ER-positive Tumors Research Articles

A phenocopy signature of TP53 loss predicts response to chemotherapy

In preclinical studies, p53 loss of function impacts chemotherapy response, but this has not been consistently validated clinically. We trained a TP53-loss phenocopy gene expression signature from pan-cancer clinical samples in the TCGA. In vitro, the TP53-loss phenocopy signature predicted chemotherapy response across cancer types. In a clinical dataset of 3003 breast cancer samples treated with neoadjuvant chemotherapy, the TP53-loss phenocopy samples were 56% more likely to have a pathologic complete response (pCR), with a significant association between TP53-loss phenocopy and pCR in both ER positive and ER negative tumors. In an independent clinical validation in the I-SPY2 trial (N = 987), we confirmed the association with neoadjuvant chemotherapy pCR and found higher rates of chemoimmunotherapy response in TP53-loss phenocopy tumors compared to non-TP53-loss phenocopy tumors (64% vs. 28%). The TP53-loss phenocopy signature predicts chemotherapy response across cancer types in vitro, and in a proof-of-concept clinical validation is associated with neoadjuvant chemotherapy response across multiple clinical breast cancer cohorts.

The prevalence of ER-low-positive breast cancer and its relation to tumor characteristics in Syria

Abstract Background: Breast cancer is a heterogeneous disease with varying clinical behaviors and responses to endocrine therapy. In particular, estrogen receptor (ER)-positive breast cancer can present with various subtypes, and the effectiveness of anti-hormone therapy on ER-low-positive tumors is unclear. This study aimed to evaluate and characterize ER-positive subtypes in patients admitted to the Surgical Oncology Clinic in the National Hospital of Jableh in Syria between 2020 and 2022. Patients and Methods: This study included 120 patients diagnosed with breast cancer; the data from each patient’s report were collected to classify them according to grade, stage, LNR, tumor size, and nodal stage. Results: The prevalence of ER-low-positive subtype was 23.33%. There was a significant difference between ER-negative and ER-positive subtypes concerning age, grade, stage, and LNR. Additionally, we confirmed a variation between ER-low-positive and ER-high-positive tumors, which may explain the difference in therapeutic response in ER-positive tumor patients taking anti-ER drugs. Conclusion: Further research is necessary to study the association between therapeutic response and ER-staining intensity breast cancer subtypes.

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.

Serum and urinary cadmium and zinc profiles in breast cancer patients and their association with estrogen and HER-2 receptors, and redox status

BackgroundCadmium, a metal implicated in environmental toxicity, is linked to tumor growth and cancer. On the other hand, zinc plays an essential function in oxidative stress and can counteract cadmium toxicity and carcinogenicity. This research aims to evaluate the urine and serum values of cadmium and zinc in breast cancer (BC) patients and their association with estrogen (ER) and HER-2 receptors, and redox status. MethodsForty BC patients and thirty healthy subjects participated in this study. Cadmium and zinc levels were measured in serum and urine samples by atomic absorption spectrophotometer. Redox status markers were determined by colorimetric methods. ResultsThe amount of cadmium in the BC patients was substantially greater than in the healthy subjects. Zinc levels were significantly lower in patients with BC compared to controls. Breast cancer patients with ER-positive tumors had significantly higher urinary cadmium concentrations (U-Cd) compared to patients with ER-negative tumors. There was no significant difference between the parameters of redox status and the value of cadmium and zinc between patients with BC in the HER-2 subgroup. Malondialdehyde levels in the serum were substantially greater in BC patients than in healthy subjects. Total thiol level and catalase and superoxide dismutase activity in serum were considerably lower in BC patients than in healthy subjects. ConclusionsThe etiology of BC may be due to a disturbance in redox status and levels of elements. Increasing U-Cd and lowering zinc levels in the serum could be the risk factors for BC.

Dynamic methylation and expression of alternative promoters for oestrogen receptor alpha in cell line models of fulvestrant resistance.

Oestrogen receptor alpha (ER; gene symbol ESR1) is the most important prognostic and treatment-predictive biomarker in breast cancer. Drugs targeting oestrogen and ER for endocrine therapy of breast cancer include aromatase inhibitors, the selective ER modulator tamoxifen and the selective ER degrader fulvestrant. Tumours can develop resistance to endocrine therapy through several mechanisms, which is often linked to altered expression of ER. To investigate the role of promoter methylation in the regulation of ESR1 expression, we used bisulfite sequencing to measure methylation at CpG sites in alternative ER promoter regions for six cell line models of fulvestrant resistance. Both CpG methylation and expression of alternative first exons changed dynamically, with striking differences between cell lines that had stable or unstable resistance upon fulvestrant withdrawal. Methylation at some CpG sites was strongly negatively correlated with expression of specific first exons. In a breast tumour cohort, higher relative expression of upstream alternative first exons was associated with worse prognosis in post-menopausal women with ER-positive tumours who received endocrine therapy.

68Ga-OncoFAP microPET/CT imaging in different breast cancer mouse models

BackgroundBreast cancer (BC) is currently the most common malignancy worldwide and the leading cause of cancer-related death in women. Positron emission tomography/computed tomography (PET/CT) with fluorine-18-2-fluoro-2-deoxy-glucose (18F-FDG-PET) plays an important role in staging breast cancer, and now many promising tracers for tumor imaging are striving for superior breast cancer detection and monitoring. Some studies have reported better results regarding the diagnostic and therapeutic value of FAP ligands, especially in the diagnostic evaluation of primary BC. MethodsIn this study, we have successfully radiolabeled the 68Ga-OncoFAP, which is FAP (Fibroblast activation protein) targeting tracer, and tested the imaging efficacy in both subcutaneous ER-positive MCF-7 breast cancer tumors models and orthotopic triple negative MDA-MB-231 breast cancer tumor models. ResultsMCF-7 subcutaneous tumors and MDA-MB-231 orthotopic tumors exhibited a high uptake of 68Ga-OncoFAP, which correlated with the corresponding pathological results. Between 30 and 100 min post injection, the tumor-to-background ratio (TBR) of MDA-MB-231 orthotopic tumors gradually decreased, but to a limited extent, all less than 10%. 68Ga-labeled OncoFAP could be applied for noninvasive imaging of breast cancer, and we could observe the metabolism of the probe by the MicroPET imaging. Conclusions68Ga-OncoFAP could selectively image fibroblast activation protein in mice models and is very promising for the diagnosis of different histological and molecular subtypes of breast cancer.

Pathological Changes Following Neoadjuvant Endocrine Therapy (NAET): A Multicentre Study of 391 Breast Cancers.

Oestrogen receptor (ER)-positive breast cancer (BC) is generally well responsive to endocrine therapy. Neoadjuvant endocrine therapy (NAET) is increasingly being used for downstaging ER-positive tumours. This study aims to analyse the effect of NAET on a well-characterised cohort of ER-positive BC with particular emphasis on receptor expression. This is a retrospective United Kingdom (UK) multicentre study of 391 patients who received NAET between October 2012 and October 2020. Detailed analyses of the paired pre- and post-NAET morphological changes and hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) expression were performed. The median duration of NAET was 86 days, with median survival and overall survival rates of 380 days and 93.4%, respectively. A total of 90.3% of cases achieved a pathological partial response, with a significantly higher rate of response in the HER2-low cancers. Following NAET, BC displayed some pathological changes involving the tumour stroma including central scarring and an increase in tumour infiltrating lymphocytes (TILs) and tumour cell morphology. Significant changes associated with the duration of NAET were observed in tumour grade (30.6% of cases), with downgrading identified in 19.3% of tumours (p < 0.001). The conversion of ER status from positive to low or negative was insignificant. The conversion of progesterone receptor (PR) and HER2 status to negative status was observed in 31.3% and 38.1% of cases, respectively (p < 0.001). HER2-low breast cancer decreased from 63% to 37% following NAET in the paired samples. Significant morphological and biomarker changes involving PR and HER2 expression occurred following NAET. The findings support biomarker testing on pre-treatment core biopsies and post-treatment residual carcinoma.

ER-Targeted PET for Initial Staging and Suspected Recurrence in ER-Positive Breast Cancer

There are insufficient data comparing 16α-18F-fluoro-17β-estradiol (FES) positron emission tomography (PET) computed tomography (CT) with standard-of-care imaging (SOC) for staging locally advanced breast cancer (LABC) or evaluating suspected recurrence. To determine the detection rate of FES PET/CT and SOC for distant metastases in patients with estrogen receptor (ER)-positive LABC and recurrences in patients with ER-positive BC and suspected recurrence. This diagnostic study was conducted as a single-center phase 2 trial, from January 2021 to September 2023. The study design provided 80% power to find a 20% detection rate difference. Participants included patients with ER-positive LABC (cohort 1) or suspected recurrence (cohort 2). Data were analyzed from September 2023 to February 2024. Participants underwent both SOC imaging and experimental FES PET/CT. When there were suspicious lesions on imaging, 1 was biopsied for histopathological reference standard to confirm presence (true positive) or absence (false positive) of malignant neoplasm. The outcome of interest was the detection rate of FES PET CT vs SOC for distant metastases and recurrences. A total of 124 patients were accrued, with 62 in cohort 1 (median [IQR] age, 52 [32-84] years) and 62 in cohort 2 (median [IQR] age, 66 [30-93] years). In cohort 1, of 14 true-positive findings, SOC imaging detected 12 and FES detected 11 (P > .99). In cohort 2, of 23 true-positive findings, SOC detected 16 and FES detected 18 (P = .77). In 30 patients with lobular histology, of 11 true-positive findings, SOC detected 5 and FES detected 9 (P = .29). There were 6 false-positive findings on SOC and 1 false-positive finding on FES PET/CT (P = .13). In this diagnostic study with pathological findings as the reference standard, no difference was found between FES PET/CT and current SOC imaging for detecting distant metastases in patients with ER-positive LABC or recurrences in patients with ER-positive tumors and suspected recurrence. FES PET/CT could be considered for both clinical indications, which are not part of current Appropriate Use Criteria for FES PET. The findings regarding FES PET/CT in patients with lobular tumors, and for lower false positives than current SOC imaging, warrant further investigation.

Association of mammographic breast density measurements and hormone receptor status of breast cancer.

Breast cancer is the most frequent cancer in women, with significant mortality. Mammography is a routine investigation for breast disease. A known risk factor for breast cancer is increased breast density. Here, we tried to observe if mammographic density also affects the hormone receptor status of breast cancer, which will help in the understanding of the biological mechanisms of breast cancer development. Suspected breast cancer patients at Lok Nayak Hospital, Delhi, underwent mammography in the Department of Radiodiagnosis. The density of breast contralateral to the mass was assessed using Hologic Quantra software version 2.1.1 [Area Breast Density(ABD)]. The hormone receptor status of all the tumours was recorded on histopathology. Of these, 100 confirmed cases were included in the study. ER-positive, PR-positive, and HER2-positive tumours were seen in 41%, 33%, and 34% patients, respectively. Regarding ER receptor status, the mean ABD for positive and negative tumours was 27% and 23%, respectively, p-value = 0.01, showing significant relation between them. Mean ABD for HER2-positive and -negative tumours was 25% and 24%, respectively, p-value = 0.75. Mean ABD for PR-positive and PR-negative tumours was 23% and 25%, respectively, p-value = 0.42 (not significant). We found that ER-positive tumours were common in dense breasts, which was statistically significant. However, this was not true for PR and HER2 receptor status. Limited studies have been done to study MD using computerised software and its effect on hormone receptor status, with conflicting results. Further, large, multicentric studies can be useful in understanding the mechanism and providing better treatment for breast cancer patients.

Biologic and prognostic significance of HER2-low and ER-low expressions in de novo metastatic breast cancer.

e13170 Background: It is unclear whether ER-low-positive (ER-low) and HER2-low-positive (HER2-low) biomarkers, as new biological subtypes, have different biological and clinicopathological characteristics in de novo metastatic breast cancer (dnMBC). Per ASCO/CAP guidelines, tumors were defined as HER2-low-positive (HER2-low) if they had an HER2 immunohistochemical (IHC) score of 1+ or 2+ with negative in situ hybridization assay and HER2-0 if they had an HER2 IHC score of 0; ER-low refers to the tumor IHC staining of 1%-10%, if the staining is less than 1%, it is defined as ER-0. This study aimed to investigate whether ER-low and HER2-low expressions is associated with clinicopathologic characteristics and prognosis among patients with de novo metastatic breast cancer. The study was approved by the Ethics Committee of Hebei Cangzhou Hospital of Integrated Traditional Chinese and Western Medicine (2017-AF29-058). Methods: Using hospital-based database, we identified patients with dnMBC diagnosed between 2010 and 2017, retrospectively collecting demographic data, tumor characteristics, treatment types, histopathological report and survival data. According to ASCO/CAP guideline recommendations, patient-specific histopathological results were classified, and IHC-based breast cancer markers, mainly including ER-low and HER2-low, were evaluated and analyzed. Median survival time (MST) was estimated by Kaplan-Meier method and log rank test. Univariable and multivariable analyses were performed using the Cox proportional hazard model to identify statistically significant prognostic factors. All statistical analyses were performed using Stata 18.0. Results: A total of 518 patients (median age of 53 years) were included in this study, including 194 patients with HER2-low, 201 patients with HER2-low, 36 patients with ER-low, and 179 patients with ER-0. Expression of HER2-low was significantly more common among ER-positive tumors (excluding the ER-low) compared with HER2-0 tumors (71.1% vs. 62.2%; P &lt; .001). The MST in the HER2-low cohort was longer than that in the HER2-0 cohort (40 vs. 30 months; HR,0.65; 95% CI, 0.52-0.82, p=.0001); while the MST of ER-low cohort was slightly longer than that of the ER-0 cohort (27 vs. 20 months; HR,0.75; 95% CI, 0.51-1.11, p=.231), but there was no statistical difference. Notably, in the metastasis pattern cohort, HER2-low showed a significantly higher MST compared with HER2-0 (P&lt;.001), with a MST of up to 68 months for bone-only metastases. There was no significant difference in MST between ER-low and ER-0 regardless of whether patients received endocrine therapy (P=.135). Conclusions: In the present study, for dnMBC patients, ER-low expression has similar biological and clinical outcome characteristics as ER-0. However, unlike HER2-0, HER2-low expression may predict a survival benefit in bone-only metastases.

Abstract PO5-13-10: Determining tumor-driving cell signaling pathways in breast cancer: Support for targeted therapy selection

Abstract Introduction: Success of therapeutic interventions largely rely on the pathological and biological characteristics of the tumor and varies due to the heterogeneous nature of breast cancers. Signal transduction pathways play an important role and are often used as target for specific therapies like hormone treatment, PI3K inhibitors etc. Immunohistochemistry (IHC) is currently the first assessment to divide tumors for subtyping and treatment and, especially in more advanced disease, mutation analyses are often used. Both IHC and mutation analyses only analyze a specific part of a signal transduction pathway and do not correlate well with outcome. Therefore, there is a need for new approaches to look at signaling pathways in cancer. We have developed a methodology that measures and quantifies signal transduction pathways (STPs) activities to reveal potential tumor-driving STPs to identify new options for targeted therapy in breast cancer. Method: Using the mRNA-based OncoSIGNal pathway activity profiling qPCR test (InnoSIGN), STP activities of 7 pathways (AR, ER, PI3K, MAPK, HH, TGFβ and Notch) were measured and quantified on a scale from 0-100. By using a set of non-tumor epithelial breast tissue samples, a reference range for normal physiological pathway activity was defined. A threshold was set on the 95th percentile of this range. A pathway activity score above this threshold was considered to be high (activated). Using this methodology, 201 ER positive (based on IHC) and 64 triple negative FFPE breast tumor samples obtained from different study sites and commercial biobanks were analyzed, including samples from primary and metastatic lesions, to determine for each individual tumor its pathway activity profile and identify activated tumor-driving pathways. Results: In the 195 primary ER positive tumors, the ER pathway was found to be activated in 78% of the samples, even though all samples were strongly ER immunohistochemistry stain positive. In addition to ER pathway activation, occasionally other pathways were activated: PI3K in 37%, HH in 25%, MAPK in 19%, AR in 20%, TGFβ in 6%, and Notch in 1%, of these samples. Analysis of 27 metastatic samples of ER positive tumors revealed in only 63% an active ER pathway. Additionally, more frequently PI3K pathway was observed in 70% of the samples. Other frequencies of pathway activation were: AR in 7% and MAPK in 4%, No Notch and TGFβ activity was found in this cohort. In 76 of the 78 triple negative tumors (TNBC) the ER pathway was inactive as expected. Remarkably, 2 samples appeared to have an activated ER pathway. An activated MAPK pathway was found in 50%, PI3K in 49%, HH in 18%, AR in 14%, TGFβ in 5% and Notch in 3% of these TNBC tumors. Conclusion: Compared to ER positive primary tumors we observed in metastatic ER positive tumors less frequent activation of the ER and more frequent activation of the PI3K pathway, suggesting that the latter pathway is associated with a more aggressive tumor phenotype. The triple negative subtype is characterized predominantly by activation of the PI3K, MAPK, AR and/or HH pathways, which may create new options for personalized targeted therapy of this subtype. OncoSIGNal can be used to determine the tumor driving signaling pathways in breast cancer patients, guiding selection of personalized targeted therapies. Citation Format: Paul van de Wiel, Yvonne Wesseling-Rozendaal, Anke Pierik, Dianne van Strijp, Saskia Vermeer, Fatema Tashrifwala, Josette Hartnett, Robert Babkowski, Suzanne Rose. Determining tumor-driving cell signaling pathways in breast cancer: Support for targeted therapy selection [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 PO5-13-10.

Abstract PO4-06-05: The prognostic impact of age at diagnosis of metastatic breast cancer according to estrogen receptor status: a single-center, retrospective study

Abstract Background: Young age is associated with poor prognosis and aggressive biology in early breast cancer, especially in luminal subtypes. But the prognostic impact of age in metastatic breast cancer (MBC) is unclear. Also it is known that chemotherapy is more effective in estrogen receptor (ER)-negative tumors than in ER-positive tumors and young patients respond better to chemotherapy. The authors tried to evaluate the impact of age on disease outcome according to ER status. Methods: We collected individual patient data from January 2000 to December 2022 from the Ewha Womans University Mokdong Hospital. Total 419 ER-positive and 238 ER-negative patients who had been treated for MBC were included for analysis. We compared clinical characteristics and overall survival (OS) of patients among three age groups (&amp;lt; 35, 35 to 50 and &amp;gt;50 years) at MBC diagnosis in ER-positive and -negative tumors. Results: The proportion of patients aged &amp;lt; 35, 35-50 and &amp;gt; 50 years was 3.1%, 46.6% and 32.3% in ER-positive tumors, and 2.7%, 14.8% and 18.4% in ER-negative tumors. Although most characteristics of tumors according to age were comparable, bone metastasis was more common in patients aged 35-50 years than the other age groups in ER-positive (51.8% vs. 36.0% in &amp;gt;50 years, P=0.006) and time to first metastasis was shorter in younger patients in ER-negative tumors (72.2% between 6 and 24 months vs. 31.1% in patients &amp;gt;50 years, P=0.003). The median follow-up time was 65 months. Overall survival rate was not different according to age in ER-positive tumors (P=0.909). On the other hands, younger patients had a higher risk of death in ER-negative tumors (P=0.015). In multivariate analysis, young age at MBC diagnosis (&amp;lt; 35years) with short time to metastasis (6 to 24 months), visceral metastasis, triple negative breast cancer was correlated with poor overall survival in ER-negative tumors (P=0.014, HR 1.77). Conclusions: Young age at MBC diagnosis was associated with a higher risk of death in ER-negative tumors, not in ER-positive tumors. These observations may suggest that physicians should consider the impact of age at diagnosis of metastasis and time course of disease in evaluating survival potential and determining a treatment strategy in metastatic breast cancers. Citation Format: Joohyun Woo, Ahrong Ham, Sewon Lee, Ji Eun Lee, Soo Ji Hong, Haena Lee, Sungchan Gwark, Jun Woo Lee, Hyun Goo Kim, Jungmin Jo, Woosung Lim, Byung-In Moon, Sei Hyun Ahn, Hye Ah Lee, Kyoung Eun Lee. The prognostic impact of age at diagnosis of metastatic breast cancer according to estrogen receptor status: a single-center, retrospective study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-06-05.

Abstract GS03-02: Mammographic surveillance in early breast cancer patients aged 50 years or over: results of the Mammo-50 non-inferiority trial of annual versus less frequent mammography

Abstract Introduction: Annual surveillance mammograms for an unspecified period, after treatment for early breast cancer, are widely practised in USA and Europe and represent a significant healthcare cost. Current UK guidelines recommend annual mammograms up to 5 years, then reverts to 3 year screening without specified risk stratification. Further evidence is needed to determine the optimum frequency and duration of mammographic surveillance. Methods: A multi-centre, randomised controlled, phase III trial of annual mammography versus 2-yearly for conservation surgery and 3-yearly mammograms for mastectomy patients up to 9 years. Women were eligible if aged 50 years or over at initial diagnosis of breast cancer (invasive or DCIS), and recurrence free 3 years post curative surgery. Primary outcome was breast cancer specific survival (BCSS). Secondary outcomes include recurrence free interval (RFI) and overall survival (OS). BCSS event was defined as deaths from breast cancer and RFI as any locoregional or distant invasive recurrence or new breast primary. 5000 women were needed to detect a 3% absolute non-inferiority (NI) margin for BCSS with 2.5% one-sided alpha and at least 85% power. Analyses were carried out on intention-to-treat basis. Results: 5235 women were randomised between April 2014 and September 2018. 4347 (83%) women were aged 55-75 years, 4203 (80%) had undergone conservation surgery, 4564 (87%) had invasive disease, 1162 (22%) had node positive disease, 4330 (83%) had ER positive tumours and 3812 (73%) were taking hormone therapy at the time of randomisation. Patient characteristics were balanced across arms. With a median of 5.4 years follow-up (interquartile range 4.6-5.9), 319 women have died; 104 of breast cancer (53 on annual arm; 51 on less frequent arm). BCSS at 5 years was 98.2% (95% CI 97.5-98.6%) on annual arm and 98.3% (95% CI 97.7-98.8%) on less frequent arm. Hazard ratio (HR) was 1.04 (95% CI 0.71 -1.54), demonstrating non-inferiority of less frequent mammograms at the 3% margin (NI p&amp;lt; 0.0001; critical value 2.71) and the 1% margin (NI p=0.02; critical value 1.56). 320 (6%) women had a new invasive breast cancer event (55 loco-regional recurrences, 85 new breast primaries, 139 distant recurrences and 41 with multiple invasive events); 164 on the annual arm compared to 156 on the less frequent arm. Five-year RFI was 94.2% (95% CI 93.2-95.1%) for the annual arm and 94.4% (95% CI 93.4-95.3%) for the less frequent arm; HR= 1.03; (95% CI 0.83-1.28) demonstrating non-inferiority at a 2% margin (NI p=0.006; critical value 1.36). OS at 5 years was 94.9% (95% CI 93.9-95.7%) on the annual arm and 94.3% (95% CI 93.3-95.2%) on the less frequent arm. Hazard ratio (HR) was 1.18 (95% CI 0.94 -1.47), demonstrating non-inferiority of less frequent mammograms at the 3% margin (NI p=0.003; critical value 1.61) and the 2.5% margin (NI p=0.02; critical value 1.51). A total of 14987 mammograms have been performed on the annual arm and 8047 on the less frequent arm. 1967 (75%) of 2618 women on the annual arm complied with their allocated schedule compared to 1775 (68%) of 2617 women on the less frequent arm. COVID-19 pandemic affected compliance; it is estimated that 345 (7%) women missed mammograms during the pandemic. A sensitivity analysis was performed on the 72% of women who fully complied with their scheduled mammograms as per protocol, and again NI was demonstrated for BCSS, RFI and OS. Conclusions: For patients aged 50 or older and 3 years post diagnosis, Mammo-50 demonstrated that less frequent mammograms were no worse than annual mammograms. These results provide evidence for less frequent mammographic surveillance for this patient population. Citation Format: Janet Dunn, Peter Donnelly, Nada Elbeltagi, Andrea Marshall, Alastair Thompson, Riccardo Audisio, Sarah Pinder, David Cameron, Amy Campbell, Sue Hartup, Lesley Turner, Annie Young, Helen Higgins, Eila Watson, Sophie Gasson, Peter Barrett-Lee, Claire Hulme, Bethany Shinkins, Peter Hall, Andy Evans. Mammographic surveillance in early breast cancer patients aged 50 years or over: results of the Mammo-50 non-inferiority trial of annual versus less frequent mammography [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 GS03-02.

Abstract PO5-17-09: Event-free survival in HER2-low vs HER2-zero breast cancer patients submitted to neoadjuvant chemotherapy

Abstract Background: Breast cancer (BC) with low expression of HER2 (HER2-low) might constitute a group of tumors with unique clinical and biological characteristics. However, the prognostic impact of HER2-low status vs HER2-zero in terms of pathological complete response (pCR) and event-free survival (EFS) after neoadjuvant chemotherapy (NACT) remains controversial. The aim of this study was to evaluate pCR and EFS rates in HER2-low vs HER2-zero early BC patients treated with NACT. Methods: In this cross-sectional study, we analyzed 565 consecutive patients with HER2-low and HER2-zero early BC submitted to neoadjuvant therapy from 2017 to 2021 in a single academic center. Patients with biopsy-confirmed stage I-III BC, with HER2-low or HER2-zero status, submitted to locoregional therapy after NACT were included. Clinical and pathological characteristics, pathological response, treatment protocol and RFS were analyzed and considered for statistical analysis. HER2-low was defined by IHC 1+, or 2+ ISH non-amplified; HER2-zero was defined by IHC 0. Pathological response was determined locally, and pCR defined as the absence of residual invasive disease with or without ductal carcinoma in situ in the breast and axilla. EFS was defined as the time from diagnosis to distant recurrence, a second primary, or death from any cause, whichever occurred first. Results: 441 patients were included in the analysis, 236 (53.5%) patients with HER2-low tumors, and 205 (46.5%) with HER2-zero tumors. Overall, 279 (63.3%) were estrogen receptor (ER)-positive tumors, and 162 (36.5%) were ER-negative tumors. Among ER-positive tumors, 166 (59.5%) had HER2-low status, and 113 (40.5%) were HER2-zero. For the ER-negative subgroup, the corresponding rates were 70 (43.2%) and 92 (56.8%), respectively. Most patients had stage II-III BC (423/441; 96%), and 20.2% (89/441) had high nodal tumor burden. Many patients received anthracycline- and taxane-based NACT (425/441; 96.4%), and over 90% (148/162; 91.3%) of ER-negative patients received a platinum agent. The overall pCR rate were 18.1%. Among ER+ tumors, pCR rates were 6.4%, 6.0%, and 7.0% in the overall, HER2-low and HER2-zero tumors, respectively. In ER- tumors, the corresponding pCR rates were 38.3%, 35.7, and 40.2%, respectively. The differences in pCR rates between HER2-low and HER2-zero tumors were not statistically significant (ER-positive, p=0.724; ER-negative, p=0.559). After a median follow-up of 42 months, 90 EFS events occurred. In the HER2-low group there were 56 (23.7%) EFS events, and 34 (16.6%) EFS events in the HER2-zero (HR 1.19; 95% CI 0.77-1.82; p=0.427). Among 279 patients in the ER-positive group there were 48 events, 32 in the HER2-low subgroup and 16 in the HER2-zero group (HR 1.16; 95% CI 0.64-2.13; p=0.622). Among 162 ER-negative tumors there were 42 events, 24 in the HER2-low subgroup, and 24 in the HER2-zero subgroup (HR 1.56; 95% CI 0.84-2.88; p=0.158). NACT discontinuation occurred in 86 patients (ER-positive: 45, 16.1%; ER-negative: 41, 25.3%), mainly due to toxicity (anthracycline-taxane: 10.0%; platinum: 11.7%). Disease progression during NACT were reported in 6.8% (30/441) of patients. Conclusions: Our results show similar pCR rates and RFS among HER2-low and HER2-zero early BC patients after standard NACT, which are consistent with the current literature. Despite the predictive role of low HER2 expression in selecting patients for novel antibody-drug conjugates (ADCs) therapy, its prognostic value could not be confirmed. Citation Format: Guilherme Sartori, Susana Ramalho, Leonardo Roberto da Silva, Tomás Reinert, Mahira Lopes Da Rosa, Grazielle Morais Tavares, Vivian Vasconcelos, Higor Mantovani, Ana Elisa Ribeiro Da Silva Cabello, Guilherme Coelho, Jovana Mandelli, Facundo Zaffaroni, César Cabello, Carlos Barrios, Marcia Silveira Graudenz. Event-free survival in HER2-low vs HER2-zero breast cancer patients submitted to neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-17-09.

Abstract PO5-04-10: Clinical and prognostic value of MLN51 (Metastatic lymph node gene 51)/CASC3 (Cancer susceptibility candidate gene 3) in clinical breast cancer, connection with nodal and hormonal receptor status

Abstract Introduction: Metastatic Lymph Node Gene 51 Protein (MLN51) also known as Cancer Susceptibility Candidate Gene 3 Protein (CASC3) or Barentsz (BTZ) is a molecule that was first identified in malignant breast tumours. The CASC3 gene encodes the protein that binds to mRNA and is a key component of the exon junction complex (EJC), playing an important role in the metabolism of mRNA and in cellular recovery after stress responses. It is not clear, however, if MLN51 has a clinical value in assessing the disease progression of breast cancer. Methods: We analysed the transcription expression levels of MLN51 in a cohort of human breast cancer tissues and correlated the expression pattern with clinical outcome, pathological type and hormonal receptor status. Results: High levels of MLN51 was found to be a favourable prognostic indicator for overall survival (p=0.008, Hazard Ratio [HR=0.262]), the prognostic value being independent of other clinical and pathological factors. Likewise, high levels of MLN51 were also a significant and independent predictive factor for disease free survival (DFS) (p=0.003, HR=0.262). It was found that the favourable prediction in both OS and DFS was associated with node positive tumours, with significance with OS (p=0.004), compared in node negative tumours (p=0.143) and to DFS (p=0.001 in node positive compared with p=0.079 in node negative tumours). Levels of MLN51 had a significant correlation with EGFR in both normal and tumour mammary tissues but correlated with Her-2 and Her-3 in tumour tissues only. The prognostic power of MLN51 for DFS was significant in both Her-2 positive and Her-2 negative (p=0.003 and p=0.012) tumours and in ER negative tumours (p=0.003). The prediction for OS by MLN51 was particularly strong for Her-2 positive and ER positive (p=0.007 for both) tumours. Conclusions: MLN51 (CASC3) is a favourable prognostic factor in patients with breast cancer. This is clearly linked to the nodal status and hormone receptor status, particularly ER and HER-2. Citation Format: Binbin Cong, Tracey Martin, Xiaoshan Cao, Robert E Mansel, Eleri Davies, Wen Jiang. Clinical and prognostic value of MLN51 (Metastatic lymph node gene 51)/CASC3 (Cancer susceptibility candidate gene 3) in clinical breast cancer, connection with nodal and hormonal receptor status [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-04-10.

Abstract PO5-24-06: Genomic findings in metastatic breast cancer

Abstract Introduction: Although metastatic breast cancer is the second leading cause of cancer death in women, the genomic findings in metastatic breast cancer are not as well characterized as those of primary breast cancers. Metastatic tumors are genetically heterogenous, enriched for resistance mutations, and often lack targetable alterations. Improved understanding of the molecular mechanisms that drive metastatic disease of all receptor subtypes is required to identify possible molecular targets and to develop new targeted therapies in an effort to reduce the mortality. Methods: A cohort of 50 metastatic breast cancer cases (n=33 ER+/PR+, n=3 ER+/HER2+, n=3 ER-/HER2+ n=11 TNBC) sequenced at our medical center between 2018-2023 was evaluated, and the molecular findings of the major subtypes were analyzed. Genomic data included mutations, copy number alterations, tumor mutation burden and microsatellite instability. Results: The most frequent somatic alteration were PIK3CA mutations, involving 17/33 of ER+/PR+/HER- tumors, 5/11 TNBC tumors and 5/6 HER+ cases. TP53 mutations (frameshift and missense) were more frequently identified in TNBC and HER2+ cases (p&amp;lt; 0.05). Recurrent CCND1, FGFR1 and MYC copy number amplifications were seen almost exclusively in hormone receptor positive/HER2- tumors (p &amp;gt;0.05). ESR1 mutations involved 15% of the ER positive cancers and were frequently associated with co-occurring CCND1 and FGFR1 copy number gains. Significant genomic losses that drive tumorigenesis were also detected. Both CDKN2a and PTEN deletions were found in ER/PR positive disease, as well as triple negative tumors. Genomic deletions associated with worse outcomes such as TP53 and DICER1 were also detected. ERBB2 amplification was 100% concordant with our immunohistochemical and FISH results for the 6 HER2 positive cases. All 50 cases demonstrated a low tumor mutation burden and were microsatellite stable. Conclusion: We detected driver alterations that involve multiple pathways including estrogen receptor signaling, PI3K/AKT/MTOR, the cell cycle, and receptor tyrosine kinases. The genomic alterations are enriched for resistance mechanisms, like ESR1 mutations and FGFR1 gains that mediate resistance to endocrine treatment, as well as PIK3CA, also implicated in both endocrine and HER2-targeting therapy resistance. Of particular interest, were the amplifications detected in the ER+/PR+ tumors, such as CCND1 on chromosome 11q, FGFR1 on 8p and MYC on 8q, which were detected in almost half (45%) of our hormone receptor positive cohort. Some of the identified driver amplifications also define a subset of the Integrated Molecular Subtypes (Curtis et al., Nature; 486(7403): 346–352), i.e., Clusters 2, 6 and 9 that are typically hormone receptor positive but associated with either a very poor prognosis (Cluster 2) or an intermediate prognosis (Clusters 6 and 9), unlike the copy neutral ER positive tumors or those with the classic 1p and 16q alterations. Therefore, copy number profiling of advanced-stage breast cancers may be a useful tool for determining prognosis, identifying possible targetable driver pathways and selecting appropriate patients for molecularly guided clinical trials. Citation Format: Kimberly Cole, Melissa Tjota, Jeremy Segal, Peng Wang, Susanne Crespo-Ramos. Genomic findings in metastatic 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 PO5-24-06.

Abstract PO4-20-10: Value of 16α-18F-fluoro-17β-fluoroestradiol PET imaging in ER-positive breast cancer: a case report

Abstract Introduction: An appropriate use criteria workgroup recently recommended the use of PET imaging utilizing the 16α-18F-fluoro-17β-fluoroestradiol (FES) radiotracer as a measure of disease progression and endocrine treatment response for ER-positive breast cancers. Past studies report limitations of decreased FDG uptake, the most common PET radiotracer, when measuring low Ki-67 scoring tumors; FES-PET may noninvasively address this shortcoming in FDG activity detection. Its benefit of detecting low-grade, ER-positive tumor activity was demonstrated in a patient with breast cancer who exhibited tumor growth only on FES-PET while FDG-PET showed no measurable disease. Clinical Case: A 57-year-old postmenopausal woman presented in December 2017 with de novo metastatic invasive ductal carcinoma that was ER+ (100%), PR+ (100%), and HER2- involving the right breast, bone, lungs, and internal mammary, subcarinal, and right hilar lymph nodes. She received nab-paclitaxel and radiation to the right breast, regional lymph nodes, and T11 bone. In March 2019, she underwent a right mastectomy with pathology that noted residual disease in the breast measuring &amp;lt;5 mm and was placed on exemestane in April 2019. She transferred her care to City of Hope and follow-up FDG-PET restaging showed no evidence of new metabolically active metastatic disease. Her cancer antigen 27.29 levels were also within normal limits. In the absence of measurable disease growth, she continued to be treated with single agent exemestane. Due to persistent back discomfort that she attributed to breast asymmetry, she requested the left breast to be removed. One week prior to surgery, both FDG-PET/CT and bloodwork inclusive of tumor markers were normal. She underwent a left mastectomy in March 2023. Pathology identified an incidental 1.4 cm lymph node in the 2000 g specimen that was ER+ (&amp;gt;95%), PR-, and HER2- with a Ki-67 of 1-3%. Somatic gene testing of the tumor revealed an ESR1 D538G mutation. As her progressive disease was not evident on previous FDG-PET imaging, an FES-PET/CT was performed and demonstrated uptake in the ilium, T10, and T12 bones that was not identified on FDG-PET/CT. With objective evidence of evaluable disease, exemestane was discontinued and fulvestrant and ribociclib were initiated. Clinically, she has evidence of early response to therapy with improvement in back pain. Discussion: This case demonstrates the value of FES-PET/CT in identifying disease that was not appreciated on FDG-PET/CT or by cancer antigen 27.29 monitoring. Additionally, ESR1 status has not been consistently reported in studies of patients undergoing FES-PET imaging that investigate the radiotracer’s value in predicting response to subsequent endocrine therapy. Our patient has a documented ESR1 mutation, her disease was clearly identified only on FES-PET/CT, and FES uptake predicted for response to subsequent endocrine therapy. Incorporating FES-PET in routine staging should be considered in patients with metastatic breast cancer that is low-grade and ER-positive. Further evidence of response prediction in patients with ESR1 mutations will enhance the utility of FES-PET in the clinical management of these patients. Citation Format: Megan Wong, Veronica Jones, Dave Yamauchi, Joanne Mortimer. Value of 16α-18F-fluoro-17β-fluoroestradiol PET imaging in ER-positive breast cancer: a case report [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 PO4-20-10.

Kataegis in clinical and molecular subgroups of primary breast cancer

Kataegis is a hypermutation phenomenon characterized by localized clusters of single base pair substitution (SBS) reported in multiple cancer types. Despite a high frequency in breast cancer, large-scale analyses of kataegis patterns and associations with clinicopathological and molecular variables in established breast cancer subgroups are lacking. Therefore, WGS profiled primary breast cancers (n = 791) with associated clinical and molecular data layers, like RNA-sequencing data, were analyzed for kataegis frequency, recurrence, and associations with genomic contexts and functional elements, transcriptional patterns, driver alterations, homologous recombination deficiency (HRD), and prognosis in tumor subgroups defined by ER, PR, and HER2/ERBB2 status. Kataegis frequency was highest in the HER2-positive(p) subgroups, including both ER-negative(n)/positive(p) tumors (ERnHER2p/ERpHER2p). In TNBC, kataegis was neither associated with PAM50 nor TNBC mRNA subtypes nor with distant relapse in chemotherapy-treated patients. In ERpHER2n tumors, kataegis was associated with aggressive characteristics, including PR-negativity, molecular Luminal B subtype, higher mutational burden, higher grade, and expression of proliferation-associated genes. Recurrent kataegis loci frequently targeted regions commonly amplified in ER-positive tumors, while few recurrent loci were observed in TNBC. SBSs in kataegis loci appeared enriched in regions of open chromatin. Kataegis status was not associated with HRD in any subgroup or with distinct transcriptional patterns in unsupervised or supervised analysis. In summary, kataegis is a common hypermutation phenomenon in established breast cancer subgroups, particularly in HER2p subgroups, coinciding with an aggressive tumor phenotype in ERpHER2n disease. In TNBC, the molecular implications and associations of kataegis are less clear, including its prognostic value.

A Cross-Sectional Study of Tumor Budding in Correlation with Clinicopathological Parameters in Invasive Breast Carcinoma

Introduction: Breast carcinoma is the largest cause of mortality from cancer among women in India. Tumor budding is usually defined as isolated single cancer cells or clusters of up to four cancer cells located at the invasive tumor front. Tumor budding is associated with poor clinicopathological characteristics, such as Tumor size, tumor differentiation, lymph node invasion, lymphatic or vascular invasion etc. Aim: To study tumor budding and its association with known clinicopathological parameters and hormone receptor status in invasive breast carcinoma. Methods : A Cross-sectional study was conducted after approval from the ethics committee. The duration of study was 1.5 years (Jan 2022- June 2023). Results: A total of fifty cases of invasive breast carcinomas were included in this study. 70% (35cases) were &gt;50yrs of age, 65% (33cases) were of T2 (tumor size) category. 82%(41cases) of Invasive duct carcinoma, No specific type, 12% (6 cases) of mixed carcinomas followed by three cases, one is invasive lobular carcinoma(6%), others are high grade papillary duct carcinoma(6%) and mucinous carcinoma (6%). 76%(38cases) showed presence of lymphovascular invasion, 74%(37cases) showed absence of necrosis, 54%(27 cases) are categorized as grade 2. High grade tumor budding was seen in 54% (27 cases). Conclusion: The following variables had a significant association with the tumor budding in present study: Tumor size, TNM staging, treatment status, lymphovascular invasion showing a p-value of &lt;0.05. ER positive tumors are also associated with high grade tumor budding. Keywords: Breast Carcinoma, Clinicopathological Variables, Lymphovascular Invasion, Tumor Budding

Expression of Cathepsin D in early-stage breast cancer and its prognostic and predictive value

PurposeCathepsin D is a proteolytic enzyme that is normally localized in the lysosomes and is involved in the malignant progression of breast cancer. There are conflicting results regarding Cathepsin D significance as prognostic and predictor marker in breast cancer. This study aimed to evaluate the expression and prognostic significance of Cathepsin D in early-stage breast cancer.MethodsExpression of Cathepsin D was assessed by immunohistochemical staining of tissue microarrays, in a large well-characterized series of early-stage operable breast cancer (n = 954) from Nottingham Primary Breast Carcinoma Series between the period of 1988 and 1998 who underwent primary surgery. Correlation of Cathepsin D expression with clinicopathological parameters and prognosis was evaluated.ResultsCathepsin D expression was positive in 71.2% (679/954) of breast cancer tumours. Positive expression of Cathepsin D was significantly associated with high histological grade (p = 0.007), pleomorphism (p = 0.002), poor Nottingham Prognostic Index (NPI) score (p < 0.002), recurrence (p = 0.005) and distant metastasis (p < 0.0001). Kaplan–Meier analysis showed that Cathepsin D expression was significantly associated with shorter breast cancer-specific survival (p = 0.001), higher risk of recurrence (p = 0.001) and distant metastasis (p < 0.0001). ER-positive tumours expressing Cathepsin D and treated with tamoxifen demonstrated a significantly higher risk of distant metastasis.ConclusionCathepsin D expression significantly predicts poor prognosis in breast cancer and is associated with variables of poor prognosis and shorter outcome. The strong association of Cathepsin D with aggressive tumour characteristics and poor outcomes warrants further research of its potential as a therapeutic target The results also suggest a possible interaction between Cathepsin D and tamoxifen therapy in ER-positive breast cancer which needs further investigation to elucidate the underlying mechanisms.