Invasive Lobular Breast Cancer Research Articles

Comprehensive Review of Molecular Mechanisms and Clinical Features of Invasive Lobular Cancer.

Invasive lobular carcinoma (ILC) accounts for 10% to 15% of breast cancers in the United States, 80% of which are estrogen receptor (ER)-positive, with an unusual metastatic pattern of spread to sites such as the serosa, meninges, and ovaries, among others. Lobular cancer presents significant challenges in detection and clinical management given its multifocality and multicentricity at presentation. Despite the unique features of ILC, it is often lumped with hormone receptor-positive invasive ductal cancers (IDC); consequently, ILC screening, treatment, and follow-up strategies are largely based on data from IDC. Despite both being treated as ER-positive breast cancer, querying the Cancer Genome Atlas database shows distinctive molecular aberrations in ILC compared with IDC, such as E-cadherin loss (66% vs. 3%), FOXA1 mutations (7% vs. 2%), and GATA3 mutations (5% vs. 20%). Moreover, compared with patients with IDC, patients with ILC are less likely to undergo breast-conserving surgery, with lower rates of complete response following therapy as these tumors are less chemosensitive. Taken together, this suggests that ILC is biologically distinct, which may influence tumorigenesis and therapeutic strategies. Long-term survival and clinical outcomes in patients with ILC are worse than in stage- and grade-matched patients with IDC; therefore, nuanced criteria are needed to better define treatment goals and protocols tailored to ILC's unique biology. This comprehensive review highlights the histologic and clinicopathologic features that distinguish ILC from IDC, with an in-depth discussion of ILC's molecular alterations and biomarkers, clinical trials and treatment strategies, and future targets for therapy. IMPLICATIONS FOR PRACTICE: The majority of invasive lobular breast cancers (ILCs) are hormone receptor (HR)-positive and low grade. Clinically, ILC is treated similar to HR-positive invasive ductal cancer (IDC). However, ILC differs distinctly from IDC in its clinicopathologic characteristics and molecular alterations. ILC also differs in response to systemic therapy, with studies showing ILC as less sensitive to chemotherapy. Patients with ILC have worse clinical outcomes with late recurrences. Despite these differences, clinical trials treat HR-positive breast cancers as a single disease, and there is an unmet need for studies addressing the unique challenges faced by patients diagnosed with ILC.

Outcomes After Accelerated Partial Breast Irradiation in Women With Triple Negative Subtype and Other "High Risk" Variables Categorized as Cautionary in The ASTRO Guidelines.

PurposeTo report a primary objective clinical outcome of ipsilateral breast recurrence following accelerated partial breast irradiation (APBI) in women with triple negative and other high risk breast cancer (as described in 2017 ASTRO guidelines) (i.e., age 40–49, size 2.1–3.0 cm, estrogen receptor negative and invasive lobular breast cancer). Secondary objectives of axillary and regional failure as well as overall survival are also reported.Methods and MaterialPatients from two clinical trials (NCT01185145, NCT01185132) were treated with 38.5 Gy IMRT or 3D-CRT APBI w/3.85 Gy fraction/BID fractionation for 10 fractions. Triple negative and other high risk patients (n=269) were compared to a total of 478 low risk patients which ASTRO defined as “suitable” for APBI. High risk patients, for the purpose of this study, were defined as those who possess one or more high risk criteria: triple negative (n=30), tumor size >2 cm <3 cm (n=50), HER 2+ (n=54), age range 40–50 years (n=120), ER- (n=43), and ILC histology (n=52).ResultsMedian follow up was 4.0 years for all patients. No significant difference was found for this high-risk cohort at 5 years for ipsilateral breast, or regional recurrences. Axillary recurrence was significantly adversely impacted by triple negative and ER- statuses (p=0.01, p=0.04). There were significant correlations between triple negative type and axillary recurrence on multivariate analysis (p=0.03). Overall survival for all patients was unaffected by any of the high-risk categories.ConclusionThe data from this study suggests that women possessing high risk features are at no more meaningful risk for recurrence than other patients considered to be acceptable for APBI treatment. However, the finding of axillary recurrence in patients with triple negative breast cancer does warrant a degree of caution in proceeding with accelerated partial breast irradiation technique in this patient group.

LATE LIVER METASTASIS 20 YEARS AFTER THE INITIAL DIAGNOSIS: A CASE REPORT OF METACHRONOUS HORMONE DEPENDENT TUMORS OF BREAST AND ENDOMETRIUM

Breast cancer is the most common cancer and a significant cause of morbidity and mortality in female population worldwide. The liver is the third most common metastatic site for invasive breast malignancy besides bones, lungs and brain. Breast cancer has been linked with metachronous bone, endometrial, colon/rectal, connective tissue (sarcoma), leukemia, lung, ovary or thyroid cancer. Studies have shown an increased risk of secondary malignancies in women treated for breast malignancy in connection to adjuvant treatment in certain cases. We present a case of a 71 year old woman who was diagnosed with breast cancer 20 years ago. The primary diagnosis was invasive lobular breast cancer localized in left lower lateral quadrant. Micromorphological, histochemical and immunohistochemical analyses rendered diagnosis inconclusive due to lack of tissue so after 4 months rebiopsy was performed. Clinico-pathological correlation of the second biopsy was in favor of liver metastasis of partially hormone dependent breast cancer. Immunohistochemistry was vital for the diagnosis on the liver biopsy, in particular GATA3 positivity and vimentin negative staining which helped us exclude endometrial cancer metastasis which was diagnosed before the initial liver biopsy. GATA 3(+)/vimentin(-) panel proved to be superior to GCDFP-15 and mammaglobin in proving the breast origin of the secondary tumor deposit.Liver metastasis from primary breast cancer can in certain cases occur many years after the initial diagnosis which shows the importance and necessity for long term follow-up of these patients, while considering the possibility of metachronous tumors as well.

Abstract PS11-02: Comprehensive comparative analysis of invasive ductal and lobular breast cancer cases in great lakes breast cancer consortium

Abstract Background: Invasive lobular breast cancer (ILC) is the second most common histologic subtype of breast cancer following invasive ductal cancer (IDC). ILC accounts for ~10-15% of all breast cancers (~26-40,000 cases annually in the US) and ranks as the 6th most common cancer in women in the US. While there is increasing recognition that ILC has distinct clinical, histologic, molecular, and biological characteristics compared to IDC, it remains understudied. There are very few large cohort analyses comparing clinic-pathological features of ILC, and therefore we performed a large multi-institutional retrospective cohort study. Methods: Investigators from UPMC Hillman Cancer Center, James Cancer Hospital/OSU, and Cleveland Clinic Taussig Cancer Institute/CWRU formed the Great Lakes Breast Cancer consortium, and worked with their respective cancer registries to collect comprehensive data on patients with IDC and ILC seen at their institutions between 1990 and 2017. Descriptive statistics were performed to compare clinic-pathological features, treatments, metastases sites, and co-morbidities. Survival rates were analyzed using the Kaplan-Meier (KM) method and compared using the Cox proportional hazards model. A total of N=38,175 records (N=15,792 for UPMC, N=13,040 for CCF, and N=9,343 for OSU) were included in the study. Results Among the N=38,175 records, we identified N=30,100 unique IDC (not otherwise specific, NOS) (89.3%) and N=3,618 unique ILC cases (10.7%). There were no significant differences between IDC and ILC with respect to laterality of the cancer (IDC: Left 51%, Right 49%; 0.2% Other vs ILC: Left 51%, Right 48%, Other 0.5%) and body mass index (IDC: 28.4 vs ILC: 28.2). In contrast, we observed significant difference with respect to age - patients with ILC were significantly older (61.2 vs 57.5 years; p&amp;lt;0.0001), and there were significant differences in race (7.6% vs 9.2% African American patients in ILC vs IDC, respectively; p=0.004). Among ILC cases, there were fewer grade III tumors (11.4% vs 40.3% in IDC; p&amp;lt;0.0001). ILCs were more frequently stage III (16.6% vs 8.0% in IDC) and stage IV (3.7% vs 2.4% in IDC) (p&amp;lt;0.0001), and ILC were significantly larger than IDC (13.7% T3 vs 2.8% in IDC, p&amp;lt;0.0001). There was also significantly more lymph node involvement in patients with ILC (N2: 5.3% vs 4.0%; N3: 4.6% vs 1.5%) (p&amp;lt;0.0001). The ILC cohort had significantly fewer HER2+ cases (5.5% vs 18.1% in IDC) (p&amp;lt;0.0001), and the proportion of patients with a high recurrence score as determined by 21 gene recurrence score was significantly lower in ILC compared to IDC (1.7% vs 10.4% in IDC; p&amp;lt;0.0001). As expected, there was a significant enrichment of ER+ tumors in ILC (96.1% compared to IDC (76.6%) (p&amp;lt;0.0001). Age, stage, grade, ER, Her2, and lymph node involvement remained significantly associated with histology in a logistic regression analysis. KM analysis showed significantly shortened disease-free (p=0.041) and overall survival (p&amp;lt;0.0001) for patients with ER+ ILC (N=2,565) compared to ER+ IDC N=17,278). The estimated 5yr and 10yr DFS rates for patients with IDC are 0.94 and 0.89, and for ILC 0.94 and 0.86, confirming prior data of late recurrences in patients with ILC. Conclusions: In the largest cohort of patients with ILC made possible by multi-center collaborations we show that lobular histology carries distinct prognostic implications and that outcomes are significantly worse. This highlights the need for more ILC research and clinical trials for patients with ILC. Citation Format: Steffi Oesterreich, Azadeh Nasrazadani, Jian Zou, Tiffany Onger, Matthew Wright, George Tseng, Bhuvana Ramaswamy, Adrian V Lee, Nicole Williams, Megan Kruse. Comprehensive comparative analysis of invasive ductal and lobular breast cancer cases in great lakes breast cancer consortium [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS11-02.

Abstract PS11-16: Rare patients in routine care: Treatment and outcome in advanced invasive lobular breast cancer in the prospective German research platform OPAL

Abstract Introduction Invasive lobular breast cancer (ILC) is with 5-10% the second most common histologic type of invasive breast cancer after invasive ductal breast cancer (IDC). ILC differs from IDC, for example in its metastatic pattern. However, guidelines do not provide special treatment recommendations for this subtype and specific clinical studies are rare. Here we present prospective data on characteristics, treatment and outcome of patients (pts) with advanced ILC in routine care in Germany. Methods The Tumor Registry Breast Cancer (TMK) has prospectively documented data of pts with breast cancer by oncologists in Germany since 2007. Since 2017 OPAL continues the TMK work with representation of all specialists (medical and gynecologic oncologists) treating advanced breast cancer (ABC). Both projects are prospective, observational, open, longitudinal multicenter cohort studies (clinical registries). Pts at the start of their treatment can be included after signing informed consent. Together over 7500 pts (4250 with ABC) will be recruited from over 150 sites in Germany. There is no treatment specification. Details on all (sequential) treatments, patient and tumor characteristics, clinical and patient-reported outcomes are documented. Follow-Up is until death or up to 5 years. Here, data as of March, 31st 2020 are presented. Results Pts with advanced ILC (n=372) were older at start of first-line treatment (median 68 vs. 63 years) while ECOG performance status (ECOG 0 25% vs 29%) and Charlson Comorbidity Index (CCI 0: 82% vs 84%) were similar compared to pts with IDC (n=1745). The lobular tumor was more often hormone receptor (HR) positive (87% vs 74%) and less often HER2 positive (14% vs 27%). The percentage of primary metastatic disease (M1) was 34% in both groups, while grade at diagnosis was more frequently G1/2 in the ILC group (73% vs 51%). The metastatic pattern was more often non-visceral only for the ILC group (26% vs 19%), and metastases were found more often in bone (52% vs 42%) and peritoneum (9% vs 2%) and less often in liver (20% vs 25%) and lung (7% vs 25%). Overall, pts with ILC were treated more often with endocrine therapy (ET) +/- CDK4/6-inhibitors (CDK4/6i) than pts with IDC (52% vs 33%), yet, ILC is more often HR-positive than IDC. Of pts receiving chemotherapy (CT) 53% of ILC and 56% of IDC tumors were treated with taxanes as first-line treatment. 20% of ILC vs. 24% of IDC tumors received a combination-CT. First-line treatment strategy was analyzed for the HR-positive, HER2-negative subgroup. From 2007-16 pts with ILC received more often ET (ILC (n=162) 54% vs IDC (n=696) 44%), while IDC were more often treated with CT first-line. Since approval of CDK4/6i, distribution of treatment strategies has been quite similar (ILC (n=123): CDK4/6i: 76%, ET: 15%, CT: 10% and IDC (n=311): CDK4/6i: 72%, ET: 12%, CT: 15%). Overall survival (OS) from start of first-line treatment was estimated for all pts recruited by 2016 (follow-up of at least 3 years). Median OS was comparable: ILC (n=224) 30.6 months (68% events, 95%-CI 26.1 - 36.9 months) and IDC (n=1217) 34.1 months (60% events, 95%-CI 30.6 - 38.4 months). For the HR-positive, HER2-negative subgroup, OS was also similar. A multivariate regression analysis on factors affecting OS will be presented. Conclusion Registries, like TMK/OPAL, can provide data on rare tumor subtypes. We show that ABC with an invasive lobular histology differs in receptor status (more often HR-positive) and metastatic pattern (e.g. more often non-visceral) from the invasive ductal subtype. Nevertheless, treatment strategies for first-line treatment are similar and median OS is comparable despite ILC pts being markedly older. Future research should focus on identifying pts who could benefit from personalized treatment approaches including tumor subtype as a factor to consider. Citation Format: Marc Thill, Mark-Oliver Zahn, Anja Welt, Elmar Stickeler, Arnd Nusch, Thomas Fietz, Jacqueline Rauh, Natalie Wetzel, Lisa Kruggel, Martina Jänicke, Norbert Marschner, Nadia Harbeck, Achim Wöckel, Thomas Decker, OPAL study group. Rare patients in routine care: Treatment and outcome in advanced invasive lobular breast cancer in the prospective German research platform OPAL [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS11-16.

Abstract PS16-03: Clonal relatedness of LCIS with synchronous and asynchronous invasive disease

Abstract Background: Lobular carcinoma in situ (LCIS) is typically clinically undetectable but is being increasingly diagnosed as a result of breast screening mammography and is often found associated with other breast pathologies such as invasive lobular breast cancer (ILC), invasive carcinoma of ductal /no special type (IDC) and ductal carcinoma in situ (DCIS). It is also considered a risk factor for the development of subsequent invasive breast disease. The aim of this study was to understand the genetic relationship between LCIS that presents with synchronous DCIS, IDC and/or ILC in order to ascertain whether the components have common precursors and also to understand the clonal relationship between LCIS and subsequent invasive disease. Methods: 25 cases of LCIS with synchronous ILC, 7 cases of LCIS with synchronous DCIS &amp; IDC, and 8 pure LCIS that developed a subsequent invasive recurrence were identified from the GLACIER study (MREC 06/Q1702/64). DNA was extracted from archival paraffin embedded tissue and underwent copy number analysis using either the Oncoscan™ Array (Affymetrix) or HumanCytoSNP FFPE-12 BeadChip (Illumina). Four of 7 cases of LCIS with synchronous DCIS &amp; IDC also underwent targeted sequencing using a custom 121 breast cancer-associated gene panel (SureSelectXT HS kit, Agilent Technologies). Clonal relatedness was assessed using a novel methodology based on the presence of shared copy number aberration breakpoints and mutations. Results: Of the 25 synchronous LCIS and ILC cases, 17 appeared related, 4 were ambiguous (sharing the typical lobular signature of 1q gain and 16q loss) and 4 demonstrated no evidence of relatedness. Of the 7 cases with synchronous LCIS, DCIS and IDC, all had copy number data available and 4 had mutation data available. In 3 cases the synchronous LCIS, DCIS and IDC were clonally related according to copy number and for two there was mutation data that supported this (one sharing PIK3CA and CDH1 mutations, the other a TP53 mutation). In two cases the LCIS was not related to the DCIS or IDC, but the DCIS and IDC were related to each other; while in one case LCIS was related to IDC but not to the DCIS by copy number but all components shared the same CHEK2 mutation. Finally in one case none of the three components were related to each other by copy number but the LCIS and IDC shared a PIK3CA mutation, albeit at much lower allele frequency in LCIS than in IDC. Of the 8 patients with pure LCIS, 4 developed an ipsilateral invasive recurrence of various combinations of morphologies: 1 ILC &amp; LCIS, 1 ILC &amp; DCIS, 1 IDC &amp; DCIS, 1 ILC &amp; IDC, and 4 a contralateral recurrence (1 tubular, 1 IDC, 2 ILC), with a median time to recurrence of 69 months (range 34-175). The primary LCIS was related to at least one component of the recurrent disease in all four ipsilateral cases; in two the primary LCIS and all components of the recurrent disease were related, and in the remainder we observed a variety of putative evolutionary patterns. Conclusions: The majority (68%) of cases of synchronous LCIS and ILC appeared to be clonally related by copy number. 50% of cases of co-existing LCIS and IDC appeared to have a common clonal origin by either copy number or targeted sequencing. As these are genomically stable tumours, copy number data may also be underestimating relatedness. In the four cases of pure primary LCIS that developed an ipsilateral recurrence, different subtypes of breast cancer were noted as the recurrence morphology, supporting the historical view that LCIS is a risk lesion rather than a true precursor. However, in all cases the preceding LCIS was found to be related to at least one component of the subsequent invasive tumour including DCIS and IDC. This data shows that clonal relatedness between LCIS and both synchronous and asynchronous invasive disease and DCIS is more complex than previously thought, with LCIS acting as a precursor lesion even in some cases of IDC. Citation Format: Elinor Sawyer, Mateja Sborchia, Anargyros Megalios, Vandna Shah, Salpie Nowinski, Cloe Vassart, Anita Grigoriadis, Alastair Thompson, Ian Tomlinson, Rebecca Roylance, Sarah Pinder. Clonal relatedness of LCIS with synchronous and asynchronous invasive disease [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-03.

Abstract SP068: The unique epigenetic state of invasive lobular breast cancers

Abstract Although the majority of invasive lobular breast cancers (ILC) are strongly hormone receptor positive and are rarely high-grade, they present a number of unique clinical problems compared with invasive ductal cancer (IDC). These include challenges for early detection, decreased response to chemotherapy and evidence of relative resistance specifically to adjuvant tamoxifen treatment. In addition to uniform loss of e-cadherin, ILCs possess genetic alterations that are suggestive of a unique estrogen receptor axis, including an increase in the frequency of FOXA1 mutations and decrease in GATA3 mutations. In this study we performed a comprehensive analysis of the estrogen receptor axis in pre-clinical models and clinical samples of ILC and IDC. We found that ILC has a unique chromatin state that stems from gained FOXA1 chromatin binding and leads the remodeling of ER chromatin binding. We demonstrated that FOXA1 recruitment can classify primary hormone receptor positive breast cancers to ILC and IDC histological subtypes. Moreover, we show that gained FOXA1 recruitment leads to the transcription of a gene signature associated with resistance to adjuvant tamoxifen in estrogen receptor positive breast cancers and is a mechanism for the divergent pattern of response to specific endocrine treatments in ILC. Collectively, these studies unveil key insights to the fundamental biology unique to ILC, set the stage for precision endocrine treatment in estrogen receptor positive breast cancer, and offer potential treatment targets to improve outcomes for patients with ILC. Citation Format: R Jeselsohn. The unique epigenetic state of invasive lobular breast cancers [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr SP068.

Abstract PS17-41: In depth single cell profiling of a case of bone metastases with associated organoid models reveals a precision medicine approach to treatment

Abstract Occurring in 65-80% of metastatic breast cancer (BC), bone metastasis (BoM) is the major cause of BC related mortality. Under current standard of care, 5 year overall survival for patients with BoM is 20-25%, warranting the need of improved treatments. Like other cancers, BC BoM has high inter- and intra-patient heterogeneity. Thus, understanding disease evolution and heterogeneity of BoM at the individual patient level will be key to guide precise application of targeted therapies. In this study, we describe in depth histologic and single cell molecular characterization of a case of invasive lobular breast cancer (ILC) metastasis to bone. We collected fixed primary tumor (ER+/PR-/HER2- ILC) and fresh pelvis and tibia BoMs from a patient. H&amp;E/IHC staining and whole exome sequencing (WES) of DNA and RNA of the samples were performed. Organoids were derived from the two BoMs and single cell RNA sequencing was applied to these cultures and the BoMs. Based on H&amp;E/IHC staining, this case evolved from a ER+ primary ILC to ER- BoM with mixed lobular and ductal carcinoma features. WES revealed 208 missense somatic mutations in the BoMs. 15 were predicted as BC drivers, two of which are druggable including PIK3CA (E545K) and BRCA1 (D1834H, H399P). Notably, BRCA1 (D1834H) was not found in the primary tumor. Based on RNA sequencing, estrogen signaling was downregulated, while TGF-β, Wnt beta catenin and PI3K signaling, epithelial to mesenchymal transition (EMT) and angiogenesis were upregulated, all of which have been reported to be potential targets in BoMs. scRNAseq of BoMs revealed 5 major cell populations and pronounced heterogeneity. The two BoMs showed similar cellular compositions, including epithelial (30-50%), fibroblasts (50%), immune (5-10%), osteoclasts (1-2%) and endothelial cells (1-2%). Within epithelial cells, there were 5 major clusters exhibiting unique transcriptomic features, including a TNF-α signaling high cluster, two clusters showing high partial EMT (pEMT) signatures majorly regulated by PRRX1/2, TWIST1/2, and FOXS1, a cluster in active cell proliferation, and a cluster showing high signatures related to endocrine resistance. In fibroblasts, 3 clusters were identified representing ECM remodeling, angiogenesis (VEGFA high) and myofibroblasts. Immune cells majorly composed of macrophages, CD4+, CD8+ and Treg T cells. 2.2% tumor and 3.2% T cells express PDL1, exceeding the 1% threshold to select patients eligible for anti-PDL1 therapy. Based on CellPhoneDB, epithelial cells with high pEMT signature show the most interactions and uniquely interact with Treg cells through TNFSF4-TNFRSF4 which has been reported to promote Treg cell proliferation, and is investigated in clinic for immune therapy. Organoids were developed to evaluate therapeutic potential of targetable mutations, upregulated genes and susceptible cell populations. WES showed organoids preserved the mutational signatures of the matched tumor. scRNAseq showed all epithelial populations in the tumor were preserved in the matched organoids at comparable abundance. Consistent with the BRCA1 and PIK3CA mutations, organids were responsive to a PARP (Talazoparib: IC50 1.3uM/1.3uM) and PI3K (Alpelisib: IC50 9uM/4uM) inhibitor. We are currently examining the therapeutic potential of inhibiting pEMT, TNF-α, and genes upregulated in BoM. In summary, we have demonstrated a precision medicine approach to understand the evolution and heterogeneity of BC BoM. We have identified potential therapeutic targets and evaluated those in patient-specific organoids, thereby providing insights for the design of a precision medicine based clinical treatment strategy. Citation Format: Kai Ding, Fangyuan Chen, Nolan Priedigkeit, Daniel D. Brown, Tanya Heim, Rebecca Watters, Kurt Weiss, Jennifer Atkinson, Steffi Oesterreich, Adrian Lee. In depth single cell profiling of a case of bone metastases with associated organoid models reveals a precision medicine approach to treatment [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-41.

Abstract PS17-27: Molecular evaluation of immunogenicity and genomic alterations in invasive lobular breast cancer

Abstract Background: Invasive lobular carcinoma (ILC) is the second most common type of invasive breast cancer and accounts for 10-15% of all cases. Though ILC has distinct clinical, prognostic and molecular features, studies are limited and include few patients. ILCs show a decreased response to neoadjuvant chemotherapy and an increased resistance to endocrine therapy. Thus, there is a great need to identify alternative therapies, such as immunotherapy, that could improve overall survival. Success of immunotherapy largely depends on tumor immunogenicity which varies with histologic type. Determination of predictive and prognostic biomarkers for ILC will help determine who can benefit the most. Our study investigates canonical markers of immunogenicity - PD-L1 expression and Tumor Mutational Burden (TMB) - in patients with ILC compared to invasive ductal carcinoma (IDC). We further correlate these markers in different subtypes i.e. hormone receptor positive (HR+), HER2 positive (HER2+), and in triple negative breast cancers (TNBC). We also analyze differences in immune cell profiles constituting the tumor microenvironment (TME) and differences in genomic alterations between ILC and IDC. Methods: A retrospective data analysis was performed to identify breast cancer tumors with ILC or IDC histology profiled at Caris Life Sciences (Phoenix, AZ) that were tested for PD-L1 by SP142 assay and had whole transcriptome sequencing data available. ILC and IDC cases were further subtyped as HR+ and HER2+ and TNBC. PD-L1 expression in immune cell was assessed using Ventana PD-L1 (SP142) histochemical assay and PD-L1 expression in tumor cell was assessed by laboratory developed test using SP142 clone with staining higher than 2+ considered positive. TMB was measured by counting somatic non-synonymous missense mutations on the 592 gene panel (Nextseq) next generation sequencing (NGS) assay, and ≥ 10 mutations/megabase (mut/Mb) was considered high. Using the whole transcriptome RNA sequencing (NovaSeq) data we analyzed the difference in immune cell profiles constituting the TME using a computational RNA deconvolution approach. NGS was used to identify significant differences in genomic alterations between ILC and IDC. Results: We identified 1,359 breast cancer patients (ILC: 194 vs IDC: 1,165). Among ILC, 79% were HR +, 11% TNBC, &amp;lt;2% HER2+ and the rest were of unclear subtype, compared to 55% HR +, 31% TNBC, 10% HER2+ in the IDC group. PD-L1 expression in immune cells was lower in ILC (PD-L1≥ 1% ILC: 13% vs. IDC: 35% p &amp;lt;0.0001; PD-L1&amp;gt;10% ILC: 1% vs. IDC: 5% p=0.017). PD-L1 expression in tumor cells was also lower in ILC (ILC 1% vs IDC 5%; p =0.0136). All subtypes of ILC had lower PD-L1 expression in immune and tumor cells when compared to IDC. TMB was similar and comparable in IDC and ILC (median TMB 7 mut/Mb). Assessment of TME showed a significantly increased abundance of cytotoxic lymphocytes and monocytic cells in IDC, and stromal endothelial cells in ILC. Androgen receptor (AR) expression, and mutations in CDH1 (ILC 76% vs IDC 2%) and PIK3CA (ILC 44% vs IDC 30%) were more common in ILC. CDH1 mutation was significantly higher in both TN ILC (ILC 60% vs IDC 1%; p&amp;lt;0.05) and HR+ ILC (77% vs IDC 2%; p&amp;lt;0.05) subtypes of ILC. TP53 mutation was lower in ILC (ILC 26% vs IDC 65%) irrespective of subtype. Conclusion: In summary, PD-L1 expression in immune cells and tumor cells was lower in ILC, however TMB was comparable between ILC and IDC. Immune cell profiling supports a cold or less immunogenic TME for ILC. A composite immune biomarker may be able to better characterize immunogenicity of ILC. Citation Format: Upama Giri, Joanne Xiu, Tatiana Karadimitriou, Sofi Castanon, Foluso Ademuyiwa, Paula Pohlmann, Elias Obeid, Jasgit Sachdev, Elisa Krill-Jackson, Michael Simon, Antoinette Tan, Neelima Denduluri, Lee Schwartzberg, Michael Korn, Evanthia T Roussos Torres. Molecular evaluation of immunogenicity and genomic alterations in invasive lobular breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-27.

Abstract PS4-23: An analysis of the clinical and economic impact of the 21-gene recurrence score (RS) in invasive lobular early-stage breast cancer (ESBC) in Ireland

Abstract Background: The use of the 21-gene recurrence score assay (RS) has reduced chemotherapy (CT) administration in patients with hormone receptor (HR)-positive, HER-2 negative, lymph-node negative, early stage breast cancer (ESBC). Invasive lobular carcinoma (ILC) accounts for up to 15% of all breast cancers. This study uses real world data to assess (1) the effect of RS testing on treatment decision making in patients with ILC and (2) the economic benefit of testing in this subgroup. Methods: From October 2011 to February 2019, a retrospective, cross-sectional, observational study was conducted on HR+, HER-2 negative, lymph-node negative, ESBC patients with ILC who had RS testing in Ireland. For the decision impact analysis, a survey of Irish breast medical oncologists presumed that, without RS testing, CT would be recommended to patients with histological grade (G) 2 and 3 tumours and not for G1 tumours. In accordance with TAILOR-x results, patients were classified overall as low risk (RS≤25) and high risk (RS&amp;gt;25) and patients ≤50 years old were low risk (RS 0-15), intermediate risk (RS 16-25), and high risk (RS&amp;gt;25). Data were collected from electronic patient records. Descriptive statistics were used. Cost data were obtained from the National Healthcare Pricing Regulatory Authority. The economic analysis was adjusted for changing treatment and assay costs over the study period. Results: 166 patients with ILC were identified. Mean age was 59 years. Mean tumour size was 2.3cm (range 0.7-5.8). The majority had G2 tumors (n=152, 92%) with a small number of G3 (n=7, 4%) and G1 (n=7,4%). Overall, 153 patients (92.2%) had a low RS (≤25), 12 (7.2%) had high RS (&amp;gt;25), and 1(0.6%) was unknown. All 12 patients with RS&amp;gt;25 had G2 tumours, 6/12 (50%) had tumour size &amp;gt;3cm, 4(33.3%) were PR+ and 8(66.7%) were PR negative. In 29/166 (17.5%) patients, aged ≤50 at diagnosis, RS was ≤15 in 16(55%), 16-20 in 6(21%), 21-25 in 5(17%), &amp;gt;25 in 1(3.5%) and unknown in 1(3.5%). The majority of these patients (27, 93%) had G2 tumours, 1 had G1 and 1 had G3. Post RS testing 124 patients (74.5%) had a change in CT recommendation; all from CT to hormone therapy. In total, only 35 patients (21%) received CT. In this group, RS was 0-15 in 3(9%), RS 16-25 in 19(54%), RS &amp;gt;25 in 12 (34%) and unknown in 1(3%). Eight of 35 patients (23%) were aged ≤50. The most common CT regimen administered was docetaxel plus cyclophosphamide (TC). RS testing achieved a 78% reduction in chemotherapy use. This resulted in savings of €900,000 in treatment costs. With the incorporation of the assay cost, the net savings totalled approximately €400,000. Conclusions: Ireland was the first public health care system to reimburse the 21-gene recurrence score assay in Europe. There is limited evidence demonstrating the benefits of RS in ILC. In our study, the use of the test has resulted in a 78% reduction in chemotherapy use in an Irish ILC patient population and a substantial cost saving (greater than €400,000) to the Irish Healthcare System. Citation Format: Mehala Tharmabala, Lynda McSorley, Fathiya Al Rahbi, Evoy Denis, James G Geraghty, Rothwell Jane, Damian McCartan, Enda McDermott, Maccon M Keane, John Kennedy, Seamus O'Reilly, Steve Millen, John Crown, Lilian Mary Smyth, Catherine Margaret Kelly, Prichard Ruth, Cecily Quinn, Janice M Walshe. An analysis of the clinical and economic impact of the 21-gene recurrence score (RS) in invasive lobular early-stage breast cancer (ESBC) in Ireland [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-23.

Abstract PD6-08: DCE-MRI derived imaging features for characterizing invasive lobular breast cancer and predicting recurrence-free survival after neoadjuvant therapy

Abstract Background With current imaging technologies, assessing response to neoadjuvant chemotherapy (NAC) or neoadjuvant endocrine therapy (NET) remains a challenge for patients with invasive lobular carcinoma (ILC). Therefore, we evaluated imaging features from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) before and after neoadjuvant therapy in a cohort of patients with ILC, including the longest tumor diameter (LD), functional tumor volume (FTV), and peak signal enhancement ratio (SER). FTV is the sum of all image voxels enhancing above a set threshold within a defined region, and has been validated as a predictor of recurrence-free survival (RFS) for breast cancer. SER is a measure of contrast wash-in and wash-out and reflects neovascularity of tumors. We determined whether baseline and post-treatment imaging features differed by type of neoadjuvant therapy and if they were associated with RFS in neoadjuvantly treated ILC regardless of treatment type. Methods With institutional review board approval, a retrospective analysis of pre- and post-treatment breast DCE-MRI was performed on a cohort of ILC patients receiving neoadjuvant therapy between 1998 and 2017. We compared pre-treatment, post-treatment, and percent reduction (α) in LD, FTV, and peak SER by neoadjuvant treatment type (i.e. NAC or NET) using the Wilcoxon rank-sum test. Univariate t-tests, Chi-squared tests, analysis of variance, and Spearmen’s correlation were used to evaluate associations of clinicopathologic features and treatment type. Univariate and multivariate associations with RFS in the entire neoadjuvantly treated cohort adjusting for treatment type were evaluated using the log-rank test and Cox proportional hazards models. Results A cohort of 76 patients with pre- and post-treatment MRI were included in this study, of whom 42 (55.3%) received NAC and 34 (44.7%) received NET. The NAC group was significantly younger (55 vs. 60 years, p=0.013), less likely to have stage 1 disease (26.2% vs. 73.5%, p&amp;lt;0.001), and showed a trend of having more human epidermal growth factor 2 receptor-positive (HER2) tumors. The mean follow up time was 4.9 years with no difference between treatment groups. Patients in the NAC group had significantly larger pre-treatment LD and FTV but no difference was found in pre-treatment peak SER between groups. Post-treatment LD, FTV, and peak SER did not differ between treatment groups (Table 1). Those receiving NAC had significantly greater reduction in FTV compared to those receiving NET; αLD and α peak SER did not differ. In a multivariate Cox proportional hazards model including all patients in the cohort, higher pre-treatment peak SER was significantly associated with worse RFS regardless of neoadjuvant treatment type when adjusting for age, stage, receptor subtype, and tumor grade (hazard ratio 1.3, p=0.005, 95% CI 1.1-1.6). Neither LD nor FTV were associated with RFS on multivariate analysis. ConclusionPre-treatment peak SER measured by MRI may provide prognostic information beyond standard clinicopathologic variables in patients with ILC receiving either neoadjuvant chemotherapy or endocrine therapy. Further evaluation in a larger ILC cohort is needed to validate our initial findings. Table 1. Comparison of MR imaging features of ILC patients receiving neoadjuvant chemotherapy and neoadjuvant endocrine therapy.Overall(n=76)NAC(n=42)NET(n=34)P-valuePre-treatment (median, IQR)LD (cm)2.7, 1.6-5.44.6, 2.5-71.8, 1.4-3.20.0006FTV (cc)5.8, 2.2-16.48.7, 4.1-24.23.0, 0.9-80.0004SER0.9, 0.8-1.00.9, 0.9-1.00.9, 0.8-1.10.8335Post-treatment (median, IQR)LD (cm)1.1, 0-1.91.0, 0-1.81.3, 0-1.90.6071FTV (cc)0.5, 0.1-1.80.3, 0.1-1.80.7, 0.3-1.80.2196SER0.9, 0.8-1.00.8, 0.8-1.00.9, 0.8-1.10.2321Percent reduction (%)LD44.6, 15.1-10079.6, 33.8-10033.8, 10.1-1000.0958FTV93, 72.5-97.495.8, 90.7-99.172.6, 43.1-94.5&amp;lt;0.0001SER8.5, -11.1-19.710.7, -6.0-21.81.9, -15.1-17.90.3041 Citation Format: Geraldine Tran, Ella Jones, Wen Li, Kelly Fahrner-Scott, David Newitt, Bonnie Joe, Laura Esserman, Nola Hylton, Rita Mukhtar. DCE-MRI derived imaging features for characterizing invasive lobular breast cancer and predicting recurrence-free survival after neoadjuvant therapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD6-08.

Association of variably methylated tumour DNA regions with overall survival for invasive lobular breast cancer

BackgroundTumour DNA methylation profiling has shown potential to refine disease subtyping and improve the diagnosis and prognosis prediction of breast cancer. However, limited data exist regarding invasive lobular breast cancer (ILBC). Here, we investigated the genome-wide variability of DNA methylation levels across ILBC tumours and assessed the association between methylation levels at the variably methylated regions and overall survival in women with ILBC.MethodsTumour-enriched DNA was prepared by macrodissecting formalin-fixed paraffin embedded (FFPE) tumour tissue from 130 ILBCs diagnosed in the participants of the Melbourne Collaborative Cohort Study (MCCS). Genome-wide tumour DNA methylation was measured using the HumanMethylation 450K (HM450K) BeadChip array. Variably methylated regions (VMRs) were identified using the DMRcate package in R. Cox proportional hazards regression models were used to assess the association between methylation levels at the ten most significant VMRs and overall survival. Gene set enrichment analyses were undertaken using the web-based tool Metaspace. Replication of the VMR and survival analysis findings was examined using data retrieved from The Cancer Genome Atlas (TCGA) for 168 ILBC cases. We also examined the correlation between methylation and gene expression for the ten VMRs of interest using TCGA data.ResultsWe identified 2771 VMRs (P < 10−8) in ILBC tumours. The ten most variably methylated clusters were predominantly located in the promoter region of the genes: ISM1, APC, TMEM101, ASCL2, NKX6, HIST3H2A/HIST3H2BB, HCG4P3, HES5, CELF2 and EFCAB4B. Higher methylation level at several of these VMRs showed an association with reduced overall survival in the MCCS. In TCGA, all associations were in the same direction, however stronger than in the MCCS. The pooled analysis of the MCCS and TCGA data showed that methylation at four of the ten genes was associated with reduced overall survival, independently of age and tumour stage; APC: Hazard Ratio (95% Confidence interval) per one-unit M-value increase: 1.18 (1.02–1.36), TMEM101: 1.23 (1.02–1.48), HCG4P3: 1.37 (1.05–1.79) and CELF2: 1.21 (1.02–1.43). A negative correlation was observed between methylation and gene expression for CELF2 (R = − 0.25, P = 0.001), but not for TMEM101 and APC.ConclusionsOur study identified regions showing greatest variability across the ILBC tumour genome and found methylation at several genes to potentially serve as a biomarker of survival for women with ILBC.

Single-Cell Transcriptomic Heterogeneity in Invasive Ductal and Lobular Breast Cancer Cells.

Invasive lobular breast carcinoma (ILC), one of the major breast cancer histologic subtypes, exhibits unique features compared with the well-studied ductal cancer subtype (IDC). The pathognomonic feature of ILC is loss of E-cadherin, mainly caused by inactivating mutations, but the contribution of this genetic alteration to ILC-specific molecular characteristics remains largely understudied. To profile these features transcriptionally, we conducted single-cell RNA sequencing on a panel of IDC and ILC cell lines, and an IDC cell line (T47D) with CRISPR-Cas9-mediated E-cadherin knockout (KO). Inspection of intracell line heterogeneity illustrated genetically and transcriptionally distinct subpopulations in multiple cell lines and highlighted rare populations of MCF7 cells highly expressing an apoptosis-related signature, positively correlated with a preadaptation signature to estrogen deprivation. Investigation of E-cadherin KO-induced alterations showed transcriptomic membranous systems remodeling, elevated resemblance to ILCs in regulon activation, and increased sensitivity to IFNγ-mediated growth inhibition via activation of IRF1. This study reveals single-cell transcriptional heterogeneity in breast cancer cell lines and provides a resource to identify drivers of cancer progression and drug resistance. SIGNIFICANCE: This study represents a key step towards understanding heterogeneity in cancer cell lines and the role of E-cadherin depletion in contributing to the molecular features of invasive lobular breast carcinoma.

The Clinical Impact of the Late Imaging with 18F-Fluorodeoxyglucose PET Texture Analysis in Invasive Lobular Breast Cancer

The Clinical Impact of the Late Imaging with 18F-Fluorodeoxyglucose PET Texture Analysis in Invasive Lobular Breast Cancer

E-cadherin to P-cadherin switching in lobular breast cancer with tubular elements

Loss of E-cadherin expression due to mutation of the CDH1 gene is a characteristic feature of invasive lobular breast cancer (ILBC). Beta-catenin, which binds to the cytoplasmic domain of E-cadherin, is simultaneously downregulated, reflecting disassembly of adherens junctions (AJs) and loss of cell adhesion. E-cadherin to P-cadherin expression switching can rescue AJs and cell adhesion. However, P-cadherin has not been implicated in ILBC, so far. We aimed to characterize 13 ILBCs with exceptional histomorphology, which we termed ILBCs with tubular elements. The CDH1 mutational status was determined by next generation sequencing and whole-genome copy number (CN) profiling. Expression of cadherins was assessed by immunohistochemistry. ILBCs with tubular elements were ER-positive (13/13) and HER2-negative (13/13) and harbored deleterious CDH1 mutations (11/13) accompanied by loss of heterozygosity due to deletion of chromosome 16q22.1 (9/11). E-cadherin expression was lost or reduced in noncohesive tumor cells and in admixed tubular elements (13/13). Beta-catenin expression was lost in noncohesive tumor cells, but was retained in tubular elements (11/13), indicating focal rescue of AJ formation. N-cadherin and R-cadherin were always negative (0/13). Strikingly, P-cadherin was commonly positive (12/13) and immunoreactivity was accentuated in tubular elements. Adjacent lobular carcinoma in situ (LCIS) was always P-cadherin-negative (0/7). In a reference cohort of LCIS specimens, P-cadherin was constantly not expressed (0/25). In a reference cohort of invasive mammary carcinomas, P-cadherin-positive cases (36/268, 13%) were associated with triple-negative nonlobular breast cancer (P < 0.001). Compared with ILBCs from the reference cohort, P-cadherin expression was more common in ILBCs with tubular elements (12/13 versus 7/84, P < 0.001). In summary, E-cadherin to P-cadherin switching occurs in a subset of ILBCs. P-cadherin is the molecular determinant of a mixed-appearing histomorphology in ILBCs with tubular elements.

1LBA - Differential impact of prognostic parameters in hormone receptor-positive lobular early breast cancer in the WSG PlanB trial

Background: Invasive lobular breast cancer is the second most common breast cancer (BC) subtype. Clinicopathological parameters associated with lobular BC and their prognostic implications are still controversial.

Significance of E-cadherin Gene Mutations in Patients With Hereditary Diffuse Gastric Cancer Syndrome: A Systematic Review.

Gastric cancer is the third-most fatal cancer in the world. Though over the years, we saw patients mostly with intestinal type accounting for the highest mortality rate, the recent rise of the diffuse form with germline E-cadherin (CDH1) mutations has added a whole new level of interest to study in detail about the association between CDH1 and diffuse gastric cancer (DGC). This introduced a set guideline formulated by Internal Gastric Cancer Linkage Consortium (IGCLC) for patients with family history of diffuse gastric cancer and invasive lobular breast cancer (ILBC). The analysis of this link was also important to set proper management protocol for patients who were CDH1 mutation carriers which now involves genetic counselling, endoscopic surveillance and screening and prophylactic total gastrectomy (PTG). The study was conducted in accordance to the ‘PRISMA guidelines for reporting systematic review and meta-analysis’. Peer-reviewed studies were included from the PubMed database and relevant articles were selected to be included in the study. Appropriate inclusion/exclusion criteria with free full text English articles were applied while selecting the articles. A total of 10 studies on review with different study populations showed that of the 42 patients who were diagnosed with diffuse gastric cancer, 88% of them showed a positive germline E-cadherin gene mutation and 100% of the CDH1 mutation carriers showed microscopic changes of signet ring cell adenocarcinoma of the stomach. The beneficial effects of PTG with better survival rates and low mortality rates has outweighed other treatment modalities. Laparoscopic approach has proved to be more useful and a safer approach for gastrectomy surgeries with better post-operative management. The need for prophylactic mastectomy is also increased in the recent times and thus this requires a new set of guidelines for ILBC patients with hereditary diffuse gastric cancer (HDGC) syndrome.

Prognostic Value of EndoPredict in Women with Hormone Receptor-Positive, HER2-Negative Invasive Lobular Breast Cancer.

Invasive lobular carcinoma (ILC) accounts for approximately 5%-15% of all invasive breast cancer cases. Most of the correlations between multigene assays and patient outcome were derived from studies based on patients with invasive ductal carcinoma (IDC) or without distinction between the subtypes. Here, we investigate the prognostic value of EndoPredict (EPclin) in a large cohort of ILCs pooled from three phase III randomized trials (ABCSG-6, ABCSG-8, TransATAC). The primary objective of this analysis was to determine the prognostic value of EPclin for distant recurrence (DR) in years 0-10 in postmenopausal women with ILC. The primary outcome was DR. 470 women (17.9%) presented with ILC, 1,944 (73.9%) with IDC, and 216 (8.2%) with other histologic types. EPclin was highly prognostic in women with ILC [HR = 3.32 (2.54-4.34)] and provided more prognostic value than the Clinical Treatment Score [CTS; HR = 2.17 (1.73-2.72)]. 63.4% of women were categorized into the low EPclin risk group and they had a 10-year DR of 4.8% (2.7-8.4) compared with 36.6% of women in the high-risk group with a 10-year DR risk of 26.6% (20.0-35.0). EPclin also provided highly prognostic information in women with node-negative disease [HR = 2.56 (1.63-4.02)] and node-positive disease [HR = 3.70 (2.49-5.50)]. EPclin provided highly significant prognostic value and significant risk stratification for women with ILC. Ten-year DR risk in the EPclin low-risk groups were similar between ILC and IDC. Our results show that EPclin is informative in women with ILC and suggest that it is equally valid in both histologic subtypes.

Contribution of Fluorodeoxyglucose-Positron Emission Tomography Late Imaging to Diagnosis and Correlation with Histopathology in Invasive Lobular Breast Cancer

Contribution of Fluorodeoxyglucose-Positron Emission Tomography Late Imaging to Diagnosis and Correlation with Histopathology in Invasive Lobular Breast Cancer

MRI background parenchymal enhancement, fibroglandular tissue, and mammographic breast density in patients with invasive lobular breast cancer on adjuvant endocrine hormonal treatment: associations with survival

BackgroundTo investigate if baseline and/or changes in contralateral background parenchymal enhancement (BPE) and fibroglandular tissue (FGT) measured on magnetic resonance imaging (MRI) and mammographic breast density (MD) can be used as imaging biomarkers for overall and recurrence-free survival in patients with invasive lobular carcinomas (ILCs) undergoing adjuvant endocrine treatment.MethodsWomen who fulfilled the following inclusion criteria were included in this retrospective HIPAA-compliant IRB-approved study: unilateral ILC, pre-treatment breast MRI and/or mammography from 2000 to 2010, adjuvant endocrine treatment, follow-up MRI, and/or mammography 1–2 years after treatment onset. BPE, FGT, and mammographic MD of the contralateral breast were independently graded by four dedicated breast radiologists according to BI-RADS. Associations between the baseline levels and change in levels of BPE, FGT, and MD with overall survival and recurrence-free survival were assessed using Kaplan–Meier survival curves and Cox regression analysis.ResultsTwo hundred ninety-eight patients (average age = 54.1 years, range = 31–79) fulfilled the inclusion criteria. The average follow-up duration was 11.8 years (range = 2–19). Baseline and change in levels of BPE, FGT, and MD were not significantly associated with recurrence-free or overall survival. Recurrence-free and overall survival were affected by histological subtype (p < 0.0001), number of metastatic axillary lymph nodes (p < 0.0001), age (p = 0.01), and adjuvant endocrine treatment duration (p < 0.001).ConclusionsQualitative evaluation of BPE, FGT, and mammographic MD changes cannot predict which patients are more likely to benefit from adjuvant endocrine treatment.