The prognostic and predictive impact of low estrogen receptor expression in early breast cancer: a systematic review and meta-analysis

The evolving landscape of metastatic HER2-positive, hormone receptor-positive Breast Cancer

Therapeutic agents targeting Human Epidermal Growth Factor Receptor 2 (HER2) demonstrated to positively impact the prognosis of HER2-positive breast cancer. HER2-positive breast cancer can present either as hormone receptor-negative or positive, defining Triple-positive breast cancer (TPBC). TPBC demonstrate unique gene expression profiles, showing reduced HER2-driven gene expression, as recapitulated by a higher proportion of Luminal-type intrinsic subtypes. The different molecular landscape of TPBC dictates distinctive clinical features, including reduced chemotherapy sensitivity, different patterns of recurrence, and better overall prognosis. Cross-talk between HER2 and hormone receptor signaling seems to be critical to determine resistance to HER2-directed agents. Accordingly, superior outcomes have been achieved with the use of endocrine therapy, representing the first subtype-specific pharmacological intervention unique to this subgroup. Additional targeted agents capable to tackle resistance mechanisms to anti-HER2, hormone agents, or both might further improve the efficacy of treatments, such as PI3K/AKT/mTOR inhibitors, particularly in a biomarker-enriched setting, and CDK4/6-inhibitors, with preliminary data suggesting a role of PAM50 subtyping to predict higher benefits in luminal tumors. Finally, the distinct biology of triple-positive tumors may yield the rationale for considering combinations within antibody-drug conjugate regimens. Accordingly, in this review, we summarized the current evidence and rationale for considering TPBC as a different entity, in which distinct therapeutical approaches leveraging on the different biological profile of TPBC may result in superior anticancer regimens and improved patient-centric outcomes.

Low progesterone receptor levels in high-grade DCIS correlate with HER2 upregulation and the presence of invasive components

Objective

In this study, we investigated pivotal molecular markers in human high-grade breast ductal carcinoma in situ (DCIS). Expression status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth receptor 2 (HER2) was measured among various subtypes (Luminal (Lum) A, LumB HER2-, LumB HER2+, HER2-enriched and triple-negative).

Methods

In total, 357 DCIS cases were classified into respective subtypes, according to the 2013 St. Gallen guidelines. Each subtype was categorized into three subcategories: "Pure" (those without an invasive component), "W/invasive" (those with an invasive component), and "All" (the entire group of the given subtype). ER and PR expression were registered as intervals. Equivocal HER2 immunohistochemistry (IHC) cases (2+) were further investigated using dual-color in situ hybridization.

Results

The majority of patients (71%) were over the age of 50. We discovered no significant differences in the proportion of age between the "Pure" and "W/invasive" groups. There was no significant difference in ER/PR expression between "Pure" luminal subtypes of DCIS and "W/invasive" cases. We compared the HER2 IHC scores of "0", "1+", and "2+" among LumA and LumB HER2 subtypes and identified no statistically significant differences between "Pure" and "W/invasive" (p = 0.603). ER and PR expression ≥ 50% cutoff value was present in > 90% of all LumA cases. The incidences of cases with ER expression at cutoff values of < 10% and ≥ 50% in LumA were significantly different compared to other luminal subtypes (p < 0.0001). The proportion of cases with PR expression < 20% showed significant differences in the various luminal subtypes. In luminal B subtypes, low PR expression (< 20%) was significantly associated with both strong HER2 expression (3+) and the presence of an invasive component (p = 0.0001 and p = 0.0365, respectively).

Conclusions

ER and PR expression at ≥ 50% cutoff values were found in more than 90% of LumA cases. Samples with ER < 10% and ≥ 50% in LumA were significantly different compared to other luminal subtypes (p < 0.0001). Low PR expression in high-grade DCIS was strongly associated with HER2 overexpression (3+) and an invasive component (p = 0.0001 and p = 0.0365, respectively).

Checkpoint inhibition for early-stage hormone receptor-positive breast cancer

INTRODUCTION

Most patients with breast cancer have early-stage hormone receptor (HR)-positive, human epidermal growth factor receptor-2 (HER2)-negative disease. Even though the prognosis for most of these patients is good, there is a need to identify patients at risk for poor outcomes and to develop strategies to mitigate this risk.

AREAS COVERED

The addition of immunotherapy to standard neoadjuvant chemotherapy represents a promising option for select patients with HR-positive early breast cancer. Three randomized clinical trials have shown favorable results to date. In this review, we discuss the findings of I-SPY2, CheckMate 7FL (NCT04109066), and KEYNOTE-756 (NCT03725059).

EXPERT OPINION

Despite the promising results of these trials, there are unanswered questions that need to be considered before incorporating neo/adjuvant immunotherapy in the treatment paradigm of early-stage HR-positive breast cancer. One example of an unanswered question is patient selection. Because the regimens used in these protocols are associated with long-term toxicities, identifying the patients who are more likely to derive a benefit from these agents, such as through the use of biomarkers, is critical. A second example is the optimal integration of adjuvant therapies that improve invasive disease-free survival, such as abemaciclib and ribociclib, which are not safely administered concurrently with immunotherapy.

Defining the Biology of Estrogen Receptor-Low-Positive Breast Cancer

BACKGROUND

We sought to better define estrogen receptor-low-positive (ER-low+) breast cancer biology and determine the utility of the Oncotype DX Breast Recurrence Score® (RS) assay in this population.

METHODS

Patients with information regarding percentage ER positivity and PAM50 subtype were identified in The Cancer Genome Atlas (TCGA) and subtype distribution was determined. Next, patients with ER-low+ (ER 1-10%), HER2- breast cancer undergoing upfront surgery with known RS result were identified in the National Cancer Database (NCDB) and our institutional Dana-Farber Brigham Cancer Center (DF/BCC) database; RS distribution was examined. Finally, patients with ER-low+, HER2- breast cancer treated at DF/BCC from 2011 to 2020 without prior RS results and in whom tissue was available to perform the assay were identified. RS results, treatment, recurrence and breast cancer-specific survival (BCSS) were determined.

RESULTS

Of 1033 patients in TCGA, ER percentage and PAM50 subtype were available for 342 (33.1%) patients. Forty-six (13.5%) had ER-low+/HER2- tumors, among whom 82.6% were basal and 4.3% were luminal A. Among 3423 patients with ER-low+/HER2- disease in the NCDB, RS results were available for 689 (20.1%) patients; 67% had an RS ≥26. In our institutional database, only two patients with ER-low+/HER2- disease and an RS were identified, both with RS ≥26. Among 37 patients in our institutional cohort without prior RS, 35 (97.4%) had an RS ≥26, determined with testing. After a median follow-up of 40 months (range 3-106), three patients, all treated with chemotherapy, recurred. Three-year BCSS was 97.0% (95% confidence interval 96.9-97.1%).

CONCLUSIONS

Most ER-low+/HER2- breast cancers are basal-like, with RS ≥26 suggesting these tumors are similar to triple-negative disease.

Predictive Markers of Treatment Response to Neoadjuvant Systemic Therapy with Dual HER2-Blockade

In patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer, achievement of pathologic complete response (pCR) is a known prognostic indicator after neoadjuvant systemic therapy (NAST). We investigated the clinicopathological factors associated with pCR in patients with HER2-positive breast cancer treated with dual HER2-blockade. In this retrospective study, 348 patients with HER2-positive breast cancer who received NAST with docetaxel and carboplatin, combined with trastuzumab and pertuzumab (TCHP), were included. Of the 348 patients with HER2 protein expression data, 278 (79.9%) had HER2 immunochemistry (IHC) 3+. Data on tumor-infiltrating lymphocyte (TIL) levels were available for 305 patients, showing a median TIL level of 20% (IQR 5-50), among which 121 (39.7%) had high TIL levels (≥30%). Estrogen receptor (ER) status (77.9% in ER-negative vs. 47.5% in ER-positive; p < 0.001), HER2 protein expression (71.6% in IHC 3+ vs. 34.3% in IHC 2+; p < 0.001), and TIL levels (71.9% in high vs. 57.6% in low; p = 0.011) were significantly associated with the pCR rate. In addition, we observed a significant link between numerical TIL levels (per 10% increment) and the pCR rate. After adjusting other clinicopathologic factors, ER status (low expression [defined as 1-9% expression] or negative), HER2 IHC 3+ and numerical TIL levels (per 10% increment), and high TIL levels (≥30%) were found to be independent predictors of pCR. Notably, in ER-negative breast cancer, the treatment response was excellent, irrespective of HER2 expression and TIL levels. Conversely, in ER-positive cases, low ER expression, HER2 IHC 3+, and numerical TIL levels or high TIL levels emerged as independent predictors of pCR. Our results suggest that ER expression, HER2 protein expression, and TIL levels serve as valuable predictors of the treatment response to neoadjuvant TCHP.

The Clinical and Pathological Characteristics That Differentiate Cases With "Low Estrogen Receptor Expression" From Triple-Negative Breast Cancer

Objective

Estrogen receptor (ER) expression is an immunohistochemical marker that is examined in all invasive breast cancers and has prognostic and predictive value. ER-positive breast cancers refer to those that show positivity for ER at 1% cellular expression or higher. The American Society of Clinical Oncology/College of American Pathologists guidelines suggest using the term "low ER-positive breast cancer" for tumors with ER expression between 1% and 10%. Low ER-positive breast cancers exhibit similarities, in terms of disease-free survival and overall survival rates, to triple-negative breast cancers (TNBCs) rather than ER-positive breast cancers. In this study, our aim was to compare the clinicopathological characteristics of low ER-positive breast cancer cases diagnosed and followed in our clinic with TNBCs.

Materials and Methods

A total of 26 cases of low ER-positive breast cancer diagnosed at University of Health Sciences Turkey, İzmir Tepecik Training and Research Hospital between 2010 and 2016 were retrieved from hospital records. The relevant histopathology slides and blocks were retrieved and re-evaluated retrospectively through microscopic examination. Thirteen cases that met the criteria were included in the study. Additionally, a consecutive series of 13 TNBC cases that did not receive neoadjuvant treatment within the same time period were identified.

Results

In the low ER-positive group, the presence of tumor necrosis, as well as histological grade, nuclear grade and Ki-67 proliferation index were significantly lower compared to the TNBC group. Ductal carcinoma in situ (DCIS) was significantly more common in the low ER-positive group compared to the TNBC group. There were no significant differences between the two groups in terms of tumor size, histological tumor type, axillary lymph node involvement, tumor margins, peritumoral and intratumoral inflammation, local recurrence, distant metastasis, survival, and other characteristics.

Conclusion

Although our study consisted of a small number of cases, some features showed significant differences between low ER-positive breast cancers and TNBCs. Histological and nuclear grades, as well as the presence of a DCIS component, were associated with low ER-positive breast cancer. In contrast, the presence of tumor necrosis, as well as Grade 3 features and a high Ki-67 proliferation index indicated TNBC.

Prognostic impact of HER2-low positivity in patients with HR-positive, HER2-negative, node-positive early breast cancer

Adjuvant therapy for patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, node-positive, early breast cancer (EBC) remains challenging. The prognostic significance of HER2-low positivity in these patients is not fully understood. In our retrospective study, we analyzed 647 patients with HR-positive, HER2-negative, node-positive EBC, stratifying them into three cohorts based on axillary lymph node involvement, tumor size, and characteristics. Cohort 1 included patients with either ≥ 4 positive axillary lymph nodes or 1-3 positive nodes with histological grade 3 or tumor size ≥ 5 cm. Cohort 2 consisted of patients with 1-3 positive nodes, histological grade < 3, tumor size < 5 cm, and Ki-67 ≥ 20%. Cohort 3 comprised patients with 1-3 positive nodes, histological grade < 3, tumor size < 5 cm, and Ki-67 < 20%. We compared invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) between HER2-low (IHC1+ or IHC2+/FISH-) and HER2-zero (IHC0) groups in each cohort. In cohort 1, HER2-low patients exhibited significantly better 5-year IDFS (84.2% vs. 73.6%, p = 0.0213) and DRFS (88.2% vs. 79.8%, p = 0.0154). However, no significant differences were observed in cohorts 2 and 3. Our findings suggest HER2-low positivity as a prognostic factor in HR-positive, HER2-negative, and node-positive EBC.

Estrogen-Receptor-Low-Positive Breast Cancer: Pathological and Clinical Perspectives

The expression of estrogen receptors (ERs) in breast cancer (BC) represents a strong prognostic and predictive biomarker and directs therapeutic decisions in early and advanced stages. ER-low-positive BC, defined by the immunohistochemical (IHC) expression of ERs from 1% to 9%, constitutes a distinct subset of total BC cases. Guidelines recommend that a low expression of ERs be reported in pathology reports since the benefit of endocrine therapy in patients with ER-low-positive BC is uncertain. Recently, several cohorts, mostly of a retrospective nature, have been published, reporting the clinicopathological characteristics and outcomes of ER-low-positive BC. However, the majority of the data focus on early-stage BC and the use of (neo)adjuvant therapy, and there is a significant lack of data regarding metastatic ER-low-positive BC. Further factors, including tumor heterogeneity as well as the potential loss of ER expression due to endocrine resistance, should be considered. Including patients with ER-low-positive BC in clinical trials for triple-negative breast cancer (TNBC) might improve the understanding of this entity and allow novel therapeutic approaches. The design and conduction of randomized clinical trials regarding this subgroup of patients are greatly anticipated.

Statin Use, Cholesterol Level, and Mortality Among Females With Breast Cancer

Importance

Several studies have reported an association between the use of statins and breast cancer (BC) mortality. However, most of these studies did not take into account the underlying cholesterol level.

Objective

To investigate the association between serum cholesterol, statin use, and BC mortality.

Design, Setting, and Participants

This cohort study included females with invasive BC that was newly diagnosed between January 1, 1995, and December 31, 2013, in Finland. The cohort had available hormone receptor data and at least 1 cholesterol measurement. All data were obtained from Finnish national registries. Statistical analyses were performed from January to May 2022.

Exposure

Use of statins; statin dose; and serum cholesterol, low-density lipoprotein, high-density lipoprotein, and triglyceride levels measured separately before and after BC diagnosis.

Main Outcomes and Measures

Breast cancer mortality and overall mortality between date of BC diagnosis and December 31, 2015.

Results

A total of 13 378 female patients with BC (median [IQR] age, 62 [54-69] years) participated in the study. The median (IQR) follow-up was 4.5 (2.4-9.8) years after BC diagnosis, during which 16.4% of patients died and 7.0% died of BC. Prediagnostic statin use was a risk factor for BC death even after adjustment for total cholesterol level (hazard ratio [HR], 1.22; 95% CI, 1.02-1.46; P = .03). Reduced risk for BC death was seen for postdiagnostic statin use (HR, 0.85; 95% CI, 0.73-1.00; P = .05). The risk reduction was robust in participants whose cholesterol level decreased after starting statins (HR, 0.49; 95% CI, 0.32-0.75; P = .001) but was nonsignificant if cholesterol level did not subsequently decrease (HR, 0.69; 95% CI, 0.34-1.40; P = .30). Reduced BC mortality among statin users was also observed in females with estrogen receptor-positive tumors (HR, 0.82; 95% CI, 0.68-0.99; P = .03). Overall mortality was lower among statin users vs nonusers when adjusted for serum cholesterol level (HR, 0.80; 95% CI, 0.72-0.88; P < .001).

Conclusions and Relevance

Results of this cohort study showed that postdiagnostic use of statins was associated with reduced BC mortality compared with nonuse, and the risk was associated with subsequent change in serum cholesterol level. This finding suggests that cholesterol-lowering interventions with statins may be beneficial for patients with BC.

The Clinical and Biological Significance of Estrogen Receptor-Low Positive Breast Cancer

Estrogen receptor (ER) status in breast cancer (BC) is determined using immunohistochemistry (IHC) with nuclear expression in ≥1% of cells defined as ER-positive. BC with 1%-9% expression (ER-low-positive), is a clinically and biologically unique subgroup. In this study, we hypothesized that ER-low-positive BC represents a heterogeneous group with a mixture of ER-positive and ER-negative tumor, which may explain their divergent clinical behavior. A large BC cohort (n = 8171) was investigated and categorized into 3 groups: ER-low-positive (1%-9%), ER-positive (≥10%), and ER-negative (<1%) where clinicopathological and outcome characteristics were compared. A subset of ER-low-positive cases was further evaluated using IHC, RNAscope, and RT-qPCR. PAM50 subtyping and ESR1 mRNA expression levels were assessed in ER-low-positive cases within The Cancer Genome Atlas data set. The reliability of image analysis software in assessment of ER expression in the ER-low-positive category was also assessed. ER-low-positive tumors constituted <2% of BC cases examined and showed significant clinicopathological similarity to ER-negative tumors. Most of these tumors were nonluminal types showing low ESR1 mRNA expression. Further validation of ER status revealed that 45% of these tumors were ER-negative with repeated IHC staining and confirmed by RNAscope and RT-qPCR. ER-low-positive tumors diagnosed on needle core biopsy were enriched with false-positive ER staining. BCs with 10% ER behaved similar to ER-positive, rather than ER-negative or low-positive BCs. Moderate concordance was found in assessment of ER-low-positive tumors, and this was not improved by image analysis. Routinely diagnosed ER-low-positive BC includes a proportion of ER-negative cases. We recommend repeat testing of BC showing 1%-9% ER expression and using a cutoff ≥10% expression to define ER positivity to help better inform treatment decisions.

Hormone receptors in breast cancer: An update on the uncommon subtypes

Breast cancer is the most common cancer affecting women and is the second leading cause of cancer death among US women. Estrogen receptor (ER) signaling plays a crucial role in mammary gland development and carcinogenesis. Near 80 % of invasive breast cancers are ER-positive (ER+). Endocrine therapies targeting ER have significantly improved the prognostic outcomes in the patients with ER+ breast cancer, and the therapeutic effects are strongly correlated with the levels of the ER expression in tumor cells. Despite being an ER-dependent gene product, PR is not always overexpressed in ER+ tumors, and a small subset of breast cancers demonstrates an ER+/PR- phenotype, and a rare ER-/PR+ subtype also exists. There have been controversies on the biology of these tumor types and the predictive and prognostic power of PR status. Compelling data have shown the distinct biologic characteristics of ER+/PR- and ER-/PR+ tumors. Despite that ER-low breast cancers demonstrate more similarity to ER- tumors, at least a subset of ER-low carcinomas may have a functional ER signaling. Thus, adequate PR expression is essential as its absence indicates impaired ER pathway. Assessment of PR status may not only distinguish the ER+/PR- subset from the ER+ and ER-low tumors, but also differentiate the ER-/PR+ phenotype from the ER- carcinomas, both with therapeutic implications. This article was aimed to provide an up-to-date review focusing on the clinicopathologic characteristics of uncommon subtypes of breast cancer, including ER+/PR-, ER-/PR+, and ER-low breast cancers.

Missing link between tissue specific expressing pattern of ERβ and the clinical manifestations in LGBLEL

Purpose

Lacrimal gland benign lymphoepithelial lesion (LGBLEL) is an IgG4-related disease of unknown etiology with a risk for malignant transformation. Estrogen is considered to be related to LGBLEL onset.

Methods

Seventy-eight LGBLEL and 13 control clinical samples were collected and studied to determine the relationship between estrogen and its receptors and LGBLEL development.

Results

The serological analysis revealed no significant differences in the levels of three estrogens be-tween the LGBLEL and control groups. However, immunohistochemical analyses indicated that the expression levels of ERβ and its downstream receptor RERG were relatively lower in LGBLEL samples than in control samples, with higher expression in the lacrimal gland and lower expression in the lymphocyte infiltration region. However, low expression of ERα was detected. The transcriptome sequence analysis revealed upregulated genes associated with LGBLEL enriched in lymphocyte proliferation and activation function; downregulated genes were enriched in epithelial and vascular proliferation functions. The key genes and gene networks were further analyzed. Interactions between B cells and epithelial cells were analyzed due to the identified involvement of leukocyte subsets and epithelial cells. B cell proliferation was found to potentially contribute to lacrimal gland apoptosis.

Conclusion

Therefore, the tissue-heterogeneous expression pattern of ERβ is potentially related to the clinical manifestations and progression of LGBLEL, although further investigations are required to confirm this finding.

Immune landscape of breast tumors with low and intermediate estrogen receptor expression

Immune checkpoint blockade (ICB) is currently approved for patients with triple-negative breast cancer (TNBC), whereas responses to ICB are also observed in a small subgroup of Estrogen Receptor (ER)-positive breast cancer. The cut-off for ER-positivity (≥1%) is based on likelihood of endocrine treatment response, but ER-positive breast cancer represents a very heterogeneous group. This raises the question whether selection based on ER-negativity should be revisited to select patients for ICB treatment in the context of clinical trials. Stromal tumor-infiltrating lymphocytes (sTILs) and other immune parameters are higher in TNBC compared to ER-positive breast cancer, but it is unknown whether lower ER levels are associated with more inflamed tumor microenvironments (TME). We collected a consecutive series of primary tumors from 173 HER2-negative breast cancer patients, enriched for tumors with ER expression between 1 and 99% and found levels of stromal TILs, CD8 + T cells, and PD-L1 positivity in breast tumors with ER 1-9% and ER 10-50% to be comparable to tumors with ER 0%. Expression of immune-related gene signatures in tumors with ER 1-9% and ER 10-50% was comparable to ER 0%, and higher than in tumors with ER 51-99% and ER 100%. Our results suggest that the immune landscape of ER low tumors (1-9%) and ER intermediate tumors (10-50%) mimic that of primary TNBC.

Optimizing choices and sequences in the diagnostic-therapeutic landscape of advanced triple-negative breast cancer: An Italian consensus paper and critical review

Triple-negative (TN) metastatic breast cancer (mBC) represents the most challenging scenario withing mBC framework, and it has been only slightly affected by the tremendous advancements in terms of drug availability and survival prolongation we have witnessed in the last years for advanced disease. However, although chemotherapy still represents the mainstay of TN mBC management, in the past years, several novel effective agents have been developed and made available in the clinical practice setting. Within this framework, a panel composed of a scientific board of 17 internationally recognized breast oncologists and 42 oncologists working within local spoke centers, addressed 26 high-priority statements, including grey areas, regarding the management of TN mBC. A structured methodology based on a modified Delphi approach to administer the survey and the Nominal Group Technique to capture perceptions and preferences on the management of TN mBC within the Italian Oncology community were adopted. The Panel produced a set of prioritized considerations/consensus statements reflecting the Panel position on diagnostic and staging approach, first-line and second-line treatments of PD-L1-positive/germline BRCA (gBRCA) wild-type, PD-L1-positive/gBRCA mutated, PD-L1-negative/gBRCA wild-type and PD-L1-negative/gBRCA mutated TN mBC. The Panel critically and comprehensively discussed the most relevant and/or unexpected results and put forward possible interpretations for statements not reaching the consensus threshold.

Incorporating weekly carboplatin in anthracycline and paclitaxel-containing neoadjuvant chemotherapy for triple-negative breast cancer: propensity-score matching analysis and TIL evaluation

BACKGROUND

The generation of data capturing the risk-benefit ratio of incorporating carboplatin (Cb) to neoadjuvant chemotherapy (NACT) for triple-negative breast cancer (TNBC) in a clinical practice setting is urgently needed. Tumour-infiltrating lymphocytes (TILs) have an established role in TNBC receiving NACT, however, the role of TIL dynamics under NACT exposure in patients receiving the current standard of care is largely uncharted.

METHODS

Consecutive TNBC patients receiving anthracycline-taxane [A-T] +/- Cb NACT at three Institutions were enrolled. Stromal-TILs were evaluated on pre-NACT and residual disease (RD) specimens. In the clinical cohort, propensity-score-matching was used to control selection bias.

RESULTS

In total, 247 patients were included (A-T = 40.5%, A-TCb = 59.5%). After propensity-score-matching, pCR was significantly higher for A-TCb vs A-T (51.9% vs 34.2%, multivariate: OR = 2.40, P = 0.01). No differences in grade ≥3 haematological toxicities were observed. TILs increased from baseline to RD in the overall population and across A-T/A-TCb subgroups. TIL increase from baseline to RD was positively and independently associated with distant disease-free survival (multivariate: HR = 0.43, P = 0.05).

CONCLUSIONS

We confirmed in a clinical practice setting of TNBC patients receiving A-T NACT that the incorporation of weekly Cb significantly improved pCR. In addition, A-T +/- Cb enhanced immune infiltration from baseline to RD. Finally, we reported a positive independent prognostic role of TIL increase after NACT exposure.

Clinical implication of low estrogen receptor (ER-low) expression in breast cancer

Breast cancer is a heterogeneous disease, and the estrogen receptor (ER) remains the most important biomarker in breast oncology. Most guidelines set a positive expression threshold of 1% staining in immunohistochemistry (IHC) to define ER positivity. However, different expression levels may be associated with diverse degrees of sensitivity to endocrine therapy as ER expression may impact breast cancer molecular biology as a continuous variable. ER-lo tumors, defined as those with 1-10% ER expression, represent a relatively small subgroup of breast cancer patients, with an estimated prevalence of 2-7%. These tumors are similar to ERneg disease in their molecular landscape, clinicopathological characteristics, prognosis, and response to therapy. Nevertheless, a proportion may retain some degree of ER signaling dependency, and the possibility of responding to some degree to endocrine therapy cannot be completely ruled out. This review article discusses the most important considerations regarding the definition of ER positivity, pathology assessment, prognosis, and therapeutic implication of ERlo breast cancer from the medical oncology perspective.

Pathological complete response, long-term outcomes, and recurrence patterns in HER2-low versus HER2-zero breast cancer after neoadjuvant chemotherapy

BACKGROUND

The interest in HER2-low breast cancer (BC) has increased in recent years with the development of novel anti-HER2 antibody-drug conjugates. Here, we investigated the clinical outcomes and relapse patterns of patients with HER2-low or -zero BCs in an Asian population.

METHODS

We retrospectively identified HER2-low or -zero BC patients with stage I-III tumours who were treated with neoadjuvant chemotherapy and underwent curative surgery, between 2014 and 2018 at Asan Medical Center, Seoul, Korea.

RESULTS

A total of 818 and 754 HER2-zero and HER2-low BC patients, respectively, were consecutively included in this analysis. The HER2-low group had more hormone receptor [HR]-positive patients (81% versus 56%, P < 0.001). The HER2-zero group had a higher proportion of patients who achieved pathological complete response (pCR) (14.7% versus 9.8%, P = 0.003); however, no significant differences of pCR rate by HER2 status were identified in the HR-positive (P = 0.4) and HR-negative groups (P = 0.3) when analysed separately. The HER2-low BC cases had higher 5-year overall survival (OS) and disease-free survival (DFS) rates (P < 0.001 for OS; P = 0.002 for DFS); however, no differences were observed in terms of OS and DFS by HER2 status in the HR-positive group (P = 0.21 for OS and P = 0.66 for DFS).

CONCLUSIONS

Our current findings do not support that HER2-low BC had different biology and clinical features compared to HER2-zero BC in patients who treated with neoadjuvant chemotherapy. However, the prognostic impact of HER2-low status in BC remains controversial; thus warranting further research.

Contribution of endocrine therapy in oestrogen receptor-positive pT1a-b breast cancer: Results of a retrospective study

INTRODUCTION

Few data have been reported regarding endocrine therapy (ET) in patients with small pT1a-b ER-postive breast cancer (BC). Thus, we conducted a study to detect possible survival improvements due to ET in such patients.

METHODS

Our retrospective observational study included 5545 patients with pT1a-b ER-positive BC treated in 15 French centres, excluding patients with HER2-positive status, neoadjuvant chemotherapy, ER-negative status, unknown pN status or in situ BC. We estimated disease-free survival (DFS), recurrence-free survival (RFS) and overall survival (OS) via univariate analysis and multivariate Cox regression.

RESULTS

Most patients (80.3%: 4453) received ET and-when compared to those without ET-experienced increases of 2.5% and 3.3% in DFS and 1.9% and 4.3% in RFS after 5 and 7 years of follow-up, respectively, with little difference in OS. In Cox regression analysis, no ET was significantly associated with decreased DFS (hazard ratio, HR = 1.275, p = 0.047, 95% CI[1.003-1.620]) but not OS or RFS in all patients, while in 2363 patients with pT1a-b ER-positive grade 2-3 BC, no ET was significantly associated with decreased DFS (HR = 1.502, p = 0.049, 95% CI[1.001-2.252]), but not OS (HR = 1.361, p = 0.272). ET omission was not significantly associated with decreased survival in 3047 patients with pT1a-b ER-positive grade 1 BC.

CONCLUSION

Our results indicate that while ET provided a beneficial impact on survival to patients with pT1a-bN0 ER-positive BC-and especially in those with grade 2-3 tumours-no such impact was observed in grade 1 tumours. Consequently, ET should be discussed with these patients, particularly in those with pT1a grade 1 tumours.

Emerging Targeted Therapies for Early Breast Cancer

Breast cancer is the most common malignancy and the second leading cause of cancer-related mortality in the United States (US). Most patients are diagnosed with early-stage disease; however, there is still a need to prevent recurrences that often present as incurable metastatic disease. The treatment landscape of early-stage breast cancer is evolving rapidly. The immune checkpoint inhibitor pembrolizumab is approved in combination with neoadjuvant chemotherapy for the treatment of high-risk triple-negative breast cancer (TNBC). The cyclin-dependent kinase (CDK) 4 and 6 inhibitor abemaciclib is approved for adjuvant treatment of patients with high-risk hormone receptor (HR)-positive disease. While adjuvant olaparib has shown significant improvement in outcomes for patients with pathogenic/likely pathogenic BRCA1/2 mutations and high-risk human epidermal growth factor receptor 2 (HER2)-negative breast cancer, and is approved in this setting. For the HER2-positive subtype, the post-neoadjuvant therapy can be tailored based on the response to neoadjuvant chemotherapy and HER2-targeted agents. In this narrative review, we summarize the most recent approvals for early-stage breast cancer as well as frequently encountered clinical challenges utilizing these medications.

Role of Estrogen Receptor-Positive/Negative Ratios in Regulating Breast Cancer

The alpha estrogen receptor (ERα) contributes to breast cancer progression and recent guidelines define ER positivity as ≥1% stained cells, and a few tumor tissues show no ERα expression at all or are at 100%. Although ER and aromatase inhibitors are widely used to treat hormone receptor-positive (HR+) breast cancer, their effect on tumor activity at different ERα levels remains unclear. Therefore, we investigated the role of ERα+/ERα− ratios in determining the ERα level. We used ERα stably transfected and wild-type MDA-MB-231 cells (MDA-MB-231^Trans−ER and MDA-MB-231^WT, respectively) as represented ER+ and ER− cells, respectively, and MCF-7 cells were the positive control. MDA-MB-231^Trans−ER and MDA-MB-231^WT cells were mixed and cocultured at a ratio of 0%, 20%, 40%, 70%, and 100%. Migration and invasion functions at different cell ratios were evaluated in vitro using the Transwell and scratch test. In a xenograft mouse model, the polarization of the tumor-associated (M2) macrophage and the expression of breast cancer gene 1 (BRCA1), human epidermal growth factor receptor 2 (HER2), vascular endothelial growth factor (VEGF), and tumor necrosis factor (TNF)-α were measured. The results showed that the cell invasion and migration were significantly higher at 40% and 70% than they were at other ratios. Additionally, in vivo, the 70% ERα+/ERα-ratio was a critical indicator of cell activity and cytokine expression. The highest M2 level and expression of VEGR, TNF-α, BRCA1, and HER2 were shown at a ratio of 70%. Moreover, the effects of ERα were not linear in breast cancer, indicating that the ERα status requires continuous monitoring during long-term endocrine treatment. These results indicate that during HR+ breast cancer treatment, the ERα+/ERα− ratio may be a useful predictor and should be evaluated further.

PD-L1 (SP142 and 22C3) Immunohistochemistry in Clinical Metastatic Triple Negative or Low Hormone Receptor Breast Carcinomas: Experience from a Large Academic Institution

The discovery of new immune checkpoint molecules has led to the emergence of new treatment for metastatic breast carcinoma. We aimed to investigate PD-L1 (SP142 and 22C3) expression in 77 clinical metastatic triple negative or low hormone receptor (<10%) breast carcinomas (TNBC/LHRBC). SP142 was positive in 23.4% (18/77) of cases. SP142 positive (SP142+) cases showed lower liver metastasis and androgen receptor expression, but increased tumor infiltrating lymphocytes than SP142 negative (SP142-) cases in univariate analysis, but only increased tumor infiltrating lymphocyte in multivariate analysis. 22C3 testing was available in 21 cases including 14 with combined positive score (CPS) ≥10 (9 SP142- and 5 SP142+) and 7 with CPS <10 (7 SP142-). Ten (13%) patients received immunotherapy including 8 SP142+ (7 with atezolizumab, 1 with pembrolizumab) and 2 SP142- cases (2 with pembrolizumab). Survival data showed a trend of increased survival rate in SP142+ (72.2%) when comparing to SP142- patients (55.9%). Our study provides unique insights into the distribution of PD-L1 staining in metastatic breast carcinomas in a real-world clinical setting.

Breast Cancer Phenotype Associated With Li-Fraumeni Syndrome: A Brazilian Cohort Enriched by TP53 p.R337H Carriers

Breast cancer (BC) is the most prevalent malignancy in women with Li-Fraumeni syndrome (LFS). The literature on BC in LFS is limited due to its rarity worldwide. A TP53 founder pathogenic variant (c.1010G>A; p.R337H) is responsible for the higher prevalence of this syndrome among women of Brazilian ancestry.

Impact of the EndoPredict genomic assay on treatment decisions for oestrogen receptor-positive early breast cancer patients: benefits of physician selective testing

PURPOSE

Genomic tests improve accuracy of risk prediction for early breast cancers but these are expensive. This study evaluated the clinical utility of EndoPredict®, in terms of impact on adjuvant therapy recommendations and identification of parameters to guide selective application.

METHODS

Patients with ER-positive, HER2-negative, and early-stage invasive breast cancer were tested with EndoPredict®. Two cohorts were recruited: one consecutively and another at clinical team discretion. Systemic treatment recommendations were recorded before and after EndoPredict® results were revealed to the multidisciplinary team.

RESULTS

233 patients were recruited across five sites: 123 consecutive and 110 at clinical team discretion. In the consecutive cohort 50.6% (62/123) cases were classified high risk of recurrence by EndoPredict®, compared with 62.7% (69/110) in the selective cohort. A change in treatment recommendation was significantly more likely (p < 0.0001) in the selective cohort (43/110, 39.1%) compared to the consecutive group (11/123, 8.9%). The strongest driver of selective recruitment was intermediate grade histology, whilst logistic regression modelling demonstrated that nodal status (p < 0.001), proliferative rate (p = 0.001), and progesterone receptor positivity (p < 0.001) were the strongest discriminators of risk.

CONCLUSION

Whilst molecular risk can be predicted by traditional variables in a high proportion of cases, EndoPredict® had a greater impact on treatment decisions in those cases selected for testing at team discretion. This is indicative of the robust ability of the clinical team to identify cases most likely to benefit from testing, underscoring the value of genomic tests in the oncologists' tool kit.