Invasive Lobular Breast Cancer Research Articles

Preoperative breast MRI-examination for all patients with histologically proven breast cancer? A concept for a prospective multicenter trial.

Background A published retrospective data of our study group demonstrated that premenopausal women, patients with lobular invasive breast cancer or patients with high breast density [American College of Radiology (ACR) classification 3+4] significantly benefit from magnetic resonance imaging (MRI) leading to additional detection of malignant foci of 20.2% in the index and 2.5% in the contralateral breast, which would otherwise not be detected by routine imaging. Critics of preoperative MRI focus on higher false-positive rates leading to unnecessary surgical procedures and mastectomies. Therefore, MRI in preoperative imaging remains controversial. Methods To validate our retrospective data we initiate a prospective one-armed multicenter trial for patients with histologically confirmed breast cancer performing routine imaging by ultrasound and mammography followed by MRI imaging based on menopause status, histologic subtype, ACR and Breast Imaging Reporting and Data System (BIRADS)-classification. Primary endpoint is the rate of additional findings and change of treatment strategy, secondary endpoints are local recurrence-free, distant recurrence-free and overall survival. Additional MRI findings are calculated to be above 10% with a number of 100 patients recruited and a power of 80%. Conclusion MRI is detecting more tumor foci than conventional imaging but remains controversial in primary breast cancer for preoperative imaging because of the fear of over-diagnosis and the increased morbidity of additional potentially unnecessary surgical procedures. This planned one-armed prospective multicenter trial is designed to confirm our retrospectively revealed data defining subgroups with significant benefit of preoperative MRI to come to a consensus avoiding over-diagnosis and false-positive results leading to clinically beneficial and cost-effective use of preoperative MRI.

Treatment and survival outcomes of lobular carcinoma in situ of the breast: a SEER population based study.

Lobular carcinoma in situ (LCIS) represents 5.3% of in situ specimens, and is thought to carry a low risk for developing to the invasive lobular breast cancer (ILC). There is still no standard care approach for patients with LCIS. We aimed to define the impacts of surgical and radiation intervention on survival outcomes of LCIS. LCIS cases from 2004 to 2013 of the recent Surveillance, Epidemiology, and End Results (SEER) database were analyzed. Clinicopathologic features were analyzed in 16002 patients between 2004 and 2013. Treatment modalities included no surgery (NS), lumpectomy alone (LA), lumpectomy with radiation treatment (LRT), mastectomy alone (MA) and mastectomy with radiation treatment (MRT). The overall survival (OS) was calculated by the Kaplan-Meier method. Univariate and multivariate analyses were performed using the variables of treatment, race, hormone receptor status, grade and age. Among 16002 patients, median follow-up was 54 months. Patients treated with LA had superior OS for NS (P = 0.001), MA (P < 0.001) and MRT P = 0.018). LRT only had superior OS for MRT (P = 0.009). There was no statistically significance between LA and LRT (P = 0.317). Improved OS was also correlated with younger age (P < 0.001), progesterone receptor positive (P = 0.001). Black patients had the worst OS (P < 0.001). There was no obvious survival difference among grade groups (P = 0.536). The LCIS patients treated with LA or LRT had better survival comparing with other groups. Considering the medical expense and the risk of radiotherapy, LA may be the most appropriate therapy for patients with LCIS.

Integrated molecular analysis of Tamoxifen-resistant invasive lobular breast cancer cells identifies MAPK and GRM/mGluR signaling as therapeutic vulnerabilities.

Invasive lobular breast cancer (ILC) is an understudied malignancy with distinct clinical, pathological, and molecular features that distinguish it from the more common invasive ductal carcinoma (IDC). Mounting evidence suggests that estrogen receptor-alpha positive (ER+) ILC has a poor response to Tamoxifen (TAM), but the mechanistic drivers of this are undefined. In the current work, we comprehensively characterize the SUM44/LCCTam ILC cell model system through integrated analysis of gene expression, copy number, and mutation, with the goal of identifying actionable alterations relevant to clinical ILC that can be co-targeted along with ER to improve treatment outcomes. We show that TAM has several distinct effects on the transcriptome of LCCTam cells, that this resistant cell model has acquired copy number alterations and mutations that impinge on MAPK and metabotropic glutamate receptor (GRM/mGluR) signaling networks, and that pharmacological inhibition of either improves or restores the growth-inhibitory actions of endocrine therapy.

Adrenal crisis in metastatic breast cancer

A female patient with oestrogen receptor-positive and human epidermal growth factor receptor 2 (HER2)-positive invasive lobular breast cancer presented with progressive disease on CT scan. Some days after initiation of...

Subclonal analysis in a lobular breast cancer with classical and solid growth pattern mimicking a solid-papillary carcinoma.

Recently, a new variant of invasive lobular breast cancer (ILBC) with solid‐papillary‐like growth pattern has been described. We present a case of ILBC with solid‐papillary‐like growth pattern in the main tumour mass and classical invasive lobular growth pattern in adjacent satellite foci. The two tumour components were subjected to comprehensive molecular analyses. Both components were ER/PR‐positive, HER2‐negative, and showed a complete loss of E‐cadherin and beta‐catenin protein expression, as determined by immunohistochemistry. Gene expression profiling classified the main tumour and a satellite focus as luminal‐B and luminal‐A subtypes, respectively. Whole‐genome copy number profiles were highly similar in both tumour components. Shared copy number alterations (CNAs) included gains of chromosome 1q21.1–q43 and losses of chromosome 16q11.2–q24.3, the locus of the CDH1/E‐cadherin tumour suppressor gene. CNAs detected only in the main tumour included a gain of chromosome 20q12–q13.33 and a loss of chromosome 1p36.33–p34.3, which has recently been associated with the solid variant of ILBC. Next generation sequencing revealed an identical, truncating CDH1 mutation (p.G169fs*5) in both tumour components confirming a common clonal ancestry. In conclusion, we confirm the recently described variant of ILBC with solid‐papillary‐like growth pattern and provide evidence that it evolves from classical ILBC by subclonal evolution.

Abstract 4674: Epigenetic modulators for the treatment of invasive lobular carcinoma breast cancer

Abstract Invasive lobular carcinoma (ILC) is a breast cancer subtype comprising 10% of breast tumors. The majority of ILC (90%) are estrogen receptor (ER)-positive and therefore candidates for endocrine therapy. Unfortunately, de novo resistant to endocrine therapies occurs in 33% of women and a further 40% will relapse on treatment. Therefore, novel therapeutic targets are required for ILC. Deregulated transcription is a recurring theme in cancer, which can be due to epigenetic events. The bromdomain &amp; extra-terminal domain (BET) family of proteins (BRD2, BRD3, BRD4, BRDT) function as chromatin readers that bind acetylated lysine residues on histones and regulate transcription. We performed RNA-Sequencing analysis on 61 primary ILC samples and found that high expression of BRD3 is associated with poor survival in ILC (log rank test, p=0.037). We validated this finding, that high expression of BRD3 is associated with poor survival, in a second cohort of 99 ILC primary samples from the METABRIC dataset (log rank test, p=0.0157). Next, we tested if ILC cell lines were sensitive to BET inhibition using the small molecule inhibitor JQ1, which inhibits all BET family proteins. JQ1 downregulates growth and survival genes in ILC cell lines including MYC, ER and BCL-XL. Pathway analysis following RNA sequencing revealed that JQ1 targets the apoptotic and Wnt signalling pathways in ILC cell lines. Interestingly, JQ1 inhibited the cell growth in all ILC cell lines tested, however apoptosis was only induced in two ILC cell lines. Furthermore, ILC cell lines which were relatively resistant to JQ1-induced apoptosis expressed both the BCL-2 and BCL-XL anti-apoptotic proteins. This led us to assess the combination of JQ1 and the BH3 mimetics, ABT-199 and ABT-263. ABT-199 is a selective small molecule inhibitor of BCL-2, whereas ABT-263 is an inhibitor of BCL-2, BCL-XL and BCL-W proteins. We found the combination of JQ1 and ABT-263, but not the combination of JQ1 &amp; ABT-199, to be synergistic and enhance apoptosis in ILC cell lines. This is in accordance with BH3 profiling of ILC cell lines which indicated that ILC cell lines are dependent on BCL-2/ BCL-XL proteins for cell survival. As JQ1 is a pan-BET family inhibitor, we also wish to determine which BET protein is responsible for sensitivity to JQ1. Following knockdown of each BET protein in the CAMA-1 cell line we found that BRD3 and BRD4 were responsible for loss of cell viability. Future work will include determining the specific role of BRD3 in ILC and the effectiveness of the JQ1 and ABT-263 combination in vivo. Our work suggests that inhibition of BET proteins in combination with BH3 mimetics may be a rational therapeutic combination for ILC. Citation Format: Louise Walsh, Bruce Moran, Sudipto Das, Finbarr Tarrant, Philip Schouten, Suet-Feung Chin, Rene Bernards, Carlos Caldas, William Gallagher, Tríona Ní Chonghaile*, Darran O'Connor*. Epigenetic modulators for the treatment of invasive lobular carcinoma breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4674. doi:10.1158/1538-7445.AM2017-4674

Abstract 1859: Hsp90 targeted near infrared molecular imaging to detect mammografically occult invasive lobular breast cancer

Abstract Background: Early diagnosis of Invasive lobular carcinomas (ILCs) is clinically challenging due to its histopathologic features making it difficult to detect using mammography. Because of the diffuse infiltration of ILC cells into the surrounding stroma, ILC is also associated with a higher incidence of positive resection margins after breast-conserving surgery. Therefore, there is a significant unmet need for improved imaging for early detection, clinical staging, and possibly intraoperative imaging to assess surgical margins. We propose to detect mammografically occult ILC by the in vivo detecting of malignant signaling pathways activated in ILC. Heat shock protein 90 (Hsp90) comprises 1-3% of the total cellular protein in most cells and acts as a molecular chaperone for more than 200 reported client proteins. Recently, we developed a series of tethered Hsp90 inhibitors that specifically target a tumor specific form of Hsp90 associated with poor outcomes. Using near infrared (nIR) probe-tethered Hsp90 inhibitors, we demonstrated that Hsp90 is actively re-internalized and can be used to image murine and human breast cancer in vitro and in vivo. Methods and Results: We tested the imaging efficacy of the nIR-tethered Hsp90 inhibitor, HS196, in ILC models in vitro and in vivo. An inactive structural analog HS199 was used as a control to monitor for non-specific (non-Hsp90 dependent) uptake. Two ILC cell lines, MDA-MB-134 VI and SUM44-PE, and one patient-derived ILC xenograft, HCI-013 EI, were tested. nIR signals of HS196 in vitro and in vivo were detected by Odyssey (LI-COR) and Pearl Trilogy (LI-COR)/SPY ELITE imager (Novadaq), respectively. High uptake of HS196 was observed in vitro by both cell lines (&amp;gt; 1 µM), while the control HS199 resulted in weaker nIR signals in these cells. In vivo imaging efficacy of HS196 was tested using HCI-013 EI xenograft in SCID-beige mice. After injection of 10 nmol compounds via tail vein, quick and stronger accumulation and longer retention of the HS196 in the ILC xenograft was observed, while HS199 showed significantly weaker accumulation and faster clearance (by 24 h after injection). Significant uptake of HS196 by HCI-013 EI tumors was confirmed by ex vivo imaging of tumors 24 h after compound injection. Histological and flow cytometry analysis of HCI-013 EI tumors showed strong nIR signals in tumor cells. Conclusions: The non-radioactive, nIR imaging strategy, using a novel nIR-Hsp90 inhibitor compound, HS196, was effective in the non-invasive imaging of ILC tumors. This finding suggests that new molecular imaging techniques, not dependent on micro calcifications or architectural distortion, may be a novel strategy to met the need of ILC patients to detect, clinically stage and assess margins during surgical resection. Ongoing pre-clinical models will be employed and first in human testing of this approach in planned. Citation Format: Takuya Osada, Kensuke Kaneko, Zachary Hartman, Amy Hobeika, Philip Hughes, Timothy Haystead, Michael Morse, H. Kim Lyerly. Hsp90 targeted near infrared molecular imaging to detect mammografically occult invasive lobular breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1859. doi:10.1158/1538-7445.AM2017-1859

Prognostic impact of proliferation for resected early stage ‘pure’ invasive lobular breast cancer: Cut-off analysis of Ki67 according to histology and clinical validation

IntroductionThe intent of this analysis was to investigate and validate the prognostic potential of Ki67 in a multi-center series of patients affected by early stage ‘pure’ invasive lobular carcinoma (ILC). MethodsClinical-pathological data of patients affected by ILC were correlated with overall survival and disease-free survival (OS/DFS); data from a parallel invasive ductal carcinoma (IDC) patients' cohort were gathered as well. The maximally selected Log-Rank statistics analysis was applied to Ki67 continuous variable to estimate the appropriate cut-off. The Subpopulation Treatment Effect Pattern Plot (STEPP) analysis was performed as well. ResultsData from overall 1097 (457/222 ILC: training/validation set; 418 IDC) patients were gathered. The identified optimal Ki67 cut-offs were 4% and 14% for DFS in ILC and IDC cohort, respectively. In ILC patients, the Ki67 cut-off was an independent OS predictor. Ten-years OS and DFS were 89.9% and 77.2% (p = 0.007) and 79.4% and 69.2% (p = 0.03) for patients with Ki67 ≤ 4% and >4%, respectively. In IDC patients, 10-years OS was 93.8% and 71.7%, p = 0.02, DFS was 84.0% and 52.6%, p = 0.0003, for patients with Ki67 ≤ 14% and >14%, respectively. In the validation set, the optimal Ki67 OS cut-off was 5%. The STEPP analysis showed that in the presence of low Ki67 values, IDC patients have a better DFS than ILC patients, while with the increase of values the prognosis tends to overlap. ConclusionsDespite the retrospective design of the study, the prognostic relevance of Ki67 (as well as its optimal cut-off) seems to significantly differ according to breast cancer histology.

Perforated Gastric Metastasis From Neglected Breast Cancer: A Case Report

Gastric perforation from metastatic breast cancer is a rare complication that is difficult to treat. Herein, we report a case of an 81-year-old female patient with neglected invasive lobular breast cancer causing gastric perforation due to metastasis. She underwent palliative surgical intervention with partial gastric resection. After 6 months, she is doing well. J Med Cases. 2017;8(6):200-202 doi: https://doi.org/10.14740/jmc2838w

Dual histone reader ZMYND8 inhibits cancer cell invasion by positively regulating epithelial genes.

Enhanced migratory potential and invasiveness of cancer cells contribute crucially to cancer progression. These phenotypes are achieved by precise alteration of invasion-associated genes through local epigenetic modifications which are recognized by a class of proteins termed a chromatin reader. ZMYND8 [zinc finger MYND (myeloid, Nervy and DEAF-1)-type containing 8], a key component of the transcription regulatory network, has recently been shown to be a novel reader of H3.1K36Me2/H4K16Ac marks. Through differential gene expression analysis upon silencing this chromatin reader, we identified a subset of genes involved in cell proliferation and invasion/migration regulated by ZMYND8. Detailed analysis uncovered its antiproliferative activity through BrdU incorporation, alteration in the expression of proliferation markers, and cell cycle regulating genes and cell viability assays. In addition, performing wound healing and invasion/migration assays, its anti-invasive nature is evident. Interestingly, epithelial-mesenchymal transition (EMT), a key mechanism of cellular invasion, is regulated by ZMYND8 where we identified its selective enrichment on promoters of CLDN1/CDH1 genes, rich in H3K36Me2/H4K16Ac marks, leading to their up-regulation. Thus, the presence of ZMYND8 could be implicated in maintaining the epithelial phenotype of cells. Furthermore, syngeneic mice, injected with ZMYND8-overexpressed invasive breast cancer cells, showed reduction in tumor volume and weight. In concert with this, we observed a significant down-regulation of ZMYND8 in invasive ductal and lobular breast cancer tissues compared with normal tissue. Taken together, our study elucidates a novel function of ZMYND8 in regulating EMT and invasion of cancer cells, possibly through its chromatin reader function.

Quality of Patient Decisions About Breast Reconstruction After Mastectomy

ImportanceBreast reconstruction has the potential to improve a person’s body image and quality of life but has important risks. Variations in who undergoes breast reconstruction have led to questions about the quality of patient decisions.ObjectiveTo assess the quality of patient decisions about breast reconstruction.Design, Setting, and ParticipantsA prospective, cross-sectional survey study was conducted from June 27, 2012, to February 28, 2014, at a single, academic, multidisciplinary oncology clinic among women planning to undergo mastectomy for stage I to III invasive ductal or lobular breast cancer, ductal carcinoma in situ, or prophylaxis. ExposuresMastectomy only and mastectomy with reconstruction.Main Outcome and MeasuresKnowledge, as ascertained using the Decision Quality Instrument; preference concordance, based on rating and ranking of key attributes; and decision quality, defined as having knowledge of 50% or more and preference concordance.ResultsDuring the 20-month period, 214 patients were eligible, 182 were approached, and 32 missed. We enrolled 145 patients (79.7% enrollment rate), and received surveys from 131 patients (72.0% participation rate). Five participants became ineligible. The final study population was 126 patients. Among the 126 women in the study (mean [SD] age, 53.2 [12.1] years), the mean (SD) knowledge score was 58.5% (16.2%) and did not differ by treatment group (mastectomy only, 55.2% [15.0%]; mastectomy with reconstruction, 60.5% [16.5%]). A total of 82 of 123 participants (66.7%) had a calculated treatment preference of mastectomy only; 39 of these women (47.6%) underwent mastectomy only. A total of 41 participants (32.5%) had a calculated treatment preference of mastectomy with reconstruction; 36 of these women (87.8%) underwent mastectomy with reconstruction. Overall, 52 of 120 participants (43.3%) made a high-quality decision. In multivariable analysis, white race/ethnicity (odds ratio [OR], 2.72; 95% CI, 1.00-7.38; P = .05), having private insurance (OR, 1.61; 95% CI, 1.35-1.93; P < .001), having a high school education or less (vs some college) (OR, 4.84; 95% CI, 1.22-19.21; P = .02), having a college degree (vs some college) (OR, 1.95; 95% CI, 1.53-2.49; P < .001), and not having a malignant neoplasm (eg, BRCA carriers) (OR, 3.13; 95% CI, 1.25-7.85; P = .01) were independently associated with making a high-quality decision.Conclusions and RelevanceA minority of patients undergoing mastectomy in a single academic center made a high-quality decision about reconstruction. Shared decision making is needed to support decisions about breast reconstruction.

Preoperative axillary ultrasound is less sensitive in invasive lobular breast cancer than in invasive ductal breast cancer

Preoperative axillary ultrasound is less sensitive in invasive lobular breast cancer than in invasive ductal breast cancer

Transcriptomic and genomic features of invasive lobular breast cancer

Accounting for 10-15% of all breast neoplasms, invasive lobular breast cancer (ILC) is the second most common histological subtype of breast cancer after invasive ductal breast cancer (IDC). Understanding ILC biology, which differs from IDC in terms of clinical presentation, treatment response, relapse timing and patterns, is essential in order to adopt novel, disease-specific management strategies. While the contribution of the histological subtypes to tumour biology has been poorly investigated and acknowledged in the past, recently several major, independent efforts have led to the assembly and molecular characterization of well-annotated ILC case sets. In this review, we provide a critical overview of the literature exploring ILC, through comprehensive and multiomic methods. The first part specifically focuses on ILC transcriptomic features by reviewing the intrinsic molecular subtypes, the application of gene expression scores for the prediction of recurrence, and the identification of gene expression subtypes. The second part describes the main research efforts that lead to the identification of the genomic landscape of ILC, with a special focus to findings that differentiate ILC from IDC and carry potential clinical relevance.

Repeated surgeries in invasive lobular breast cancer with preoperative MRI: Role of additional carcinoma in situ and background parenchymal enhancement

ObjectivesAnalysing the influence of additional carcinoma in situ (CIS) and background parenchymal enhancement (BPE) in preoperative MRI on repeated surgeries in patients with invasive lobular carcinoma (ILC) of the breast. MethodsRetrospective analysis of 106 patients (mean age 58.6±9.9years) with 108 ILC. Preoperative tumour size as assessed by MRI, mammography and sonography was recorded and compared to histopathology. In contrast-enhanced MRI, the degree of BPE was categorised by two readers. The influence of additionally detected CIS and BPE on the rate of repeated surgeries was analysed. ResultsAdditional CIS was present in 45.4% of the cases (49/108). The degree of BPE was minimal or mild in 80% of the cases and moderate or marked in 20% of the cases. In 17 cases (15.7%) at least one repeated surgery was performed. In n=15 of these cases, repeated surgery was performed after BCT (n=9 re-excisions, n=6 conversions to mastectomy), in n=2 cases after initial mastectomy. The initial surgical procedure (p=0.008) and additional CIS (p=0.046) significantly influenced the rate of repeated surgeries, while tumour size, patient age and BPE did not (p=ns). ConclusionsAdditional CIS was associated with a higher rate of repeated surgeries, whereas BPE had no influence.

Abstract P1-07-10: Prediction of 10yr distant recurrence (DR) using the Prosigna® (PAM50) assay in histological subgroups of a Danish breast cancer group (DBCG) cohort of postmenopausal Danish women with hormone receptor-positive (HR+) early breast cancer (EBC) allocated to 5yr of endocrine therapy (ET) alone

Abstract Background: The Prosigna (PAM50) risk of recurrence (ROR) score predicts 10yr DR in early breast cancer patients treated with ET alone (level 1 evidence). Invasive lobular breast cancer (ILBC) accounts for 10-15% of all breast cancer histological subtypes. Sporadic ILBC is characterized by somatic CDH1 mutations with loss of E-cadherin and a majority of low proliferative ER positive/HER2 negative tumors consistent with Luminal A subtype. Here we examine the ability of PAM50/ROR to predict 10yr DR in postmenopausal women who following a diagnosis of HR+ early ILBC were allocated to 5yr of ET alone. Methods: Using the population based clinical DBCG database FFPE primary tumor blocks, treatment, and follow-up data were collected from all patients diagnosed from 2000-2003 with HR+, postmenopausal EBC (N0-N1) who by nationwide guidelines were allocated to 5yr of ET alone, N=2,722 (1256 N0, 1466 N1). PAM50 intrinsic subtype classification (Luminal A, Luminal B, HER2-enriched, Basal-like) was conducted using the NanoString nCounter®Analysis System. Univariate and multivariate analyses tested the ability of PAM50 to predict DR. Patients were categorized as Low or High Risk based upon pre-specified ROR cutoff value of 40. HER2 positive tumors by immunohistochemistry were excluded from analysis. Results: Median follow-up was 9.25 years. Risk of 10yr DR by ROR and PAM50 (Luminal A and Luminal B) is shown in the table by ILBC as compared to invasive ductal breast cancer (IDBC) type. Cumulative incidence for 10 yr distant recurrence (DR)Histological subtypeRisk Group % [95% CI](N row%)Intrinsic Subtype % [95% CI](N row%)Histological subtype% [95% CI](N) LowHighLuminal ALuminal BAllDuctal3.8 [2.5-5.6] (738 35%)16.6 [14.4-18.8] (1388 65%)6.6 [5.1-8.4] (1174 59%)18.1 [15.2-21.3] (832 41%)12.1% [10.6-13.7] (2126)Lobular9.7 [5.5-15.4] (181 53%)23.9 [16.8-31.6] (159 47%)12.7 [8.6-17.8] (256 77%)24.1 [14.5-35.1] (77 23%)16.4 [12.2-21.1] (340) In this specific cohort the ILBC subgroup had a worse 10yr DR of 16.4% [12.2-21.1] as compared to IDBC of 12.1% [10.6-13.7] (Gray´s test, p = 0.046). A significant difference regarding the distribution of ILBC into both High and Low Risk Group and intrinsic subtypes as compared to IDBC was identified (p &amp;lt; 0.0001). Molecular intrinsic subtype analysis for ILBC by Prosigna (PAM50) showed DR 12.7 [8.6-17.8] for Luminal A vs 24.1 [14.5-35.1] for Luminal B. The difference between ILBC subtypes was not significant (p = 0.09). Adding ROR to a Fine and Gray's proportional sub-hazards model containing clinical and pathological variables significantly improved the model for ILBC, (likelihood ratio: p = 0.0001); HR for a 20-point change in ROR = 1.84 [1.37-2.48] notable with DR 9.7 [5.5-15.4] for the Low Risk Group. Conclusions: Following 5-yr of endocrine treatment alone patients with ILBC in this large population-based study had an inferior DR as compared to patients with IDBC and the apparent difference between ILBC and IDBC must be interpreted with caution. Citation Format: Laenkholm A-V, Jensen M-B, Buckingham W, Schaper C, Knoop A, Eriksen JO, Rasmussen BB, Ferree S, Haffner T, Kiboel T, Ejlertsen B. Prediction of 10yr distant recurrence (DR) using the Prosigna® (PAM50) assay in histological subgroups of a Danish breast cancer group (DBCG) cohort of postmenopausal Danish women with hormone receptor-positive (HR+) early breast cancer (EBC) allocated to 5yr of endocrine therapy (ET) alone [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-07-10.

Abstract P3-04-04: Detection of ESR1 mutations in matched primary and metastatic samples from endocrine-resistant lobular breast cancer patients

Abstract Background: Invasive lobular breast cancer (ILBC) represents the second most common histology of breast cancer (BC) and accounts for 10-15% of all invasive cases. Since &amp;gt;90% of ILBCs express the estrogen receptor (ER, coded by the ESR1 gene), the vast majority of these patients receive endocrine therapy. ESR1 mutations have mainly been identified in metastases from ER-positive BC at a frequency ranging from 11 to 50% and were shown to be associated with resistance to endocrine therapy. Nevertheless, ESR1 mutations have never been assessed in metastatic ILBC, hence the present study. Patients and methods: We aimed at interrogating the five most commonly reported ESR1 mutations (Y537S/C/N, D538G, E380Q) by droplet digital PCR (BioRad) in matched primary, axillary and metastatic ILBC samples (N=212) from 69 endocrine-resistant patients collected retrospectively from five hospitals. Results: We present here the results for the two most frequent ESR1 mutations (Y537S and D538G); data from the remaining mutations will be available at the time of the conference. We observed Y537S and D538G mutations in metastases from three and four patients, respectively. For one patient, the sampled metastasis harbored both the Y537S and the D538G mutations, confirming that ESR1 polyclonality can be present in the same metastasis. For another patient, two metastases were sampled and the D538G mutation was only present in one metastasis. Intriguingly, for two patients we observed D538G mutations only in the primary tumor but not in the corresponding metastasis, and for another only in an axillary lymph node. We could hypothesize that the clone carrying the mutation in the early setting has been removed either by the primary surgery or subsequent adjuvant chemotherapy. The ESR1 Y537S and D538G mutational frequencies observed in our metastatic ILC cohort (3/69, 4.35% and 4/69, 5.80%, respectively) are not statistically different from the frequencies reported in breast cancer metastases in the literature across the different studies (6.62% and 6.20%, respectively). All patients with ESR1-mutated metastases received at least 4 years of endocrine therapy and all but one were treated with an aromatase inhibitor (AI). However, half of these patients received exclusively endocrine therapy in the adjuvant setting. Conclusion: This is to the best of our knowledge, the first metastatic ILBC series in which the most frequently reported ESR1 mutations are being investigated, and the largest series in which ESR1 mutations are being investigated in matched metastatic, primary tumor and axillary lymph node samples. The frequencies that we found for the Y537S and D538G mutations are in line with those reported in the literature in metastatic biopsies for the general BC population. We further demonstrated using multiple samples from the primary tumor and an ultra-sensitive technology that there was no patient presenting an ESR1 mutation both in the early and metastatic disease. Data on the remaining mutations (Y537S/N, E380Q) will complete these results. Citation Format: Desmedt C, Pingitore J, Rothé F, Rouas G, Bertucci F, Galant C, Rotmensz N, van den Eynden G, Salgado R, Larsimont D, Pruneri G, Sotiriou C. Detection of ESR1 mutations in matched primary and metastatic samples from endocrine-resistant lobular breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-04.

Abstract P5-10-02: African Americans have more aggressive invasive lobular carcinoma subtypes and inferior early outcomes: SEER 2010-2013

Abstract Introduction: African Americans (AA) present more frequently with triple negative breast cancer (TN) and other aggressive breast cancer subtypes. Invasive lobular (ILC) breast cancer most commonly presents as estrogen receptor (ER)+, progesterone receptor (PR)+ and HER2-, though less frequently the more aggressive ER- or PR- luminal, TN or HER2+ subtypes occur. For women presenting with ILC 2010-2013, we report by race, differences in disease subtype, grade and stage at presentation and 2-year outcomes. Methods: We conducted a retrospective cohort analysis using Surveillance, Epidemiology and End Results Program. Women diagnosed with first primary malignant lobular breast cancer from 2010-2013 were included. Subtypes were categorized into four exclusive groups: ER+ and PR+ HER2-, ER+ or PR+ HER2-, TN and HER2+. Two-year survival was compared across race, and a multivariate cox model assessed overall survival. Results: ILC occurred less frequently in non-whites (Table 1). AA and other non-whites were younger at diagnosis than whites (p&amp;lt;0.001). AAs and other non-whites were less likely to have ER+ and PR+ HER2- disease (OR 0.85, p= 0.019 and OR 0.79, p=0.003 respectively). AAs had ILC of significantly higher grade and presented with more advanced stage disease than other race categories (p&amp;lt;0.001 for both). On multivariate analysis, survival was inferior for AA relative to whites (HR 1.32, p&amp;lt;0.010). Other non-whites had better survival than whites (HR 0.58, p=0.008). For AAs 2-year survival by disease subtype was: ER+ and PR+ HER2- (91.3%), ER+ or PR+ HER2- (90.5%), TN (59.5%), HER2+ (84.0%). For these subtypes, the proportion of women presenting with Stage IV ILC was 8.1%, 10.8%, 22.6% and 15.9% respectively. Conclusion: In this large, recent ILC cohort there were significant racial disparities in disease biology at presentation, with non-whites having more aggressive ILC subtypes, but only AAs having higher grade ILC. Short-term survival outcomes were inferior for AAs. Whether AAs presenting with advanced stage disease more frequently is due to biology or access to care is unknown. Further study of disease biology and healthcare delivery disparities could offer improved outcomes for AAs with ILC. Table 1: ILC Characteristics by Race WhiteAA Other non-white N13,5571,445 957 ILC - % diagnoses per race category9.67.2 5.8 Rate of ILC (per 100,000 women of that race)10.56.4 4.4 Median Age6461 60 %%OR*p%OR*pSubtype ER+ and PR+ HER2-80.978.30.850.01977.00.790.003ER+ or PR+ HER2-12.914.41.140.10615.31.220.036TN1.52.11.440.0642.11.400.158HER2+4.75.11.090.4735.61.210.186Stage I40.536.4 39.0 &amp;lt;0.001II36.534.5 40.4 III17.019.9 14.9 IV6.09.2 5.6 Grade (Differentiation) Well or Moderate91.287.5 89.5 &amp;lt;0.001Poor or Undifferentiated8.812.5 10.5 2-year survival93.9%90.0% 96.3% *compared to white (reference group) Table 2: Multivariate Cox Model for 2-year Survival HRp95% CIRace Whiteref AA1.320.0101.071.64Other non-white0.580.0080.380.87Subtype ER+ and PR+ HER2-ref ER+ or PR+ HER2-1.80&amp;lt;0.0011.512.16TN2.89&amp;lt;0.0012.074.03HER2+0.970.8670.691.37Stage Iref II1.91&amp;lt;0.0011.512.42III3.44&amp;lt;0.0012.714.37IV22.34&amp;lt;0.00117.7828.07Grade (Differentiation) Well or Moderateref Poor or Undifferentiated1.400.0011.141.71 Citation Format: Thomas A, Altekruse S, Avery TP, Melin SA, Howard-McNatt MM, Schroeder MC. African Americans have more aggressive invasive lobular carcinoma subtypes and inferior early outcomes: SEER 2010-2013 [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-10-02.

Abstract P3-03-03: An acquired HER2 T798I gatekeeper mutation induces resistance to neratinib in a patient with HER2 mutant-driven breast cancer

Abstract ERBB2, the gene encoding HER2, is mutated in 2-4% of breast cancers. The HER2 irreversible tyrosine kinase inhibitor (TKI) neratinib has shown clinical activity against breast cancer cells harboring HER2 activating mutations. Here, we report for the first time an acquired gatekeeper HER2T798I mutation in a patient with HER2-mutant breast cancer after an initial exceptional response to neratinib. A patient with ER+/PR+/HER2-negative invasive lobular breast cancer progressing on standard therapy was found to harbor a L869R kinase domain mutation in HER2. HER2L869R is homologous to the known activating mutation EGFRL861R/Q. MCF10A breast epithelial cells expressing HER2L869R displayed enhanced HER2-mediated signaling and were resistant to lapatinib and trastuzumab but sensitive to neratinib. The patient was enrolled in the phase II SUMMIT trial (NCT01953926) and treated with neratinib, achieving a partial response lasting 16 months before developing progression. Next gen sequencing of DNA from both a new skin metastasis and plasma cell-free DNA (cfDNA) identified HER2L869R (8.7% cfDNA), whereas a novel HER2T798I mutation was detected only in plasma at 1.3%. Deep sequencing of pre-therapy tumor tissue and plasma did not detect HER2T798I, suggesting that this mutation arose upon resistance. HER2T798I has not been reported in TCGA, COSMIC, or among plasma samples from 17,345 cancer patients subjected to digital DNA sequencing using the Guardant360 assay. HER2T798I is homologous to the EGFRT790M, KITT670I and BCR-ABLT315I gatekeeper mutations known to mediate resistance to erlotinib/gefitinib and imatinib. To examine if HER2T798I mediates resistance to neratinib, we employed biochemical and biological assays and molecular modeling of wild-type (WT) HER2 and HER2T798I. Structural modeling showed the increased bulk of the isoleucine at position 798 would result in a steric clash with neratinib, thus reducing drug binding. We stably expressed HER2WT, HER2T798I, HER2L869R and HER2L869R/T798I in MCF10A cells and NR6 mouse fibroblasts. Neratinib (10-100 nM) blocked HER2-mediated signaling in cells expressing HER2WT or HER2L869R but did not in cells expressing HER2T798I. The EGFR irreversible TKI osimertinib (100 nM), which isselective for mutant EGFR (including EGFRT790M) and approved for treatment of NSCLC expressing EGFRT790M, failed to inhibit HER2WT, HER2L869R or HER2T798I. In contrast, either the EGFR/HER2 irreversible TKI afatinib or AZ5104, a metabolite of osimertinib, strongly blocked signaling induced by HER2WT, HER2L869R or HER2T798I. Cells expressing HER2T798M displayed a significantly higher IC50 to neratinib than cells expressing HER2WT, whereas afatinib or AZ5014 were very active against all cells (IC50&amp;lt;10 nM). Conclusions: The acquisition of a T798I gatekeeper mutation in HER2 upon development of clinical resistance to neratinib in a breast cancer with an initial activating mutation in HER2 strongly suggests that HER2L869R is a driver mutation. We speculate that HER2T798I may arise as a secondary mutation following response to effective HER2 TKIs in other cancers with HER2 activating mutations. Certain irreversible EGFR inhibitors may be effective in patients with HER2-driven breast cancer resistant to neratinib. Citation Format: Hanker AB, Red Brewer M, Sheehan JH, Koch JP, Lanman R, Hyman DM, Cutler, Jr. RE, Lalani AS, Cross D, Lovly CM, Meiler J, Arteaga CL. An acquired HER2 T798I gatekeeper mutation induces resistance to neratinib in a patient with HER2 mutant-driven breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-03-03.

Abstract B41: Statins show synthetic lethality in E-cadherin-deficient cells and are synergistic with SRC and HDAC inhibitors

Abstract E-cadherin (CDH1) is a cell-cell adhesion protein implicated in the epithelial-mesenchymal transition and frequently dysregulated in diffuse gastric cancer (DGC) and invasive lobular breast cancer (ILBC). Germline CDH1 mutations define hereditary diffuse gastric cancer (HDGC), a rare cancer syndrome characterised by highly penetrant DGC and an elevated rate of ILBC in females. There is a strong need to develop specific chemopreventative strategies for CDH1 germline mutation carriers which are capable of reducing the viability of early stage CDH1-deficient cancers whilst minimizing side effects. We have previously applied a synthetic lethal approach to an isogenic pair of MCF10A breast cell lines, one with and one without functional CDH1 expression (MCF10A CDH1-/-), to screen for drugs which preferentially reduce the viability of CDH1-deficient cells. This led to our finding that histone deacetylase inhibitors (HDACi; entinostat and vorinostat) and SRC inhibitors (SRCi; saracatinib) are involved in synthetic lethal interactions with MCF10A CDH1-/- cells. Single agent therapy, however, only produces a modest synthetic lethal effect, leading to our interest in developing synergistic drug combinations. We have now shown that statins, inhibitors of the HMG-CoA reductase enzyme, also show a synthetic lethal phenotype in the MCF10A isogenic cell line pair. This result suggests that survival of E-cadherin-deficient cells may be enhanced by the mevalonate pathway, a metabolic pathway responsible for synthesizing prenyl groups and subsequently activating the small GTPase proteins Rho, Rac, and Cdc42. SRC is also a known activator of GTPase proteins and combined statin and saracatinib treatment caused an enhanced reduction in cell viability in the isogenic MCF10A cells whilst maintaining the synthetic lethal phenotype. This drug combination was shown to be synergistic in both cell lines using the Chou-Talalay median effect analysis and is the first known example of synergy between a statin and SRC inhibitor. Combined statin and HDACi treatment also enhanced cell viability inhibition and was synthetic lethal in the MCF10A pair. This effect was observed using both class-I specific (entinostat) and pan- (vorinostat) HDACi and was synergistic in both cell lines using median effect analysis. These are the first known examples of synergistic drug combinations being used in the field of synthetic lethality and serve as a foundation for novel DGC and ILBC treatment options. Citation Format: Andrew Single, Augustine Chen, Bryony Telford, Henry Beetham, Parry Guilford. Statins show synthetic lethality in E-cadherin-deficient cells and are synergistic with SRC and HDAC inhibitors. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr B41.

Epithelial cadherins and associated molecules in invasive lobular breast cancer

to estimate the expression of cell adhesion molecules E- and P-cadherin, as well as that of cadherin-catenin complexes in invasive lobular breast cancer (BC) cells. 250 cases of postoperative material from patients diagnosed with invasive lobular BC were studied. The expressions of cell adhesion molecules E-cadherin, P-cadherin, β-catenin, p120 catenin, and vimentin were determined by immunohistochemical assay in all cases. The examined cases were divided into molecular biological subtypes, based on the evaluation of estrogen receptors (ER), progesterone receptors (PR), HER-2/neu, and Ki-67 proliferative index. The membrane expression of E-cadherin on the tumor cells was found to be preserved in 93%; the cytoplasmic expression of β-catenin and p120-catenin appeared in 60 and 72% of cases, respectively. The expression of P-cadherin was detected in 82% of cases. The coexpression of E- and P-cadherin was noted in 90% of all the examined cases. There was a correlation between the expression of E- and P-cadherins (V=0.34; p<0.05). The BC cells showed the coexpression of E- and P-cadherins, as well as release of the molecules β- and p120-catenins into the cytoplasm of tumor cells, which leads to the activation of intracellular mechanisms for changing the structure of the cytoskeleton and the level of proliferation. The above-mentioned mechanisms are accompanied by the activation of epithelial-mesenchymal transition. The intracellular mechanisms resulted in progressive cancer and its metastasis.