Estrogen Receptor Immunohistochemistry Research Articles

Clinical Validity of 16α-[18F]Fluoro-17β-Estradiol Positron Emission Tomography/Computed Tomography to Assess Estrogen Receptor Status in Newly Diagnosed Metastatic Breast Cancer.

Determining the estrogen receptor (ER) status is essential in metastatic breast cancer (MBC) management. Whole-body ER imaging with 16α-[18F]fluoro-17β-estradiol positron emission tomography ([18F]FES-PET) is increasingly used for this purpose. To establish the clinical validity of the [18F]FES-PET, we studied the diagnostic accuracy of qualitative and quantitative [18F]FES-PET assessment to predict ER expression by immunohistochemistry in a metastasis. In a prospective multicenter trial, 200 patients with newly diagnosed MBC underwent extensive workup including molecular imaging. For this subanalysis, ER expression in the biopsied metastasis was related to qualitative whole-body [18F]FES-PET evaluation and quantitative [18F]FES uptake in the corresponding metastasis. A review and meta-analysis regarding [18F]FES-PET diagnostic performance were performed. Whole-body [18F]FES-PET assessment predicted ER expression in the biopsied metastasis with good accuracy: a sensitivity of 95% (95% CI, 89 to 97), a specificity of 80% (66 to 89), a positive predictive value (PPV) of 93% (87 to 96), and a negative predictive value (NPV) of 85% (72 to 92) in 181 of 200 evaluable patients. Quantitative [18F]FES uptake predicted ER immunohistochemistry in the corresponding metastasis with a sensitivity/specificity of 91%/69% and a PPV/NPV of 90%/71% in 156 of 200 evaluable patients. For bone metastases, PPV/NPV was 92%/81%. Meta-analysis with addition of our data has increased diagnostic performance and narrowed the 95% CIs compared with previous studies with a sensitivity/specificity of both 86% (81 to 90 and 73 to 93, respectively). In this largest prospective series so far, we established the clinical validity of [18F]FES-PET to determine tumor ER status in MBC. In view of the high diagnostic accuracy of qualitatively assessed whole-body [18F]FES-PET, this noninvasive imaging modality can be considered a valid alternative to a biopsy of a metastasis to determine ER status in newly MBC (ClinicalTrials.gov identifier: NCT01957332).

Abstract P1-05-02: Intratumor molecular tumor heterogeneity in low ER-expressing primary breast tumors

Abstract Background: Change in estrogen receptor (ER) status between primary breast cancer and distant recurrence are seen in the clinic in up to 15-20% of patients. This is difficult to reconcile with the current understanding of breast cancer molecular subtypes, the large-scale molecular differences between ER-positive (ER+) and ER-negative (ER-) cancers suggest different cellular origins, luminal versus basal breast epithelium, respectively. A potential explanation for ER status switch is the presence of mixed molecular subtypes at diagnosis. ER+ cancers with less than 100% positivity may be composed by both luminal and basal-like cancer cells, and a recurrence might arise from one subtype that survived adjuvant therapy. The goal of this study was to test if molecular subtype heterogeneity exists at diagnosis in less than 100% ER+ breast cancer using the NanoString GeoMx™ platform. Methods: GeoMx™ is a highly multiplexed assay that quantifies RNA expression from spatially discrete regions of interest (ROIs) within formalin fixed paraffin embedded (FFPE) tissue sections. We identified 4 cancers with 30-40% ER-positivity on routine immunohistochemistry (IHC) staining (clone SP1). Eight ROIs per case were selected to represent both ER-high and -low regions of the section using ER IHC (clone 1D5). Invasive tumor cells were defined as PanCK positive cells. 1,825 mRNA species were measured separately in each ROI. mRNA expression results (unique molecular index [UMI] counts) were quantile normalized and differential expression analyses for all genes, ESR1, ER-regulated gene set, and PAM50 gene set were performed between ROIs within the same cancer. We also assessed PAM50 subtypes of each cases on bulk RNA using NanoString BC360 panel. Results: Three of the 4 cases had heterogenous ER IHC (1D5) staining; the fourth case was uniformly ER-negative during ROI selection. For this last case, ROIs were selected based on PanCK staining from different locations in the cancer. Bulk PAM50 subtyping indicated 1 basal-like, 2 HER2-enriched (HER2-E), and 1 luminal (lum)A cancer. We also attempted ROI-level subtyping; however, Pearson correlations to the nearest centroid were low (<0.5) for all ROIs, possibly due to low expression of PAM50 genes or to the exploratory methodology used. There was substantial within cancer, between ROI, expression heterogeneity for many genes including ESR1 and sensitivity to endocrine therapy (SET) index genes. Conclusions: ER- and ER+ cells are intermixed which makes defining low and high ER regions challenging. We observed region to region variation in ESR1 and SET index gene expression. ROI-level PAM50 subtyping was unstable. The novel NanoString GeoMx™ DSP technology can be used to study intratumor molecular heterogeneity in regions of interest on FFPE breast cancer tissue sections. We found substantial region-to-region gene expression differences within tissue sections. Case ID1234ER IHC SP130%40%40%30%ER IHC 1D50%40%40%30%Bulk PAM50 SubtypeBasalHER2-ELumAHER2-EESR1 UMI average (range across ROIs)28.45 (22.4-34.6)64.9 (18.8-173)179.9 (114-245)34.8 (25.1-45.4)SET Index (genes positively correlated with ESR1) UMI average (range across ROIs)41.5 (39.1-44.8)120.1 (86.9-182.9)94.9 (72.9-118.4)143.5 (124.9-150.3)SET Index (genes negatively correlated with ESR1) UMI average (range across ROIs)57.6 (45-75.3)43.4 (38.8-52.6)33.7 (31.8-36.7)44.8 (41.4-50.6) Citation Format: Julia Foldi, Emily Reisenbichler, Liuliu Pan, Krsitina Sorg, Sarah E. Church, Lajos Pusztai. Intratumor molecular tumor heterogeneity in low ER-expressing primary breast tumors [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-05-02.

Abstract P1-02-06: Prediction of Prosigna® breast cancer intrinsic subtype by immunohistochemical ER, PR and Ki67 expression

Abstract The present study evaluated whether Prosigna® breast cancer assay intrinsic subtype (IST) can be predicted using a specified cutoff for Ki67 proliferation index and immunohistochemical (IHC) biological subtype estimation, complemented by estrogen receptor (ER) and progesterone receptor (PR) expression in a clinical cohort. Our study included 185 cases of early stage ER-positive, HER2-negative breast cancer treated at the Comprehensive Cancer Center of the Medical University of Vienna between 2014 and 2019. Prosigna® breast cancer assay was performed when recommended by the institutional multidisciplinary tumor board to aid adjuvant therapy decision. Pathological diagnostics was carried out according to current WHO and EU breast cancer screening and diagnostics guidelines. Immunohistochemical assessment of ER, PR, human epidermal growth factor receptor 2 (HER2) and proliferation index by Ki67 was performed using Ventana Benchmark Ultra (Tucson, AR, USA) according to recent ASCO/USCAP guidelines. Univariable logistic regression was used to verify that Ki67 positivity is predictive for IST LumA and LumB tumors according to Prosigna® IST. Probability for luminal B IST was estimated by receiver operating characteristics and Youden index was calculated. Next, multivariable logistic regression was applied to test the hypothesis that additional inclusion of ER and PR receptor expression contain additional information regarding IST. Median age of patients was 56 years. 52 patients (28%) had tumors larger than 2 cm (pT2-pT3). 75 patients (41%) had lymph node metastases. 83 (45%), 98 (53%) and 3 (2%) of tumors were diagnosed as luminal A, luminal B and HER2-enriched subtype by Prosigna®, respectively. 19 (10%), 77 (42%) and 89 (48%) tumors could be allocated in the low, intermediate and high risk groups, respectively. Univariable logistic regression confirmed that higher Ki67 positivity significantly, yet insufficiently predicts luminal B tumor subtype (p<0.0001). There was no justification for an optimal Ki67 cutoff and irrespective of its value, no more than 70% of tumors could correctly be assigned to the IST, according to a Youden-Index of maximum 0.42. The hypothesis that including ER and PR expression improves accuracy could not be confirmed (p=0.14). Although higher Ki67 positivity significantly predicted luminal B tumor subtype, the Prosigna® breast cancer assay provided independent information for adjuvant therapy decision in cases where Ki67 IST estimation alone is not sufficient. Irrespective of the chosen cutoff value, a maximum accuracy of 70% was achieved for correctly predicting IST, including ER and PR expression into our model did not improve accuracy. Therefore, IST determination by the Prosigna® breast cancer assay cannot be replaced by immunohistochemical parameters. Citation Format: Ulrike Heber, Kristina Tendl-Schulz, Stefan Heber, Sabine Danzinger, Rupert Bartsch, Christian F. Singer, Florian Fitzal, Ruth Exner, Michael F. Gnant, Leonhard Müllauer, Zsuzsanna Bago-Horvath. Prediction of Prosigna® breast cancer intrinsic subtype by immunohistochemical ER, PR and Ki67 expression [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-02-06.

Abstract PD15-06: Estrogen receptor expression thresholds by IHC and mRNA for Ki67 response to aromatase inhibition: A POETIC study

Abstract Background. Estrogen receptor (ER) expression is the key determinant for endocrine treatment of breast cancer (BC). In clinical practise ER analysis is currently almost entirely by immunohistochemistry (IHC). ASCO/CAP recommends cut-offs of <1% (negative) and 1-10% (low) to minimise the risk of false negatives. There is uncertainty in the level of responsiveness of those with low ER. mRNA assessment could be acceptable or preferable if a similar or better threshold was shown to identify response to endocrine therapies. Change of Ki67 after 2 weeks’ presurgical treatment with aromatase inhibitors (AIs) relates to reduction in risk of recurrence. We aimed to define IHC and mRNA cut-points for predicting change in Ki67 in response to AI. Method. POETIC is a phase III trial in postmenopausal patients with ER+ (by local assessment) BC randomized to receive 2-weeks’ pre-surgical AI vs no presurgical treatment. Cases were selected from the AI treatment group. All HER2+ cases were analysed. To enrich the HER2- study set for lower ER values, we selected all of the 15% poorest Ki67 suppression (ie PR, <40% suppression) and 30% of the remainder categorised as intermediate (IR, 40-79%) and good-responders (GR, >79%). 770 baseline FFPE samples were analysed (582 HER2-, 188 HER2+). IHC used the NCL-L-ER6F11 (Novocastra, Leica) antibody with the DAKO Flex kit and were scored centrally. mRNA was assessed by rtPCR. Values were expressed according to an arbitrary scale (“A units”). Results. ER IHC was available from 517 HER2- and 188 HER2+ tumors and ER mRNA from 376 HER2- and 173 HER2+ tumors. The correlation between ER levels by IHC and rtPCR was moderately high (Rho=0.616, p<0.00001). In IHC <1%, 1-10% and >10% tumors median (range) mRNA levels were 1.290 (0.188-11.346), 2.368 (0.575-13.863) and 111.150 (0.826-1001.423), respectively. The tables show the %age of PR, IR and GR for each category of ER by IHC or mRNA. The number of cases was adjusted to cater for the analysis of only 30% of the HER2- IR and GR , by multiplying the HER2- IR and GR number of cases by 3.3, resulting in this not being an integer for some categories. IHC: 87% of cases had >60% of cells +ve and only 11-12% of these were PRs. For cases with <10% cells +ve (4.9% of the population) over 90% of cases were PRs and there were no GRs. Cases between 1 and 10% +ve were not less responsive than those <1% +ve. For cases with >10% <20% cells +ve there was a substantial number of GRs and IRs (14.6% and 19.0%, respectively). mRNA: 82% of cases had ≥ 40 A units and only 10-14% of these showed PR. For cases with 5 A units (4.2% of the population) there were 9.5% % IR and no GR. In the next category, ≥5 <10 A units, 34.4% of cases were IR or GR. The levels of ER that distinguished PRs from IR/GRs was no different between HER2+ and HER2- cases. Conclusions. Ki67 responsiveness increases with increasing levels of ER by both IHC and mRNA. There was little responsiveness at IHC<10% and no distinction in responsiveness between <1% and 1-10% cells positive. Above 10% positive cells substantial numbers of patients showed IR or GR. Similar separation of PRs from IR/GRs was achieved by IHC and mRNA. IHC (%)0 < 1≥1 < 10≥10 < 20≥20 < 40≥40 < 60≥60 < 80≥80No. of cases42.32922.625.671.7239.81010.6PR87.596.566.462.541.811.710.8IR12.53.419.020.741.640.933.1GR0.00.014.616.816.647.456.1 mRNA (A units)<5≥5 < 10≥10 < 20≥20 < 40≥40 < 80≥80 < 120≥120No. of cases45.318.336.589.2168.1177.6550.4PR90.565.638.426.913.710.710.7IR9.416.458.947.946.835.226.8GR0.018.02.725.239.554.162.5 Citation Format: Elena Lopez Knowles, Simone Detre, Margaret Hills, Gene F Schuster, Maggie CU Cheang, Holly Tovey, Lucy Kilburn, Judith Bliss, John Robertson, Ian Smith, Mitch Dowsett, POETIC investigators. Estrogen receptor expression thresholds by IHC and mRNA for Ki67 response to aromatase inhibition: A POETIC study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD15-06.

Comparative Analysis of Ki-67 in Different Scoring Patterns and its Association with other Prognostic Markers of Breast Carcinoma

Introduction: Immunohistochemical evaluation of Ki-67 is widely used for estimation of tumour proliferation in breast cancer. Till date, no specific method or a cut-off point for Ki-67 exists. Aim: To perform a comparative analysis between different scoring patterns and mean Ki-67 value and association of mean Ki-67 with other prognostic markers like tumour size, lymph node status, tumour stage and grade and different molecular subtypes of breast cancer. Materials and Methods: A cross-sectional study was conducted at Dr. D.Y Patil Medical College, Hospital and Research Centre, Pune, Maharashtra, India, between August 2019 to August 2021. Total of 50 new diagnosed cases of breast cancer were studied for the histologic type, grade and stage of the tumour. Immunohistochemistry for Oestrogen Receptor (ER), Progesterone Receptor (PR), Human Epidermal Growth Factor Receptor 2 (HER2) and Ki-67 was performed. Association of Ki-67 with other prognostic markers like tumour size, lymph node status, tumour stage and grade and different molecular subtypes of breast cancer was evaluated by expressing Ki-67 as a continuous variable (mean±SD) and also by dividing Ki-67 into different scoring patterns (I: ≤14%, >14%, II: ≤15%, 16- 30%, >30% and III: <20%, 20-50%, ≥50%). Statistical tests like Kruskal-Wallis test (mean Ki-67 with tumour size, tumour grade and molecular subtypes), Mann-Whitney Rank Sum Test (mean Ki-67 with lymph node status) and Analysis of variance (ANOVA) (mean Ki-67 with staging) respectively. Results: Out of 50 patients, 40 (80%) were older than 50-yearold. Twenty six (52%) cases affected the left breast. A total of 49 (98%) were diagnosed as Invasive Ductal Carcinoma (IDC). Among them 26 (52%) cases were of grade III and 25 (50%) cases were of Luminal A. Mean Ki-67 and molecular subtypes of breast cancer had statistically significant association (p= 0.002). No association was found between mean Ki-67 and tumour size (p=0.608), lymph node status (p=0.506) stage (p=0.979) and grade (p=0.095) of the tumour. Although scoring pattern I and III had no remarkable findings. Notably, scoring pattern II showed higher tumour sizes, lymph node positivity, higher stage and grade and basal-like tumours demonstrated a higher Ki-67 index. Conclusion: Evaluation of Ki-67 as a continuous variable yielded significant association with other prognostic markers of breast cancer. There was no single “best” scoring pattern identified. A direct association of Ki-67 was found with molecular subtypes of breast cancer.

Integrating and validating automated digital imaging analysis of estrogen receptor immunohistochemistry in a fully digital workflow for clinical use

BackgroundThe Visiopharm automated estrogen receptor (ER) digital imaging analysis (DIA) algorithm assesses digitized ER immunohistochemistry (IHC) by segmenting tumor nuclei and detecting stained nuclei automatically. We aimed to integrate and validate this algorithm in a digital pathology workflow for clinical use. DesignThe study cohort consisted of a serial collection of 97 invasive breast carcinoma specimens including 73 biopsies and 24 resections. ER IHC slides were scanned into Philips Image Management System (IMS) during our routine digital workflow and digital images were directly streamed into Visiopharm platform and analyzed using automated ER algorithm to obtain the positively stained tumor nuclei and staining intensity. ER DIA scores were compared with pathologists’ manual scores. ResultsThe overall concordance between pathologists’ reads and DIA reads was excellent (91/97, 93.8%). Pearson Correlation Coefficient of the percentage of ER positive nuclei between the original reads and VIS reads was 0.72. Six cases (3 ER-negative and 3 ER-positive) had discordant results. All 3 false negative cases had very weak ER staining and no more than 10% positivity. The causes for false positive DIA were mainly pre-analytic/pre-imaging and included intermixed benign glands in tumor area, ductal carcinoma in-situ (DCIS) components, and tissue folding. ConclusionsAutomated ER DIA demonstrates excellent concordance with pathologists’ scores and accurately discriminates ER positive from negative cases. Furthermore, integrating automated biomarker DIA into a busy clinical digital workflow is feasible and may save time and labor for pathologists.

Endometrial Disease in Six Cats with Clinical and Histopathological Features Resembling Atypical Endometrial Hyperplasia in Humans

In humans, atypical endometrial hyperplasia (AEH) is considered as a precancerous lesion of endometrial adenocarcinoma (EA), from which it must be distinguished. Precancerous lesions have not been reported in cats with EA. We now document the histopathological features of endometrial lesions in six cats, which histopathologically resembled human AEH and had a good prognosis following ovariohysterectomy. Grossly, one cat presented with papillomatous nodules and three cats had pyometra. Histopathologically, proliferation of endometrial epithelial cells without atypia was observed in all cases. In some regions of the endometrium, cells had increased atypia and were arranged in stratified layers, which formed irregular ducts and papillary structures. No invasive behaviour or vascular invasion was observed. On the basis of these findings, the cats were diagnosed with non-invasive or early-stage adenocarcinoma. Immunohistochemistry for oestrogen receptor and progesterone receptor revealed an inverse correlation with the severity of the endometrial lesions and degree of malignancy of tumour cells. Ki67 labelling revealed that mitotic activity increased as the lesion developed. All cats survived, with a median survival time of 385 days (range: 229-744 days). The distribution of the histopathological endometrial changes and the non-invasive behaviour in these feline cases resemble cases of AEH in humans.

Colorectal endometriosis with a large polypoid lesion

A 39-year-old woman was referred to our hospital because of a positive fecal occult blood test result. She had undergone uterine myomectomy 6 years earlier, and she had been treated with levothyroxine for hypothyroidism after thyroidectomy for Graves’s disease. A physical examination revealed a left-sided abdominal mass without tenderness. A laboratory test showed that the levels of serum tumor markers were within normal range. A barium enema revealed a 4-cm protruding lesion in the descending colon (A). The lesion looked like a submucosal tumor with reddish mucosa and dilatated vessels (B). Magnifying endoscopy with crystal violet staining showed 2 types of pit pattern: most was regular and rounded, whereas a small area had an enlarged and irregular pit pattern (C). Surgical histopathologic examination confirmed that the protruding lesion was composed of endometrial glands and stroma surrounded by smooth muscle bundles (D, H&E, orig. mag. ×40). The results of testing for immunohistochemistry, estrogen receptor (ER), and progesterone receptor were positive. Therefore, we diagnosed polypoid endometriosis. Retrospectively, a biopsy specimen from the lesion with irregular pits showed that a few glands were positive for ER (E, Immunohistochemistry for ER, orig. mag. ×200). Colorectal endometriosis usually presents as eccentric wall thickening and surface nodularities, and diagnosis by endoscopic biopsy is difficult. Our case suggests that magnifying endoscopy is useful for diagnosis with target biopsy for intestinal endometriosis.

Effect of EDTA decalcification on estrogen receptor and progesterone receptor immunohistochemistry and HER2/neu fluorescence in situ hybridization in breast carcinoma

Bone is the most common site of metastasis in breast carcinoma (BC). Treatments for metastatic BC depend on various factors, including the tumor's estrogen receptor (ER), progesterone receptor (PR), and HER2 status. Bone biopsies require decalcification which may affect the accuracy of ER and PR immunohistochemistry (IHC) and HER2 situ hybridization (FISH) studies. Ethylenediaminetetraacetic acid (EDTA) decalcifying solutions have been theorized to have no significant impact on ER and PR IHC or HER2 FISH analyses. We completed a prospective study of the effect of EDTA decalcification on ER and PR IHC and HER2 FISH in 29 cases of BC. Samples from 29 BC resections were collected and formalin fixed between 12 and 24h. Control samples were routinely processed, whereas test samples were placed in EDTA for 48h. ER and PR slides were blinded, randomized, and evaluated. Blinded samples underwent HER2 FISH assays where an average HER2 copy number and HER2/CEP17 ratio were calculated. Paired differences between EDTA and control samples were compared for ER and PR positivity, average HER2 copy number, and HER2/CEP17 ratios using paired-samples t-tests (PST) and Wilcoxon signed-rank test (WSR). PST and WSR tests yielded no significant difference between EDTA and control tissue for ER% (PST: P=1; WSR: P=0.916), PR% (PST: P=0.973; WSR: P=0.984), HER2 copy number (PST: P=0.124; WSR: P=0.103), and HER2/CEP17 ratio (PST: P=0.25; WSR: P=0.105). The use of EDTA in bony tissue is therefore a valid decalcification method to ensure accurate assessment of ER and PR IHC and HER2 FISH in metastatic BC.

A CROSS SECTIONAL STUDY OF BREAST CANCER HISTOMORPHOLOGY AND ITS CORRELATION WITH ER/PR, HER 2NEU AND KI-67 EXPRESSION IN A TERTIARY CARE HOSPITAL AT KANPUR

BACKGROUND Breast carcinoma is the most well-known malignancy in women. Different predictive and prognostic factors, for example, estrogen receptors (ER), progesterone receptors (PR) and human epidermal growth factor receptor (Her2neu), and Ki67 could inuence breast carcinoma behaviour, yet to date no authoritative connection has been set up among them and breast carcinoma subtypes. In this way present study was done to determine the interrelationships of these predictive and prognostic factors for breast carcinoma. METHODS In this cross sectional study, a total of 50 lumpectomy, modied radical mastectomy specimens of diagnosed carcinoma breast were included in this study. The histopathological grading of the breast carcinoma was performed by Nottingham modication of the Bloom Richardson grading system. All the cases went through immunohistochemistry for ER, PR, Her2neu and Ki67 expression. Association of ER, PR, Her2neu and Ki67 with different histomorphology was established. RESULTS The ER positivity was signicantly lower in tumors >5 cm size whereas Ki67was signicantly increased with increased tumor size. The ER positivity was signicantly lower in high grade tumors as compared to low grade tumors. The positive ER, PR, Her2neu and Ki67 were comparable in between premenopausal and post-menopausal age groups CONCLUSION The present study concludes that ER, PR show inverse while ki67 showed a direct relationship with the tumor grade. Correlation of histomorphology of breast tumor and Her2neu status could not be established.

Sex Difference in the Tolerance of Hepatic Ischemia-reperfusion Injury and Hepatic Estrogen Receptor Expression According to Age and Macrosteatosis in Healthy Living Liver Donors.

Hepatic estrogen signaling, which is important in liver injury/recovery, is determined by the level of systemic estrogen and hepatic estrogen receptor. We aimed to evaluate whether females' advantage in the tolerance of hepatic ischemia-reperfusion injury decreases according to the age of 40 y (systemic estrogen decrease) and macrosteatosis (hepatic estrogen receptor decrease). We included 358 living liver donors (128 female and 230 male individuals). The tolerance of hepatic ischemia-reperfusion injury was determined by the slope of the linear regression line modeling the relationship between the duration of intraoperative hepatic ischemia and the peak postoperative transaminase level. Estrogen receptor content was measured in the biopsied liver samples using immunohistochemistry. In the whole cohort, the regression slope for aspartate transaminase was comparable between female and male individuals (P = 0.940). Within the subgroup of donors aged ≤40 y, the regression slope was significantly smaller in female individuals (P = 0.031), whereas it was comparable within donors aged >40 y (P = 0.867). Within the subgroup of nonmacrosteatotic donors aged ≤40 y, the regression slope was significantly smaller in female individuals in univariable (P = 0.002) and multivariable analysis (P = 0.006), whereas the sex difference was not found within macrosteatotic donors aged ≤40 y (P = 0.685). Estrogen receptor content was significantly greater in female individuals within nonmacrosteatotic donors aged ≤40 y (P = 0.021), whereas it was not different in others of age >40 y or with macrosteatosis (P = 0.450). The tolerance of hepatic ischemia-reperfusion injury was greater in female individuals than in male individuals only when they were <40 y and without macrosteatosis. The results were in agreement with the hepatic estrogen receptor immunohistochemistry study.

Abstract PS5-46: Introduction and clinical validation of metrology standards for immunohistochemistry (IHC); New tool for standardization of estrogen receptor (ER) IHC assay in breast cancer

Abstract Traceability of measurement to a higher order reference standard is a foundation of laboratory testing. There is as yet no method for creating reference standards for cellular proteins in situ in an analogous fashion as for soluble analytes. At present, IHC laboratories produce results for breast cancer hormone receptors without connection to a reference standard. Not surprisingly, high rates of testing variation as well as discrepancies among IHC laboratories have been reported. To address this need, we developed a system of measurement traceability using a linked fluorescein tag for creating reference standards for any cellular analyte and, as a first test, validate it for estrogen receptor (ER) testing. In this study, the newly developed ER standard defines and compares the thresholds separating “high positive”, “low positive”, and “negative” tests according to updated ASCO/CAP guidelines as detected by clinical IHC laboratories in a national external quality assessment survey. This reference standard utilizes NIST Standard Reference Material (SRM) 1934 as a universal IHC standard. We calculated ER concentration based on a linked fluorescence measurement traceable to NIST SRM 1934 as each ER is linked to a single fluorescein, and fluorescein concentration equals ER concentration. Each laboratory’s lowest detected ER concentration (i.e. “limit of detection”, LOD) was compared to their results with 80 tumor samples enriched for triple negative breast cases. For the Canadian Immunohistochemistry Quality Control (CIQC) ER proficiency testing run, calibrator sets with peptides for the SP1, EP1, and 6F11 epitopes were created. The various concentrations were pipetted onto histology slides used by CIQC to place its 80-case breast cancer tissue microarray. These slides were stained by participating laboratories using their routine ER IHC protocols and returned to the CIQC. For the purpose of this study, Histology Score and ASCO/CAP categorical scoring recommendation was used for the readout. Results with SP1 clone are reported here because it was employed by overwhelming majority of laboratories. A total of 3,038 readouts were included in the analysis. Most IHC laboratories had a LOD between 10,000 – 25,000 molecules ER per microbead. Highly sensitive ER assays (low LODs) detected more positive cases while those with poorly sensitive assay detected fewer. The LOD correlated with the percent positive cases (R2= -.767, p &amp;lt; 0.0001, Spearman Correlation) as well as with cumulative individual laboratory Histology Score (R2= -.612, p &amp;lt; 0.0001, Spearman Correlation). The tumor samples accounting for this difference were principally “low positive” (ASCO/CAP classification) while ER-high positive tumors were less affected. Although the concept of a non-quantitative IHC LOD has been introduced with critical assay performance controls (iCAPCs, e.g. germinal center cells in the tonsil for ER), there were no tools until now to actually measure LOD for ER IHC testing. With the calibrators introduced here, it is now possible to measure the LOD for ER IHC assays. Furthermore, our data show that ER low positive and some cases of ER high positive breast cancers are highly affected by the variability of analytic sensitivity between clinical IHC laboratories. These data argue for the urgent need to standardize testing to a defined analytic sensitivity range, which is now possible for the first time. Beyond inter-laboratory standardization, known measured LOD also enables: i) methodology transfer from clinical trials to clinical laboratories; ii) determination of optimal analytical sensitivity to produce assays with highest clinical and analytical validity, and iii) daily monitoring of analytical sensitivity for each tested IHC slide. Citation Format: Emina Emilia Torlakovic, Seshi R. Sompuram, Kodela Vani, Lili Wang, Anika K Schaedle, Paul C. DeRose, Steven A. Bogen. Introduction and clinical validation of metrology standards for immunohistochemistry (IHC); New tool for standardization of estrogen receptor (ER) IHC assay in 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 PS5-46.

Abstract PS10-02: A good prognosis of endocrine-dependent tumors among residual invasive cancer after anti-HER2 therapy: CALGB 40601 (Alliance) and validation studies

Abstract Background: Patients with HER2+ breast cancer who have residual disease after neoadjuvant anti-HER2 plus chemotherapy have a high risk of recurrence and benefit from adjuvant trastuzumab emtansine (T-DM1). We hypothesize that endocrine-responsive residual tumors after neoadjuvant treatments may have good outcomes among patients receiving only adjuvant endocrine therapy plus trastuzumab. Using paired pre- and post-treatment samples from CALGB 40601 and other neoadjuvant cohorts that did not include adjuvant T-DM1, we investigated survival by pretreatment and residual disease ESR1 and PgR gene expression in CALGB 40601, and by estrogen receptor (ER) and progesterone receptor (PR) immunohistochemistry (IHC) in the other cohorts. We considered endocrine-responsive tumors those with ER and/or PR expression by gene expression or IHC. Methods: CALGB 40601 is a randomized neoadjuvant trial of single vs. dual HER2-targeting (trastuzumab and/or lapatinib added to paclitaxel). We only included those patients who had not suffered from disease progression or death during their preoperative treatments. In total, 77 patients with paired pretreatment and residual disease tumors were profiled by mRNA sequencing and studied. Cutoffs for ESR1 and PgR mRNA expression mimicking clinical positivity were obtained using 265 pretreatment CALGB 40601 tumors (and 1,045 TCGA samples for ESR1). We also examined ER and PR IHC in paired tumors from 202 patients treated at 4 different collaborating institutions; all had residual disease after neoadjuvant HER2 targeting plus chemotherapy. We considered ER- or PR-positive as ≥10% positively staining cells. The primary endpoint was EFS, defined as the time from randomization to event in CALGB 40601 and from the first systemic therapy to event in the 4-institution validation cohort. Results: In 77 patients from CALGB 40601 with paired (pretreatment/residual disease) specimens, 38 (49.3%) had ESR1+/ESR1+ tumors. The EFS was superior in the ESR1+/ESR1+ (n=38) group than in the remaining others (the log-rank test, p=0.011). The 5- and 7-year EFS rates for the ESR1+/ESR1+ (n=38) were 92.1% and 89.2%, whereas the rates were uniformly &amp;lt; 70% in the others. In particular, the 5-year EFS rate among 11 patients with ESR1+/ESR1- tumors was 61.4%. This remained significant in multivariable analysis with clinical stage and treatment arm; the hazard ratio (HR) for EFS in ESR1+/ESR1+ versus all others was 0.29 (95% CI, 0.09-0.90). In ESR1+/ESR1+ tumors, 5-year EFS rates were high for those whose residual disease and also being PgR+ (n=32) or PAM50 LumA or Normal-like (n=34) (93.8% and 97.1%, respectively). In the institutional validation cohort, pretreatment /residual disease ER(+)/ER(+) tumors (n=113) had superior 3-year EFS versus all others (p=0.010). At a median follow-up of 35.9 months, the 3-year EFS rates for ER(+)/ER(+) and all other groups were 96.6% and 82.6%, respectively. This remained strongly significant in multivariable analysis with clinical stage; the HR for EFS in ER(+)/ER(+) versus all other groups was 0.28 (95% CI, 0.09-0.88). Among 46 who also had PR+ in the residual disease, the 3-year EFS was 100.0%. Conclusions: HER2+ patients with ER+ pretreatment and ER+ residual disease after neoadjuvant chemotherapy + HER2-targeting have a very good survival outcome despite not receiving additional anti-HER2 targeting with T-DM1. This may provide a simple mechanism to better tailor therapy within residual disease patients using serial ER measurements. Citation Format: Sung Gwe Ahn, Aranzazu Fernandez-Martinez, Mei-Yin C. Polley, Soong June Bae, Seho Park, Núria Chic, Fara Brasó-Maristany, Benedetta Conte, Valentina Guarneri, Maria Vittoria Dieci, Gaia Griguolo, PierFranco Conte, Joon Jeong, Aleix Prat, Lisa A. Carey, Charles M Perou. A good prognosis of endocrine-dependent tumors among residual invasive cancer after anti-HER2 therapy: CALGB 40601 (Alliance) and validation studies [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 PS10-02.

Abstract PS12-04: Rintodestrant (G1T48), an oral selective estrogen receptor degrader in ER+/HER2- locally advanced or metastatic breast cancer: Updated phase 1 results and dose selection

Abstract Background: Rintodestrant (G1T48) is a potent oral selective estrogen receptor degrader (SERD) that competitively binds to the estrogen receptor (ER) and blocks ER signaling in tumors resistant to other endocrine therapies. Preliminary results from Part 1 dose escalation showed robust target engagement on 18F-fluoroestradiol positron emission tomography (FES-PET), a favorable safety profile, and encouraging antitumor activity in patients with heavily pretreated ER+/HER2- advanced breast cancer (ABC), including those with ESR1 mutations (Dees et al., ESMO 2019 [abstract #3587]). Here, we present updated results from dose escalation and expansion (Parts 1 and 2). Methods: This Phase 1, first-in-human, open-label study evaluated rintodestrant monotherapy in women with ER+/HER2- ABC after progression on endocrine therapy. Part 1 was a 3+3 dose escalation (200-1000 mg once daily [QD]); Part 2 expanded 600 and 1000 mg QD; and Part 3 was added to assess rintodestrant with palbociclib in patients in earlier lines in the advanced setting. Primary objectives included dose-limiting toxicities (DLTs), maximum tolerated dose (MTD), safety, and recommended Phase 2 dose. Secondary objectives included pharmacokinetics and antitumor activity (RECIST v1.1). Exploratory objectives included pharmacodynamic inhibition of ER target engagement (FES-PET), mutation profiling (cell-free DNA [cfDNA]), and change in ER expression from baseline to on-treatment tumor biopsies. Results: As of May 13, 2020, 67 patients (Part 1: n = 26; Part 2: n = 41) were treated, with a median age of 61 years (range 34-83) and ECOG PS of 0 (49%) or 1 (51%). Median number of prior lines in the advanced setting was 2 (range 0-9), including prior fulvestrant (64%), CDK4/6 inhibitor (69%), mTOR inhibitor (22%), and/or chemotherapy (46%). Median number of prior lines of endocrine therapy in the advanced setting was 2 (range 0-5), with 61% of patients having received ≥2 lines. Treatment-related adverse events (TRAEs) were reported in 70% of patients. The most common TRAEs in ≥10% of patients included hot flush (24%), fatigue (21%), nausea (19%), diarrhea (18%), and vomiting (10%), mostly grade 1 or 2. No DLTs were reported and MTD was not reached. Dose reduction due to TRAEs occurred in 1 patient (1%), with elevated transaminases (grade 3 ALT and grade 2 AST) at 600 mg. Serious TRAEs occurred in 2 patients at 1000 mg (grade 5 cerebral hemorrhage in the setting of low molecular weight heparin and grade 2 upper abdominal pain). Two patients (3%) discontinued treatment due to TRAEs. Overall, the frequency of patients with TRAEs at 800 mg was comparable with that at 600 mg (57% vs 63%) and less than that at 1000 mg (81%). Of 67 patients, 16 were on study treatment for ≥24 weeks and 3 (n = 1 at 600 mg; n = 2 at 1000 mg, including 1 with ESR1 mutation) had a confirmed partial response (clinical benefit rate [CBR]: 28%). FES-PET standard uptake values decreased at week 4 with a mean reduction of 87% (±8%) at doses ≥ 600 mg. Of 59 patients tested for baseline cfDNA, 41% harbored ≥1 ESR1 mutation, with a similar CBR in both groups (33% in ESR1 mutant and 29% in ESR1 wild-type). Seven of 9 patients had a decrease in ER immunohistochemistry H-score at both 600 and 1000 mg (median [range]: -27.8% [-33.8%, -3.4%]), irrespective of ESR1 mutation status. Based on safety, efficacy, and ER degradation, 800 mg was selected as the optimal dose for further study. Conclusions: Rintodestrant continues to demonstrate an excellent safety/tolerability profile across all doses, with promising antitumor activity in patients with heavily pretreated ER+/HER2- ABC, including those with tumors harboring ESR1 mutations. Part 3 of this study, evaluating rintodestrant 800 mg QD with palbociclib in a more endocrine-sensitive population, is ongoing (NCT03455270). Citation Format: Philippe Aftimos, Patrick Neven, Mark Pegram, Catharina Willemien Menke-van der Houven van Oordt, E. Claire Dees, Carolien Schröder, Agnes Jager, Iurie Bulat, Linnea Chap, Marina Maglakelidze, Erika Hamilton, Massimo Cristofanilli, Susanna Ulahannan, Jorianne Boers, Ramsha Iqbal, Adrian Crijanovschi, Curt D Wolfgang, Wenli Tao, Christina Sipes, Rajesh Malik, Sarika Jain. Rintodestrant (G1T48), an oral selective estrogen receptor degrader in ER+/HER2- locally advanced or metastatic breast cancer: Updated phase 1 results and dose selection [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 PS12-04.

AN ANALYSIS AND SIGNIFICANCE OF IMMUNOHISTOCHEMISTRY ER, PR AND HER2 TESTING FOR BREAST MALIGNANCY IN A TERTIARY CARE CENTER

Background: A significant development in the Breast malignancy, the expression of Hormone receptors in the tumor cells for the management and prognosis. Aim of Study : This study was conducted to correlate Immunohistochemical expression of markers such as estrogen receptor( ER) , progesterone receptor (PR ),and Her-2/neu with clinical mainly age, sex and Histopathological parameters . Materials and Methods: This prospective study was done at the tertiary care hospital from January 2019 to January 2020. 296 cases of Breast malignancy were studied. Immunohistochemistry (IHC) for ER, PR, and Her-2/neu was performed. The laboratory reporting was done according to the standard scoring system from CAP protocol 2019. Results: According to the molecular basis of Breast tumor, the ER positive and Her-2 Negative was observed in 24.6% ( 73/296) cases , ER Positive and Her-2/neu Positive in 22.9 % ( 68/296) cases, whereas ER negative and Her-2 /neu positive in 21.6 % ( 64/296) cases. Triple marker (ER , PR and Her-2) negative cases were seen in 23.9 % ( 71/296). Triple marker positive cases were 6.75 % ( 20/296). Conclusion: IHC markers studies in Breast malignancy is still gold standard for treating the patients and prognostic aspect.

Wnt/β-Catenin and Hippo Pathway Deregulation in Mammary Tumors of Humans, Dogs, and Cats.

Mammary cancer is a common neoplasm in women, dogs, and cats that still represents a therapeutic challenge. Wnt/β-catenin and Hippo pathways are involved in tumor progression, cell differentiation, and metastasis. The aim of this study was to evaluate mRNA and protein expression of molecules involved in these pathways in human (HBC), canine (CMT), and feline mammary tumors (FMT). Real-time quantitative polymerase chain reaction (qPCR) for β-catenin, CCND1, YAP, TAZ, CTGF, and ANKRD1, western blotting for YAP, TAZ, and β-catenin, and immunohistochemistry for estrogen receptor (ER), progesterone receptor (PR), ERBB2, β-catenin, and YAP/TAZ were performed on mammary tumor tissues. The protein expression of active β-catenin was higher in tumors than in healthy tissues in all 3 species. The mRNA expression of the downstream gene CCND1 was increased in HBC ER+ and CMTs compared to healthy tissues. Membranous and cytoplasmic protein expression of β-catenin were strongly negatively correlated in all 3 species. Tumors showed an increased protein expression of YAP/TAZ when compared to healthy tissues. Notably, YAP/TAZ expression was higher in triple negative breast cancers when compared to HBC ER+ and in FMTs when compared to CMTs. The mRNA expression of β-catenin, YAP, TAZ, CTGF, and ANKRD1 was not different between tumors and healthy mammary gland in the 3 species. This study demonstrates deregulation of Wnt/β-catenin and Hippo pathways in mammary tumors, which was more evident at the protein rather than the mRNA level. Wnt/β-catenin and Hippo pathways seem to be involved in mammary carcinogenesis and therefore represent interesting therapeutic targets that should be further investigated.

Correlation of ER, PR, Her2neu and Ki67 with other Prognostic factors in Breast Carcinoma

Background:In females, breast carcinoma is the most common malignancy accounting for 23% of all malignant tumours. Various predictive and prognostic factors affect tumour progression. In addition to estrogen receptors (ER), progesterone receptors (PR) and human epidermal growth factor receptor (Her2neu), recently Ki67, a proliferative marker has been recognized as an important predictive and prognostic marker in many studies. The aim of the study was to find the correlation of ER, PR, Her2neu and Ki67 tumour markers with menopausal status, tumour size, histopathological grade, mitotic index, lymphovascular invasion and lymph node metastasis. Methods:The present study was conducted on 50 cases of breast carcinomas. The histopathological grading of the breast carcinoma was done according to the Nottingham modification of the Bloom Richardson grading system. All the cases underwent immunohistochemistry for ER, PR, Her2neu and Ki67 expression. Correlation of ER, PR, Her2neu and Ki67 with various prognostic factors was done. Results:The expression of ER and PR decreased as the grade of the tumour increased. Ki67 proliferative index increased as the grade of the tumour increased. Ki67 proliferative index also increased as the mitotic count increased. None of these markers showed a correlation with other prognostic factors. Conclusion: The present study concludes that ER, PR reveals inverse relationship and Ki67 showed a direct relationship with the grade of the tumour. Increased Ki67 proliferative index was associated with increased mitotic activity and less expression of ER, PR; thus carrying a poor prognosis.

Molecular characterization of breast cancer needle core biopsy specimens by the 21-gene Breast Recurrence Score test.

Background and ObjectiveRecent COVID‐19 pandemic guidelines recommend genomic assessment of core biopsies to help guide treatment decisions in estrogen receptor (ER)‐positive early‐stage breast cancer. Herein we characterize biopsy and excisional breast cancer specimens submitted for 21‐gene testing.MethodsUS samples submitted to Genomic Health for 21‐gene testing (01/2004‐04/2020) were assessed by pathologists and analyzed by a standardized quantitative reverse transcription‐polymerase chain reaction. Predefined cutoffs were: ESR1 (positive ≥6.5), PGR (positive ≥5.5), and ERBB2 (negative <10.7). ER status by immunohistochemistry (IHC) and lymph node status were determined locally. Median and interquartile range were reported for continuous variables, and total and percent for categorical variables. Distributions were assessed overall, by age, and by nodal involvement.ResultsOf 919 701 samples analyzed, 13% were biopsies and 87% were excisions. Initial assay success rates were 94.5% (biopsies) and 97.3% (excisions). ER IHC concordance with central ESR1 was 96.8% (biopsies) and 97.6% (excisions). Biopsy and excisional medians were: Recurrence Score results 16 (each); ESR1 10.2 (each); PGR 7.7 and 7.6; ERBB2 9.4 and 9.2, respectively.ConclusionsBiopsy submissions for 21‐gene testing are common and consistently generate results that are very similar to the experience with excisions. The 21‐gene test can be performed reliably on core biopsies.

Can pathology diagnostic services for cancer be stratified and serve global health?

Before initiating cancer therapy, a diagnostic tumor tissue sample evaluated within a pathology laboratory by a pathologist is essential to confirm the malignancy type and provide key prognostic factors that direct the treatment offered. Pathology evaluation includes multiple expensive reagents, complex equipment, and both laboratory and pathologist technical skills. By using breast cancer as an example, at a minimum, key tumor prognostic information required before the initiation of treatment includes subtype, tumor grade, tumor size, lymph node status when possible, and biomarker expression determined by immunohistochemistry for estrogen receptor. The additional determination of biomarker expression of progesterone receptor and human epidermal growth factor receptor (HER2) is the standard of care in high-resource settings, but assays may not be affordable in low-income and middle-income countries. With positive tests, patients are eligible for either tamoxifen (for estrogen receptor-positive/progesterone receptor-positive cancers) or monoclonal antibody therapy (for HER2-positive cancers). For settings in which endocrine therapy and/or HER2-targeted therapy is unavailable, biomarker studies have no utility, and high-resource setting standards for pathology evaluation and reporting are unachievable. Resource-stratified pathology evaluation guidelines in cancer diagnosis have not been developed, in contrast to excellent comprehensive, resource-stratified clinical guidelines for use in low-income and middle-income countries, and these are long overdue. The challenges of pathology evaluation in the context of global health are being met by innovative solutions, which may change the face of pathology practice.

Abstract P4-10-07: Tumor ER protein modulation, molecular characterization and monitoring of cfDNA in phase 1 study of LSZ102 and LSZ102 + ribociclib in patients with ER+ MBC

Abstract Background: LSZ102 is an orally bioavailable selective estrogen receptor degrader (SERD) that inhibits estrogen receptor (ER) mediated gene transcription, induces receptor degradation, and blocks ER-dependent cell growth in preclinical models. This first-in-human study of LSZ102 is evaluating LSZ102 as a single agent (SA) and in combination with the CDK4/6 inhibitor ribociclib or the PI3K inhibitor alpelisib (BYL719) in patients (pts) with locally advanced/metastatic ER-positive (ER+) breast cancer (BC). Here, we present the immunohistochemistry (IHC) and circulating tumor DNA (ctDNA) data obtained from a subset of pts treated with either LSZ102 SA or the combination of LSZ102 and ribociclib. Methods: ER IHC was performed with an antirabbit antibody (clone SP1) on FFPE samples collected at baseline and cycle 1 day 15 (C1D15), and the ER value was reported using the H-score method. A Novartis exploratory PanCancer next-generation sequencing ~600 gene panel for cell-free DNA (cfDNA) was used on plasma samples collected from pts treated with SA or the combination at baseline, on treatment (C1D1, C2D1/C3D1, C5D1, CXD1) at radiological assessments and at the end of treatment (EOT). Results: One hundred fifty-three pts with MBC (median number of prior lines of therapy in metastatic setting = 4; range, 0-10) were treated with LSZ102 SA or the combination of LSZ102 and ribociclib (data cutoff, November 30, 2018). ER protein levels, assessed by IHC H-score, are downregulated in about 75% of C1D15 samples in both SA and combination-treated pts. In this cohort of heavily pretreated pts, cfDNA sequencing was performed on approximately 400 samples from 135 pts, and the genomic landscape is described both at baseline and EOT for pts with detectable ctDNA (~77% of pts). At baseline, approximately 40% of pts had mutations in the ESR1 ligand-binding domain (LBD), and approximately 40% of pts had PIK3CA activating mutations. LBD ESR1 mutations were mainly subclonal with several pts harboring multiple mutations at baseline. The frequency of ESR1 Y537S mutation was no higher in EOT samples after LSZ102 treatment compared with baseline. Moreover, the tumor reduction of target lesions &amp;gt; 30% was observed in pts harboring different baseline ESR1 mutations, including Y537S, treated with either SA or the combination. Furthermore, the longitudinal cfDNA analysis showed a consistent reduction of the overall circulating tumor fraction (ctDNA fraction), from baseline for the majority of patients who achieved either partial response or stable disease with either SA or the combination. Conclusions: Consistent with being a SERD, LSZ102 treatment leads to the degradation of ER in tumor biopsies. The addition of ribociclib does not alter LSZ102-induced ER downregulation. The most common genetic alterations found in cfDNA collected from enrolled ER+ MBC patients before the study treatment were ESR1 and PIK3CA mutations. Importantly, the antitumor activity was observed in pts harboring a variety of ESR1 LBD mutations. Furthermore, enrichment of ESR1 Y537S mutations was not observed after LSZ102 treatment. Finally, the on-treatment longitudinal assessment of cfDNA measuring ctDNA fraction and mutation dynamics is maturing as a useful tool for monitoring the treatment efficacy. Citation Format: Komal Jhaveri, Dejan Juric, Sara Cresta, Yoon-Sim Yap, Francois P. Duhoux, Catherine Terret, Rachel Layman, Alejandro Balbin, Qing Sheng, Serena Liao, Adam Crystal, Giuseppe Curigliano. Tumor ER protein modulation, molecular characterization and monitoring of cfDNA in phase 1 study of LSZ102 and LSZ102 + ribociclib in patients with ER+ MBC [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-10-07.