Collective Wisdom: Lobular Carcinoma of the Breast

Nomograms to predict the long-term prognosis for non-metastatic invasive lobular breast carcinoma: a population-based study

Invasive lobular breast carcinoma (ILC) is one potential subset that "clinicopathologic features" can conflict with "long-term outcome" and the optimal management strategy is unknown in such discordant situations. The present study aims to predict the long-term, overall survival (OS) and cancer-specific survival (CSS) of ILC. The clinical information of patients with non-metastatic ILC was retrieved from the Surveillance, Epidemiology, and End Results (SEER) database between 2004 and 2020. A total of 31451 patients were enrolled and divided into the training cohort (n=22,017) and validation cohort (n=9434). The last follow-up was December, 31, 2020 and the median follow-up period was 99 months (1-203). Age, marriage, estrogen (ER) status, progesterone (PR) status, grade, tumor size, lymph node ratio (LNR) and combined summary (CS) stage were prognostic factors for both OS and CSS of ILC, whereas chemotherapy and radiation were independent protect factors for OS. The nomograms exhibited satisfactory discriminative ability. For the training and validation cohorts, the C-index of the OS nomogram was 0.765 (95% CI 0.762-0.768) and 0.757 (95% CI 0.747-0.767), and the C-index of the CSS nomogram were 0.812 (95% CI 0.804-0.820) and 0.813 (95% CI 0.799-0.827), respectively. Additionally, decision curve analysis (DCA) demonstrated that the nomograms had superior predictive performance than traditional American Joint Committee on Cancer (AJCC) TNM stage. The novel nomograms to predict long-term prognosis based on LNR are reliable tools to predict survival, which may assist clinicians in identifying high-risk patients and devising individual treatments for patients with ILC. Our findings should aid public health prevention strategies to reduce cancer burden. We provide two R/Shiny apps ( https://ilc-survival2024.shinyapps.io/osnomogram/ ; https://ilc-survival2024.shinyapps.io/cssnomogram/ ) to visualize findings.

E-cadherin staining in the diagnosis of lobular versus ductal neoplasms of the breast: the emperor has no clothes

Categorizing breast neoplasia as ductal or lobular is a daily exercise that relies on a combination of histologic and immunohistochemical tools. The historically robust link between loss of the E-cadherin molecule and lobular neoplasia has rendered staining for E-cadherin by immunohistochemistry a staple of this diagnostic process. Unfortunately, discordances between E-cadherin expression and histomorphology, and variations in E-cadherin staining patterns and intensities abound in clinical practice, but are often neglected in favour of a binary interpretation of the E-cadherin result. In this article, we highlight the complexities of E-cadherin expression through a review of the E-cadherin protein and its associated gene (CDH1), the mechanisms leading to aberrant/absent E-cadherin expression, and the implications of these factors on the reliability of the E-cadherin immunohistochemical stain in the classification of ductal versus lobular mammary neoplasia.

Variation in surgical treatment by body mass index in patients with invasive lobular carcinoma of the breast

PURPOSE

Patients with invasive lobular carcinoma (ILC) face high rates of positive margins and completion mastectomy, which can be improved with the use of specific techniques, such as oncoplastic surgery. However, prior studies have shown that type of breast cancer surgery performed is also associated with patient factors such as elevated body mass index (BMI). Thus, this study investigates whether BMI impacts the type of surgical interventions in patients with ILC.

METHODS

A retrospective analysis of 705 patients with stage I-III ILC from an institutional database was conducted. Patients were stratified by BMI (underweight, normal weight, overweight, obese). Pearson's Chi-square, ANOVA, and multivariable logistic regression were used to evaluate the relationship between BMI and surgical procedures.

RESULTS

Breast-conserving surgery (BCS) was the initial operation in 60% of patients, with no significant difference by BMI. Among those undergoing BCS, patients with obese BMI were significantly more likely to undergo oncoplastic surgery (46.9% vs. 7.7%, 37.3%, and 33.6% for underweight, normal, and overweight, respectively, p = 0.032). Obese BMI patients undergoing mastectomy were less likely to have reconstruction compared to those with underweight, normal weight, and overweight BMI (44.2% vs. 50%, 71.1%, and 64.1%, p = 0.002).

CONCLUSION

Overweight/obese BMI patients with ILC underwent different surgical interventions compared to those with lower BMI. While initial BCS rates were similar, overweight/obese patients had higher oncoplastic surgery rates in BCS and lower reconstruction rates in mastectomy. Further research is needed to understand BMI's impact on surgical decisions and outcomes in ILC.

Spatial molecular profiling of mixed invasive ductal and lobular breast cancers reveals heterogeneity in intrinsic molecular subtypes, oncogenic signatures, and mutations

Mixed invasive ductal and lobular carcinoma (MDLC) is a rare histologic subtype of breast cancer displaying both E-cadherin positive ductal and E-cadherin negative lobular morphologies within the same tumor, posing challenges with regard to anticipated clinical management. It remains unclear whether these distinct morphologies also have distinct biology and risk of recurrence. Our spatially resolved transcriptomic, genomic, and single-cell profiling revealed clinically significant differences between ductal and lobular tumor regions including distinct intrinsic subtype heterogeneity - e.g., MDLC with triple-negative breast cancer (TNBC) or basal ductal and estrogen receptor positive (ER+) luminal lobular regions, distinct enrichment of cell cycle arrest/senescence and oncogenic (ER and MYC) signatures, genetic and epigenetic CDH1 inactivation in lobular but not ductal regions, and single-cell ductal and lobular subpopulations with unique oncogenic signatures further highlighting intraregional heterogeneity. Altogether, we demonstrated that the intratumoral morphological/histological heterogeneity within MDLC is underpinned by intrinsic subtype and oncogenic heterogeneity which may result in prognostic uncertainty and therapeutic dilemma.

Effect of histological breast cancer subtypes invasive lobular versus non-special type on survival in early intermediate-to-high-risk breast carcinoma: results from the SUCCESS trials

BACKGROUND

Invasive lobular breast carcinomas (ILC) have different histological features compared to non-special type carcinomas (NST), but the effect of histological subtypes on survival is controversial. In this study, we compared clinicopathological characteristics and outcomes between ILC and NST based on a large pooled data set from three adjuvant breast cancer trials (SUCCESS A, B, and C) and investigated a potential differential effect of recurrence risk related to nodal stage on survival.

METHODS

From 2005 to 2017, the large randomized controlled SUCCESS A, B, and C trials enrolled 8190 patients with primary, intermediate-to-high-risk breast carcinoma. All patients received adjuvant chemotherapy, and endocrine and/or HER2-targeted treatment was given where appropriate. Survival outcomes in terms of disease-free survival (DFS), overall survival (OS), breast cancer-specific survival (BCSS), and distant disease-free survival (DDFS) were estimated using the Kaplan-Meier method and analyzed using log-rank tests as well as univariable and adjusted multivariable Cox regression models.

RESULTS

In the SUCCESS trials, 6284 patients had NST and 952 had ILC. The median follow-up time was 64 months. ILC patients were older, more likely to receive mastectomy, and more likely to have larger tumor sizes, lymph node infiltration, hormone receptor-positive, HER2neu-negative, and luminal A-like tumors than NST patients. In the overall cohort, no significant differences between ILC and NST were detectable regarding the four survival endpoints, with hazard ratios obtained in adjusted multivariable cox regressions of 0.96 (95% CI 0.77-1.21, p = 0.743) for DFS, 1.13 (95% CI 0.85-1.50, p = 0.414) for OS, 1.21 (95% CI 0.89-1.66, p = 0.229) for BCSS, and 0.95 (95% CI 0.73-1.24, p = 0.689) for DDFS. However, a differential effect of nodal stage on survival was observed, with better survival for ILC patients with pN0/pN1 tumors and worse survival for ILC patients with pN2/pN3 tumors compared to NST patients.

CONCLUSIONS

Our results revealed that ILC was associated with worse survival compared to NST for patients at high risk of recurrence due to advanced lymph node infiltration. These findings should be taken into account for treatment decisions and monitoring.

Lobular Carcinoma of the Breast: A Comprehensive Review with Translational Insights

The second most common breast carcinoma, invasive lobular carcinoma, accounts for approximately 15% of tumors of breast origin. Its incidence has increased in recent times due in part to hormone replacement therapy and improvement in diagnostic modalities. Although believed to arise from the same cell type as their ductal counterpart, invasive lobular carcinomas (ILCs) are a distinct entity with different regulating genetic pathways, characteristic histologies, and different biology. The features most unique to lobular carcinomas include loss of E-Cadherin leading to discohesion and formation of a characteristic single file pattern on histology. Because most of these tumors exhibit estrogen receptor positivity and Her2 neu negativity, endocrine therapy has predominated to treat these tumors. However novel treatments like CDK4/6 inhibitors have shown importance and antibody drug conjugates may be instrumental considering newer categories of Her 2 Low breast tumors. In this narrative review, we explore multiple pathological aspects and translational features of this unique entity. In addition, due to advancement in technologies like spatial transcriptomics and other hi-plex technologies, we have tried to enlist upon the characteristics of the tumor microenvironment and the latest associated findings to better understand the new prospective therapeutic options in the current era of personalized treatment.

Association of body mass index with clinicopathological features and survival in patients with primary invasive lobular breast cancer

PURPOSE

Invasive lobular carcinoma (ILC) represents up to 15% of all breast carcinomas. While the proportion of women with overweight and obesity increases globally, the impact of body mass index (BMI) at primary diagnosis on clinicopathological features of ILC and the prognosis of the patients has not been investigated yet.

PATIENTS AND METHODS

We performed a multicentric retrospective study including patients diagnosed with non-metastatic pure ILC. The association of BMI at diagnosis with clinicopathological variables was assessed using linear or multinomial logistic regression. Univariable and multivariable survival analyses were performed to evaluate the association of BMI with disease-free survival (DFS), distant recurrence-free survival (DRFS), and overall survival (OS).

RESULTS

The data of 2856 patients with ILC and available BMI at diagnosis were collected, of which 2570/2856 (90.0%) had oestrogen receptor (ER)-positive and human epidermal growth factor receptor (HER2) not amplified/overexpressed (ER+/HER2-) ILC. Of these 2570 patients, 80 were underweight (3.1%), 1410 were lean (54.9%), 712 were overweight (27.7%), and 368 were obese (14.3%). Older age at diagnosis, a higher tumour grade, a larger tumour size, a nodal involvement, and multifocality were associated with a higher BMI. In univariable models, higher BMI was associated with worse outcomes for all end-points (DFS: hazard ratio (HR) 1.21, 95CI 1.12-1.31, p value<0.01; DRFS: HR 1.25, 95CI 1.12-1.40, p value<0.01; OS: HR 1.25, 95CI 1.13-1.37, p value<0.01). This association was not statistically significant in multivariable analyses (DFS: HR 1.09, 95CI 0.99-1.20, p value 0.08; DRFS: HR 1.03, 95CI 0.89-1.20, p value 0.67; OS: HR 1.11, 95CI 0.99-1.24, p value 0.08), whereas grade, tumour size, and nodal involvement were still prognostic for all end-points.

CONCLUSION

Worse prognostic factors such as higher grade, larger tumour size, and nodal involvement are associated with higher BMI in ER+/HER2- ILC, while there was no statistical evidence for an independent prognostic role for BMI. Therefore, we hypothesise that the effect of BMI on survival could be mediated through its association with these clinicopathological variables.

PD-L1 blockade in combination with carboplatin as immune induction in metastatic lobular breast cancer: the GELATO trial

Invasive lobular breast cancer (ILC) is the second most common histological breast cancer subtype, but ILC-specific trials are lacking. Translational research revealed an immune-related ILC subset, and in mouse ILC models, synergy between immune checkpoint blockade and platinum was observed. In the phase II GELATO trial ( NCT03147040 ), patients with metastatic ILC were treated with weekly carboplatin (area under the curve 1.5 mg ml-1 min-1) as immune induction for 12 weeks and atezolizumab (PD-L1 blockade; triweekly) from the third week until progression. Four of 23 evaluable patients had a partial response (17%), and 2 had stable disease, resulting in a clinical benefit rate of 26%. From these six patients, four had triple-negative ILC (TN-ILC). We observed higher CD8+ T cell infiltration, immune checkpoint expression and exhausted T cells after treatment. With this GELATO trial, we show that ILC-specific clinical trials are feasible and demonstrate promising antitumor activity of atezolizumab with carboplatin, particularly for TN-ILC, and provide insights for the design of highly needed ILC-specific trials.

Evolution of biological features of invasive lobular breast cancer: comparison between primary tumor and metastases

BACKGROUND

Invasive lobular carcinoma (ILC) has unique clinical-biological features. Phenotypical differences between primary tumours (PTs) and metastases (M) have been described for invasive ductal carcinoma, but data on ILC are limited.

METHODS

We retrospectively analysed patients with recurrent ILC from our institution from 2013 to 2020. We evaluated the discordance of the oestrogen receptor (ER), progesterone receptor (PgR) and HER2 between PT and M, to understand prognostic and therapeutic implications.

RESULTS

Thirteen percent (n = 91) of all patients had ILC. We observed 15%, 44% and 5% of ER, PgR and HER2 status discordance between PT and M. ER/PgR discordance was related to receptor loss and HER2 mainly due to gain. PT presented a luminal-like phenotype (93%); 6% and 1% were triple-negative (TNBC) and HER2-positive. In M, there was an increase in TNBC (16%) and HER2-positive (5%). Metastasis-free survival and overall survival (OS) were different according to clinical phenotype, with poorer prognosis for HER2+ and TNBC (p < 0.001); OS after metastatic progression did not differ across phenotypes (p = 0.079). In luminal-like ILC (n = 85) at diagnosis, we found that OS after relapse was poorer in patients experiencing a phenotype switch to TNBC but improved in patients with HER2 gain (p = 0.0028). Poorer survival was reported in patients with a PgR and/or ER expression loss of ≥25%. There was HER2-low enrichment in M1 (from 37% to 58%): this change was not associated with OS (p > 0.05).

CONCLUSION

Our results suggest that phenotype switch after metastatic progression may be associated with patients' outcomes. Tumour biopsy in recurrent ILC could drive treatment decision-making, with prognostic implications.

Transversal Perspectives of Integrative Oncology Care in Gastric and Lobular Breast Cancer

The occurrence of gastric cancer has been associated with an increased risk of lobular breast tumors in a subset of patients harboring selected germline mutations. Among all, the germline alteration of the gene coding for E-Cadherin (CDH1) was associated with an increased risk of gastric cancer diffuse-histotype and lobular breast cancer. However, the risk assessment of breast neoplasms and the role of multiple prophylactic procedures in these patients has never been systematically addressed. In addition, the performance of the common screening procedures for lobular breast cancer like mammography is suboptimal. Therefore, recalling the need for a better articulation of the patient-centered strategies of surveillance for individuals with germline CDH1 and other similar alterations, to offer comprehensive approaches for prevention, early diagnosis, and treatment. Accordingly, this chapter aims to discuss the value and the role of integrated oncological care in the era of oncology sub-specializations. Additionally, it sheds light on how the harmonization across the health providers can enhance patient care in this setting.

Current and future diagnostic and treatment strategies for patients with invasive lobular breast cancer

BACKGROUND

Invasive lobular breast cancer (ILC) is the second most common type of breast cancer after invasive breast cancer of no special type (NST), representing up to 15% of all breast cancers.

DESIGN

Latest data on ILC are presented, focusing on diagnosis, molecular make-up according to the European Society for Medical Oncology Scale for Clinical Actionability of molecular Targets (ESCAT) guidelines, treatment in the early and metastatic setting and ILC-focused clinical trials.

RESULTS

At the imaging level, magnetic resonance imaging-based and novel positron emission tomography/computed tomography-based techniques can overcome the limitations of currently used imaging techniques for diagnosing ILC. At the pathology level, E-cadherin immunohistochemistry could help improving inter-pathologist agreement. The majority of patients with ILC do not seem to benefit as much from (neo-)adjuvant chemotherapy as patients with NST, although chemotherapy might be required in a subset of high-risk patients. No differences in treatment efficacy are seen for anti-human epidermal growth factor receptor 2 (HER2) therapies in the adjuvant setting and cyclin-dependent kinases 4 and 6 inhibitors in the metastatic setting. The clinical utility of the commercially available prognostic gene expression-based tests is unclear for patients with ILC. Several ESCAT alterations differ in frequency between ILC and NST. Germline BRCA1 and PALB2 alterations are less frequent in patients with ILC, while germline CDH1 (gene coding for E-cadherin) alterations are more frequent in patients with ILC. Somatic HER2 mutations are more frequent in ILC, especially in metastases (15% ILC versus 5% NST). A high tumour mutational burden, relevant for immune checkpoint inhibition, is more frequent in ILC metastases (16%) than in NST metastases (5%). Tumours with somatic inactivating CDH1 mutations may be vulnerable for treatment with ROS1 inhibitors, a concept currently investigated in early and metastatic ILC.

CONCLUSION

ILC is a unique malignancy based on its pathological and biological features leading to differences in diagnosis as well as in treatment response, resistance and targets as compared to NST.

The 21-Gene Recurrence Score in Clinically High-Risk Lobular and Ductal Breast Cancer: A National Cancer Database Study

Objective

The aim of this study was to evaluate whether patients with invasive lobular carcinoma (ILC) are more likely to have discordant clinical and genomic risk than those with invasive ductal carcinoma (IDC) when using the 21-gene recurrence score (RS), and to assess overall survival outcomes of patients with 1–3 positive nodes and RS ≤25 with and without chemotherapy, stratified by histology.

Methods

We performed a cohort study using the National Cancer Database and included patients with hormone receptor-positive, HER2-negative, stage I–III invasive breast cancer who underwent 21-gene RS testing. Our primary outcome was rate of discordant clinical and genomic risk status by histologic subtype. Propensity score matching was used to compare 60-month overall survival in individuals with 1–3 positive nodes and RS ≤25 who did and did not receive chemotherapy.

Results

Overall, 186,867 patients were included in our analysis, including 37,685 (20.2%) patients with ILC. There was a significantly higher rate of discordant clinical and genomic risk in patients with ILC compared with IDC. Among patients with 1–3 positive nodes and RS ≤25, there was no significant difference in survival between those who did and did not receive chemotherapy in the IDC or ILC cohorts. Unadjusted exploratory analyses of patients under age 50 years with 1–3 positive nodes and RS ≤25 showed improved overall survival in IDC patients who received chemotherapy, but not among those with ILC.

Conclusion

Our findings highlight the importance of lobular-specific tools for stratifying clinical and genomic risk, as well as the need for histologic subtype-specific analyses in randomized trials.

Supplementary Information

The online version contains supplementary material available at 10.1245/s10434-022-12065-3.

Invasive Lobular Carcinoma of the Breast With Rectal Metastasis: A Rare Case Report

The rectum is a relatively unusual site for metastasis from invasive lobular carcinoma (ILC) of the breast, and it carries dangers such as perforation and blockage. We reported a case of a 47-year-old female patient complaining of breast ILC for one year. Recently, the patient complained of abdominal distention, mild generalized abdominal pain, and weight loss. The abdominal ultrasound (US) showed moderate ascites without hepatomegaly, and ascitic tapping was positive for malignant cells. Lower colonoscopy showed a congested mass of 8 cm, and anal verge biopsy showed colonic mucosa laminal propria infiltrated with atypical cells and adenocarcinoma metastatic from the breast. In a patient with breast cancer, particularly ILC, who has developed new gastrointestinal tract (GIT) symptoms, there is significantly a high chance of rectal metastatic illness. Early detection is critical for successful treatment.

The incidence of discordant clinical and genomic risk in patients with invasive lobular or ductal carcinoma of the breast: a National Cancer Database Study

When molecular testing classifies breast tumors as low risk but clinical risk is high, the optimal management strategy is unknown. One group of patients who may be more likely to have such discordant risk are those with invasive lobular carcinoma of the breast. We sought to examine whether patients with invasive lobular carcinoma are more likely to have clinical high/genomic low-risk tumors compared to those with invasive ductal carcinoma, and to evaluate the impact on receipt of chemotherapy and overall survival. We conducted a cohort study using the National Cancer Database from 2010–2016. Patients with hormone receptor positive, HER2 negative, stage I-III breast cancer who underwent 70-gene signature testing were included. We evaluated the proportion of patients with discordant clinical and genomic risk by histology using Kaplan-Meier plots, log-rank tests, and Cox proportional hazards models with and without propensity score matching. A total of 7399 patients (1497 with invasive lobular carcinoma [20.2%]) were identified. Patients with invasive lobular carcinoma were significantly more likely to fall into a discordant risk category compared to those with invasive ductal carcinoma (46.8% versus 37.1%, p < 0.001), especially in the clinical high/genomic low risk subgroup (35.6% versus 19.2%, p < 0.001). In unadjusted analysis of the clinical high/genomic low-risk cohort who received chemotherapy, invasive ductal carcinoma patients had significantly improved overall survival compared to those with invasive lobular carcinoma (p = 0.02). These findings suggest that current tools for stratifying clinical and genomic risk could be improved for those with invasive lobular carcinoma to better tailor treatment selection.

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

Purpose

We investigated the relationship between obesity, menopausal status, and invasive lobular carcinoma (ILC), the second most common histological subtype of breast cancer. Specifically, we evaluated the association between body mass index (BMI), metabolic syndrome, the 21-gene Oncotype Recurrence Score (Oncotype RS), and pathological features in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor-2-negative ILC.

Methods

The study cohort included 491 patients from a prospectively maintained institutional database consisting of patients with stage I-III, HR-positive ILC who underwent surgical treatment between 1996 and 2019.

Results

Contrary to our expectations, we found that lower BMI was significantly associated with having higher Oncotype RS (18.9% versus 4.8%, p = 0.028) in post-menopausal patients, but was not related to tumor characteristics in pre-menopausal patients. Multivariate network analyses suggested a strong relationship between post-menopausal status itself and tumor characteristics, with lesser influence of BMI.

Conclusion

These findings provide further insight into the recently appreciated heterogeneity within ILC and support the need for further investigation into the drivers of this disease and tailored treatment strategies.

Atlas of Lobular Breast Cancer Models: Challenges and Strategic Directions

Invasive lobular carcinoma (ILC) accounts for up to 15% of all breast cancer (BC) cases and responds well to endocrine treatment when estrogen receptor α-positive (ER+) yet differs in many biological aspects from other ER+ BC subtypes. Up to 30% of patients with ILC will develop late-onset metastatic disease up to ten years after initial tumor diagnosis and may experience failure of systemic therapy. Unfortunately, preclinical models to study ILC progression and predict the efficacy of novel therapeutics are scarce. Here, we review the current advances in ILC modeling, including cell lines and organotypic models, genetically engineered mouse models, and patient-derived xenografts. We also underscore four critical challenges that can be addressed using ILC models: drug resistance, lobular tumor microenvironment, tumor dormancy, and metastasis. Finally, we highlight the advantages of shared experimental ILC resources and provide essential considerations from the perspective of the European Lobular Breast Cancer Consortium (ELBCC), which is devoted to better understanding and translating the molecular cues that underpin ILC to clinical diagnosis and intervention. This review will guide investigators who are considering the implementation of ILC models in their research programs.

Decreased enrollment in breast cancer trials by histologic subtype: does invasive lobular carcinoma resist RECIST?

Enrollment in metastatic breast cancer trials usually requires measurable lesions, but patients with invasive lobular carcinoma (ILC) tend to form diffuse disease. We found that the proportion of patients with metastatic ILC enrolled in clinical trials at our institution was significantly lower than that of patients with invasive ductal carcinoma (IDC). Possible links between requiring measurable disease and decreased enrollment of ILC patients require further study to ensure equitable trial access.

Prognostic Utility of Breast Cancer Index to Stratify Distant Recurrence Risk in Invasive Lobular Carcinoma

PURPOSE

The prognostic utility of Breast Cancer Index (BCI) for risk assessment of overall (0-10 years), early (0-5 years), and late (5-10 years) distant recurrence (DR) in hormone receptor-positive (HR+) invasive lobular carcinoma (ILC) was evaluated.

EXPERIMENTAL DESIGN

BCI gene expression analysis was performed blinded to clinical outcome utilizing tumor specimens from patients with HR+ ILC from a multi-institutional cohort. The primary endpoint was time to DR. Kaplan-Meier analyses of overall, early, and late DR risk were performed, and statistical significance was evaluated by log-rank test and Cox proportional hazards regression. The prognostic contribution of BCI in addition to clinicopathologic factors was evaluated by likelihood ratio analysis.

RESULTS

Analysis of 307 patients (99% ER+, 53% T1, 42% N+, 70% grade II) showed significant differences in DR over 10 years based on BCI risk categories. BCI low- and intermediate-risk patients demonstrated similar DR rates of 7.6% and 8.0%, respectively, compared with 27.0% for BCI high-risk patients. BCI was a significant independent prognostic factor for overall 10-year DR [HR = 4.09; 95% confidence interval (CI), 2.00-8.34; P = 0.0001] as well as for both early (HR = 8.19; 95% CI, 1.85-36.30; P = 0.0042) and late (HR = 3.04; 95% CI, 1.32-7.00; P = 0.0224) DR. In multivariate analysis, BCI remained the only statistically significant prognostic factor for DR (HR = 3.49; 95% CI, 1.28-9.54; P = 0.0150).

CONCLUSIONS

BCI is an independent prognostic factor for ILC and significantly stratified patients for cumulative risk of 10-year, early, and late DR. BCI added prognostic value beyond clinicopathologic characteristics in this distinct subtype of breast cancer.

Invasive Lobular Breast Cancer: Data to Support Surgical Decision Making

BACKGROUND

Invasive lobular carcinoma (ILC) is thought be a unique entity with higher rates of multifocal/multicentric and bilateral disease. This study aimed to evaluate the true extent of the disease, risk of bilaterality, lymph node involvement, and impact of preoperative imaging to help guide surgical decision making.

METHODS

A retrospective analysis identified patients treated for ILC between 2004 and 2017. Clinical staging and pathologic results were compared. Follow-up details including local recurrence, contralateral breast cancer (CBC), and survival outcomes were evaluated.

RESULTS

The study identified 692 patients with ILC, including 43 patients (6%) with a diagnosis of CBC and 232 patients (33%) with a diagnosis of multifocal/multicentric disease at presentation. Preoperative magnetic resonance imaging (MRI) led to an identification of additional disease in 20% of the patients. Preoperative MRI resulted in a more accurate prediction of tumor size staging but did not improve the discordance between clinical and pathologic nodal staging. Overall, the rate of imaging occult lymph node disease was 24%. At the 6-year follow-up evaluation, a local recurrence had developed in 2.3%, a CBC in 2.3, and a distant metastasis in 9.4% of the patients. The overall survival rate was 96% at 3 years and 91% at 5 years.

CONCLUSIONS

Invasive lobular carcinoma is a distinct subset of cancer that poses a diagnostic staging challenge. The results of this study favor MRI for accurate tumor staging and for improving detection of multicentricity and bilaterality. However, clinicians should be aware of the higher likelihood of occult lymph node involvement with ILC and subsequent early metastasis.

Positive margins after mastectomy in patients with invasive lobular carcinoma of the breast: Incidence and management strategies

BACKGROUND

Surgical treatment of invasive lobular carcinoma (ILC) is challenging due to its diffuse growth pattern, and the positive margin rate after mastectomy is poorly described.

METHODS

We retrospectively determined the positive margin rate in those with stage I-III ILC undergoing mastectomy. We evaluated the relationship between management strategy and recurrence free survival (RFS).

RESULTS

In 357 patients, the positive margin rate was 10.6% overall and 18.7% in those with T3 tumors. Having a positive margin was associated with significantly shorter RFS on multivariate analysis (p = 0.01). Undergoing additional local treatment (radiation or re-excision) for a positive margin was significantly associated with improved RFS (p = 0.004). Older women with positive margins were significantly less likely to undergo additional local therapy.

CONCLUSIONS

Even mastectomy fails to clear margins in a high proportion of patients with large ILC tumors, a finding which may warrant testing neoadjuvant strategies even prior to planned mastectomy.

Accuracy of breast MRI in evaluating nodal status after neoadjuvant therapy in invasive lobular carcinoma

Neoadjuvant therapy in breast cancer can downstage axillary lymph nodes and reduce extent of axillary surgery. As such, accurate determination of nodal status after neoadjuvant therapy and before surgery impacts surgical management. There are scarce data on the diagnostic accuracy of breast magnetic resonance imaging (MRI) for nodal evaluation after neoadjuvant therapy in patients with invasive lobular carcinoma (ILC), a diffusely growing tumor type. We retrospectively analyzed patients with stage 1–3 ILC who underwent pre-operative breast MRI after either neoadjuvant chemotherapy or endocrine therapy at our institution between 2006 and 2019. Two breast radiologists reviewed MRIs and evaluated axillary nodes for suspicious features. All patients underwent either sentinel node biopsy or axillary dissection. We evaluated sensitivity, specificity, negative and positive predictive values, and overall accuracy of the post-treatment breast MRI in predicting pathologic nodal status. Of 79 patients, 58.2% received neoadjuvant chemotherapy and 41.8% neoadjuvant endocrine therapy. The sensitivity and negative predictive value of MRI were significantly higher in the neoadjuvant endocrine therapy cohort than in the neoadjuvant chemotherapy cohort (66.7 vs. 37.9%, p = 0.012 and 70.6 vs. 40%, p = 0.007, respectively), while overall accuracy was similar. Upstaging from clinically node negative to pathologically node positive occurred in 28.0 and 41.7%, respectively. In clinically node positive patients, those with an abnormal post-treatment MRI had a significantly higher proportion of patients with ≥4 positive nodes on pathology compared to those with a normal MRI (61.1 versus 16.7%, p = 0.034). Overall, accuracy of breast MRI for predicting nodal status after neoadjuvant therapy in ILC was low in both chemotherapy and endocrine therapy cohorts. However, post-treatment breast MRI may help identify patients with a high burden of nodal disease (≥4 positive nodes), which could impact pre-operative systemic therapy decisions. Further studies are needed to assess other imaging modalities to evaluate for nodal disease following neoadjuvant therapy and to improve clinical staging in patients with ILC.

Lobular Breast Cancer: A Review

Invasive lobular carcinoma accounts for 5%-15% of all invasive breast cancers, with a marked increase in incidence rates over the past two decades. Distinctive biological hallmarks of invasive lobular carcinoma include the loss of cell adhesion molecule E-cadherin leading to cells with a discohesive morphology, proliferating into single-file strands and estrogen receptor positivity. These key molecular features can make diagnosis difficult, as invasive lobular carcinoma is challenging to detect both physically and with current standard imaging. Treatment of invasive lobular carcinoma strongly favors endocrine therapy due to low chemosensitivity and lower rates of pathological response as a result. This review will summarize the distinct biological and molecular features of invasive lobular carcinoma, focusing on the diagnostic challenges faced and the subsequent surgical and medical management strategies. Prospective therapeutic options will also be explored, highlighting how furthering our understanding of the unique biology of lobular breast carcinoma is essential in guiding and informing the treatment of patients in the future.

Oncological Outcomes of Total Skin-Sparing Mastectomy for Invasive Lobular Carcinoma of the Breast: A 20-Year Institutional Experience

BACKGROUND

Although rates of total skin-sparing (nipple-sparing) mastectomies are increasing, the oncologic safety of this procedure has not been evaluated in invasive lobular carcinoma (ILC). ILC is the second most common type of breast cancer, and its diffuse growth pattern and high positive margin rates potentially increase the risk of poor outcomes from less extensive surgical resection.

METHODS

We compared time to local recurrence and positive margin rates in a cohort of 300 patients with ILC undergoing either total skin-sparing mastectomy (TSSM), skin-sparing mastectomy, or simple mastectomy between the years 2000-2020. Data were obtained from a prospectively maintained institutional database and were analyzed by using univariate statistics, the log-rank test, and multivariate Cox proportional hazards models.

RESULTS

Of 300 cases, mastectomy type was TSSM in 119 (39.7%), skin-sparing mastectomy in 52 (17.3%), and simple mastectomy in 129 (43%). The rate of TSSM increased significantly with time (p < 0.001) and was associated with younger age at diagnosis (p = 0.0007). There was no difference in time to local recurrence on univariate and multivariate analysis, nor difference in positive margin rates by mastectomy type. Factors significantly associated with shorter local recurrence-free survival were higher tumor stage and tumor grade.

CONCLUSIONS

TSSM can be safely offered to patients with ILC, despite the diffuse growth pattern seen in this tumor type.

Breast conservation therapy versus mastectomy in the surgical management of invasive lobular carcinoma measuring 4 cm or greater

BACKGROUND

The safety of breast conservation therapy (BCT) has not been demonstrated in large ILC tumors, potentially contributing to the higher mastectomy rates seen in ILC.

METHODS

We queried a prospectively maintained database to identify patients with ILC measuring ≥4 cm and evaluated difference in recurrence free survival (RFS) between those treated with BCT versus mastectomy using a multivariate model.

RESULTS

Of 180 patients, 30 (16.7%) underwent BCT and 150 (83.3%) underwent mastectomy. Patients undergoing mastectomy were younger (56.6 vs. 64.3 years, p = 0.003) and had larger tumors (7.2 vs. 5.4 cm, p < 0.001). While tumor size, nodal stage, receptor subtype, and margin status were significantly associated with RFS, there was no difference in RFS at 5 (p = 0.88) or 10 (p = 0.65) years for individuals undergoing BCT versus mastectomy.

CONCLUSIONS

For patients with ILC ≥4 cm, BCT provides similar tumor control as mastectomy, provided that negative margins are achieved.

Clinico-pathological characteristics and treatment outcome in invasive lobular carcinoma of the breast: An Indian experience

BACKGROUND

Invasive lobular carcinoma (ILC) is the second most common histologic subtype of breast cancer and accounts for 10%-15% of all breast cancers in the west. There is a scarcity of data on ILC from the Indian subcontinent. This report intends to present the patterns of care, survival outcomes, and prognostic factors of ILC treated in a tertiary care institute.

MATERIALS AND METHODS

This retrospective analysis included consecutive patients diagnosed with ILC and registered at our Institute between 2009 and 2016.

RESULTS

We included 97 patients with a median age of 53 years (range 28-80). American Joint Committee on Cancer (7^th edition) stage distribution was stage I-8.24%, stage II-45.36%, stage III- 34.10%, and stage IV-12.30%. Bilateral breast cancer was seen in 8 cases. Estrogen receptor, progesterone receptor, and HER 2/neu positivity was 90%, 85%, and 9%, respectively. Triple-negative breast cancer constituted 5% of cases. Twenty-nine events were recorded (systemic and locoregional relapse) with a median follow-up of 3.5 years. Three years relapse-free survival (RFS) and overall survival were 80% and 60%, respectively. Bones were the most common site of metastasis. Age <45 years [HR-1.4 (0.8-2.1), P < 0.001] and advanced clinical tumor stage [T4, HR-2.1 (1.1-3.8), P = 0.001] were associated with poor RFS.

CONCLUSION

ILC constituted 2.5% of breast cancer cases at our institute. Triple negativity and HER-2/neu positivity were seen in 9% and 5% of cases, respectively. Age <45 years and advanced clinical tumor stage were associated with poor RFS.

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.