Histological Subtype Of Breast Cancer Research Articles

Invasive lobular carcinoma with extracellular mucin (ILCEM): clinicopathologic and molecular characterization of a rare entity

AbstractInvasive lobular carcinoma with extracellular mucin (ILCEM) is a rare histologic subtype of breast cancer. Little is known about the pathologic or genomic signatures that distinguish ILCEM from classic invasive lobular carcinoma (ILC) or mucinous carcinoma. We studied 17 breast cancers with lobular morphology and extracellular mucin. Thirteen tumors with sufficient tissue for DNA extraction were analyzed by a next generation sequencing (NGS) assay that interrogates 447 genes for mutations and copy number variations (CNVs). Median patient age was 66 yrs (range: 31–77 yrs). Sixteen patients presented with masses, 7 of which were >2 cm. Seven patients had lymph node metastases. The cases of ILCEM were moderately (n = 13) or poorly differentiated (n = 4), frequently exhibiting variant morphology that has not been previously described or emphasized, including grade 3 nuclei (n = 11), diffuse signet ring cells (n = 10), solid growth (n = 4), tumor necrosis (n = 3) or apocrine features (n = 2). All tumors showed absent or reduced membranous E-cadherin expression. Concurrent lobular carcinoma in situ (LCIS) was seen in 11/17 cases, 1 of which was a striking example of signet ring cell LCIS with extracellular mucin. Receptor profiles were ER+/HER2− (n = 15) and ER+/HER2+ (n = 2). With a median follow-up of 83.5 months (range: 3–171 months) in 12 patients with available information, 8 patients had recurrences resulting in 4 cancer-related deaths. The most common CNVs were 16q loss (n = 11) and 1q gain (n = 9). CDH1 gene-level alterations were detected in all but one case, including frameshift (n = 7), nonsense (n = 2), and donor splice site (n = 1) mutations and indels (n = 2). Recurrent mutations were also seen in PIK3CA (n = 3), POLQ (n = 3), TP53 (n = 3), ERBB3 (n = 3), ERBB2 (n = 2), and RUNX1 (n = 2). Genes with recurrent amplifications included GATA3 (n = 4), FOXA1 (n = 3), CCND1 (n = 2). Our data highlights ILCEM as a distinct variant of ILC that often presents with higher-grade and variant morphologic features and is associated with an aggressive clinical course. NGS data support an overall lobular-type molecular profile and reveal potentially targetable alterations in a subset of cases with recurrence.

Inhibitory effect of the novel tyrosine kinase inhibitor DCC-2036 on triple-negative breast cancer stem cells through AXL-KLF5 positive feedback loop

Triple-negative breast cancer (TNBC), an aggressive histological subtype of breast cancer, exhibits a high risk of early recurrence rate and a poor prognosis, and it is primarily associated with the abundance of cancer stem cells (CSCs). At present, the strategies for effectively eradicating or inhibiting TNBC CSCs are still limited, which makes the development of novel drugs with anti-CSCs function be of great value for the treatment of TNBC, especially the refractory TNBC. In this study, we found that the small-molecule tyrosine kinase inhibitor DCC-2036 suppressed TNBC stem cells by inhibiting the tyrosine kinase AXL and the transcription factor KLF5. DCC-2036 downregulated the expression of KLF5 by decreasing the protein stability of KLF5 via the AXL-Akt-GSK3β signal axis, and in turn, the downregulation of KLF5 further reduced the expression of AXL via binding to its promotor (−171 to −162 bp). In addition, p-AXL/AXL levels were positively correlated with KLF5 expression in human TNBC specimens. These findings indicated that DCC-2036 is able to suppress the CSCs in TNBC by targeting the AXL-KLF5 positive feedback loop. Moreover, our findings indicated that DCC-2036 increased the sensitivity of TNBC chemotherapy. Therefore, this study proposes a potential drug candidate and several targets for the treatment of refractory TNBC.

Chromatin accessibility landscape and active transcription factors in primary human invasive lobular and ductal breast carcinomas

BackgroundInvasive lobular breast carcinoma (ILC), the second most prevalent histological subtype of breast cancer, exhibits unique molecular features compared with the more common invasive ductal carcinoma (IDC). While genomic and transcriptomic features of ILC and IDC have been characterized, genome-wide chromatin accessibility pattern differences between ILC and IDC remain largely unexplored.MethodsHere, we characterized tumor-intrinsic chromatin accessibility differences between ILC and IDC using primary tumors from The Cancer Genome Atlas (TCGA) breast cancer assay for transposase-accessible chromatin with sequencing (ATAC-seq) dataset.ResultsWe identified distinct patterns of genome-wide chromatin accessibility in ILC and IDC. Inferred patient-specific transcription factor (TF) motif activities revealed regulatory differences between and within ILC and IDC tumors. EGR1, RUNX3, TP63, STAT6, SOX family, and TEAD family TFs were higher in ILC, while ATF4, PBX3, SPDEF, PITX family, and FOX family TFs were higher in IDC.ConclusionsThis study reveals the distinct epigenomic features of ILC and IDC and the active TFs driving cancer progression that may provide valuable information on patient prognosis.

Integrating Immunotherapy Into the Treatment Landscape for Patients With Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is the most aggressive histologic subtype of breast cancer for which, until recently, treatment options have been limited to chemotherapy. In recent years, an improved understanding of the importance of tumor-infiltrating lymphocytes and the tumor microenvironment in TNBC has led to investigation of immune checkpoint inhibitors for treatment. There is now evidence from several randomized controlled trials that supports the addition of immune checkpoint inhibitors to first-line treatment of advanced TNBC and to neoadjuvant chemotherapy for stage II-III TNBC. In parallel, the PARP inhibitors have emerged as a targeted therapy option for patients with HER2-negative breast cancer harboring mutations in BRCA1, BRCA2, and PALB2. Here, we review the recent clinical trials that inform the integration of immune checkpoint inhibitors into treatments for TNBC and discuss ongoing challenges-including patient selection, management of resistance to post-checkpoint inhibitor therapy, and combining immunotherapy with targeted therapies, including PARP inhibitors.

Abstract 956: Role of E-cadherin in progression of invasive breast lobular carcinoma

Abstract Invasive lobular carcinoma (ILC) is the second most frequently diagnosed histologic subtype of invasive breast cancer following invasive ductal carcinoma (IDC) and accounts for 15% of all cases. The hallmark of ILC is the genetic loss of E-cadherin (CDH1) causing the disruption of adherens junctions and resulting in discohesive, linear growth of ILC cells in tissues. Beyond its effects on this unique histology, there is limited data on the role of E-cadherin loss in ILC metastasis. Therefore, we generated three ILC cell lines (MDA-MB-134, SUM44PE and BCK4) with inducible E-cadherin overexpression. Using immunoblotting and immunofluorescence microscopy we confirmed E-cadherin expression, re-expression of other adherens junction proteins including α and β-catenin, and re-localization of cytoplasmic p120-catenin to the membrane. Successful cell adhesion to E-cadherin coated plates suggested formation of functional junctions. E-cadherin expression had no effect on 2D growth but did diminish cell growth in ultra-low attachment (ULA) conditions consistent with its previously described role in anoikis. We confirmed increased cell death of MM134 with E-cadherin overexpression compared to control cells when grown in ULA. Overexpression of E-cadherin failed to rescue poor migratory and invasive ability of ILC cell lines as measured by transwell assays. However, E-cadherin expression in SUM44PE lead to decreased haptotaxis to collagen I, and altered morphology from loose grape-like structure to tight sphere-like formation when embedded in collagen I.In vivo analyses revealed reduced primary tumor formation in E-cadherin-overexpression SUM44PE cells after mammary fat pad injection. Additional studies aimed at understanding E-cadherin’s effect on in vivo metastasis are ongoing.Collectively, our studies using novel cell line models will lead to an improved understanding of the hallmark loss of E-cadherin and disease mechanisms in ILC, which we hope will ultimately enable the development of more effective therapies and improve the outcome of patients with this understudied histological subtype of breast cancer. Citation Format: Laura Savariau, Nilgun Tasdemir, Ashuvinee Elangovan, Kai Ding, Pooja Sree Tallapaneni, Jagmohan Hooda, Jennifer M. Atkinson, Adrian V. Lee, Steffi Oesterreich. Role of E-cadherin in progression of invasive breast lobular carcinoma [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 956.

ROSALINE: a phase II, neoadjuvant study targeting ROS1 in combination with endocrine therapy in invasive lobular carcinoma of the breast.

Invasive lobular carcinoma (ILC) is the most common histologic subtype of breast cancer after invasive ductal carcinoma (i.e., no special type [NST]). ILC differs from NST in clinical presentation, site-specific metastasesand response to conventional therapies. Loss of E-cadherin protein expression, due to alterations in its encoding gene CDH1, is the most frequent oncogenic event in ILC. Synthetic lethality approaches have shown promising antitumor effects of ROS1 inhibitors in models of E-cadherin-defective breast cancer in in vivo studies and provide the rationale for testing their clinical activity in patients with ILC. Entrectinib is a tyrosine kinase inhibitor targeting TRK, ROS1 and ALK tyrosine kinases. Here, the authors present ROSALINE (NCT04551495), a phase II study testing neoadjuvant entrectinib and endocrine therapy in women with estrogen receptor-positive, HER2-negative early ILC.

Loss of E-cadherin Induces IGF1R Activation and Reveals a Targetable Pathway in Invasive Lobular Breast Carcinoma.

Overall, this suggests that these targets require further exploration in ILC treatment and that CDH1 loss may be exploited as a biomarker of response for patient stratification.

A prospective real-world study to assess the effectiveness and safety of trastuzumab biosimilar in the adjuvant treatment of HER2-positive breast cancer: Preliminary safety results.

e12524 Background: The U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) defines a biosimilar as a biological molecule product that is highly similar to and has no clinically meaningful differences from an existing approved reference product. The trastuzumab biosimilar was the first oncology biosimilar approved in Brazil for HER2-positive breast cancer (BC) and advanced gastric cancer treatment. This study aimed to assess the effectiveness and safety of trastuzumab biosimilar (named as Zedora in Brazil) in the adjuvant setting among HER2-positive BC patients treated in Brazil. Methods: This is a national, multicentric, observational, and prospective real-world study. Patients with early-stage HER2-positive BC who received at least one dose of trastuzumab biosimilar as adjuvant therapy were eligible. At the present date, 126 of 170 planned patients were recruited. Here, we present the preliminary safety data of the first 42 patients recruited in the study. The safety endpoint is the occurrence of adverse events (AEs), and the safety population included all patients who received at least one dose of trastuzumab biosimilar. We analyzed the AEs collected from the signature of the consent form until the end of adjuvant treatment. Results: Baseline patient characteristics among the 42 evaluated patients included a median age of 48.5 years, with 78.6% of them having a node-negative disease. Most patients had hormone-receptor-positive tumors (71.4% estrogen-receptor-positive and 57.1% progesterone-receptor-positive). The number of patients undergoing conservative surgery (59.5%) was higher than mastectomy (40.5%). The most frequent histological BC subtype was invasive ductal carcinoma (97.6%). Neoadjuvant therapy included the trastuzumab biosimilar administration (25%) and the dual anti-HER2 block (trastuzumab biosimilar + pertuzumab) (68.8%). Only 6.3% of patients received the reference trastuzumab in neoadjuvant therapy. In total, 25/42 (59,5%) patients had at least one AE, two of them were serious AEs (4.8%). The incidence of grade 3 or 4 AEs was 35.7%, and no death occurred. The table lists the most reported AEs according to SOC (System Organ Class). Conclusions: The nature and severity of AEs observed were consistent with the known safety profile of trastuzumab. Clinical trial information: NCT03892655. [Table: see text]

Adherence to a western dietary pattern and risk of invasive ductal and lobular breast carcinomas: a case\u2013control study

Little is known about the role of diet in the risk of invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) of the breast, the most common histological subtypes of breast cancer (BC). This is because, the majority of studies on the association of diet and the risk of BC are focused on single food items, and studies considering the overall diet in terms of dietary patterns are limited. Also, the potential heterogeneity in the impact of Western diet (WD) on histological subtypes of BC is not established. This, the age-frequency-matched case–control study included 1009 incident BC cases and 1009 healthy controls. The required data was obtained from the patients’ medical files and interviews using a previously validated researcher-designed questionnaire for collecting data on socio-economic and anthropometric statuses and a valid food frequency questionnaire (FFQ) to measure the participants’ dietary intake. We used multinomial logistic regression, and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. A positive and significant association was observed between higher adherence to a WD and risk of IDC (OR comparing highest with the lowest tertile: 2.45, 95% CI 1.88, 3.17; p-trend < 0.001), whereas no significant association was observed between adherence to the WD and the risk of ILC (OR comparing highest with the lowest tertile: 1.63, 95% CI 0.63, 3.25) (p for heterogeneity = 0.03). The results of an analysis stratified by menopausal status suggested a similar pattern. We provided evidence that adherence to a WD raises the risk of IDC, but not ILC, suggesting different etiological mechanisms for IDC and ILC.

Invasive lobular carcinoma: an understudied emergent subtype of breast cancer.

Invasive lobular carcinoma (ILC) is the second most common histologic subtype of breast cancer after invasive ductal carcinoma (IDC), accounting for 10-15% of all breast cancer cases. Although most ILCs are of the luminal A intrinsic subtype, with favorable prognostic features, conflicting literature data are available on their outcomes compared to IDC with reports suggesting a higher risk of distant recurrence after 10years. Historically, studies have combined ILC and IDC, with outcomes largely driven by the behavior of IDC given that it represents 90% of breast cancers. However, over the past 5years, reports of several studies aimed at understanding ILC at the clinical, cellular, and molecular levels have been published, showing that IDC and ILC are distinct entities. In this review, we highlight the unique characteristics of ILC and describe the need for dedicated ILC clinical trials.

Artificial intelligence for histological subtype classification of breast cancer: combining multi-scale feature maps and the recurrent attention model.

The aim of this study was to apply a two-stage deep model combining multi-scale feature maps and the recurrent attention model (RAM) to assist with the pathological diagnosis of breast cancer histological subtypes by the use of whole slide images (WSIs). In this article, we propose an integrated framework combining multi-scale feature maps from Inception V3 and the recurrent attention model to classify the six histological subtypes of breast cancer. This model was trained with 194 WSIs, and on 63 validation WSIs the model achieved accuracies of 0.9030 for patch-level classification and 0.8889 for WSI-level classification. In the testing stage, a total of 65 WSIs were used to achieve an accuracy of 0.8462 without any form of datacuration. The t-distributed stochastic neighbour embedding showed that features extracted by the feature network of the RAM from WSIs of the same category can cluster together after training, and the visualization of decision steps showed that the decision-making glimpses are focused on the middle tumour area of an example from test WSIs. Finally, the false classification patches indicated that the morphological similarities between tumour tissues of different subtypes or non-tumour tissues and tumour tissues in patches might contribute to misclassification. This model can imitate the diagnostic process of pathologists, pay attention to a series of local features on the pathology image, and summarize related information, in order to accurately classify breast cancer into its histological subtypes, which is important for treatment and prognosis.

Abstract P1-08-13: Comparison of gene expression profiling results and clinical outcomes among patients with pleomorphic ILC and classic ILC

Abstract Background Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer. Pleomorphic ILC (pILC) is a pathologically defined subtype of ILC that often presents at a higher stage compared to Classical ILC (cILC). pILC is traditionally thought to have poor outcomes compared with cILC. Utility and application of gene expression profiling, such as Oncotype Dx testing, for these patients is unknown. The purpose of this study is to compare Oncotype Dx recurrence scores, treatment patterns, and clinical outcomes for patients with cILC and pILC at our institution. Methods A retrospective analysis of a large institutional cancer database was performed to identify patients with ILC treated between 2004 and 2017. Patient and disease characteristics were collected, including subtype of ILC (classical vs pleomorphic), staging, treatment history, and presence of Oncotype Dx testing. Findings were analyzed for differences in clinical characteristics, Oncotype Dx results, progression free survival (PFS) and overall survival (OS) between patients who received endocrine therapy/chemotherapy (CET) versus endocrine therapy alone (ET) in both cILC and pILC groups. Results: 692 patients with ILC were identified with 100 (14.5%) categorized as pILC. The mean age at presentation was 62 for cILC and 60 for pILC. cILC was more frequently ER positive (98.5% vs. 94.0%, p=0.004). and less likely HER2 positive (7.0% vs 12.2%, p=0.07). pILC more commonly had more advanced tumor stage (Stages II-III 61% vs 41%, p&amp;lt;0.001) but lower nodal stage (N+ 48.5% vs 66%, p&amp;lt;0.001) 25% (25/100) of pILC patients had Oncotype Dx testing performed compared to 33% (198/592) of cILC patients. The majority of patients who had testing had T1cN0 or T2N0 disease (36% and 44% for pILC vs 34%, and 27% for cILC, respectively). A low risk recurrence score (0-10) accounted for 8% (2/25) of pILC cases and 18.2% (36/198) of cILC. Intermediate risk (11-25) accounted for 72% (18/25) of pILC and 73.2% (145/198) of cILC. High risk (26+) accounted for 20% (5/25) of pILC and 8.6% (17/198) of cILC. There was no statistically significant difference in Oncotype Dx recurrence score distribution between pILC and cILC (p=0.117). More patients with pILC received CET compared to cILC (62.0% vs 36.7%, p&amp;lt;0.001). Among pILC cases, 62% received CET and 34% received ET. There was no significant difference in RFS or OS between CET and ET among pILC cases (10-year RFS 74.7% (ET) vs. 76.6% (CET), p=0.52. 10-year OS 92.6% (ET) vs 78.0% (CET), p=0.40). Conclusions At our institution, patients with cILC more often had Oncotype Dx testing compared to those with pILC. Some of the difference may be related to more frequent HER2-positivity in pILC. When testing was done, pILC was twice as likely to have a high risk recurrence score compared to cILC, but this result was not statistically significant. Patients with pILC were more likely to receive CET than patients with cILC. There was no difference in survival between patients with pILC treated with CET versus those treated with ET alone although the sample size is small and this is worthy of further study in a larger population. These results suggest that gene expression testing may be underutilized in pILC. Citation Format: Marcus Dempster, Matthew Wright, Daniela Cocco, Ayat Elsherif, Stephanie A Valente, Hong Li, Megan L Kruse. Comparison of gene expression profiling results and clinical outcomes among patients with pleomorphic ILC and classic ILC [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-08-13.

Abstract P3-02-01: Initial experience of FES-dedicated breast PET imaging of early-stage ER+ invasive lobular carcinoma

Abstract BACKGROUND: Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer, representing 15% of all invasive breast cancers. Most ILC tumors are estrogen receptor-positive (ER+) and may respond to endocrine therapy. However, tumor biologic factors such as ER functionality, cell proliferation, and molecular traits may influence endocrine treatment response and long-term recurrence risk, thus necessitating a comprehensive approach to characterize the primary breast tumor. [18F]fluoroestradiol (FES) is a radiotracer developed for positron emission tomography (PET) imaging of ER status. For this work, we studied the utility of imaging FES uptake in early-stage primary ER+ ILC lesions, using high-resolution dedicated breast PET (dbPET) to assess the relationship between FES uptake and tumor characteristics. METHODS: With institutional review board approval, patients with biopsy-proven ER+/HER2- ILC were prospectively imaged using dbPET with 5 mCi of FES before treatment. FES uptake (SUVmax, SUVmean, and SUVpeak), tumor uptake volume (TUV), and background parenchymal uptake (BPU) values were calculated. Background values (SUVbkg) were obtained from the normal region of the ipsilateral breast. Lesions with background-corrected SUVmax 2 times higher than SUVbkg were considered FES-avid. Tumor grade, Ki67 cell proliferation index, and ER expression were obtained from core biopsies before treatment. Ki67 was dichotomized to low and high using a 20% cutoff1. Tumor size (longest diameter) was measured by magnetic resonance imaging (MRI). Spearman rank correlation was used to assess the relationship between FES uptake and tumor size. Differences between FES uptake at high and low Ki67 were compared using a Wilcoxon rank-sum test. RESULTS: 13 treatment-naïve ILC patients aged 32-82 years were included in this analysis (Table 1). Despite all lesions exhibiting strongly positive ER expression &amp;gt;90% by immunohistochemistry (IHC), we observed varying FES avidity with 9 FES avid and 4 FES non-avid ILC lesions. SUVmax, TUV, and TBR had substantial median differences between Ki67 high and low lesions (5.9, 4.3, and 9.6, respectively), but the difference did not achieve statistical significance. FES tumor uptake also correlated with tumor size, with the highest correlation observed for SUVpeak (ρ = 0.71 (95% CI: 0.22, 0.91), p=0.010) (Table 2). CONCLUSION: We found that not all highly ER expressing ILC by IHC were FES-avid. As FES-dbPET captures information from the entire tumor, it provides a more comprehensive assessment of functional ER status than IHC of a limited tumor sample. FES uptake in ILC also relates to tumor size and Ki67. This is an ongoing study; additional data may help to guide endocrine therapy decisions. Future studies with a larger cohort are planned to assess the relationship between FES uptake and tumor grade and molecular risk profiles. 1. Acs, B. et al. Ki-67 as a controversial predictive and prognostic marker in breast cancer patients treated with neoadjuvant chemotherapy. Diagn Pathol 12, 20, doi:10.1186/s13000-017-0608-5 (2017). Patient and tumor characteristicsCharacteristicsNumber of patients (Total N=13)Age (median (range))56.0 (32-80)Pre-menopausal3Post-menopausal10MRI tumor size (median (interquartile range)4.1 (2.4-6.8)Tumor grade132931Ki6712Low/High3/9FES13Avid/Non-avid9/4 Summary of FES uptake values and correlation coefficients.FES avidity (N=13)Ki67 (N=12)MRI tumor size (N=12)Avid vs Non-avidHigh vs LowSpearman rank correlationMedian Difference (95% CI)P-valueMedian Difference (95% CI)P-valueSpearman ρ (95% CI)P-valueSUVmax8.68 (2.86, 12)0.0075.9 (-19.5, 11.6)0.140.67 (0.16, 0.9)0.017SUVmean2.56 (1.43, 4.86)0.0071.34 (-4.14, 3.1)0.200.6 (0.042, 0.87)0.039SUVpeak2.86 (1.14, 4.59)0.0112.15 (-14.4, 3.72)0.190.71 (0.22, 0.91)0.01BPU-0.31 (-1.89, 1.02)0.82-0.73 (-2.34, 0.28)0.0960.01 (-0.57, 0.58)0.98TUV (cm3)5.45 (1.04, 10)0.014.3 (-185, 10)0.190.70 (0.21, 0.91)0.011TBR3.61 (2.2, 13)0.0079.57 (-19.6, 12.4)0.0640.66 (0.13, 0.89)0.02 Citation Format: Ella F Jones, Deep K Hathi, Natalia Konovalova, Julissa Molina-Vega, David C Newitt, Courtney Lawhn-Heath, Kimberly M Ray, Bonnie N Joe, Diane Heditsian, Susie Brain, I-SPY 2 TRIAL Imaging Working Group, I-SPY 2 TRIAL Consortium, A. Jo Chien, Laura J Esserman, Nola M Hylton, Rita A Mukhtar. Initial experience of FES-dedicated breast PET imaging of early-stage ER+ invasive lobular carcinoma [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-02-01.

Abstract PD11-01: An artificial intelligence-based predictor of CDH1 biallelic mutations and invasive lobular carcinoma

Abstract Introduction: Invasive lobular carcinoma (ILC) is the most frequent special histologic subtype of breast cancer (BC). ILC is identifiable by pathologic assessment given its distinctive discohesive growth pattern, largely caused by CDH1 inactivation. Compared to common forms of BC, ILCs display lower responses to chemotherapy and selective estrogen receptor modulators. The low interobserver agreement for the diagnosis of ILC, however, renders the inclusion of histologic subtyping in therapeutic decision-making challenging. Artificial intelligence (AI)-based algorithms hold promise for improving pathologic diagnosis; their performance, however, depends on the ground truth labeling used. Here, we seek to develop an AI-based methodology for detection of ILC using ‘CDH1 biallelic mutations’ (i.e., mutation + loss-of-heterozygosity of the wild-type allele or two pathogenic somatic mutations) as ground truth, reasoning that in BC, &amp;gt;95% of CDH1 bi-allelic inactivation is found in ILCs.Materials and methods: We developed a convolutional neural network system to detect CDH1 biallelic genetic inactivation (AI-CDH1) using whole slide images (WSI) of 1,100 primary BCs with available targeted sequencing data. The model was trained using a 10-fold cross-validation method to detect biallelic mutations. The mean number of positive and negative samples in the training set was 85.2 (SD=2.57) and 562.8 (SD=10.51) per fold, respectively. The evaluation set consisted of a mean of 14.2 (SD=2.04) positive and 93.8 (SD=9.13) negative samples. We evaluated the performance of the AI-CDH1 classifier to predict the lobular phenotype and CDH1 status using original and revised labels, following a histopathologic re-review of the histologic type and CDH1 status curation. The latter was conducted by incorporating information on biallelic CDH1 inactivation beyond CDH1 mutations (homozygous deletions, deleterious structural rearrangements, and loss-of-heterozygosity and gene promoter methylation).Results: The AI-CDH1 classifier predicted biallelic CDH1 mutations with an area under the curve (AUC)=0.944 (95 CI: 0.925-0.963), sensitivity=91.6% and specificity=85.9%, PPV=49.8%, NPV=98.5% and accuracy=86.7%, and the original ‘lobular phenotype’ with an AUC=0.941 (95 CI: 0.922-0.960), sensitivity=89%, specificity=86.7%, PPV=55.6%, NPV=97.7% and accuracy=87.1%. Review of the CDH1 gene status revealed that 7/957 BCs lacking CDH1 biallelic mutations harbored biallelic CDH1 inactivation by promoter methylation, homozygous deletions or structural rearrangements. The AI-CDH1 classifier detected all seven reclassified BCs and predicted the revised CDH1 biallelic inactivation with an AUC=0.948 (95 CI: 0.930-0.966), sensitivity=92%, specificity=86.5%, PPV=52.3%, NPV=98.5% and accuracy=87.2%. Upon histologic re-review, which resulted in reclassification of 36/927 non-lobular BCs as ‘lobular’ and 5/173 ‘lobular’ BCs as ‘non-lobular’, the AI-CDH1 classifier detected the ‘lobular phenotype’ with an AUC=0.953 (95 CI: 0.935-0.971), sensitivity=90.7%, specificity=89.7%, PPV=66.8%, NPV=97.7% and accuracy=89.9%. Using the revised histologic re-classification and CDH1 biallelic inactivation status labels, the AI-CDH1 classifier predicted the lobular phenotype irrespective of CDH1 status (P&amp;gt;0.05).Conclusions: By training a machine learning system to detect ‘CDH1 biallelic mutations’, as ground truth rather than histologic diagnosis of lobular carcinoma, which might be confounded by human subjectivity, we developed an AI-based system that can detect ILCs accurately, providing a new paradigm for the development of AI-based cancer classification systems. Citation Format: Jorge S Reis-Filho, Fresia Pareja, Fatemeh Derakhshan, David N Brown, Jillian Sue, Pier Selenica, Yi Kan Wang, Arnaud Da Cruz Paula, Monami Banerjee, Zahra Ebrahimzadeh, Manuel Isava, Matthew Lee, Ran Godrich, Adam Casson, Ruben Padron, George Shaikovski, Alexander van Eck, Antonio Marra, Higinio Dopeso, Hannah Y Wen, Edi Brogi, Matthew G Hanna, Chris Kanan, Jeremy D Kunz, Felipe C Geyer, Carla Leibowitz, David Klimstra, Leo Grady, Thomas J Fuchs. An artificial intelligence-based predictor of CDH1 biallelic mutations and invasive lobular carcinoma [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD11-01.

Abstract P3-09-18: The association between genomic alterations and body mass index in patients with early breast cancer

Abstract Background: High body mass index (BMI) is an established risk factor for developing breast cancer (BC), especially estrogen receptor (ER)-positive, and also has been associated with adverse survival. Still, patients with BC are currently treated independently of their BMI given limited understandings of the association between BC biology and patient adiposity. In this study, using retrospective data retrieved from two large BC studies, we aimed to identify genomic alterations of primary BC that are associated with BMI in the most common histological BC subtype - invasive carcinoma of no special type (NST). Patients, Data and Methods: Clinicopathological and genomic alteration data were retrieved from two study cohorts: METABRIC (Pereira et al. 2016) and ICGC (Nik-Zainal et al. 2016), with BMI recorded at the time of diagnosis and represented as either a continuous variable or a categorical variable of three categories - lean, overweight and obese. Stratification according to ER and HER2 status resulted in two focused subgroups: NST ER+/HER2- (n=392) and NST ER-/HER2- (n=152). Mutations classified as oncogenic using a set of predefined criteria were used to determine gene-level mutation status. Copy number alteration (CNA) calls were distinguished into three event types: amplification, hemizygous deletion and homozygous deletion. We used multivariable Firth’s logistic regression models with the presence of a genomic alteration as the response variable, BMI as the predicting variable of interest, and data cohort (METABRIC vs ICGC), age group (≤50 vs &amp;gt;50) and tumor grade (I &amp; II vs III) as covariates, to assess the associations between BMI and recurrent gene-level genomic alterations, including gene mutations and CNAs. In a similar manner, we performed multivariable linear regression analysis, adjusting for age and tumor grade, to evaluate the associations of BMI with mutational signatures (MS) and tumor mutational burden in the ICGC NST subsets where these data are available. Results: Considering BMI as a categorical variable, we observed in the NST ER+/HER2- subgroup that PIK3CA was significantly less frequently mutated in obese compared to lean patients (33% vs 46%, odds ratio (OR) = 0.57 (95% confidence interval = (0.33, 0.97)), p = .039), while PTEN and TBX3 showed an increased frequency in overweight (6% vs 1%, OR = 4.14 (1.1, 22.34), p = .034) and obese (8% vs 1%, OR = 7.41 (1.82, 70.65), p = .008) patients, respectively. Regression analyses with BMI as a continuous variable revealed an increased prevalence of mutations in CDH1 and TBX3 genes as BMI increases by 1kg/m2 (OR = 1.14 (1.05, 1.24), p = .002, and OR = 1.13 (1.04, 1.22), p = .005, respectively) in patients with NST ER+/HER2- BC. No associations between BMI and oncogenic mutations was observed in the NST ER-/HER2- subgroup. Interrogation of gene-level CNAs in both subgroups demonstrated differences according to BMI in the prevalence of CNAs affecting a number of genes, many of which are known or have been presented with evidence to be involved in regulation of or regulated by hallmark pathways of BC, such as the MAPK/ERK, JAK/STAT and Wnt/β-catenin signaling pathways. We report a strong positive association between the single-base substitution signature 1 (SBS1), an age-correlated MS, and both continuous (coefficient (coef) = 18.3 (7.7, 28.9), p &amp;lt; .001) and categorical BMI (obese vs lean, coef = 336.3 (187.9, 484.8), p &amp;lt; .001) in the ICGC NST ER+/HER2- subgroup. Conclusion: This exploratory retrospective study suggests that the genomic profiles of primary BC may differ according to BMI. Clinical implications of these differences, especially the decreased prevalence of PIK3CA mutations in obese patients in the context of alpelisib, warrant further investigation. These results however indicate that patient adiposity should be taken into account in the era of personalized medicine. Citation Format: Ha-Linh Nguyen, Tatjana Geukens, Marion Maetens, Karen Van Baelen, Maxim De Schepper, Sophia Leduc, Edoardo Isnaldi, Sam Aparicio, Ake Borg, Jane Brock, Annegien Broeks, Carlos Caldas, Andrew Green, Hazem Khout, Eyfjörð Jórunn, Stian Knappskog, Savitri Krishnamurthy, Sunil Lakhani, Anita Langerod, John WM Martens, Leigh Murphy, Serena Nik-Zainal, Colin Purdie, Emad Rakha, Andrea Richardson, Anne Salomon, Peter Simpson, Christos Sotiriou, Paul Span, Benita Kiat-Tee Tan, Alastair Thompson, Stefania Tommasi, Marc Van de Vijver, Steven Van Laere, Alain Viari, Giuseppe Floris, Elia Biganzoli, François Richard, Christine Desmedt. The association between genomic alterations and body mass index in patients with early breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-09-18.

Characterisation of the Stromal Microenvironment in Lobular Breast Cancer.

Simple SummaryInvasive lobular breast cancer (ILC) accounts for approximately 5–15% of breast cancers, and although response rates to treatments are initially good, an ILC diagnosis is associated with adverse long-term outcomes; better treatments, specifically targeted to this sub-type of breast cancer, are required to improve patient survival. The tumor microenvironment (TME) plays an important role in determining how cancers respond to treatment, and in this study, we carried out an in-depth analysis of the TME in ILC following laser-capture microdissection of the tumor stroma, and analysis of primary cancer-associated fibroblasts (CAFs), which comprise the majority of non-malignant cells within tumors. This identified changes in genes involved in regulation of the extracellular matrix and also growth factor signaling pathways that were differentially regulated in ILC. Further analysis of breast cancer datasets showed that two of these genes which encode a secreted metalloproteinase (PAPPA) and a metalloproteinase inhibitor (TIMP2) were associated with survival outcomes in ILC.Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer, and it exhibits a number of clinico-pathological characteristics distinct from the more common invasive ductal carcinoma (IDC). We set out to identify alterations in the tumor microenvironment (TME) of ILC. We used laser-capture microdissection to separate tumor epithelium from stroma in 23 ER+ ILC primary tumors. Gene expression analysis identified 45 genes involved in regulation of the extracellular matrix (ECM) that were enriched in the non-immune stroma of ILC, but not in non-immune stroma from ER+ IDC or normal breast. Of these, 10 were expressed in cancer-associated fibroblasts (CAFs) and were increased in ILC compared to IDC in bulk gene expression datasets, with PAPPA and TIMP2 being associated with better survival in ILC but not IDC. PAPPA, a gene involved in IGF-1 signaling, was the most enriched in the stroma compared to the tumor epithelial compartment in ILC. Analysis of PAPPA- and IGF1-associated genes identified a paracrine signaling pathway, and active PAPP-A was shown to be secreted from primary CAFs. This is the first study to demonstrate molecular differences in the TME between ILC and IDC identifying differences in matrix organization and growth factor signaling pathways.

Rare histological subtypes of breast cancer: A study of 10 years’ experience at (SATH) UK District General Hospital.

Background: Breast cancer is a heterogeneous disease with different histologic subtypes, molecular characteristics, oestrogen receptors (ER) and HER2 status. Common subtype include lobular and ductal cancers. The rare subtypes are a heterogeneous group with differing behaviour specific for each subtype. This study aims to determine the clinicopathological features, management pathway and survival outcome of rare subtypes of invasive breast cancer (IBC) at a single U.K. hospital.

Integrated Metabolic Profiling and Transcriptional Analysis Reveals Therapeutic Modalities for Targeting Rapidly Proliferating Breast Cancers.

A multiomics strategy that integrates metabolic and gene expression profiling in patient tumor samples and animal models identifies effective pharmacologic approaches to target rapidly proliferating breast tumor subtypes.

Prevalence of Molecular Subtypes of Breast Carcinoma and Its Comparison between Two Different Age Groups: A Retrospective Study from a Tertiary Care Center of Northeast India

Objective The aim of the study is to see the prevalence of different molecular subtypes in breast cancer patients among two different age groups: ≤40 years and >40 years. Materials and Methods Retrospective study was conducted from January 2019 to December 2019. We studied 568 cases of breast carcinoma and classified them into four molecular subtypes—luminal A, luminal B, human epidermal growth factor-2 (HER 2), and triple negative. Cases were divided into two different groups: (1) ≤40 years and (2) >40 years. Statistical Analysis was done by using SPSS software version 20.0. Results Out of 568 cases, 151 (26.6%) were ≤40 years of age and 417 (73.4%) were >40 years of age. The most common histological subtype of breast cancer was ductal carcinoma in 548 cases and the most common grade was grade III. Immunohistochemistry was done in 432 patients. In younger age group, the most common molecular subtype was luminal B (31%) followed by triple negative (20%), luminal A (14%), and then HER 2 (5.3%), while in the older age group most common molecular subtype was luminal B (27.8%) followed by triple negative (14%), HER 2 (12.2%), and then luminal A (12%). Conclusion Luminal B is found to be the most common subtype in Northeast Indian women with breast cancer, as compared with other studies in which luminal A was the most common subtype. This could be due to the reason that K i -67 was not done in most of the other studies.

Obesity and menopausal status impact the features and molecular phenotype of invasive lobular breast cancer

PurposeWe investigated the relationship between obesity, menopausal status, and invasive lobular carcinoma (ILC), the second most common histological subtype of breast cancer. Specifically, we evaluated the association between body mass index (BMI), metabolic syndrome, the 21-gene Oncotype Recurrence Score (Oncotype RS), and pathological features in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor-2-negative ILC.MethodsThe study cohort included 491 patients from a prospectively maintained institutional database consisting of patients with stage I-III, HR-positive ILC who underwent surgical treatment between 1996 and 2019.ResultsContrary to our expectations, we found that lower BMI was significantly associated with having higher Oncotype RS (18.9% versus 4.8%, p = 0.028) in post-menopausal patients, but was not related to tumor characteristics in pre-menopausal patients. Multivariate network analyses suggested a strong relationship between post-menopausal status itself and tumor characteristics, with lesser influence of BMI.ConclusionThese findings provide further insight into the recently appreciated heterogeneity within ILC and support the need for further investigation into the drivers of this disease and tailored treatment strategies.