Novel oral selective estrogen receptor degraders (SERDs) to target hormone receptor positive breast cancer: Elacestrant as the poster-child

INTRODUCTION

Estrogen receptor positive (ER+) breast cancer is the most common breast cancer subtype, and therapeutic management relies primarily on inhibiting ER signaling. In the metastatic setting, ER signaling is typically targeted by selective estrogen receptor degraders (SERDs) or aromatase inhibitors (AIs), the latter of which prevent estrogen production. Activating ESR1 mutations are among the most common emergent breast cancer mutations and confer resistance to AIs.

AREAS COVERED

Until 2023, fulvestrant was the only approved SERD; fulvestrant is administered intramuscularly, and in some cases may also have limited efficacy in the setting of certain ESR1 mutations. In 2023, the first oral SERD, elacestrant, was approved for use in ESR1-mutated, ER+/HER2- advanced breast cancer and represents a new class of therapeutic options. While the initial approval was as monotherapy, ongoing studies are evaluating elacestrant (as well as other oral SERDs) in combination with other therapies including CDK4/6 inhibitors and PI3K inhibitors, which parallels the current combination uses of fulvestrant.

EXPERT OPINION

Elacestrant's recent approval sheds light on the use of biomarkers such as ESR1 to gauge a tumor's endocrine sensitivity. Ongoing therapeutic and correlative biomarker studies will offer new insight and expanding treatment options for patients with advanced breast cancer.

Interplay between ESR1/PIK3CA codon variants, oncogenic pathway alterations and clinical phenotype in patients with metastatic breast cancer (MBC): comprehensive circulating tumor DNA (ctDNA) analysis

BACKGROUND

although being central for the biology and druggability of hormone-receptor positive, HER2 negative metastatic breast cancer (MBC), ESR1 and PIK3CA mutations are simplistically dichotomized as mutated or wild type in current clinical practice.

METHODS

The study analyzed a multi-institutional cohort comprising 703 patients with luminal-like MBC characterized for circulating tumor DNA through next generation sequencing (NGS). Pathway classification was defined based on previous work (i.e., RTK, RAS, RAF, MEK, NRF2, ER, WNT, MYC, P53, cell cycle, notch, PI3K). Single nucleotide variations (SNVs) were annotated for their oncogenicity through OncoKB. Only pathogenic variants were included in the models. Associations among clinical characteristics, pathway classification, and ESR1/PIK3CA codon variants were explored.

RESULTS

The results showed a differential pattern of associations for ESR1 and PIK3CA codon variants in terms of co-occurring pathway alterations patterns of metastatic dissemination, and prognosis. ESR1 537 was associated with SNVs in the ER and RAF pathways, CNVs in the MYC pathway and bone metastases, while ESR1 538 with SNVs in the cell cycle pathway and liver metastases. PIK3CA 1047 and 542 were associated with CNVs in the PI3K pathway and with bone metastases.

CONCLUSIONS

The study demonstrated how ESR1 and PIK3CA codon variants, together with alterations in specific oncogenic pathways, can differentially impact the biology and clinical phenotype of luminal-like MBC. As novel endocrine therapy agents such as selective estrogen receptor degraders (SERDS) and PI3K inhibitors are being developed, these results highlight the pivotal role of ctDNA NGS to describe tumor evolution and optimize clinical decision making.

Genetic Alterations Detected by Circulating Tumor DNA in HER2-Low Metastatic Breast Cancer

PURPOSE

About 50% of breast cancers are defined as HER2-low and may benefit from HER2-directed antibody-drug conjugates. While tissue sequencing has evaluated potential differences in genomic profiles for patients with HER2-low breast cancer, genetic alterations in circulating tumor DNA (ctDNA) have not been well described.

EXPERIMENTAL DESIGN

We retrospectively analyzed 749 patients with metastatic breast cancer (MBC) and ctDNA evaluation by Guardant360 from three academic medical centers. Tumors were classified as HER2-low, HER2-0 (IHC 0) or HER2-positive. Single-nucleotide variants, copy-number variants, and oncogenic pathways were compared across the spectrum of HER2 expression. Overall survival (OS) was evaluated by HER2 status and according to oncogenic pathways.

RESULTS

Patients with HER2-low had higher rates of PIK3CA mutations [relative risk ratio (RRR), 1.57; P = 0.024] compared with HER2-0 MBC. There were no differences in ERBB2 alterations or oncogenic pathways between HER2-low and HER2-0 MBC. Patients with HER2-positive MBC had more ERBB2 alterations (RRR, 12.43; P = 0.002 for amplification; RRR, 3.22; P = 0.047 for mutations, in the hormone receptor-positive cohort), fewer ERS1 mutations (RRR, 0.458; P = 0.029), and fewer ER pathway alterations (RRR, 0.321; P < 0.001). There was no difference in OS for HER2-low and HER2-0 MBC [HR, 1.01; 95% confidence interval (CI), 0.79-1.29], while OS was improved in HER2-positive MBC (HR, 0.32; 95% CI, 0.21-0.49; P < 0.001).

CONCLUSIONS

We observed a higher rate of PIK3CA mutations, but no significant difference in ERBB2 alterations, oncogenic pathways, or prognosis, between patients with HER2-low and HER2-0 MBC. If validated, our findings support the conclusion that HER2-low MBC does not represent a unique biological subtype.

Cyclin-Dependent Kinase 4/6 Inhibitors Beyond Progression in Metastatic Breast Cancer: A Retrospective Real-World Biomarker Analysis

PURPOSE

As the continuation beyond progression (BP) of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) is becoming increasingly attractive for the treatment of patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC), the definition of resistance factors is crucial. The aim of the study was to investigate the impact of CDK 4/6i BP and to explore potential genomic stratification factors.

MATERIALS AND METHODS

We retrospectively analyzed a multi-institutional cohort of patients with HR-positive HER2-negative MBC characterized for circulating tumor DNA through next-generation sequencing before treatment start. Differences across subgroups were analyzed by chi-square test, and survival was tested by univariable and multivariable Cox regression. Further correction was applied by propensity score matching.

RESULTS

Among the 214 patients previously exposed to CDK4/6i, 172 were treated with non-CDK4/6i-based treatment (non-CDK) and 42 with CDK4/6i BP. Multivariable analysis showed a significant impact of CDK4/6i BP, TP53 single-nucleotide variants, liver involvement, and treatment line on both progression-free survival (PFS) and overall survival (OS). Propensity score matching confirmed the prognostic role of CDK4/6i BP both for PFS and OS. The favorable impact of CDK4/6i BP was consistent across all subgroups, and a differential benefit was suggested for ESR1-mutated patients. ESR1 and RB1 mutations were more represented in the CDK4/6i BP subgroup with respect to CDK4/6i upfront.

CONCLUSION

The study highlighted a significant prognostic impact of the CDK4/6i BP strategy with a potential added benefit in patients with ESR1 mutations suggesting the need for an extensive biomarker characterization.

Abstract P5-02-13: TRK inhibitor in a patient with metastatic triple negative breast cancer and NTRK fusions identified via cell-free DNA analysis

Introduction: Tissue-agnostic indications for targeted therapies are expanding options for patients with advanced solid tumors. The FDA approvals of the PD-1 inhibitor pembrolizumab and the TRK inhibitors larotrectinib and entrectinib provide rationale for next generation sequencing (NGS) in effectively all advanced solid tumor patients, as findings may indicate targeted therapy even in disease that may seem otherwise refractory. Here, we present the case of a post-menopausal woman with metastatic triple negative breast cancer (TNBC) who had disease progression on multiple lines of therapy prior to the identification of two actionable NTRK mutations, identified via cell-free DNA (cfDNA) and tissue-based NGS. She was subsequently started on the TRK inhibitor larotrectinib and had a marked clinical response. Case Presentation: A 64-year-old woman presented with metastatic TNBC five years after being treated for a localized breast cancer. The cancer rapidly progressed through 4 lines of therapy in the metastatic setting, including immunotherapy [atezolizumab/nab-paclitaxel (progression after 5 months)], antibody-drug conjugate-based therapy [sacituzumab govitecan (progression after 2 months)], and chemotherapy [gemcitabine/carboplatin (progression after 3 months), eribulin (progression after 2 months)]. Her CA 15-3 had also been consistently increasing to a peak of 206 IU/mL. Germline genetic testing was negative. Ultimately, NGS evaluation of cfDNA via an 83-gene assay (Guardant Health, Inc.) identified two NTRK3 fusions: an ETV6-NTRK3 fusion [mutant allele fraction (MAF) = 10.9%] associated with the rare secretory breast carcinoma, and CRTC3-NTRK3 (MAF = 3.2%), a fusion partner previously undescribed in breast cancer. Liver biopsy was sent for whole exome sequencing and RNA-seq analysis (BostonGene, Inc), which provided orthogonal confirmation of both the ETV6-NTRK3 and CRTC3-NTRK3 fusions. Review of the tumor pathology showed invasive ductal carcinoma with secretory features; this pathology and the ETV6-NTRK3 fusion were consistent with a diagnosis of secretory breast carcinoma. She was started on the TRK inhibitor larotrectinib, and she had a significant clinical and radiographic response after only two months of therapy. Recheck of her CA 15-3 showed a decrease to 48 IU/mL, the lowest level in our records. Repeat cfDNA testing showed a decrease of the ETV6-NTRK3 fusion to MAF 0.40% and the CRTC3-NTRK3 fusion to MAF 0.07%. The patient took larotrectinib for 7 months with good disease control. Unfortunately, unrelated to her therapy, she had experienced multiple fractures secondary to her existing osseous metastases, and these led to significant morbidity. She and her family elected to transition to comfort measures, after which she passed away. Discussion: In the presented case, the identification of NTRK fusions by plasma-based genotyping resulted in matched selection of genotype-directed therapy, and this otherwise refractory TNBC exhibited marked response to targeted therapy. While TNBC had historically been considered a subtype of breast cancer without targetable options, the expanding roles of NGS testing and targeted therapies are changing the paradigm. The actionability of rare genomic events such as NTRK fusions makes identifying them critical for individual patients, particularly in heterogeneous diseases such as TNBC. Tissue-agnostic targeted therapies now give reason for NGS testing in most solid tumors, as reflected in updated consensus guidelines. This case demonstrates the significant potential benefits of NGS testing in advanced and refractory cancers.

Citation Format: Jennifer C. Keenan, Arielle J. Medford, Lauren J. Oshry, Baris Boyraz, Charles S. Dai, Lesli A. Kiedrowski, Sofia Menshikova, Anna Butusova, Tasos Gogakos, Rachel Occhiogrosso, Phoebe Ryan, Jochen Lennerz, Laura M. Spring, Beverly Moy, Leif Ellisen, Aditya Bardia. TRK inhibitor in a patient with metastatic triple negative breast cancer and NTRK fusions identified via cell-free DNA analysis. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-13.

Abstract PD10-01: PD10-01 Impact of ESR1 mutations on Selective Estrogen Receptor Degraders and Modulators: an integrated liquid-biopsy and pharmacodynamics approach

Background: ESR1 hotspot mutations (HS) (i.e. 380, 536, 537, and 538) are important drivers of resistance to aromatase inhibitors, but the differential impact of genomic variants (HS vs non-HS) on response to endocrine therapies (ET) under clinical development, such as novel oral Selective Estrogen Receptor Degraders and Modulators (SERDs and SERMs), is not known. The aim of the study was to evaluate the impact of non-HS ESR1 mutations on the pharmacodynamics of SERDs and SERMs as an additional ET resistance mechanism. Materials and Methods: The study analyzed a multi-institutional cohort of 1008 patients with hormone receptor positive metastatic breast cancer characterized by circulating tumor DNA (ctDNA). Pathway classification was defined based on previous work (i.e. RTK, RAS, RAF, MEK, NRF2, ER, WNT, MYC, p53, Cell Cycle, Notch, PI3K). Single nucleotide variations (SNVs) were annotated through OncoKB; co-occurrence was tested by Fisher’s exact test. A structure-based computational strategy was used to create 3D-models of ESR1 mutants and predict changes in binding affinity (dAff) across approved and experimental drugs. A positive dAff reflects a lower affinity of the drug for mutant ESR1 compared with wild type and thus a potential for a reduced response. Results: Among the total 680 detected ESR1 mutations, 633 were missense, and 631 were gain-of-function. The most frequent mutations were in codon 537 (N=305), followed by 538 (N=224). No significant MAF differences were observed across ESR1 variants (P=0.0829). The L391F mutation resulted in an increased binding affinity for Lasofoxifene (LAS) (dAff -0.34), Giredestrant (GIR) (dAff -0.18), Elacestrant (ELA) (dAff -0.08) and Amcenestrant (AMC) (dAff -0.41), while a decreased binding affinity was observed for 4OH-Tamoxifen (TAM) (dAff 0.01), Imlunestrant (IML) (dAff 0.15), Fulvestrant (FUL) (dAff 0.43), and Camizestrant (CAM) (dAff 0.02). V392F decreased binding affinity for TAM (dAff 0.05), LAS (dAff 0.13), IML (dAff 0.11), GIR (dAff 0.11), FUL (dAff 0.04), CAM (dAff 0.05), AMC (dAff 0.06) but not for ELA (dAff -0.01). F404L decreased binding affinity for FUL (dAff 0.07), ELA (dAff 0.73), and CAM (dAff 0.26), while it increased binding affinity for TAM (dAff -0.27), LAS (dAff -0.02), IML (dAff -0.05), GIR (dAff -0.69), and AMC (dAff -2.01). G415E increased binding affinity for LAS, (dAff -0.15) GIR (dAff -0.02) and ELA (dAff -0.08), while it decreased binding affinity for TAM (dAff 0.11), IML (dAff 0.09), FUL (dAff 0.29), CAM (dAff 0.19) and AMC (dAff 0.10). Mutations in codon 537 did not affect dAff for TAM, GIR, and ELA; a significant decrease in binding affinity was observed for FUL and AMC, whereas it was increased for LAS. Mutational co-occurrence was tested between ESR1 mutations in FUL docking sites and oncogenic pathways. Significant associations were observed for cell cycle SNVs (P=0.047), Notch SNVs (P=0.020), and ER SNVs (P&lt; 0.001). Within these pathways, significant single-gene associations were observed for FBXW7 SNVs (P=0.020), ESR1 SNVs (P&lt; 0.001), and GATA3 SNVs (P= 0.016). Given the highly significant co-occurrence of non-HS with other ESR1 mutations, combined models were examined. The Y537/F404 combination resulted in decreased binding affinity for FUL and increased binding affinity for LAS, while L536/F404 decreased binding affinity for TAM and increased binding affinity for IML, ELA, and AMC. Notably, L540/F404 restored the FUL-ESR1 interaction resulting in an increased binding affinity (dAff -2.1). Conclusions: The study suggests that genomic variability in drug targets detectable through ctDNA may modulate therapeutic response. Preclinical models are under development to investigate the combined endocrine resistance mechanism suggested by the significant co-occurrence between ESR1 mutations in SERDs/SERMs docking sites and ESR1 hotspot mutations and provide valuable additional insights for drug development and future treatment algorithms.

Citation Format: Lorenzo Gerratana, Rossana Roncato, Mattia Sturlese, Andrew A. Davis, Marko Velimirovic, Carolina REDUZZI, Katherine K. Clifton, Whitney L. Hensing, Ami N. Shah, Charles S. Dai, Paolo D’Amico, Arielle J. Medford, Alessandra Franzoni, Linda Cucciniello, Firas Wehbe, Seth A. Wander, Barbara Belletti, William Gradishar, Amir Behdad, Giuseppe Damante, Cynthia Ma, Fabio Puglisi, Aditya Bardia, Massimo Cristofanilli. PD10-01 Impact of ESR1 mutations on Selective Estrogen Receptor Degraders and Modulators: an integrated liquid-biopsy and pharmacodynamics approach. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD10-01.

Abstract P5-02-07: Cell-free DNA detection of GATA3 mutations in metastatic hormone receptor positive breast cancer: a retrospective, observational multi-institutional analysis

Background GATA3 mutations (GATA3mut) have been reported in 10-20% of hormone receptor positive (HR+) breast cancers. It has been shown that targeting GATA3mut HR+ breast cancer with MDM2 inhibitors invokes synthetic lethality. MDM2 is an E3 ubiquitin ligase that targets p53 for degradation, and research suggests that restoring p53 by blocking MDM2 may be effective in treating GATA3mut HR+ breast cancer. One potential mechanism of this efficacy has been shown to be through the PI3K-AKT pathway. We thus sought to characterize the GATA3mut landscape in a multi-institutional cell-free DNA (cfDNA) analysis and to determine the association between GATA3mut and TP53 mutations, as well as alterations in the PI3K-AKT pathway and the impact of GATA3 on survival. Methods We analyzed cfDNA data collected at the Massachusetts General Hospital and at Washington University in St Louis via Guardant360, a next generation sequencing assay that analyzed up to 74 genes during the study period. The association of GATA3mut and co-mutations as well as number of prior therapies was estimated using Pearson’s chi-squared test for categorical variables, two-sample Wilcoxon rank-sum test for continues variables, and multivariable logistic regression. The impact of GATA3mut and GATA3 wildtype (WT) on progression-free survival (PFS) and overall survival (OS) was analyzed using multivariable Cox regression analysis, adjusting for age, number of prior therapies, visceral metastases, and de novo metastases. PFS and OS were evaluated in the overall study population, as well as in subgroups of patients that received endocrine monotherapy and chemotherapy. Results Out of 647 patients with HR+ MBC, 10% (n = 68) had non-synonymous GATA3 mutations. Among these 68 GATA3mut patients, 37% (n = 25) were mutations in exon 5, all but two of which were in the second zinc finger, and 62% (n = 42) were in exon 6. 62% (n = 42) were frameshift mutations, 20% (n = 14) were indels, and 18% (n = 12) were point mutations. Median mutant allele fraction (MAF) of GATAmut was 0.95% (range 0.03 – 30.5%). There was no statistically significant association of GATA3mut with the number of prior therapies, PR status, or the presence of ESR1, TP53, or PI3K-AKT pathway mutations. In the GATA3mut population, TP53 co-mutations (n = 21) were found with a median MAF of 0.6%. PI3K-AKT pathway alterations occurred in 47% (n=32) of GATA3mut patients (PIK3CA n = 27; AKT n = 2; PTEN n = 3). In the combined cohort, there was no significant difference in PFS or OS after adjusting for visceral metastases, de novo disease, number of prior therapies, and age. In a cohort of 80 patients that received endocrine monotherapy (GATA3 WT n = 74, GATA3mut n = 6), GATA3mut were associated with borderline worse PFS (HR 2.6; p = 0.061) and worse OS (HR 4.5; p = 0.009). There was no statistically significant difference in PFS or OS in a subgroup that received chemotherapy. Conclusions GATA3 mutations can be identified via cfDNA in patients with HR+ MBC. Co-mutations in TP53 occurred at overall low MAF. Further research is needed to characterize the functional impact of these low level TP53 co-mutations and develop therapeutic strategies to target GATA3 mutant MBC.

Citation Format: Arielle J. Medford, Marko Velimirovic, Andrzej Niemierko, Whitney L. Hensing, Andrew A. Davis, Katherine K. Clifton, Jennifer C. Keenan, Charles S. Dai, Lesli A. Kiedrowski, Ami N. Shah, Lorenzo Gerratana, Laura M. Spring, Leif Ellisen, Robert C. Doebele, Massimo Cristofanilli, Aditya Bardia. Cell-free DNA detection of GATA3 mutations in metastatic hormone receptor positive breast cancer: a retrospective, observational multi-institutional analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-07.

TRK inhibitor in a patient with metastatic triple-negative breast cancer and NTRK fusions identified via cell-free DNA analysis

Tissue-agnostic indications for targeted therapies have expanded options for patients with advanced solid tumors. The Food and Drug Administration approvals of the programmed death-ligand 1 inhibitor pembrolizumab and the TRK inhibitors larotrectinib and entrectinib provide rationale for next-generation sequencing (NGS) in effectively all advanced solid tumor patients given potential for clinical responses even in otherwise refractory disease. As proof of concept, this case report describes a 64-year-old woman with triple-negative breast cancer refractory to multiple lines of therapy, found to have a rare mutation on NGS which led to targeted therapy with meaningful response. She initially presented with metastatic recurrence 5 years after treatment for a localized breast cancer, with rapid progression through four lines of therapy in the metastatic setting, including immunotherapy, antibody-drug conjugate-based therapy, and chemotherapy. Germline genetic testing was normal. Ultimately, NGS evaluation of cell-free DNA via an 83-gene assay (Guardant Health, Inc.) identified two NTRK3 fusions: an ETV6-NTRK3 fusion associated with the rare secretory breast carcinoma, and CRTC3-NTRK3, a novel fusion partner not previously described in breast cancer. Liver biopsy was sent for whole exome sequencing and RNA-seq analysis of tissue (BostonGene, Inc., Boston, MA, USA), which provided orthogonal confirmation of both the ETV6-NTRK3 and CRTC3-NTRK3 fusions. She was started on the TRK inhibitor larotrectinib with a marked clinical and radiographic response after only 2 months of therapy. The patient granted verbal consent to share her clinical story, images, and data in this case report. This case demonstrates the significant potential benefits of NGS testing in advanced cancer and the lessons we may learn from individual patient experiences.

Abstract P2-07-02: Genomic predictors of rapid progression to first line endocrine and CDK4/6 inhibitor combination therapy in patients with estrogen receptor positive (ER+) HER-2 negative (HER2-) advanced breast cancer (ABC)

Background: Endocrine therapy with CDK 4/6 inhibitors (ET/CDK4/6i) represents the 1st line therapy for ER+/HER2- ABC. While majority of patients derive clinical benefit with combination therapy, a subset have refractory disease with progression within 6 months. However, predictive biomarkers for rapid progression are lacking. In this study, we evaluated genomic profiles associated with rapid disease progression on ET/CDK4/6i. Methods: We identified 77 patients who received 1st line ET/CDK4/6i combination therapy (AI or SERD with one of the 3 approved CDK4/6is) and had ctDNA analysis performed via plasma based genotyping utilizing the commercially available Guardant360 assay at three sites: Washington University in St. Louis, MO, Northwestern University (Chicago, IL), and Massachusetts General Hospital (Boston, MA). We aimed to look at the differences in patient characteristics and genomic profiles of the tumors assessed from baseline ctDNA specimens between the patients with rapid progression (time to progression TTP&lt;=6 months) vs others. In particular, we focused on growth factor receptors (FGFR, EGFR) given that previous studies have shown that activation of FGFR1 and EGFR signaling may be implicated in resistance to endocrine based therapy in breast cancer. Time to progression was estimated by using Cox regression. Variable associations were estimated via logistic regression. Results: In the combined cohort, FGFR1 amplification (FGFR1amp) was detected in 15/77 patients (19.5%). FGFR1amp was seen in 5/10 (50%) of patients with rapid progression, consistent with existing knowledge that FGFR1amp contributes to resistance to CDK4/6i and/or ET. Presence of FGFR1amp was independently associated with shorter TTP (11.2 vs. 34.7 months, HR=3.14, p=0.02). EGFR mutations (EGFRmut) were detected in 8/77 (10.4%) patients, 3 of which were found among patients with rapid progression and another 5 among those with TTP&lt;=15 months. Presence of EGFRmut was also associated with shorter TTP (8.5 vs. 31.7 months, HR=6.50, p&lt;0.001) in multivariable analysis. Of the 4 patients with shortest TTP (&lt;3 months) 3 harbored both FGFR1amp and EGFRmut. In another 3 patients we observed FGFR1amp and co-activation of genes implicated in G1/S phase cell cycle transition, suggesting that FGFR1 amplified cells may require a co-activating downstream event that ultimately, via multiple pathway cross-talk, renders them resistant to ET/CDK4/6 inhibition. Patients with FGFR1 amplified tumors were younger compared to those without FGFR1amp (54.3 vs. 62.7 years, p=0.04). Presence of FGFR1amp was associated with presence of liver (p=0.01) but not bone or lung metastases which could be one of the explanations why patients with higher liver tumor burden are more resistant to ET/CDK4/6i inhibition. PIK3CA and TP53 gene mutations in our cohort were frequent (found in 41% and 30% of the patients, respectively) but were independently not associated with TTP (PIK3CAmut+ HR=1.31, p=0.55, TP53mut+ HR=0.67, p=0.36). ESR1 mutations were rarely encountered (9%) as the cohort had only been exposed to adjuvant endocrine therapy. Conclusions: These findings highlight how ctDNA can be used for patient stratification prior to initiation of first line of therapy in ER+/HER2- ABC since it is evident that not all patients derive the same benefit from ET/CDK4/6i. Certain genomic alterations, particularly in FGFR1, EGFR, and G1/S phase cell cycle transition are associated with rapid progression to 1st line ET/CDK4/6i therapy, and highlight the need for clinical trials investigating combination/novel therapies for this subgroup of patients with HR+/HER2- ABC. Our findings are hypothesis-generating and require further exploration in larger datasets.

Citation Format: Marko Velimirovic, Lorenzo Gerratana, Andrew A Davis, Whitney L Hensing, Katherine Clifton, Ami N Shah, Paolo D'Amico, Charles S Dai, Elyssa N Denault, Cynthia X Ma, Seth A Wander, Dejan Juric, Massimo Cristofanilli, Bruce A Chabner, Aditya Bardia. Genomic predictors of rapid progression to first line endocrine and CDK4/6 inhibitor combination therapy in patients with estrogen receptor positive (ER+) HER-2 negative (HER2-) advanced breast cancer (ABC) [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 P2-07-02.

Abstract PD6-08: Exploring the interplay among ESR1/PIK3CA codon variants, oncogenic pathway alterations and clinical phenotype of metastatic breast cancer (MBC) through circulating tumor DNA (ctDNA) next-generation sequencing (NGS)

Background: High throughput genomic technologies such as NGS are enhancing the ability to dynamically characterize MBC but their role in describing biological evolution of multiple mutations together remains unclear. ESR1 and PIK3CA are central mutations related to the biology and druggability of hormone-receptor positive, HER2 negative (luminal-like) MBC. The aim of this study was to explore the interplay between oncogenic pathway alterations and ESR1 and PIK3CA codon variants on the impact and clinical phenotype of luminal-like MBC. Methods: The study retrospectively analyzed a multi-institutional cohort comprising 1047 MBC patients (pts) characterized for ctDNA through NGS before treatment start at Northwestern University (Chicago, IL), Massachusetts General Hospital (Boston, MA) and Washington University in St. Louis between 2015-2020. The analysis was then focused on luminal-like MBC. Pathway classification was defined based on previous work (Sanchez-Vega F et al, Cell. 2018) (i.e., RTK, RAS, RAF, MEK, NRF2, ER, WNT, MYC, P53, cell cycle, notch, PI3K). Single nucleotide variations (SNVs) were annotated for their oncogenicity through OncoKB and ClinVar. Only pathogenic variants were included in the models. Associations among, pathway classification, and ESR1/PIK3CA codon variants were explored through stepwise logistic regression. Overall survival (OS) was tested through Cox regression. Results: The luminal-like cohort comprised 702 pts. ESR1 mutations were detected in 166 pts (24%) and PIK3CA in 214 pts (31%). The most common ESR1 gene mutations were found in codons 537 (31%), 538 (21%), 536 (8%) and 380 (7%), while alterations in codons 1047 (38%), 545 (25%), and 542 (20%) were the most common for PIK3CA. Other pathogenic SNVs were observed in 33% and 17% of pts for ESR1 and PIK3CA, respectively with the former being polyclonal. SNVs alterations were mainly observed in the PI3K (35%), P53 (32%), ER (28%), RAS (8%), RTK (8%) and cell cycle (5%) pathways, while copy number variations (CNVs) were detected in the RTK (15%), cell cycle (11%), MYC (7%) PI3K (6%) and RAF (5%) pathways. ESR1 537 variants were associated with alterations in the ER and WNT pathways, 538 with cell cycle, 380 with P53 and ER, 536 with RTK. PIK3CA 1047 variants were associated with alterations in the RTK and P53 pathways, 542 with RTK, RAS and RAF, E545 with PI3K, RAS, cell cycle and P53. 1047 and 542 were also associated with CNVs in the PI3K pathway. Independent prognostic factors in terms of OS were ESR1 537/380 codon variants (HR 1.94 P = 0.001 and HR 2.29 P = 0.047), SNVs in the RAS, cell cycle, and P53 pathways (HR 1.74 P = 0.003 HR 1.84 P = 0.009 and HR 1.56 P &lt; 0.001) and CNVs in the cell cycle pathway (HR 1.96 P &lt; 0.001). Conclusions: This study demonstrated how ESR1 and PIK3CA codon variants, together with alterations in specific oncogenic pathways, can differentially impact the biology and clinical phenotype of luminal-like MBC. As novel endocrine therapy agents such as selective estrogen receptor degraders (SERDs) and PI3K inhibitors are being developed, these results highlight the pivotal role of ctDNA NGS to describe tumor evolution and optimize clinical decision making.

Odds Ratio95% Confidence IntervalPESR1 Y537ER SNVs3.341.487.530.004WNT SNVs6.251.4127.740.016ESR1 D538cell cycle SNVs5.221.7915.230.003ESR1 E380P53 SNVs4.801.4116.310.012ER SNVs5.331.3321.400.018ESR1 L536RTK CNVs4.511.1517.690.031PIK3CA H1047RTK SNVs3.751.708.290.001P53 SNVs2.611.584.34&lt; 0.001PI3K CNVs6.082.4515.08&lt; 0.001PIK3CA E542RTK SNVs5.001.9412.880.001RAS SNVs3.651.369.770.01RAF SNVs6.011.0733.870.042PI3K CNVs6.302.2917.36&lt; 0.001PIK3CA E545PI3K SNVs2.881.276.530.011RAS SNVs2.871.186.980.02cell cycle SNVs3.071.088.740.035NRF2 SNVs21.431.29356.520.033P53 SNVs3.752.046.89&lt; 0.001

Citation Format: Lorenzo Gerratana, Andrew A Davis, Marko Velimirovic, Katherine Clifton, Whitney L Hensing, Ami N Shah, Charles S Dai, Carolina Reduzzi, Paolo D’Amico, Qiang Zhang, Firas Wehbe, Seth Wander, William J Gradishar, Amir Behdad, Fabio Puglisi, Cynthia X Ma, Aditya Bardia, Massimo Cristofanilli. Exploring the interplay among ESR1/PIK3CA codon variants, oncogenic pathway alterations and clinical phenotype of metastatic breast cancer (MBC) through circulating tumor DNA (ctDNA) next-generation sequencing (NGS) [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 PD6-08.

Abstract PD14-04: Circulating tumor DNA characterization of invasive lobular carcinoma in patients with metastatic breast cancer

Background:Invasive lobular carcinoma (ILC) is the second most common histology of breast cancer, accounting for approximately 10-15% of cases. Prior studies have demonstrated that loss of E-cadherin, as well as alterations in tissue including CDH1, FOXA1, TBX3 and PTEN loss, that were more commonly observed in Luminal A ILC, while GATA3 was more commonly observed in invasive ductal carcinoma (IDC) (Ciriello et al., Cell 2015). However, data regarding the characterization of circulating tumor DNA (ctDNA) in patients (pts) with metastatic ILC are limited. We hypothesized that there would be distinct mutational profiles between pts with metastatic ILC and IDC that could be characterized using ctDNA. Methods:This retrospective cohort study included de-identified clinical, pathological, and ctDNA data from pts with metastatic breast cancer (MBC) combined under a data use agreement and approved by the institutional review boards of three sites: Washington University in St. Louis (MO), Northwestern University (Chicago, IL), and Massachusetts General Hospital (Boston, MA). All pts included in the study had ctDNA testing per standard of care with plasma-based genotyping performed by Guardant360 (Redwood City, CA) between 2015-2020. Histological classification (ILC vs. IDC) was defined based on review of pathology reports from the primary tumor or from breast biopsies of de novo MBC, and additional clinical and pathological variables were obtained via electronic medical record review. Single nucleotide variants (SNVs) were annotated using OncoKB and ClinVar and only pathogenic variants were included. Mutational profiles were compared across histologic subtypes using Fisher’s exact test to assess differences in alteration frequency across subtypes. Multivariable analysis was performed. Results:A total of 994 pts with MBC underwent ctDNA testing and were included in the analysis. 10.7% of pts had ILC (N=106) and 89.3% had IDC (N=888). 89.4% of ILC cases were categorized as hormone-receptor positive (HR+) compared with 67.1% of IDC cases. Pts with ILC had a lower frequency of triple-negative (6.7% vs. 17.7%) and HER2 positive (3.9% vs. 15.2%) breast cancer compared with IDC. Pts with ILC had a significantly higher number of pathogenic SNVs compared with IDC (mean 4.45 vs. 2.77; P=0.0037). In contrast, pts with ILC had a significantly lower number of copy number alterations as compared to pts with IDC (mean 0.40 vs. 1.03; P=0.0017). No differences were observed in mutant allele frequency between pts with ILC and IDC. The 5 most common alterations observed in pts with ILC were the following: PIK3CA, TP53, ESR1, ERBB2, and ARID1A. Alterations in AR, BRAF, CDH1, ERBB2, FGFR2, IDH2, KRAS, NF1, PIK3CA, SMAD4, and TERT were significantly higher in ILC than IDC (all P&lt;0.05). In contrast, mutations in GATA3, and amplifications in ERBB2 and MYC were significantly more common in pts with IDC (all P&lt;0.05). In multivariable analysis, mutations in BRAF, CDH1, ERBB2, IDH2, TERT remained significantly higher in ILC, while amplification of MYC was significantly higher in IDC (all P&lt;0.05). After restricting the analysis to pts with HR+ HER2 negative MBC, the following genes were significant in multivariate analysis: CDH1 and ERBB2 for pts with ILC and MYC amplification for pts with IDC (all P&lt;0.05). Discussion:In this large, multi-institutional dataset, pts with metastatic ILC were characterized by a significantly higher number of SNVs in ctDNA compared to pts with IDC, suggesting higher mutational burden. We report several alterations that were significantly different in ILC vs. IDC. These results demonstrate the ctDNA profile of pts with ILC, and future studies should explore serial plasma-based genotyping to track ILC evolution to develop targeted precision medicine based therapeutic approaches for this unique subset of pts with MBC.

Citation Format: Andrew A Davis, Lorenzo Gerratana, Katherine Clifton, Marko Velimirovic, Whitney L Hensing, Ami N Shah, Paolo D’Amico, Carolina Reduzzi, Qiang Zhang, Charles S Dai, Elyssa N Denault, Nusayba A Bagegni, Mateusz Opyrchal, Foluso O Ademuyiwa, Ron Bose, William J Gradishar, Amir Behdad, Cynthia X Ma, Aditya Bardia, Massimo Cristofanilli. Circulating tumor DNA characterization of invasive lobular carcinoma in patients with metastatic breast cancer [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 PD14-04.

Abstract P2-01-01: Genetic alterations detected by circulating tumor DNA (ctDNA) in HER2-low metastatic breast cancer (MBC)

Introduction: Approximately 40-50% of breast cancers are characterized by low HER2 expression (HER2-low), defined as immunohistochemistry (IHC) 1+ or 2+ and HER2 fluorescence in situ hybridization (FISH) unamplified, encompassing a large and heterogeneous subgroup that may confer benefit from novel HER2 directed therapies. Circulating tumor DNA (ctDNA) has emerged as a minimally invasive technique to detect cancer-specific gene aberrations. Genetic alterations in ctDNA of HER2-low MBC have not been well described, and we hypothesized that HER2-low MBC may have a distinct genomic profile, beyond standard histopathologic features. Methods: This retrospective cohort study included patients with MBC treated at Washington University in St. Louis, Northwestern University (Chicago, IL) and Massachusetts General Hospital (Boston, MA) who had undergone ctDNA analysis during the course of treatment using the commercially available Guardant360® assay. HER2 expression was evaluated by IHC/FISH according to ASCO/CAP guidelines on metastatic tissue biopsies (or primary breast tumor tissue if a metastatic site biopsy was not available). Tumors were classified as HER2-low (IHC 1+ or 2+/FISH negative), HER2-0 (IHC 0) or HER2-positive (IHC 3+ or IHC 2+/FISH amplified). Clinicopathologic characteristics and ctDNA genetic alterations for HER2-low MBC were described and compared with the HER2-0 and HER2-positive subgroups. Chi-square and Fisher’s exact tests were used for categorical variables. Logistical regression was performed for multivariable analyses. Results: A total of 991 patients with MBC were analyzed, including 160 (16.1%) HER2-positive, 351 (35.4%) HER2-0, and 480 (48.4%) HER2-low MBC. The majority (89.2%) of HER2-low MBC were estrogen-receptor positive (ER+). Compared with HER2-0 MBC, HER2-low MBC had a significantly higher incidence of PIK3CA mutations (OR 1.54, p=0.027). PDGFRA and MYC amplifications were also more common among HER2-low MBC (2.3% vs 0.28% and 8.1% vs 4.6%, respectively), although not significantly associated with this subtype in multivariable analysis. Within the ER+ MBC cohort, those with HER2-low also had higher rates of PIK3CA mutations (OR 1.66, p=0.012) and MYC amplification (OR 2.29, p=0.034), as compared to HER2-0. Compared with HER2-positive, HER2-low MBC had significantly lower rates of ERBB2 alterations (OR 0.26, p=0.0076 for ERBB2 mutations and OR 0.022, p&lt;0.001 for ERBB2 amplification). ESR1, AKT1, and RB1 mutations were more common in HER2-low compared with HER2-positive MBC (14.0% vs 6.9%; 3.1% vs none; 3.1% vs none, respectively), but were not significant in multivariable analysis. Conclusions: Among patients with ER+ MBC, HER-low had a higher incidence of PIK3CA mutations and MYC amplification compared to HER2-0 MBC, and both of these alterations have been implicated as mechanisms of endocrine resistance. We did not demonstrate a high incidence of ERBB2 alterations in patients with HER2-low MBC. To our knowledge, this is the first study to describe genetic alterations detected by ctDNA in patients with HER2-low MBC. Given the emergence of novel HER2-targeted antibody drug conjugates with clinical activity in HER2-low MBC, these findings may guide combination treatment strategies and patient selection for future studies. Further studies are needed to confirm whether HER2-low MBC represents a truly unique biologic subtype.

Citation Format: Whitney L Hensing, Lorenzo Gerratana, Katherine Clifton, Marko Velimirovic, Ami Shah, Paolo D'Amico, Carolina Reduzzi, Qiang Zhang, Charles S Dai, Nusayba A Bagegni, Mateusz Opyrchal, Foluso O Ademuyiwa, Bose Ron, Amir Behdad, Cynthia X Ma, Aditya Bardia, Massimo Cristofanilli, Andrew A Davis. Genetic alterations detected by circulating tumor DNA (ctDNA) in HER2-low metastatic breast cancer (MBC) [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 P2-01-01.

Analysis of the typical unified lattice Boltzmann models and a comprehensive multiphase model for convection-diffusion problems in multiphase systems

The present paper analyzes the typical unified lattice Boltzmann (LB) models for different convection-diffusion (CD) problems in multiphase systems. The CD problems in multiphase systems can be roughly classified into three groups: CD problems with a continuous scalar value and a continuous flux, a discontinuous scalar value and a continuous flux, a continuous scalar value and a discontinuous flux. The characteristics of the corresponding unified LB models for the three kinds of CD problems are analyzed and the equivalence between the LB models based on different perspectives or numerical schemes is revealed. Finally, a comprehensive multiphase LB model (CMLBM) capable of solving different isotropic and anisotropic CD problems in multiphase systems is proposed. Four typical CD problems in multiphase systems are calculated to validate the CMLBM; the results show that it performs well against the typical isotropic and anisotropic CD problems in multiphase systems.

Rhein inhibits renal tubular epithelial cell hypertrophy and extracellular matrix accumulation induced by transforming growth factor beta1

AIM

To investigate the effects of rhein on cell hypertrophy and accumulation of extracellular matrix (ECM) in the renal tubular epithelial cells.

METHODS

LLC-PK1 cells were incubated with transforming growth factor beta1 (TGFbeta1) 2 microg/L for 24 h to induce cell hypertrophy and production of ECM. To evaluate the effects of rhein on inhibiting the action of TGFbeta1, cell volume, cellular protein level, and [3H]leucine incorporation in LLC-PK1 cells treated with rhein at different concentrations were measured. In addition, the [3H]proline incorporation, level of fibronectin (FN) in supernatant, and mRNA expression of collagen IV and FN were also detected in rhein treated cells.

RESULTS

The cell volume, cellular protein content, and [3H]leucine incorporation were markedly increased in LLC-PK1 cells after TGFbeta1 stimulation as compared with control (P < 0.01), and this TGFbeta1-stimulated cell hypertrophy was ameliorated by rhein. It was observed that TGFbeta1 not only increased the production of FN and [3H]proline incorporation in LLC-PK1 cells (P < 0.01), but also enhanced the mRNA expression of collagen IV and FN. Rhein significantly decreased the protein production and mRNA expression of ECM in LLC-PK1 cells stimulated by TGFbeta1.

CONCLUSION

Rhein can inhibit cell hypertrophy and ECM accumulation in LLC-PK1 cells induced by TGFbeta1, which may partly account for the role of rhein in preventing and retarding the progression of diabetic nephropathy.

Radiographic findings in cotton textile workers and the relationship to cigarette smoking

A group of 140 cotton textile workers from Shanghai, Shandong, Guangxi, and Beijing have had their chest radiographs taken using similar requirements. Most had come from the preparatory departments of cotton mills and had a history of exposure to cotton dust for at least 20 years. As controls, 140 healthy individuals with no dust exposure were matched with respect to sex, age, and smoking history. All the radiographs were read according to the ILO International Pneumoconiosis Classification, and the manifestations belonging to categories 0/0 and 0/1 were grouped as "normal," whereas categories 1/0, 1/1, and 1/2 and above as "abnormal." There was no significant difference in X-ray abnormalities between cotton textile workers and controls (P greater than 0.05). But when the data on the cotton textile workers and controls were combined, an appreciable difference in the incidence of radiographic abnormalities was found between smokers and non-smokers (P less than 0.001). Cotton dust exposure may induce nonspecific interstitial pulmonary changes, but these changes were exaggerated by cigarette smoking. These two factors appeared to have an additive effect on the pulmonary X-ray findings.