p=4.4 × 10−7]. Additionally, TNBC cases trended towards exhibiting greater cell proliferation [p=0.069]. These differences were found to be driven primarily by metastatic tumors, among which TNBC tumors showed significantly higher TIGS [p=0.015], cell proliferation [p=0.021], and PD-L1 expression [p=2.9 × 10−7] than non-TNBC tumors, while none of these significant associations were observed among primary tumors. Triple negative status was significantly associated with PD-L1 expression (assessed by IHC), with a majority of PD-L1 positive cases determined to be triple negative [70% of CPS≥1% cases, p=5 × 10-5; 59% of CPS≥10% cases, p=6 × 10−4]. Several immune-related genes and immune checkpoint molecules were over-expressed in triple negative breast cancer, including CD8, GZMB, PRF1, CCL5, IFNG, TIGIT and CXCL10. A number of genes were also significantly overexpressed in metastatic tumors: KRT5 [p=0.02], TFRC [p=0.04], ABCF1 [p=0.04], FCRLA [p=0.05], LAMP3 [p=0.05], and underexpressed in metastatic tumors: ENTPD1 [p=0.05], IGSF6 [p=0.03], and ITGA1 [p=0.03]. Conclusions: Our comprehensive biomarker analyses showed that metastatic TNBC has a more inflamed tumor microenvironment and higher checkpoint target expression compared to non-TNBC. Further analysis of immune expression by site-specific metastases and correlation with immunotherapy outcomes is warranted to guide clinicians in selection of the ideal metastatic site to biopsy for therapeutic decision making. However, in a collective TNBC context, these data support the use of immunotherapy in metastatic TNBC. Citation Format: Robert Seager, Heidi Ko, Sarabjot Pabla, Maria-Fernanda Senosain, Erik Van Roey, Shuang Gao, Kyle Strickland, Rebecca Previs, Mary Nesline, Stephanie Hastings, Shengle Zhang, Jeffrey Conroy, Taylor Jensen, Marcia Eisenberg, Brian Caveney, Eric Severson, Shakti Ramkissoon, Shipra Gandhi. Metastatic triple negative breast cancer has distinct tumor immune landscape [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 PO5-06-09.

Abstract PO5-13-09: Clinical usage of a CLIA accredited protein/phosphoprotein assay for breast cancer: Primary usage cases and significant findings in the HER2- setting

Abstract Background: A CLIA-accredited assay that measures the expression and/or activation levels of 32 clinically actionable protein and phosphoprotein analytes in clinical tissue biopsy samples was launched in January 2021. The current intended use population for the assay is for patients with late/advanced stage breast cancer wherein molecular profiling is being utilized for clinical decision making. Assessment of physician ordering practices, clinical use dynamics as well as protein/phosphoprotein actionability frequencies were determined for clinically actionable biomarkers. Methods: A total of 219 cases have been processed to date, with mean turn-around time of 16.4 days. The assay utilizes laser capture microdissection to enrich tumor epithelium from FFPE core needle biopsy and resection material coupled to reverse phase protein array. Results for each of the 32 analytes are generated by comparing each patient to a reference population and reported both as a relative quartile and as a continuous percentile compared to the reference population (0-100%). For the purposes of this analysis, significant expression/activation cutpoints were set at the 40th percentile threshold. Results: To date, clinicians have requested the test most frequently to identify potential therapeutic targets in patients with HER2-negative disease (84% of all tested patients, 36% were triple-negative). Despite the majority of cases being HER2-negative, we found that phosphorylated (p) HER2 (Y1248) was found to be activated in 17% of all HER2-negative cases and 19% of triple negative breast cancer cases (TNBC). pHER2 was concurrently activated with pHER3 (Y1289) in 15% (12/80) of TNBC cases and 13% (24/187) of all HER2-negative cases. pHER2 presented concurrently with pEGFR (Y1068 or T654) in 14% (11/80) of TNBC cases and 14% (26/187) of all HER2- cases. Expression of TROP2 was observed in 16% of HER2-negative patients including 11% of ER+/HER2- and 23% of TNBC cancers. MHCII expression, a recently described candidate predictive biomarker of anti-PDL1/PD1 response in TNBC, was found to be expressed in 29% of TNBC patients. Activation frequencies of other clinically relevant drug targets in HER2-negative disease such AKT and mTOR pathway activation was also assessed. We found that pAKT (S473 and/or T308) was activated in 7% of ER+/HER2- cases and 14% of TNBC. Concurrent with AKT activation, at least one additional member of the AKT-mTOR pathway (mTORC1 (S2448), 4E-BP1 (S65), p70S6K (T389), or S6RP (S235/S236) was co-activated in 50% and 45% of ER+/HER2- and TNBC cancers respectively. Conclusion: This initial assessment of a CLIA LDT protein/phosphoprotein assay utilized to date found that physicians most often order the test for advanced stage HER2-negative breast cancer. Activation/expression of clinically important protein drug targets with potential actionability in HER2-negative disease was observed in a significant number of cases and demonstrates the power of the assay to elucidate actionable targets for potential therapeutic intervention. Citation Format: Claudius Mueller, Brian Corgiat, Emanuel Petricoin, Kayla Sparks, Joyce O'Shaughnessy, Chelsea Gawryletz, Matthew Schwartz, Justin Davis. Clinical usage of a CLIA accredited protein/phosphoprotein assay for breast cancer: Primary usage cases and significant findings in the HER2- setting [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 PO5-13-09.

Abstract PS18-09: The DARC side of Breast Cancer - DARC, Duffy-null and African ancestry influence in the Triple Negative Breast Cancer tumor microenvironment

Abstract Background. Despite a recent convergence of breast cancer (BC) incidence rates between African American (AA) and European American (EA) women, AA women continue to have ~40% higher mortality rates. BC is a heterogeneous collection of diseases, where African ancestry women are disproportionately burdened with the most aggressive subtype of BC, triple negative BC (TNBC). We have previously reported that the African ancestry-specific Duffy-null allele (FY-) is a risk factor for TNBC diagnoses. FY- is a promoter variant that removes expression of the Duffy Antigen Receptor for Chemokines (DARC/ACKR1), from red blood cells (RBCs). DARC serves as a portal of entry for Plasmodium vivax malaria parasite, and FY- confers immunity, leading to fixation of FY- among Sub-Saharan African populations. DARC is an atypical chemokine receptor that functions to modulate chemokine levels in circulation and tissues to aid immune cell recruitment. DARC is also expressed on breast tumor epithelial cells, however the significance of DARC in the TNBC tumor microenvironment (TME) has not fully been explored. Leveraging our African ancestry enriched International Study for the Center of Breast Cancer Subtypes cohort and in vivo murine models, we employed multi-omics approaches to explore the function of FY- and DARC expression across cell types in the TNBC TME. Genomics. Using transcriptomic data from the TCGA BC cohort, we have previously reported that DARC expression is highly correlated with deconvoluted immune cell abundance using CIBERSORT. To build upon this finding among TNBC patients, we have analyzed RNAseq data from two cohorts of African ancestry women to explore correlation of DARC expression status and immune cell abundance. Among TNBC cases, we report that higher DARC expression was significantly associated with increased immune cell abundance, with increases in B cell, T cell and monocyte populations. Using whole genome sequencing data across 86 African ancestry cases, we are currently investigating germline FY- status with mutational signatures. Circulating biomarkers. Patient plasma was collected prior to surgery, where Luminex multiplex assays were performed to quantify levels of &amp;gt;40 circulating chemokines and cytokines. FY- status has been determined for ~550 patients using single-plex or multiplex PCR genotyping methods from germline saliva DNA. Our univariate analyses show several circulating chemokines, including CCL2, CXCL2, CXCL6 and CXCL11, have significant differences between FY- and non-FY- BC patients. Curation of clinicopathological variables for multivariate analysis is ongoing. Murine models. We crossed C3(1)Tag BC transgenic mice with a DARC knock-out (KO) line to generate mice lacking DARC expression that spontaneously develop tumors in the mammary fat pads. The C3(1)Tag model is reported to have similar gene expression profiles to basal-like TNBC tumors. Tumors were collected at pre-determined time points of 25 and 30 weeks, where DARC KO mice had increased tumor size and tumor burden at 30 weeks. Initial fluorescent staining revealed an increase in immune cell infiltration in the TME of DARC expressing mice compared to DARC KO mice. To further explore this, we employed multiplex staining across a representative cohort of DARC expressing and KO mice at 25 and 30 weeks to capture the specific immune cell populations infiltrating the TME. Conclusions. TNBC tumors have worse prognosis due to lack of targeted therapeutic options. Increased immunogenicity of TNBC tumors, especially among African ancestry women may be driven in part by DARC expression. Characterization of FY- status, in coordination with DARC among other cell types in the TNBC TME could present new opportunities for biomarker and/or therapeutic development to improve prognosis for these underserved populations. Citation Format: Rachel Martini, Stevens Patino, Emma Guyonnet, Brian Stonaker, Isra Elhussein, Julie Sahler, Avery August, Nancy Manley, Rick Kittles, Clayton Yates, Lisa Newman, Melissa Davis. The DARC side of Breast Cancer - DARC, Duffy-null and African ancestry influence in the Triple Negative Breast Cancer tumor microenvironment [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 PS18-09.

Abstract PO3-13-05: PD-L1 and PD-L2 Protein Expression is Frequently Discordant in Breast Cancer

Abstract Background: In neoadjuvant setting, PD-1 inhibitors have shown significantly higher pathological responses in patients (pts) with early-stage triple-negative breast cancer (TNBC) irrespective of PD-L1 status. However, durable responses are less common in estrogen receptor-positive (ER+) pts. Most breast cancer (BC) clinical trials of PD-1 inhibitors have thus far focused on PD-L1 expression for patient eligibility. The alternative PD-1 ligand, PD-L2, with reported ~4-fold greater affinity for PD-1, has been largely understudied. We recently reported that high cancer cell protein levels of PD-L2 in pts with treatment-naïve ER+ BC was an independent predictor of shorter progression-free survival. PD-L2 expression was significantly high in ER- group as well, however, given the low numbers of ER- pts, the study was not powered enough to determine the correlation of PD-L2 with PFS in the ER- subgroup. These findings suggest that PD-L2 has an important role in BC and combined PD-L1/PD-L2 status may help improve BC pt selection for PD-1 inhibitors. We therefore initiated efforts to determine baseline expression patterns of PD-L1 and PD-L2 in BC. Methods: PD-L1 and PD-L2 protein levels in cancer cells and tumor-infiltrating immune cells were prospectively analyzed by immunohistochemistry (IHC) using validated antibodies in diagnostic core biopsies of 31 consecutive pts diagnosed with localized or locoregional ER+/HER2- BC or TNBC. Percent positivity of PD-L1 and PD-L2 in cancer cells and immune cells was determined by our breast pathologist. Detectable PD-L1 or PD-L2 expression in ≥1% of cancer cells or stromal immune cells was considered positive. Spearman correlation and Wilcoxon paired analyses were used to measure and correlate PD-L1 and PD-L2 protein expression in cancer and immune cells. Results: There was no significant correlation between PD-L1 and PD-L2 expression, neither across all cases (N=31), nor within ER+ (N=22) or TNBC (N=9) cases. However, PD-L1 and PD-L2 expression patterns in BC differed in several ways. PD-L1-positivity in immune cells was higher than in cancer cells (median=5.0% vs. 0.0%; p=0.001), whereas PD-L2-positivity was higher in cancer cells than in immune cells (median=30% vs. 5.0%; p&amp;lt; 0.001). PD-L1 positivity in cancer cells and immune cells were positively correlated in TNBC (rho=0.69, p=0.04) but not in ER+ BC. Conversely, PD-L2 positivity in cancer cells and immune cells were positively correlated in ER+ BC (rho=0.68, p=0.001) but not in TNBC. TNBC diverged from ER+ BC by displaying higher PD-L1 positivity in immune cells (median=20.0% vs. 1.0%; p=0.004). By the conventional cut point for positivity of ≥1% for PD-L1 and PD-L2 in cancer cells or immune cells, all TNBC tumors were PD-L1-positive (9/9), with 8 also being PD-L2-positive. Of the 22 ER+ cases, 16 were PD-L2-positive, of which only 9 were also PD-L1-positive. Table 1. shows cross tabulation data for PD-L1 and PD-L2 status by BC subtype. Conclusions: PD-L1 and PD-L2 proteins show divergent expression and are not correlated in BC. Discordant PD-L2 and PD-L1 expression may be more common in ER+ BC than in TNBC. This finding justifies efforts to explore PD-L2 as a complementary marker to PD-L1 for improved prediction of response to PD-1 inhibitors, which may benefit patients with aggressive ER+ BC that are eligible for chemotherapy. Table 1. PD-L1 vs. PD-L2 Status by Breast Cancer Subtype Citation Format: Lubna Chaudhary, Julie Jorns, Yunguang Sun, Sailaja Kamaraju, Yee Chung Cheng, Amanda Kong, Tina Yen, Caitlin Patten, Chandler Cortina, Inna Chervoneva, Christopher Chitambar, Hallgeir Rui. PD-L1 and PD-L2 Protein Expression is Frequently Discordant 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 PO3-13-05.

Abstract PO2-05-14: Prognosis and clinicopathological characteristics of HER2-negative metastatic breast cancers with low expression of hormone receptors: real world evidence from the French ESME cohort

Abstract Background: HER2-negative breast cancers expressing low (1-9 %) immunohistochemistry levels of hormone receptors (HR, estrogen and progesterone receptors), remain an uncertain category, being considered either as triple negative breast cancers (TNBC) or HR-positive (HR+) tumors across guidelines or approvals. The issues regarding this clinical subgroup are both prognostic, with the need of a better definition of their clinical outcome, as well as predictive. Methods: The ESME database is a French National cohort of all consecutive patients who initiated a first-line treatment for metastatic breast cancer (MBC) from 2008 on, in one of the 18 French Comprehensive Cancer Centers. Patients with HER2-negative (0 to 2+, ISH negative) MBC and known estrogen receptor (ER) and progesterone receptors (PR) expression levels were selected. Primary objective was to evaluate crude overall survival (OS) in HER2-/HR-low (ER and PR 0-9 and not TNBC) MBC pts compared with those with TNBC and HR+ disease defined by ER and PR &amp;lt; 1%, and ER ± PR ≥ 10%, respectively. In these 3 populations, predefined secondary objectives were to evaluate PFS under first line chemotherapy (CT), to describe clinical characteristics and the distribution of genetic abnormalities identified at the time of MBC diagnosis. Results: Out of 30,459 patients in the ESME database initiating their MBC treatment between 01/2008 and 01/2021, 19109 patients (2113 TNBC; 228 HR-low; 16768 HR+) were eligible for this analysis. Median follow-up was 58.0 months (95%CI [56.6; 59.0]). Median OS were 15.7 months [15.0-16.8], 19.1 months [15.5-22.4] and 44.6 months [43.8-45.5] in the TNBC, HR-low and HR+ subgroups, respectively. The multivariable analysis adjusted on age at MBC diagnosis, pathological grade and subtype, metastatic-free interval, number and sites of metastases and HER2 status (0 vs. 1-2+), identified no significant OS difference between HR-low and TNBC subgroups (HR=0.95, 95%CI 0.79-1.14), while HR+ patients had a better OS than TNBC patients (reference) (HR=0.50, 95%CI 0.47-0.53). Of these 19109 pts, 8910 received first-line CT regimen (1960 TNBC; 195 HR-low; 6755 HR+): taxanes-based: 66.7%, anthracyclines-based: 32.9%, capecitabine: 18%. Median PFS under first line CT were 5.3 (5.1-5.6), 5.1 (4.1-6.2) and 10.2 months (9.9-10.6) for TNBC, HR-low and HR+ subgroups, respectively. In the multivariable analysis adjusted on the same variables, the HR-low subgroup had a statistically poorer PFS compared to TNBC (HR=1.24, 95% CI 1.04-1.49). On the other hand, the HR+ subgroup had a better PFS than the TNBC (HR=0.74, 95%CI [0.70; 0.78]). Baseline germline BRCA1 mutations (at MBC diagnosis) were present in 4.5% of the TNBC cases, 2.6% of the HR-low cases, and 0.4% of the HR+ cases. The distribution of germline BRCA2 mutations was more homogeneous between the three groups (0.9% of TNBC cases, 1.3% of HR-low cases and 1.1 % of HR+ cases). Conclusions: In this large cohort, patients with HER2-negative, HR-low MBC seem to share similar general prognosis, oncogenetic features and PFS under standard chemotherapy treatment with TNBC patients. Citation Format: Marie Alexandre, Ludovic Gauthier, Audrey Mailliez, Thibault DE LA MOTTE ROUGE, Thomas Bachelot, Monica Arnedos, Florence Dalenc, Etienne Brain, Jean-Marc Ferrero, Vincent Massard, Isabelle Desmoulins, Marie-Ange Mouret-Reynier, Christelle Levy, Anthony Gonçalves, Marianne Leheurteur, Thierry Petit, Jean-Sébastien Frenel, Lise Bosquet, Suzette Delaloge, William Jacot. Prognosis and clinicopathological characteristics of HER2-negative metastatic breast cancers with low expression of hormone receptors: real world evidence from the French ESME cohort [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 PO2-05-14.