HER2-positive Breast Carcinoma Research Articles

Prognostic Evaluation of HER2-positive Early Breast Cancers Using Clinico-pathological Criteria.

HER2-positive breast carcinomas (BCs) generally behave more aggressively and show higher cytological and histological grade than HER2-negative BCs. However, the clinical properties of HER2-positive early BCs have not been studied extensively. Hence, the therapeutic significance of neoadjuvant chemotherapy (NAC) for this BC remains debatable. We retrospectively examined the clinicopathological features of 94 HER2-positive early BCs who perioperatively received anti-HER2 drugs, without undergoing NAC prior to surgery. The patients' five year-disease free survival (DFS) and overall survival (OS) rates were 95.6% and 100%, respectively. Univariate analysis demonstrated significant differences in distant metastasis-free survival (DMFS) between clinical and pathological tumor stages (T stages). Pathological T1 stage and clinical T1 stage tumors showed significantly higher DMSF than pT2-3 and cT2-3 (p=0.0002 and 0.0294). Multivariate analysis disclosed no significant differences in DFS, OS, and DMFS with respect to preoperative clinical tumor stage, patient age, type of surgery, postoperative therapy, and pathological factors. Recurrences occurred in nine patients: four (4.3%) and five (5.3%) patients showed local and distant recurrences, respectively. One patient with cT2 BC died of disease. Interestingly, four of the five BCs with distant recurrence pathologically demonstrated lymph vessel invasion. The prognoses of patients with HER2-positive stage cT1/2N0M0 BC were highly favorable. The indications for NAC in small, localized, and node-negative HER2-positive BC should be carefully assessed based on the presence of a larger tumor size, postoperative pathological evaluation of tumor size, and lymph vessel invasion.

Abstract PO5-20-06: Paraneoplastic cerebellar degeneration in anti-Yo antibody and HER2-positive metastatic breast carcinoma

Abstract Paraneoplastic cerebellar degeneration (PCD) in the context of breast carcinoma affects less than 1% of patients. In most cases, breast cancer diagnosis follows several months or even years after the onset of neurological symptoms. The first association between PCD and occult gynecologic cancers (breast or ovarian) was identified in 1938 with the discovery of antibodies directed against cytoplasmic antigens of Purkinje cells (“anti-Yo antibodies”). Since then, evidence has grown significantly to support anti-Yo antibodies as excellent diagnostic markers of PCD with underlying gynecologic and breast carcinoma. This case study evaluates a 57-year-old female who initially presented with headache and subacute cerebellar ataxia. Her symptoms progressed over a period of three months with multiple falls, onset of speech difficulties, and diplopia. She also reported 30-pound weight loss, which she attributed to dieting and starting semaglutide. Magnetic resonance imaging (MRI) of the brain and spine were unremarkable and autoimmune workup was normal. Cerebral spinal fluid (CSF) and serum studies demonstrated positive anti-Yo antibodies. Computed tomography (CT) of the abdomen and pelvis showed an enlarged left axillary lymph node concerning for metastatic disease with a 1.2cm focus of asymmetric density in the central inferior left breast parenchyma. Diagnostic mammogram one year prior was reportedly normal. Ataxia symptoms improved after a course of empiric intravenous immunoglobulins and steroids. Ultrasound-guided biopsy of the left axillary lymph node revealed metastatic mammary carcinoma: estrogen and progesterone receptor negative and human epidermal growth factor receptor 2 (HER2)-positive, cT0N2aM0, ypTxN1aM0, stage IIIa (AJCC 8th edition). She underwent further metastatic workup, including repeat CSF studies and MRI. MRI of the spine was remarkable for multiple hemangiomas throughout the cervical, thoracic, and lumbar spine, with subsequent unremarkable bone scan. MRI of the abdomen was remarkable for right hepatic lobe hemangioma and a right adrenal nodule. CSF studies showed no sign of metastases. After multidisciplinary discussion, TCHP (docetaxel, carboplatin, trastuzumab, and pertuzumab) neoadjuvant therapy was initiated and repeat imaging demonstrated favorable treatment response with a shrinking axillary mass; no primary breast mass was identified. The patient underwent left sentinel lymph node biopsy with a positive frozen section intraoperative for invasive cancer, therefore proceeded with left axillary lymph node dissection. She was offered a mastectomy but elected for only axillary surgery. Pathology revealed 1 of 14 lymph nodes were positive for metastatic ductal carcinoma. She remains in a rehabilitation center and her ataxia is improving, but her functional status remains below baseline. She is undergoing radiation to whole breast and regional lymph nodes. With this case, we aim to continue to build upon the limited base of the exceedingly rare presentation of breast cancer-associated paraneoplastic syndrome. In addition, several studies and case reports have demonstrated a strong correlation between HER2 overexpression and anti-Yo associated PCD. As we continue to diagnose and monitor breast cancer patients, we could consider starting to screen for anti-Yo antibodies in HER2-positive patients to gain insight into a patient’s prognosis and development of PCD. Citation Format: You Kim, Alison Coogan, Andrea Madrigrano. Paraneoplastic cerebellar degeneration in anti-Yo antibody and HER2-positive metastatic breast carcinoma [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 PO5-20-06.

Diagnostic utility and sensitivities of matrix Gla protein (MGP), TRPS1 and GATA3 in breast cancer: focusing on metastatic breast cancer, invasive breast carcinoma with special features, and salivary gland-type tumours

Matrix Gla protein (MGP) and trichorhinophalangeal syndrome type 1 (TRPS1) have recently emerged as novel breast-specific immunohistochemical (IHC) markers, particularly for triple-negative breast cancer (TNBC) and metaplastic carcinoma. The present study aimed to validate and compare the expression of MGP, TRPS1 and GATA binding protein 3 (GATA3) in metastatic breast carcinoma (MBC), invasive breast carcinoma (IBC) with special features, including special types of invasive breast carcinoma (IBC-STs) and invasive breast carcinoma of no special type with unique features, and mammary and non-mammary salivary gland-type tumours (SGTs). Among all enrolled cases, MGP, TRPS1 and GATA3 had comparable high positivity for ER/PR-positive (p=0.148) and HER2-positive (p=0.310) breast carcinoma (BC), while GATA3 positivity was significantly lower in TNBC (p<0.001). Similarly, the positive rates of MGP and TRPS1 in MBCs (99.4%), were higher than in GATA3 (90.9%, p<0.001). Among the IBC-STs, 98.4% of invasive lobular carcinomas (ILCs) were positive for all three markers. Among neuroendocrine tumours (NTs), all cases were positive for TRPS1 and GATA3, while MGP positivity was relatively low (81.8%, p=0.313). In the neuroendocrine carcinoma (NC) subgroup, all cases were positive for GATA3 and MGP, while one case was negative for TRPS1. All carcinomas with apocrine differentiation (APOs) were positive for GATA3 and MGP, while only 60% of the cases demonstrated moderate staining for TRPS1. Among mammary SGTs, MGP demonstrated the highest positivity (100%), followed by TRPS1 (96.0%) and GATA3 (72.0%). Positive staining for these markers was also frequently observed in non-mammary SGTs. Our findings further validate thehigh sensitivity of MGP and TRPS1 in MBCs, IBC-STs, andbreast SGTs. However, none of these markers arecapable of distinguishing between mammary and non-mammary SGTs.

Predictive markers for pathological complete response (pCR) after neo-adjuvant chemotherapy in HER2-positive breast carcinoma.

Patients with HER2-positive invasive breast cancer that is node-positive and/or larger than 3 cm are generally treated with neoadjuvant chemotherapy (NAC). We aimed to identify predictive markers for pathological complete response (pCR) after NAC in HER2-positive breast carcinoma. Hematoxylin/eosin-stained slides of 43 HER2-positive breast carcinoma biopsies were histopathologically reviewed. Immunohistochemistry (IHC) was performed on pre-NAC biopsies, comprising HER2, estrogen receptor (ER), progesterone receptor (PR), Ki-67, epidermal growth factor receptor (EGFR), mucin-4 (MUC4), p53 and p63. Dual-probe HER2 in situ hybridization (ISH) was performed to study the mean HER2 and CEP17 copy numbers. ISH and IHC data were retrospectively collected for a validation cohort, comprising 33 patients. Younger age at diagnosis, 3+ HER2 IHC scores, high mean HER2 copy numbers and high mean HER2/CEP17 ratios were significantly associated with an increased chance of achieving a pCR, and the latter two associations were confirmed in the validation cohort. No other immunohistochemical or histopathological markers were associated with pCR. This retrospective study of two community-based NAC-treated HER2-positive breast cancer patient cohorts identified high mean HER2 copy numbers as a strong predictor for pCR. Further studies on larger cohorts are required to determine a precise cut-point for this predictive marker.

Clinical Internal Dosimetry and Biodistribution of 177 Lu-DOTA-Trastuzumab in HER2-Positive Metastatic and Locally Advanced Breast Carcinoma.

The aim of this study was to assess the biodistribution and dosimetry of 177 Lu-DOTA-trastuzumab in patients with HER2-positive breast carcinoma using whole-body (WB) planar imaging at multiple time points. This study was a prospective evaluation of HER2-positive metastatic/locally advanced breast carcinoma patients who underwent gamma camera imaging for dosimetry and biodistribution studies by using 177 Lu-DOTA-trastuzumab. The standard diagnostic dosimetry protocol was followed, which included cold trastuzumab injection followed by in-house produced 177 Lu-DOTA-trastuzumab. Serial WB planar images (anterior and posterior) were obtained on gamma camera after the infusion of 177 Lu-DOTA-trastuzumab at multiple time points. Whole-body and organ regions of interest were drawn, and the numbers of disintegrations were obtained. The mean absorbed doses for the liver, spleen, kidneys, heart, red marrow, and tumor were obtained from OLINDA EXM v2.1.1 and ORIGIN software. The study included a cohort of 21 female breast carcinoma patients. Tracer activity ( 177 Lu-DOTA-trastuzumab) was noted in the physiological organs such as the liver, spleen, kidneys, heart, as well as in the tumors. On visual analysis of 177 Lu-DOTA-trastuzumab biodistribution, the liver activity showed gradual clearance over time, and although spleen was comparatively faintly visualized than liver and similarly, kidneys were faintly visualized suggestive of the alternate route of tracer excretion. The maximum number of patients (n = 12) showed 2 components of clearance, namely, fast and slow. The average effective half-life of all the patients (including single and 2 components of clearance) was 106.25 ± 22.14 hours (84.11-128.39 hours). The mean absorbed dose for the liver, spleen, kidneys, heart, whole body, and red marrow was 1.0702 ± 0.731, 1.4114 ± 0.462, 1.4232 ± 0.364, 1.4719 ± 0.602, 0.2412 ± 0.0295, and 0.1485 ± 0.0213 mGy/MBq, respectively, by OLINDA EXM and 0.5741 ± 0.333, 0.8096 ± 0.224, 0.7943 ± 0.235, 1.8971 ± 0.713, and 0.09619 ± 0.0144 for liver, spleen, kidneys, heart and whole body respectively by ORIGIN. The absorbed radiation dose for tumor was 1.94E+2 by OLINDA EXM software and 1.78E+2 by ORIGIN software. In this study, during and after infusion of 177 Lu-DOTA-trastuzumab, no major adverse effects were noted in any patient except 1 patient who had grade 1 nausea and managed conservatively by antiemetic drug. The results of our study demonstrated expected and favorable biodistribution and dosimetry with 177 Lu-DOTA-trastuzumab in HER2-positive breast carcinoma patients. We noticed the mean absorbed dose to the normal organs within the limits of maximum tolerable dose, and also tumor dose was higher than the normal liver dose. Therefore, we conclude that 177 Lu-DOTA-trastuzumab radioimmunotherapy is feasible and a safe treatment option for treating HER2-positive breast carcinoma patients.

PRAME expression and its prognostic significance in invasive breast carcinoma

ObjectivesPRAME (PReferentially expressed Antigen in MElanoma) is a carcinoma testis antigen expressed in numerous tumour types. The aim of this study was to assess PRAME expression in different surrogate subtypes of breast carcinoma and its correlation with other prognostic factors. Material and methodsA total of 220 cases of invasive breast carcinoma were selected and categorized according to ER, PgR, HER2 status, and Ki67 proliferation index in luminal A like, luminal B HER2+ like, luminal B HER2- negative like, HER2 positive like and triple-negative or basal-like. All cases were examined for PRAME expression by immunohistochemistry (IHC). ResultsA PRAME-high profile was detected in 53 (24,1 %) of all examined breast carcinoma samples. A significantly higher expression of PRAME was detected in HER2-positive carcinomas (50 %) and TN breast carcinomas (40,54 %) compared to ER-positive (luminal-like) subtype of breast carcinomas (3,38 % luminal A and 15,38 % luminal B). Percentage of PRAME positive tumour cells showed positive correlation with tumor size, Ki67 proliferation index, HER2 status, nuclear grade, TILs and presence of metastasis, and negative correlation with ER status and disease-free survival (DFS). ConclusionOur study showed that HER2 positive and TN breast carcinomas more commonly express PRAME than ER positive carcinomas and that PRAME expression shows positive correlation with certain prognostic factors, however PRAME wasn't revealed as an independent prognostic factor in our study. The importance of PRAME expression in breast carcinoma lies in its potential use as an immunotherapeutic target, particularly in patients with limited therapeutic options.

The Role of Tumor Bed Boost in Breast Cancer Patients with HER2-Positive Disease Treated with Breast Conservation Therapy

Retrospective and post-hoc trial analyses have supported the omission of the tumor bed radiation boost in HER2-positive patients undergoing breast-conservation surgery in the era of HER2-directed therapy. In this analysis, we sought to describe the national patterns of care of tumor bed boost and its association with overall survival (OS) in this population. We queried the National Cancer Database to identify all female patients with HER2-positive invasive breast carcinoma treated with lumpectomy. Patients who were treated with neoadjuvant chemotherapy and those with metastatic disease at diagnosis were excluded from analysis. Clinical and demographic information and treatments were analyzed using standard T and χ2 tests. Predictors of receipt of tumor bed boost and predictors of death were identified with multivariable logistic regression. The Kaplan-Meier method was used to evaluated overall survival. We identified 6,620 female patients diagnosed with HER2-positive invasive breast carcinoma between 2006 and 2017. Of these patients, 2,825 (43%) were treated with a boost and 3,795 (57%) were not; 4,698 (71%) were hormone receptor positive and 1,909 (29%) were hormone receptor negative; 6,333 (96%) had negative surgical margins and 287 (4%) had positive surgical margins; 1,270 (19%) were ≤50 years of age and 5,350 (81%) were >50. On multivariable analysis, receipt of tumor bed boost was associated with age ≤50 years (Odds ratio [OR] 1.3, p<0.01), hormone receptor negative (OR 1.3, p<0.01). Factors associated with a higher risk for death included age >50 years (OR 2.4, p<0.01), positive surgical margins (OR 1.7, p<0.01), pN1 (OR 1.3, p = 0.03), pN2 (OR 2.3, p<0.01), pN3 (OR 3.2, p<0.02), and pT2 (OR 2.2, p<0.01) stage. Tumor bed boost was not associated with improved OS when compared to no boost among patients with HER2-positive disease who go on to receive adjuvant systemic therapy (HR 1.06, p = 0.60), even among patients who meet ASTRO tumor bed boost recommendation criteria (HR 0.90, p = 0.60), including age ≤50 with any grade, age 51-70 with high grade, or positive margin. A tumor bed boost is commonly implemented in HER2-positive breast cancer patients undergoing breast-conserving surgery and adjuvant radiation. This data supports previous retrospective and post-hoc trial analyses in omitting the tumor bed boost and treating patients who will receive adjuvant systemic therapy with whole breast radiation alone, provided that the patient receives HER2-directed therapy.

Metastasis to the sublingual gland of metaplastic breast carcinoma – a case report

Metastatic spread to the salivary glands is rare, occurring primarily from head and neck tumors to the parotid gland. So far, only one sublingual gland metastasis has been reported in the literature. We herein report the second case of metastasis to this gland occurring in a woman in her 50s, previously diagnosed with HER2-positive metaplastic breast carcinoma (MpBC) with chondroid differentiation, with lymph node and diffuse organ metastases. The sublingual lesion presented as a tumefaction on the floor of the mouth, causing masticatory discomfort. Histologically it was formed by epithelial cells with high-grade cytomorphological features with a large central area of chondroid differentiation. The case was clinically and pathologically challenging, given the rarity of the primary MpBC and the improbable secondary location. Alternative primary salivary gland tumors with chondroid differentiation were considered, but ultimately the clinical integration was crucial in establishing the diagnosis of MpBC metastasis to the sublingual gland.

Clinicopathological characteristics and prognosis of early-stage HER2 low-expression breast cancer: A single-center retrospective study.

Owing to the emergence of drugs targeting human epidermal growth factor receptor 2 (HER2), remarkable prognostic enhancement has been seen for patients with HER2-positive breast carcinoma. However, anti-HER2 medicines are applicable merely to individuals with HER2-positive tumors, and the benefit for those with low HER2 expression is unclear. The DESTINY-Breast04 phase III and RC48 clinical trial results showed the benefit of antibody-drug couples for low HER2-expressing individuals with breast carcinoma, challenging the traditional dichotomy between HER2-negative and -positive tumors. Hence, the purposes of the present work are to explore the clinicopathological traits and prognostic differences in the HER2-low expression Chinese population with early-stage breast carcinoma. Data from the database of the Breast Center of the Affiliated Hospital of Qingdao University were collected from January 2008 to December 2017. We screened a total of 4,598 patients, of which 2,837 had HER2-0 tumors and 1,761 had HER2-low tumors. Additionally, clinicopathological characteristics, survival, and prognostic information were obtained. Difference comparisons were made between HER2-0 and HER2-low groups regarding the clinical traits and outcomes. We enrolled 4598 patients, with the HR-positive subjects suffering from HER2-low breast carcinoma higher in proportion than the HR-negative patients. In contrast to HER2-0 tumors, the HER2-low tumors were linked to an older median age at diagnosis, T1 tumors, N1 stage, a higher Ki-67 index, as well as inferior histological grade. Insignificant inter-group difference was noted regarding overall survival (OS), although the HER2-0 group exhibited better disease-free survival (DFS) than the HER2-low group for the entire (P = 0.003), lymph node-negative (P = 0.009) and HR-positive (P = 0.007) populations. According to the multivariate regression finding, low HER2 expression was an inferior DFS prognostic factor in the HER2-negative population with early-stage breast cancer (HR,1.33;95% CI, 1.06-1.66; P = 0.013). The clinical traits of the HER2-low carcinomas differed from those of HER2-0 tumors. Despite the insignificant inter-group difference in OS, the differences in DFS were found for the overall, lymph node-negative and HR-positive subjects, suggesting the possibility of HER2-low as an inferior prognostic factor for disease progression in early-stage breast cancer.

HER2 amplification by next-generation sequencing to identify HER2-positive invasive breast cancer with negative HER2 immunohistochemistry

BackgroundHuman epidermal growth factor receptor 2 (HER2) positive breast carcinomas due to HER2 amplification are associated with aggressive behavior and a poor prognosis. Anti-HER2-targeted therapies are widely used to treat HER2-positive breast carcinomas with excellent outcomes. Accurate identification of HER2 amplification status in breast carcinomas is of important diagnostic and treatment value. Currently, HER2 amplification status is routinely determined by immunohistochemistry (IHC) and/or fluorescence in situ hybridization (FISH) testing. This study will review our past HER2 data to determine and characterize discordant results between HER2 IHC and FISH. It will also determine a potential impact of HER2 amplification status by next-generation sequencing (NGS) on these patients.MethodsWe reviewed a total of 4884 breast carcinomas with coexisting HER2 IHC and HER2 FISH performed at our institution from 2010 to 2022. 57 cases also had a Next-Generation-Sequencing-based (NGS) gene panel performed. Given the advances in biostatic analysis pipelines, NGS methods were utilized to provide results on HER2 amplification status along with somatic mutations.ResultsWhile the majority (ranging from 98.5% with IHC score of 0 and 93.1% with IHC score of 1 +) of 4884 breast carcinomas had concordant results from HER2 IHC and HER2 FISH testing, a small percentage of patients (ranging from 1.5% in those with IHC score of 0, to 6.9% with IHC score of 1 +) had discordant results, with negative HER2 IHC and positive HER2 FISH results. These patients could be reported as HER2-negative breast carcinomas if only HER2 IHC testing has been performed according to a current cost-effective HER2 test strategy. 57 patients had HER2 amplification status determined by NGS, and all patients had concordant results between HER2 NGS and FISH tests. A HER2-amplified breast carcinoma by NGS had a negative IHC and a positive HER2 FISH result. This case was classified as a HER2-positive breast carcinoma, had anti-HER2-targeted therapy, and achieved a complete clinical response.ConclusionsA small percentage of HER2-positive breast carcinomas are unidentified because of a negative HER2 IHC based on our current cost-effective HER2 test strategy. It is not feasible and affordable in routine clinical practice to perform HER2 FISH for the cases with negative HER2 IHC (IHC score 0 and 1 +). Therefore, NGS assays capable of simultaneously detecting both somatic mutations and HER2 amplification could provide a more comprehensive genetic profiling for breast carcinomas in a clinical setting. Identification of HER2 amplification by NGS in HER2-positive breast carcinomas with negative HER2 IHC results is important since these cases are concealed by our current cost-effective HER2 test strategy with IHC first (for all cases) and FISH reflex (only for cases with IHC score of 2 +), and would offer the opportunity for potentially beneficial anti-HER2-targeted therapies for these patients.

Site-Specific Radiohalogenation of a HER2-Targeted Single-Domain Antibody Fragment Using a Novel Residualizing Prosthetic Agent.

Because of their rapid tumor accumulation and normal tissue clearance, single-domain antibody fragments (sdAbs) are an attractive vehicle for developing radiotherapeutics labeled with the α-emitter 211At. Herein, we have evaluated iso-[211At]AGMB-PODS, a prosthetic agent that combines a functionality for residualizing radiohalogens with a phenyloxadiazolyl methylsulfone (PODS) moiety for site-specific sdAb conjugation. Iso-[211At]AGMB-PODS and its radioiodinated analogue were evaluated for thiol-selective conjugation to anti-HER2 5F7 sdAb bearing a C-terminus GGC tail. Both radiohalogenated PODS-5F7GGC conjugates were synthesized in good radiochemical yields and retained high binding affinity on HER2-positive BT474 breast carcinoma cells. Iso-[211At]AGMB-PODS-5F7GGC was considerably more stable in vitro than its maleimide analogue in the presence of cysteine and human serum albumin (HSA) and exhibited excellent tumor uptake and high in vivo stability. Superior tumor-to-kidney activity ratios were seen for both radiohalogenated PODS-5F7GGC conjugates compared with [177Lu]Lu-DOTA-PODS-5F7GGC. These results suggest that iso-[211At]AGMB-PODS-5F7GGC warrants further evaluation for the treatment of HER2-expressing malignancies.

1721P Hereditary component of HER2-positive breast cancer

In recent years, a greater number of germinal mutations that predispose to the development of tumors have been found. Understanding the interactions between mutations and breast cancer’s subtype is essential for opening new therapeutic and preventive strategies. It is well known what type of breast cancer develops in a hereditary syndrome context; however, the prevalence of HER2 positive tumors with some deleted mutation in genes predisposing to breast cancer, is still not entirely clear. This study aims to know the prevalence of HER2-positive tumors, either with positive or negative estrogen and/or progesterone receptors, associated with some germline mutation in a hereditary syndrome context. It is a descriptive and longitudinal study, with retrospective collection of data from patients diagnosed of HER2-positive breast cancer and positive or negative hormone receptors in the intercenter Clinical Management Unit of Medical Oncology. A total of 1,070 patients diagnosed with HER2-positive breast carcinoma were obtained. Of it, 189 (17.66%) patients underwent a genetic study, finding a germline mutation in 33 patients (3.08% of the global population and 17.46% of the population studied). The most frequent genes were BRCA 1 and 2, MUTYH and ATM. Breast cancer with overexpression of the HER2 protein and a germline mutation is rare, with an unknown true prevalence. It is associated with mutations in prevalent genes such as BRCA 1 and 2, but also with less frequent ones such as TP53. Prospectives studies are needed to elucidates which patients with HER2 positive breast cancer are better candidates for a germinal test.

Integrative genomic and transcriptomic analyses illuminate the ontology of HER2-low breast carcinomas

BackgroundThe “HER2-low” nomenclature identifies breast carcinomas (BCs) displaying a HER2 score of 1+/2+ in immunohistochemistry and lacking ERBB2 amplification. Whether HER2-low BCs (HLBCs) constitute a distinct entity is debated.MethodsWe performed DNA and RNA high-throughput analysis on 99 HLBC samples (n = 34 cases with HER2 score 1+/HLBC-1, n = 15 cases with HER2 score 2+ and ERBB2 not amplified/HLBC-2N, and n = 50 cases with score 2+ and ERBB2 copy number in the equivocal range/HLBC-2E). We compared the mutation rates with data from 1317 samples in the Memorial Sloan-Kettering Cancer Center (MSKCC) BC cohort and gene expression data with those from an internal cohort of HER2-negative and HER2-positive BCs.ResultsThe most represented mutations affected PIK3CA (31/99, 31%), GATA3 (18/99, 18%), TP53 (17/99, 17%), and ERBB2 (8/99, 8%, private to HLBC-2E). Tumor mutational burden was significantly higher in HLBC-1 compared to HLBC-2E/N (P = 0.04). Comparison of mutation spectra revealed that HLBCs were different from both HER2-negative and HER2-positive BCs, with HLBC-1 resembling more HER2-negative tumors and HLBC-2 mutationally related to HER2-addicted tumors. Potentially actionable alterations (annotated by using OncoKB/ESCAT classes) affected 52 patients. Intra-group gene expression revealed overlapping features between HLBC-1 and control HER2-negative BCs, whereas the HLBC-2E tumors showed the highest diversity overall. The RNA-based class discovery analysis unveiled four subsets of tumors with (i) lymphocyte activation, (ii) unique enrichment in HER2-related features, (iii) stromal remodeling alterations, and (iv) actionability of PIK3CA mutations (LAURA classification).ConclusionsHLBCs harbor distinct genomic features when compared with HER2-positive and HER2-negative BCs; however, differences across IHC classes were also unveiled thus dissecting the full picture of heterogeneity across HER2-low disease. The HLBC-2E category harbors most distinctive features, whereas HLBC-1 seems superimposable to HER2-negative disease. Further studies are needed to ascertain whether the four genomic-driver classes of the LAURA classification hold prognostic and/or predictive implications.

Alpha-methylacyl-CoA racemase (AMACR) protein is upregulated in early proliferative lesions of the breast irrespective of apocrine differentiation

Alpha-methylacyl-CoA racemase (AMACR/P504S) is a mitochondrial and peroxisomal enzyme involved in the branched-chain fatty acid and bile acid metabolism. AMACR is a useful diagnostic biomarker for prostate carcinomas and several other malignancies. Its expression in apocrine breast lesions had been previously reported, but its role in breast cancer progression has not been fully investigated. One hundred fifty breast samples (80 with invasive carcinomas) were studied. The expression of AMACR protein was analyzed using the immunohistochemical method (IHC). Lesions were considered positive if AMACR was detected in ≥10% of the cells at any intensity comprising a histologically defined normal epithelial structure or a pathologic lesion. In addition, AMACR mRNA relative expression was calculated from the whole-transcript RNA-Seq performed on >20,000 diverse tumor samples using a 20,000+ hybrid-capture NGS assay with the transcript capture panel based on the Agilent SureSelect Human All ExonV7. Expression of AMACR protein was restricted to epithelia. It was uncommon in the normal breast (7/81 samples, 9%). Increasing AMACR expression was observed with proliferative epithelial lesions (18% of usual ductal hyperplasias/adenosis, 70% of atypical lesions and 72% of DCIS/LCIS). Invasive ductal carcinomas NST and invasive lobular carcinomas expressed AMACR in 64% and 46%, respectively. The highest AMACR expression was observed in luminal B and HER2-positive breast carcinomas (86-100%). Triple-negative breast carcinomas exhibited AMACR in 50% of the cases. Apocrine lesions showed strong, nearly uniform overexpression of AMACR (100% of metaplasias, hyperplasias and in situ carcinomas and 88% of invasive apocrine carcinomas were positive). RNA-Seq analysis also confirmed AMACR expression in breast carcinomas, although its median value was substantially lower with a lower standard deviation than in prostate carcinomas. Over-expression of AMACR characterizes various proliferative, preinvasive and invasive breast lesions and is not specific to the apocrine morphology. It points to altered lipid metabolism (branched fatty acids) as one of the general characteristics of breast carcinogenesis, like several other malignancies. Its early detection may represent a potential target for cancer progression intervention.

Comparison of HercepTest™ mAb pharmDx (Dako Omnis, GE001) with Ventana PATHWAY anti-HER-2/neu (4B5) in breast cancer: correlation with HER2 amplification and HER2 low status

Performance of the new CE-IVD-marked HercepTest™ mAb pharmDx (Dako Omnis) assay (HercepTest (mAb)) was compared against the PATHWAY® anti-HER-2/neu (4B5) (PATHWAY 4B5) assay using 119 pre-selected breast cancer samples covering the entire range of HER2 immunohistochemistry (IHC) expression scores (0, 1 + , 2 + , 3 +). The sensitivity and specificity of both assays were assessed based on consensus IHC scores and amplification status, as determined by fluorescence in situ hybridization (FISH) according to 2018 ASCO/CAP testing guidelines. There was a high concordance between results from the HercepTest (mAb) and PATHWAY 4B5 assays for HER2-negative (IHC 0, 1 + , 2 + and FISH negative) and HER2-positive (IHC 3 + , 2 + and FISH positive) breast carcinomas (98.2%). Regarding individual IHC scores, complete agreement was achieved in 69.7% (83/119) of cases, and all but one of the discordant cases were due to higher HER2-status scoring using the HercepTest (mAb). Thus, more tumors were overscored as IHC 2 + by HercepTest (mAb) (27 versus 15) as evidenced by their lower FISH positivity rate (48.1% versus 80%). However, two amplified tumors identified as IHC 2 + by HercepTest (mAb) were missed by PATHWAY 4B5 (IHC 1 +). Four additional cases identified as IHC 2 + by HercepTest (mAb), with FISH ratio < 2 but elevated gene counts (≥ 4 to < 6), were recorded negative by PATHWAY 4B5. The HercepTest (mAb) detects HER2 expression with higher sensitivity in tumors with gene amplification (ISH group 1) and increased gene counts (ISH group 4) as well as in HER2-low tumors (HER2 IHC2 + /FISH negative or IHC 1 +). Future studies will demonstrate whether this translates into improved patient selection especially for new HER2-directed therapies.

Abstract 5418: Comprehensive genomic profiling of HER2low breast carcinomas unveils unique genomic features and actionable genetic alterations

Abstract Introduction &amp; Purpose: “HER2low breast cancer” is an operational term identifying breast carcinomas (BCs) displaying a HER2 score 1+ or score 2+ in immunohistochemistry (IHC) and lacking HER2 amplification. This paradigm shift in HER2 assessment in BC stems from substantial antitumor activity of potent antibody-drug conjugates (ADCs) targeting the HER2 receptor on the tumor cell membrane. Whether these tumors constitute a distinct pathological entity is a matter of debate. Experimental procedures: To dissect the biology of HER2low BCs we performed a high throughput mutational analysis coupled with gene expression profiling on 98 HER2low BCs [34 cases score 1+ (1), 15 cases score 2+ HER2 not amplified (2N), 49 cases score 2+ with HER2 copy numbers in the equivocal range (2E)], of which 89 were estrogen receptor (ER)-positive, and 9 ER-negative. DNA and RNA were extracted and subjected to targeted DNA sequencing (Illumina TSO500 panel) and targeted gene expression analysis (NanoString BC360 panel). Mutation rates were compared with in silico data from 1317 samples of the MSK Breast Cancer cohort (PMID: 30205045). Results: The most frequently mutated genes were PIK3CA (33/98, 33%), GATA3 (18/98, 18%), TP53 (17/98, 17%), HER2 (8/98, 8%, private to 2E cases). Tumor mutational burden mean values were significantly higher in score 1+ compared to score 2+ cases (p= 0.04), with a single score 1+ tumor harboring microsatellite instability (MSI). Mutational signatures 1, 5 and 13 (APOBEC) were the most prevalent, with signature 30 being private to HER2 score 1+ cases. Comparative statistics revealed mutational drift of HER2low BCs from both HER2 negative (19 differentially mutated genes) and HER2 positive BCs (11 differentially mutated genes). Potentially actionable genetic alterations (OncoKB classes) accounted for 43 SNVs (predominantly HER2 and PIK3CA mutations) and 17 CNVs (e.g. MET amplification and PTEN homozygous deletions), including a MSI tumor, distributed over 47 independent patients.Subgroup stratifications based on gene expression were observed when considering genes involved in angiogenesis, stromal marker and cytokines signalling. HER2 mRNA levels were significantly higher in 2E versus 2N and in 2E versus 1. Differential gene expression Kegg pathway analysis identified RTK activation restricted to 2E cases. Conclusions: HER2low BCs harbour a different mutational landscape from ER- and grade- matched HER2 positive and HER2 negative BCs. Differences across IHC score classes within HER2low carcinomas were demonstrated, with the 2E category showing distinct features (private HER2 mutations, HER2 mRNA levels significantly higher compared to the other groups, RTK pathway activation). Of note, besides the option of ADCs we demonstrate that up to 48% of cases may be targeted with different approaches exploiting actionable alterations. Citation Format: Enrico Berrino, Laura Annaratone, Ivana Sarotto, Maria Cecilia Zecchillo, Laura Casorzo, Riccardo Ponzone, Filippo Montemurro, Anna Sapino, Caterina Marchio. Comprehensive genomic profiling of HER2low breast carcinomas unveils unique genomic features and actionable genetic alterations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5418.

Safety and efficacy of monoclonal antibodies and tyrosine kinase inhibitors in advanced breast carcinoma.

e13017 Background: Novel drugs that target HER2 receptors have shown promise in the treatment of Advanced breast carcinoma (BC). We study here the safety and efficacy of select monoclonal drugs (Mab) and tyrosine kinase inhibitors (TKIs) in the treatment of advanced BC. Methods: Following the PRISMA guidelines, we searched the literature on PubMed, Cochrane, Embase &amp; clinicaltrials.gov. A total of 1054 articles were screened, and 6 studies were included. Results: In a phase III trial comparing Margetuximab (MAR) vs Trastuzumab (TRA), the overall survival (OS) and Progression free survival (PFS) was superior for MAR (21.6m Vs 19.8m &amp; 5.7m Vs 4.4m respectively). However, the side effect profile is comparable for both drugs.Neutropenia (50 %) was a key problem in an ongoing trial including Zenocutuzumab (ZENO), resulting in dosage reduction. Similarly, phase III trials incorporating TKIs such as Neratinib (NER) and Tucatinib (TUC), there was improved OS (21m Vs 18.7, 24.7m Vs 19.2m respectively) as compared to Standard of care and chemotherapy. Regarding safety profile, these therapies are generally well tolerated with manageable side effects as listed in the table. Conclusions: Both monoclonal antibodies and tyrosine kinase inhibitors show clinically significant benefits in advanced HER2 positive breast carcinoma. However, more evidence and randomized clinical trials are needed to further establish their role in this rapidly evolving field.[Table: see text]

Intensity modulated radiotherapy and targeted therapy for late nonregional para-aortic lymph node metastasis from HER2 positive breast carcinoma

In the case of invasive breast carcinomas (BC) there are extremely rare late nonregional retroperitoneal lymph node recurrences, occurring after 10 years of disease diagnosis. We present a 32-year-old woman, who was diagnosed in 2010 with left HER2 positive invasive ductal BC- pT2N1M0. Complex treatment involving radical mastectomy with axillary dissection and complex adjuvant treatment (chemotherapy, radiotherapy, targeted therapy with trastuzumab, endocrine therapy with LHRH agonist plus tamoxifen) was conducted. After 4 years, disease progression with left supraclavicular lymph node enlargement has been manifested. After surgical resection of supraclavicular lymph node, the patohistological analysis establishes lymph metastasis from HER2 positive invasive ductal carcinoma. After 6 years of multimodal treatment, including eight chemotherapy cycles docetaxel, bilateral adnexectomy, 2 targeted agents trastuzumab/pertuzumab and endocrine therapy with aromatase inhibitor, PET/ CT visualizes a nonregional lymph recurrence of left retroperitoneal lymph nodes. Isolated involvement of distant nodal regions is extremely uncommon. Complex therapy, including a definitive radiotherapy of retroperitoneal para-aortic lymph nodes combined with targeted therapy achieved complete remission in nonregional abdominal lymph recurrence.

Hypofractionated Radiosurgery Re-Irradiation in Large Solitary Brain Metastasis from HER2 Positive Breast Carcinoma

Hypofractionated Radiosurgery Re-Irradiation in Large Solitary Brain Metastasis from HER2 Positive Breast Carcinoma

Intensity modulated radiotherapy and targeted therapy for late nonregional para-aortic lymph node metastasis from HER2 positive breast carcinoma

Intensity modulated radiotherapy and targeted therapy for late nonregional para-aortic lymph node metastasis from HER2 positive breast carcinoma