Circulating Tumor Cells Prediction in Hormone Receptor Positive HER2-Negative Advanced Breast Cancer: A Retrospective Analysis of the MONARCH 2 Trial

BACKGROUND

The MONARCH 2 trial (NCT02107703) showed the efficacy of abemaciclib, a cyclin-dependent kinase 4 & 6 inhibitor (CDK4/6i), in combination with fulvestrant for hormone receptor-positive, HER2-negative metastatic breast cancer (MBC). The aim of this analysis was to explore the prediction of circulating tumor cells (CTCs) stratification using machine learning for hypothesis generation of biomarker-driven clinical trials.

PATIENTS AND METHODS

Predicted CTCs were computed in the MONARCH 2 trial through a K nearest neighbor (KNN) classifier trained on a dataset comprising 2436 patients with MBC. Patients were categorized into predicted Stage IVaggressive (pStage IVaggressive, ≥5 predicted CTCs) or predicted Stage IVindolent (pStage IVindolent, <5 predicted CTCs). Prognosis was tested in terms of progression-free-survival (PFS) and overall survival (OS) through Cox regression.

RESULTS

Patients classified as predicted pStage IVaggressive and predicted pStage Stage IVindolent were, respectively, 183 (28%) and 461 (72%). After multivariable Cox regression, predicted CTCs were confirmed as independently associated with prognosis in terms of OS, together with ECOG performance status, liver involvement, bone-only disease, and treatment arm. Patients in the pStage Stage IVindolent subgroup treated with abemaciclib experienced the best prognosis both in terms of PFS and OS. The treatment effect of abemaciclib on OS was then explored through subgroup analysis, showing a consistent benefit across all subgroups.

CONCLUSION

This study is the first analysis of CTCs modeling for stage IV disease stratification. These results show the need to expand biomarker profiling in combination with CTCs stratification for improved biomarker-driven drug development.

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.

Dynamic Glycoprotein Hyposialylation Promotes Chemotherapy Evasion and Metastatic Seeding of Quiescent Circulating Tumor Cell Clusters in Breast Cancer

Most circulating tumor cells (CTC) are detected as single cells, whereas a small proportion of CTCs in multicellular clusters with stemness properties possess 20- to 100-times higher metastatic propensity than the single cells. Here we report that CTC dynamics in both singles and clusters in response to therapies predict overall survival for breast cancer. Chemotherapy-evasive CTC clusters are relatively quiescent with a specific loss of ST6GAL1-catalyzed α2,6-sialylation in glycoproteins. Dynamic hyposialylation in CTCs or deficiency of ST6GAL1 promotes cluster formation for metastatic seeding and enables cellular quiescence to evade paclitaxel treatment in breast cancer. Glycoproteomic analysis reveals newly identified protein substrates of ST6GAL1, such as adhesion or stemness markers PODXL, ICAM1, ECE1, ALCAM1, CD97, and CD44, contributing to CTC clustering (aggregation) and metastatic seeding. As a proof of concept, neutralizing antibodies against one newly identified contributor, PODXL, inhibit CTC cluster formation and lung metastasis associated with paclitaxel treatment for triple-negative breast cancer.

SIGNIFICANCE

This study discovers that dynamic loss of terminal sialylation in glycoproteins of CTC clusters contributes to the fate of cellular dormancy, advantageous evasion to chemotherapy, and enhanced metastatic seeding. It identifies PODXL as a glycoprotein substrate of ST6GAL1 and a candidate target to counter chemoevasion-associated metastasis of quiescent tumor cells. This article is featured in Selected Articles from This Issue, p. 1949.

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.

Unique molecular signatures sustained in circulating monocytes and regulatory T cells in convalescent COVID-19 patients

Over two years into the COVID-19 pandemic, the human immune response to SARS-CoV-2 during the active disease phase has been extensively studied. However, the long-term impact after recovery, which is critical to advance our understanding SARS-CoV-2 and COVID-19-associated long-term complications, remains largely unknown. Herein, we characterized single-cell profiles of circulating immune cells in the peripheral blood of 100 patients, including convalescent COVID-19 and sero-negative controls. Flow cytometry analyses revealed reduced frequencies of both short-lived monocytes and long-lived regulatory T (Treg) cells within the patients who have recovered from severe COVID-19. sc-RNA seq analysis identifies seven heterogeneous clusters of monocytes and nine Treg clusters featuring distinct molecular signatures in association with COVID-19 severity. Asymptomatic patients contain the most abundant clusters of monocytes and Tregs expressing high CD74 or IFN-responsive genes. In contrast, the patients recovered from a severe disease have shown two dominant inflammatory monocyte clusters featuring S100 family genes: one monocyte cluster of S100A8 & A9 coupled with high HLA-I and another cluster of S100A4 & A6 with high HLA-II genes, a specific non-classical monocyte cluster with distinct IFITM family genes, as well as a unique TGF-β high Treg Cluster. The outpatients and seronegative controls share most of the monocyte and Treg clusters patterns with high expression of HLA genes. Surprisingly, while presumably short-lived monocytes appear to have sustained alterations over 4 months, the decreased frequencies of long-lived Tregs (high HLA-DRA and S100A6) in the outpatients restore over the tested convalescent time (≥ 4 months). Collectively, our study identifies sustained and dynamically altered monocytes and Treg clusters with distinct molecular signatures after recovery, associated with COVID-19 severity.

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 1950: A novel ESR1 mutation assay for single circulating tumor cell by application of DEPArray࣪ System and Digital Droplet PCR

Introduction: Although circulating tumor cells (CTC) display the same spatial and temporal heterogeneity as the primary tumor, they represent a privileged window to disclose mechanisms of metastases. ESR1 mutations are a major mechanism of acquired endocrine resistance in metastatic breast cancer (MBC). We previously reported that ESR1 mutations in circulating tumor DNA (ctDNA) was associated with worse prognosis in MBC (2020 ASCO). Herein, we report a new ultra-high sensitivity approach of ESR1 mutations assay for single CTC by using DEPArray system and Droplet Digital PCR (ddPCR).

Methods: Whole blood sample (7.5ml/each) was collected from stage IV MBC patients and then CTC enumeration was performed in CellSearch™ System by targeting the EpCAM antigen (2020 AACR #3120). The single CTC and single white blood cell (WBC) were then isolated from CellSearch cartridges by using DEPArray࣪ System (Menarini). The single CTC DNA was isolated by QIAamp DNA Micro Kit (Qiagen). ESR1 mutations hotspots including p.E380Q, p.Y537S and p.D538G were analyzed by using QX200™ ddPCR System (Annealing/Extension=58 °C, 40 cycles) and the corresponding probes (Mutation-FAM and Wild type-HEX mixed) for p.E380Q-dHsaMDS500014536, p.Y537-dHsaMDS975379796, p.D538G- dHsaMDS460485301 respectively (Bio-Rad). Meanwhile, corresponding plasma ctDNA was analyzed by Guardant 360 Health NGS-based assay for a 73 genes panel for single nucleotide variants.

Results: Positive controls (using 0.00000325ng pure positive DNA) and negative control (using water) were performed in each ddPCR assay. In cohort 1: total of 8 samples including 4 single CTC samples and 4 single WBC samples were collected using the DEPArray system. Wild type ESR1 (p.E380Q, p.Y537S and p.D538G) was detected in all 4 single CTC samples and 4 single WBC samples. There were 3 copies, 3.4 copies, 1.6 copies and 1.8 copies of p.E380Q mutation droplets found in 4 single CTC samples when there were no p.Y537S or p.D538G mutations found in these samples. There was no ESR1 mutation found in the corresponding ctDNA. In cohort 2: Two samples including 4 CTCs and 100 CTCs were collected from CellSearch cartridges. There were 0.09 vs 1 copies (8.25%) and 0.1 vs 0.31 copies (24.39%) of p.E380Q mutation droplets found in these two samples respectively, compared to ctDNA results of 1.80% and 0 respectively. Furthermore, there was 0.08 vs 0.67 copies (10.66%) of p.D538G mutation droplets were found in the sample including 100 CTCs compared to 12.70% mutations detected in the corresponding ctDNA.

Conclusion: Our new approach verified the feasibility of ESR1 mutations assay in very low amount DNA from single CTCs with high sensitivity even when ESR1 mutation could be found in CTCs but not ctDNA. This approach may offer a strong evidence for early disease metastasis, efficacy of individualized treatment monitoring and personalizing cancer therapy for precision medicine.

Citation Format: Qiang Zhang, Paolo D'Amico, Marwa Manai, Carolina Reduzzi, Andrew A. Davis, Lorenzo Gerratana, Weijun Qin, Jianhua Jiao, Saya L. Jacob, Jeannine Donahue, Youbin Zhang, Lisa Flaum, Massimo Cristofanilli, Leonidas C. Platanias, Ami N. Shah, William Gradishar. A novel ESR1 mutation assay for single circulating tumor cell by application of DEPArray࣪ System and Digital Droplet PCR [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1950.

CK+/CD45+ (dual-positive) circulating cells are associated with prognosis in patients with advanced breast cancer

1093

Background: Circulating tumor cells (CTCs) expressing epithelial markers (EPCAM, cytokeratin (CK)) and lacking CD45 (a leukocyte marker) have been associated with poor outcome in many cancer types. Nonetheless, the presence of cells expressing both CK and CD45 (CK+/CD45+), circulating in the blood of cancer patients (pts) have also been reported, but not widely investigated. Early evidence indicates that circulating dual-positive cells (DPcells) are hybrids deriving from the fusion of tumor cells and macrophages. We previously reported that it is possible to detect DPcells in the blood of pts with metastatic breast cancer (BC) and that they are associated with shorter progression-free survival (PFS), in pts with <5 CK+/CD45- CTCs. Here, we investigated the impact of DPcells on overall survival (OS) in pts with advanced BC (aBC). Methods: Blood samples (7.5 ml) were collected from aBC pts before starting a new therapy and processed with the FDA-approved CellSearch platform for CTCs and DPcells enumeration. The prognostic role of CTCs and DPcells was assessed through the Kaplan-Meier method using the log-rank test. Single DPcells were isolated using the DEPArray platform and underwent whole genome amplification and lowpass whole genome sequencing (Ampli1 WGA and Ampli1 Lowpass kits). Results: Blood samples from 341 pts with luminal (n=168), HER2+ (n=76) and triple negative (n=88) BC were analyzed. Of these, 131 samples (38.4%) contained ≥5 CTCs (CTCpos), whereas DPcell were detected in 152 samples (44.6%, range 0-53), of which 66 (43.4%) were CTCpos and 86 (56.6%) CTCneg. Overall, DPcells were associated with a shorter OS: median OS 24.5 vs 35.0 months, p=0.046. However, when analyzing CTCpos and CTCneg separately, only the latter group showed a difference in OS according to DPcells presence. In particular, among CTCneg pts, those with ≥4 DPcells showed a 2.3-fold shorter OS (26.7 vs 60.6 months, p=0.025). Moreover, pts with ≥4 DPcells were less likely to experience a 6-months PFS clinical benefit (p=0.015). Interestingly, in the analysis by BC subtype, DPcells were confirmed to be associated with worse OS only in pts with triple negative BC (median OS 11.5 vs 16.9, p=0.048). To explore the exiology of DPcells, 2 out of 3 cells analyzed after single-cell isolation from 1 patient were confirmed to have copy number alterations (CNA) consistent with malignant cells. CNA and mutational profiling of additional single DPcells and CTCs are ongoing. Conclusions: DPcells are associated with worse OS in aBC pts, with the prognostic impact primarily in pts with <5 CTCs and triple negative BC. This suggests that DPcells might be an alternative way of tumor dissemination in specific pts, in which CK+/CD45- CTCs are less prevalent. More studies are needed to better elucidate DPcell clinical significance in BC, and to confirm their fusion-hybrid origin.

Unique molecular signatures sustained in circulating monocytes and regulatory T cells in Convalescent COVID-19 patients

Over two years into the COVID-19 pandemic, the human immune response to SARS-CoV-2 during the active disease phase has been extensively studied. However, the long-term impact after recovery, which is critical to advance our understanding SARS-CoV-2 and COVID-19-associated long-term complications, remains largely unknown. Herein, we characterized multi-omic single-cell profiles of circulating immune cells in the peripheral blood of 100 patients, including covenlesent COVID-19 and sero-negative controls. The reduced frequencies of both short-lived monocytes and long-lived regulatory T (Treg) cells are significantly associated with the patients recovered from severe COVID-19. Consistently, sc-RNA seq analysis reveals seven heterogeneous clusters of monocytes (M0-M6) and ten Treg clusters (T0-T9) featuring distinct molecular signatures and associated with COVID-19 severity. Asymptomatic patients contain the most abundant clusters of monocyte and Treg expressing high CD74 or IFN-responsive genes. In contrast, the patients recovered from a severe disease have shown two dominant inflammatory monocyte clusters with S100 family genes: S100A8 & A9 with high HLA-I whereas S100A4 & A6 with high HLA-II genes, a specific non-classical monocyte cluster with distinct IFITM family genes, and a unique TGF-β high Treg Cluster. The outpatients and seronegative controls share most of the monocyte and Treg clusters patterns with high expression of HLA genes. Surprisingly, while presumably short-ived monocytes appear to have sustained alterations over 4 months, the decreased frequencies of long-lived Tregs (high HLA-DRA and S100A6) in the outpatients restore over the tested convalescent time (>= 4 months). Collectively, our study identifies sustained and dynamically altered monocytes and Treg clusters with distinct molecular signatures after recovery, associated with COVID-19 severity.

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 P2-02-05: Dynamic circulating tumor cell changes in enumeration and HER2 expression during systemic therapy for metastatic breast cancer

Introduction: CTCs are tumor cells that circulate in the blood of patient with primary and MBC and, are responsible for seeing of metastasis. The monitoring of CTCs in MBC emerged as strong prognostic and possible predictive biomarker in oncology over the past couple of decades. Meanwhile, overexpression of HER2 protein has been associated with rapid cell division and worse prognosis of MBC. Here we report a significant correlation between dynamic CTCs enumeration and CTCs-HER2 expression during the systemic therapies, with potential implication to understand treatment resistance. Methods: A total of 298 whole blood samples (7.5ml/each) were collected from 149 patients with stage IV breast cancer (2016-2020) at the Northwestern University Robert H Lurie Comprehensive Cancer Center, before (Baseline) and 3 months after (Time point 2) initiation of systemic treatment. CTC enumerations were performed using the FDA approved CellSearch™ system (Menarini) which is specific for the intracellular protein cytokeratin (CK) in epithelial cells, DAPI stains the cell nucleus, anti-CD45-APC is specific for leukocytes, and anti-HER-2/neu-FLU is specific for HER-2/neu antigen. The CTCs were classified as CK+, EpCAM+, DAPI+ and CD45-. We developed a criteria for evaluation of HER2 expression by 4 different categories (0,1+,2+,3+) based on expression intensity in our lab (present in 2021 ASCO). In this study we included CTCs with all intensities of HER2 expression (1+ to 3+) which was standardized in our lab. Mann-Whitney U test was used for statistics. Results: Of the 149 baseline samples, CTC≥1 were found in 101 patients (67.8%). A change in CTCs between baseline and time point 2 for these 101 patients: Three groups were identified: Group 1: 33patients (33%) with increase CTCs; Group 2: 64 patients (63%) with decreased CTC; Group 3: 4 patients (4%) with no change The median increase of total CTCs and HER2+ CTCs in Group 1 were 7.0 and 2.0, respectively; the median decrease of total CTCs and HER2+ CTCs in Group 2 were 9.5 and 2.0, respectively. The change of HER2+ CTCs was significantly correlated with the change of total CTCs after systemic therapy, with the correlation coefficient as rs=0.662 (p&lt;0.001) for these 101 patients. A significant positive correlation between HER2+ CTCs and total CTCs were found in both Group 1 and Group 2, rs=0.717 (p&lt;0.001) and rs=0.604 (p&lt;0.001) respectively. Furthermore, the ratio of HER2+ CTCs (HER2+ CTCs/total CTCs) in both Group 1 and Group 2 was also significantly correlated with total CTCs after therapy with the corresponding correlation coefficient as rs=0.536 (p&lt;0.001) and rs=0.388 (p&lt;0.001) in Group 1 and Group 2, respectively. Conclusion: Our study demonstrated that dynamic changes of CTCs after systemic therapies, are positively correlated with the HER2 expression in CTCs in different levels of baseline CTCs amounts. Observation of HER2 expression and ratio in CTCs during the course of systemic therapy is useful in monitoring therapy efficacy and potential disease progress.

Citation Format: Qiang Zhang, Weijun Qin, Paolo D'Amico, Andrew A. Davis, Jianhua Jiao, Lorenzo Gerratana, Saya L. Jacob, Youbin Zhang, Jeannine Donahue, Wenan Qiang, Ami N Shah, Amir Behdad, Lisa Flaum, William Gradishar, Leonidas C Platanias, Massimo Cristofanilli. Dynamic circulating tumor cell changes in enumeration and HER2 expression during systemic therapy for 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 P2-02-05.

Abstract P5-13-04: NF1 mutations render HER2+ breast cancer highly sensitive to T-DM1 by altering microtubule dynamics

Background: Despite major technological and conceptual advancements, treatment decisions in HER2+ metastatic breast cancer (mBC) remain largely based on clinical evidence, with no established predictive biomarkers to direct treatment for individual patients. The tumour suppressor Neurofibromatosis 1 (NF1) has been implicated in endocrine resistance but its role remains incompletely characterized in mBC. NF1 is best known as a GTPase-activating protein (GAP) that attenuates RAS signalling. However, the GAP function is likely not limited to RAS, and NF1 has been involved in other GTP-dependent processes including cytoskeletal dynamics. Data mining and analysis of public mutational registries revealed NF1 mutations as particularly enriched in HER2+ mBC compared to other molecular subtypes. Methods: To investigate the biological consequences of NF1 loss, we generated NF1 KO HER2+ mBC cell lines (BT474 and SKBR3) by CRISPR-Cas9 and both 2D and 3D proliferations assays were used for drug sensitivity profiling; live-cell imaging, high-resolution confocal microscopy and an ad-hoc computational algorithm were employed to study cell fate and microtubule conformational changes. Patient data were obtained from the Northwestern University through a prospective observational study in mBC patients. Results: Screening of several compounds approved for HER2+ mBC showed that response was generally equal or reduced in NF1 KO vs WT cells. However, response to trastuzumab-emtansine (T-DM1) was significantly increased in NF1 KO cells (IC50 ~0,3 vs 1,6 μg/mL in NF1WT). This sensitization was not observed with other antibody drug conjugates (ADCs) like DS-8201 and was reproducible with maytansine alone, suggesting a pharmacologically relevant NF1 activity on microtubules. Using the FUCCI(Ca) reporter, which tracks cell cycle progression at single-cell level, we saw a more prominent G2/M phase arrest and cell death upon T-DM1 treatment in NF1 KO compared to WT cells. Notably, NF1 KO cells exhibited a higher frequency of aberrant mitotic figures (chromosome alignment defects and multipolar spindle formation) and stronger β-galactosidase activity, an established marker of senescence. Collectively, these results suggest that NF1 KO cells become particularly subject to T-DM1-triggered mitotic catastrophe. Dephosphorylation of GTP-bound tubulin is required for appropriate microtubular dynamics; so-called “GTP islands” within the inner microtubule region are prone to rapid repolymerization and are normally kept at low levels. We hypothesize that expanded GTP-tubulin islands generated by the loss of NF1 GAP activity is a major cause of microtubular instability in NF1 KO cells. Preliminary evidence in support of this model was obtained by quantification of GTP-tubulin with a specific antibody. Finally, we assessed the predictive role of NF1 as a biomarker for T-DM1 response in a cohort of 300 mBC patients with mutational data in circulating tumour DNA (Guardant 360); we identified 13 heavily pretreated patients (&gt;4 prior lines) who received T-DM1, of which 3 had loss-of-function NF1 mutations and 10 were NF1 WT. Median progression-free survival was higher in NF1-mutated than WT patients (334 vs 80 days); given the small sample size, these results cannot yet be considered significant (p=0.14). Conclusions: These results provide preliminary mechanistic and clinical evidence supporting the use of NF1 loss to guide treatment in HER2+ mBC. As novel HER2-specific agents are being rapidly added to the therapeutic arsenal, we propose biology-driven criteria to identify patients that may benefit specifically from T-DM1. In addition, NF1 dependence for correct microtubular dynamics may be exploited by other inhibitors of microtubular polymerization in use as ADC payloads, further extending the potential usefulness of NF1 determination.

Citation Format: Bruno A Duso, Elena Gavilán Dorronzoro, Giulia Tini, Maria R de Filippo, Emanuele Bonetti, Maria R Ippolito, Chiara Soriani, Paolo D'Amico, Simona Rodighiero, Giuseppe Curigliano, Stefano Santaguida, Massimo Cristofanilli, Pier Giuseppe Pelicci, Luca Mazzarella. NF1 mutations render HER2+ breast cancer highly sensitive to T-DM1 by altering microtubule dynamics [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 P5-13-04.

Abstract P2-08-04: Progressive metastatic breast cancer with no detectable circulating tumor DNA: Evaluating limitations of this highly sensitive tool

Background: Circulating tumor DNA (ctDNA) is being evaluated as a tool to monitor disease and guide therapy escalation and de-escalation in advanced breast cancer. The patient, disease, and treatment characteristics that influence whether tumor DNA is isolated and sequenced from the bloodstream are not well understood. We aimed to describe patient and disease characteristics of cases with undetectable ctDNA levels despite progressive metastatic breast cancer (MBC). Methods: We retrospectively identified patients (pts) with MBC who had ctDNA evaluation by the Guardant 360 assay (Redwood City, CA) as part of their routine care from 2015-2020. We correlated the ctDNA assay with the disease status at collection. We identified the patient cohort with no detectable ctDNA despite evaluation at the time of progressive disease but prior to the initiation of a new therapy (ND ctDNA/PD) and compared the clinical, pathologic, and molecular features of this group to those with detected ctDNA. Differences were tested by two proportion z-tests. Results: Of 1151 ctDNA samples collected among 473 pts with MBC, 87 (7.5%) samples had no detectable (ND) ctDNA. 54 of 87 samples with ND ctDNA were collected at a time of stable or responding disease or after a new line of therapy was started, leaving only 33 ctDNA evaluations (2.8%) among 30 pts with ND ctDNA despite collection at the time of PD prior to new therapy. Among this group there were 14 pts (47%) with HR+ HER-, 11 pts (37%) with HER2+, and 5 pts (17%) with TN MBC. This compared to 254 pts (60%) with HR+ HER2-, 82 pts (19%) with HER2+, and 85 pts (20%) with TN MBC and detectable ctDNA. HER2-positive MBC was more common in the ND ctDNA/PD group than detectable ctDNA group (p-0.02). In the ND ctDNA/PD group, the median time from MBC diagnosis to ctDNA evaluation was 7 months and pts had received a median of 0.5 prior lines of therapy for MBC. Four pts (13%) had lobular breast cancer, 24 pts (80%) had recurrent disease, 14 pts (47%) had visceral metastases, and 12 pts (40%) had oligometastatic disease. Sites of metastases at the time of ND ctDNA/PD were bone n=16 (53%), lung n=7 (23%), liver n=6 (20%), lymph node n=11 (37%), skin and soft tissue n=5 (17%), and CNS n=5 (17%). When compared to those with detectable ctDNA these differences in characteristics were not statistically significant, although numerically pts with ND ctDNA had more CNS disease (17% vs 10%) and less liver disease (20% vs 32%). At the time of ND ctDNA, the site of progression was bone n=14 (47%), CNS n=5 (17%), lymph node n=9 (30%), lung n=7 (23%), and liver n=5 (17%). There was a single site of progression in 20 pts (67%). 16 of 30 pts had repeat ctDNA analysis of which 9 pts had subsequent detectable ctDNA with a median VAF of 0.3%, a median of 1 alteration per sample, and oncogenic or likely oncogenic alterations in TP53 in 3 pts and BRCA1, CCNE1, CDH1, and PIK3CA in 1 pt each. Seven had tissue NGS, all of which showed multiple oncogenic alterations. The remaining 22 pts with ND ctDNA but no PD were responding to therapy based on imaging or had already started a new therapy since the last progression. This group also had a high proportion of HER2+ MBC (n=7, 32%) and low proportion with visceral disease (n=6, 27%) Conclusions: Although ctDNA is a highly sensitive tool to detect active MBC (&lt;3% of samples had ND ctDNA), its sensitivity may be less in some clinical scenarios, including HER2+ MBC, when there are limited sites of progression, or when there is isolated CNS progression.

Citation Format: Ami N Shah, Lorenzo Gerratana, Shruti Chandra, Dhruvika Mukhija, Neelima Katam, Anthony K Kang, Andrew A Davis, Millen Srivastava, Saya Jacob, Paolo D'Amico, Qiang Zhang, Carolina Reduzzi, Michael Gurley, Firas Wehbe, William J Gradishar, Amir Behdad, Massimo Cristofanilli. Progressive metastatic breast cancer with no detectable circulating tumor DNA: Evaluating limitations of this highly sensitive tool [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 P2-08-04.

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.

Abstract P2-01-08: Esr1 Y537 mutations are associated with increased baseline circulating tumor cells enumeration for patients with estrogen receptor positive metastatic breast cancer

Introduction: Estrogen Receptor (ER)-positive breast cancer is the most frequent breast cancer subtype. Endocrine therapy (ET) targeting the ER pathway including CDK4/6 inhibitors represents the main initial therapeutic approach. However, clinical resistance associated with progression of disease caused by ESR1 mutations is a recognized an important mechanism of ET resistance. ESR1 mutations, most often detected from liquid biopsies, have been consistently associated with a worse outcome and are being currently evaluated as a potential biomarker to guide therapeutic decisions. Here we reported a new finding on the association between ESR1 amino acid Y537 mutations in ctDNA and circulating tumor cells (CTC) in metastatic breast cancer (MBC). Methods: The study included 158 ER positive MBC patients enrolled under an IRB-approved trial (NU16B06) at Lurie Cancer Center, Northwestern University. The patients received systemic treatments in 2016-2020. Whole blood samples (7.5ml/each) were collected in EDTA tubes from patients who were longitudinally characterized for CTCs before therapy (baseline). CTCs enumeration were performed in FDA approved CELLTRACKS ANALYZERII® System (Menarini) by using CXC Kit contains antibodies targeting EpCAM antigen for capturing CTCs, anti-CK-PE which is specific for the intracellular protein cytokeratin in epithelial cells, DAPI for staining the cell nucleus, anti-CD45-APC is specific for leukocytes. The CTCs were classified based on morphology and correct phenotype as CK+, DAPI+ and CD45-. Plasma ctDNA was isolated using a Qiagen circulating nucleic acid kit, and then was analyzed using the Guardant360 next-generation sequencing (NGS)-based assay. In this study, only patients with ESR1 mutations were included for statistical analyses of correlation between the hotspot mutation with the endocrine therapy resistance by using Causal Inference approach. All statistical analyses were conducted Mann-Whitney U test by IBM SPSS version 23.0. Results: ESR1 mutations were detected in 40 out of 158 patients at baseline. ESR1 Y537(N/C/S) mutations were detected in 13 patients, among which there were 9 patients who only had the Y537(N/C/S) mutations and no other ESR1 hotspot mutations (Group 1) and there were 4 patients who had polyclonal ESR1 mutations. In the latter cohort, there were 17 ESR1 amino acid mutations detected in 31 patients (Group 2) including Q314, T347T, N359I, K362N, E380Q, V392I, G442R, F461I, S463P, S464, I487M, K520K, M528V, L536H, D538G, D545D and Q565. There were no any ESR1 mutations detected in the other 118 patients (Group 3). The CTC&gt;5/7.5mL (Stage IV aggressive) were found in 66.7%, 38.7% and 29.3% patients in Group 1, Group 2 and Group 3 respectively. The median total CTCs was 26.0/7.5mL in MBC patients with ESR1 Y537(N/C/S) mutations (Group 1). The median of total CTCs was 2.0/7.5mL in the MBC patients with polyclonal ESR1 mutations but not on Y537 (N/C/S) (Group 2), and it was 1.0/7.5mL in the group of metastatic breast cancer without ESR1 mutations (Group 3). The median total CTCs in Group 1 was significantly higher than Group 2 (Mann-Whitney U, P&lt;0.05) and Group 3 (P=0.009), which indicated that Y537(N/C/S) mutations were correlated with higher baseline CTCs. Conclusions: In this study, we demonstrated a correlation between presence of ESR1 Y537 mutations and increased CTCs (higher Stage IV aggressive cases) in patients with HR+ MBC, These preliminary data may suggest a critical role of ESR1 Y537 mutations in the metastatic process, also indicating that different ESR1 amino acids mutations may play different roles on disease progress. Larger validation studies are needed to confirm that evaluation of ESR1 Y537 variant together with CTCs numeration is an accurate tool to identify endocrine-refractory disease.

Citation Format: Qiang Zhang, Jianhua Jiao, Paolo D'Amico, Andrew A. Davis, Weijun Qin, Lorenzo Gerratana, Saya L. Jacob, Youbin Zhang, Jeannine Donahue, Wenan Qiang, Ami N. Shah, Lisa Flaum, William Gradishar, Leonidas C. Platanias, Massimo Cristofanilli. Esr1 Y537 mutations are associated with increased baseline circulating tumor cells enumeration for patients with estrogen receptor positive 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 P2-01-08.

Abstract P2-02-06: Her2-low ctcs in breast cancer: Pipeline for phenotypic driven, single-cell collection and molecular analysis

Background The presence of circulating tumor cells (CTCs) expressing HER2 at low score (HER2-low) in the peripheral blood of metastatic breast cancer (MBC) patients has been associated with resistance to treatment and more aggressive metastatic behavior. However, the biological intrinsic nature of HER2-low CTCs remains unexplored. Considering the technical challenges beyond the selective collection of immunophenotype-specific CTCs, we developed a pipeline to individually capture HER2-low CTCs to perform single-cell molecular analysis. Methods 4 different breast cancer cell lines (MDA-MB-231, T47D, MDA-MB-453, SKBR3), that are known to express HER2 at different immunohistochemistry scores (respectively classified as 0, 1+, 2+, 3+), were spiked (around 500 cells each) in healthy donor blood tubes (7.5 ml). Samples were subsequently enriched through the CellSearch™ (Menarini Silicon Biosystems, Bologna, Italy), HER2 stained using the CellSearch CTC Kit and analyzed with the ACCEPT tool (Zeune et al., 2017). Enriched cells were additionally characterized by the DEPArray NxT™ Cell Browser and subsequently collected in pooled and single cells. The HER2 signal-intensity scores (fluorescein isothiocyanate, FITC mean), detected by both tools in each cell line, was compared using the nonparametric Mann-Whitney U test. The optimal cut-offs to distinguish HER2 1+ from HER2 0 and HER2 2+ cells were calculated performing Receiving Operator Curves (ROC). Results Detected mean intensities retrieved from CellSearch™ and analyzed with the ACCEPT tool were respectively 0.34 (MDA-MB-231, 0), 1.44 (T47D, 1+), 15.28 (MDA-MB-453, 2+) 166 (SKBR3, 3+), resulting in the possibility to discriminate both 2+ and 3+ cells from 1+ and 0 (P &lt; 0.00001). No statistical significance has been observed between 1+ and 0 (P=0.19). Conversely, HER2 signal-intensity scores detected with the Cell Browser were: 3.69 (0), 4.38 (1+), 6.28 (2+) and 42.82 (3+). These results allow DEPArray Nxt to efficiently differentiate each single cell line, in particular HER2 1+ cells from both 0 and 2+ (P &lt; 0.00001), enabling the collection of these specific cells. The area under the ROC was 0.7 and 0.72 (respectively 0 vs 1+ and 1+ vs 2+) and the optimal calculated cut-offs were 3.23 (lower) and 4.61 (higher). Conclusions HER2-low CTCs can be detected and separately collected using predetermined intensity cut-offs. Downstream single-cell or pooled collection can be subsequently performed. Further molecular characterizations, as DNA genome sequencing, could highlight the underlying altered pathways responsible for resistance to treatment and molecular patterns accountable for worse prognosis.

Citation Format: Paolo D'Amico, Carolina Reduzzi, Wenan Qiang, Qiang Zhang, Lorenzo Gerratana, Ami N Shah, Andrew A Davis, Anthony Kang, Meilynn Shi, Youbin Zhang, Saya Jacob, Amir Behdad, Giuseppe Curigliano, Massimo Cristofanilli. Her2-low ctcs in breast cancer: Pipeline for phenotypic driven, single-cell collection and molecular analysis [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 P2-02-06.

ICAM1 initiates CTC cluster formation and trans-endothelial migration in lung metastasis of breast cancer

Circulating tumor cell (CTC) clusters mediate metastasis at a higher efficiency and are associated with lower overall survival in breast cancer compared to single cells. Combining single-cell RNA sequencing and protein analyses, here we report the profiles of primary tumor cells and lung metastases of triple-negative breast cancer (TNBC). ICAM1 expression increases by 200-fold in the lung metastases of three TNBC patient-derived xenografts (PDXs). Depletion of ICAM1 abrogates lung colonization of TNBC cells by inhibiting homotypic tumor cell-tumor cell cluster formation. Machine learning-based algorithms and mutagenesis analyses identify ICAM1 regions responsible for homophilic ICAM1-ICAM1 interactions, thereby directing homotypic tumor cell clustering, as well as heterotypic tumor-endothelial adhesion for trans-endothelial migration. Moreover, ICAM1 promotes metastasis by activating cellular pathways related to cell cycle and stemness. Finally, blocking ICAM1 interactions significantly inhibits CTC cluster formation, tumor cell transendothelial migration, and lung metastasis. Therefore, ICAM1 can serve as a novel therapeutic target for metastasis initiation of TNBC.

Circulating tumor cell (CTC) clusters are more efficient at mediating metastasis as compared to single cells and are associated with poor prognosis in breast cancer. Here, the authors show that ICAM1 is enriched in CTC clusters and its loss suppresses cell-cell interaction and CTC cluster formation, and propose ICAM1 as a therapeutic target for treating breast cancer metastasis.

Correlation between different levels of HER2 expression in circulating tumor cells (cHER2 ratio) and metastatic behavior in stageIVaggressive breast cancer

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Background: The presence of HER2 expressing (HER2+) circulating tumor cells (CTCs) occurs often in metastatic breast cancer (MBC) patients (pts). We have previously showed that the ratio among CTCs expressing high level of HER2 and the total number of HER2+ CTCs (circulating HER2 ratio, cHer2 ratio) has a prognostic role in MBC patients. Here we further investigate the role of the cHER2 ratio in the process of metastatic spread. Methods: Under IRB-approved study we prospectively analyzed blood samples of patients with MBC enrolled before starting a new line of therapy. Samples were collected from pts treated at Northwestern University (Chicago, IL) between 2016 and 2020. CTCs were enumerated through CellSearch (Menarini Silicon Biosystems, Bologna, Italy) and characterized for HER2 expression using the CellSearch CXC Kit. HER2+ CTCs were divided in 3 different categories (1+,2+,3+) leaning on fluorescence intensity. Pts with <5 CTCs (stage IV indolent) were excluded from the analysis. The cHER2 ratio, defined as the sum of 2+ CTCs and 3+ CTCs divided by the total number of HER2+ CTCs, was used to split the remaining pts in 2 different cohorts: cHER2 ratio high (> 0.75) (cHER2high) and cHER2 ratio low (≤0.75) (cHER2low). The frequency of each metastatic site (i.e. liver, lung, central nervous system, bone, lymph nodes, skin/soft tissue, serosa) and the total number of different sites involved (1-7, ≤2 and >2 sites) were compared among the two sub-populations and analyzed through Fisher exact test. Results: Out of 98 pts enrolled, 77 were classified as cHER2low and 21 as cHER2high. We observed a higher frequency of oligometastatic pts (≤2 sites involved) in the cHER2high cohort (16, 76%), compared to only 29 (37%) in the cHER2low (p<0.005). Moreover, the cHER2 ratio was associated with a tropism toward specific sites of disease spread with higher incidence of liver, lung and lymph nodes metastases in the cHER2low cohort (p<0.05). No other statistical associations were observed in respect of specific organ tropism. The frequency of involvement for each metastatic site among the two cohorts are reported in the table. Conclusions: Measuring CTCs enumeration and HER2 expression we identified two cohorts, cHER2high and cHER2low, associated with distinct patterns of metastatic spread. The cHER2low pts were correlated to multiple sites of metastatic involvement, with particular tropism toward liver, lung and lymph nodes. These results confirm the prognostic role of the cHER2 ratio, suggesting a peculiar biological meaning of the HER2+ 1+ CTCs.[Table: see text]

Uncovering the differential impact of ESR1 and PIK3CA codon variants on the clinical phenotype of metastatic breast cancer (MBC) through circulating tumor DNA (ctDNA) next-generation sequencing (NGS)

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Background: The exposure to endocrine therapy (ET) can induce the onset of ESR1 gene alterations that have an impact on not only treatment resistance but also clinical phenotype. We previously demonstrated the potential of liquid biopsy in describing the metastatic behavior of MBC. The aim of this study was to explore the different clinical phenotype across the main ESR1 and PIK3CA codon variants. Methods: The study retrospectively analyzed a cohort of 501 MBC patients (pts) characterized for ctDNA through NGS before treatment start at Northwestern University (Chicago, IL), Massachusetts General Hospital (Boston, MA), CRO National Cancer Institute (Aviano, IT) and ASUFC Hospital (Udine, IT) between 2014 and 2020. Associations between clinical characteristics and ESR1 and PIK3CA codon variants were explored through logistic regression corrected for sites and ESR1/ PIK3CA status. Survival was tested through Cox regression both for progression-free survival (PFS) and overall survival (OS). Results: Of the total 501 pts, 289 (58%) were diagnosed with hormone-receptor positive (HRpos) MBC, 114 (23%) with HER2-positive MBC, and 93 (19%) with triple-negative MBC. ESR1 mutations were detected in 71 pts (14%) and PIK3CA in 154 pts (31%). The most represented ESR1 gene mutations were found in codons 380 (9%), 536 (23%), 537 (34%), and 538 (34%), while alterations in codons 542 (19%), 545 (21%), and 1047 (60%) were the most common for PIK3CA. As expected, ESR1 mutations were found only in HRpos pts previously exposed to ET (P < 0.001). No significant differences were observed for PIK3CA. After multivariable analysis, ESR1mutations were confirmed as highly associated with liver and bone metastases (OR 3.31, P < 0.001 and OR 5.09, P < 0.001). Moreover, an association with lung (OR 2.07, P = 0.010) was observed in this cohort. After multivariable analysis, codon 537 mutations were associated with bone involvement (OR 12.97, P = 0.014), codon 538 with liver (OR 4.73, P = 0.010), and codon 536 with soft tissue (OR 5.84, P = 0.006) and liver (OR 4.06, P = 0.048). PIK3CA mutations were associated with bone (OR 2.61, P < 0.001) and lung metastases (OR 1.62, P = 0.044). Specifically, codon 1047 mutations were the primary driver (OR 3.14, P = 0.001 and OR 1.97, P = 0.019). In HRpos MBC, baseline mutations in ESR1 codon 537 and 538 had a negative impact on OS (HR 3.73, P < 0.010 and HR 2.99, P < 0.021), while 380 and 536 had a negative impact on PFS (HR 18.98, P < 0.001 and HR 2.60, P = 0.015). No impact was observed across PIK3CA gene variants. Conclusions: This study showed the different tumor biology across ESR1 and PIK3CA gene variants. As novel selective estrogen receptor degraders (SERDS) and PIK3CA inhibitors are gaining momentum as new ET options in MBC, these results highlight the future pivotal role of ctDNA NGS in refining tumor biology characterization.

Abstract PS2-08: Identification of incidental putative germline variants in circulating tumor DNA

Background: Circulating tumor DNA (ctDNA) has emerged as a potential tool for detecting disease recurrence, monitoring response to therapy, and identifying resistance mutations in the peripheral blood. With increased frequency of testing, there is an unmet need to recognize putative germline variants in ctDNA, and the probability that these variants are associated with inherited conditions. Here, we evaluated a large cohort of breast cancer patients who underwent ctDNA evaluation to determine the type and frequency of ctDNA mutations identified with confirmed germline testing.

Methods: We reviewed ctDNA testing from a single institution (Northwestern University). All breast cancer patients who had next-generation sequencing (NGS) performed by Guardant Health (Redwood City, CA) from 2015-2020 were included in this retrospective study. An allele frequency cutoff of 30% was pre-established as a threshold to review patient charts to determine whether genetic counseling and germline testing were performed, along with the timeframe of this testing (e.g. before or after ctDNA evaluation). Clinical information including demographics, pathology, tissue NGS testing, and germline testing were collected. Descriptive analyses and statistical associations were performed using STATA.

Results: The initial cohort consisted of 520 patients with breast cancer who underwent ctDNA testing. From this, we identified 84 patients (16.2%) who had at least one variant with allele frequency ≥30%. The most common variants identified were the following: TP53 (34%), PIK3CA (27%), BRCA1 (9%), BRCA2 (8%), and AKT1 (4%). Guardant360 classified 99% of these variants as pathogenic and 1% as a variant of unknown significance. Germline positivity using a separate CLIA-approved test for this indication was confirmed at the following frequencies: BRCA1 (2 of 8 positive, 25%), BRCA2 (2 of 5 positive, 40%), PIK3CA (0 of 5 positive), and TP53 (0 of 26 positive). In total, 14% of patients with ctDNA allele frequency ≥30% had a confirmed germline mutation. Lower age at breast cancer diagnosis was significantly associated with the probability of germline testing prior to ctDNA evaluation (P=0.0001). For patients who had a variant with allele frequency ≥30%, 24.3% never received genetic counseling or germline testing.

Conclusion: High allele frequency ctDNA variants (≥30%) were present in 16% of patients who underwent ctDNA evaluation with 14% of these variants confirmed as true germline variants. Consenting patients for ctDNA testing should include the possibility of identifying putative germline variants, and criteria should be established to refer patients for subsequent genetic counseling and germline testing, given the potential implications for patients and their family members.

Citation Format: Andrew A Davis, Michael C Burns, Lorenzo Gerratana, Paolo D'Amico, Saya Jacob, Ami Shah, Neelima Katam, Firas Wehbe, Qiang Zhang, Elena Vagia, Lisa Flaum, Kalliopi P. Siziopikou, Leonidas C Platanias, Amir Behdad, William J Gradishar, Massimo Cristofanilli. Identification of incidental putative germline variants in circulating tumor DNA [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 PS2-08.

Abstract PS2-10: Circulating tumor DNA (ctDNA) as a diagnostic tool to identify putative germline BRCA mutations

Background: As the role of precision medicine in metastatic breast cancer (MBC) expands, there is an increasing emphasis on diagnostic tools to characterize both somatic and germline alterations that drive carcinogenesis. Circulating tumor DNA (ctDNA) has provided an important means for real-time, non-invasive detection and monitoring of tumor somatic alterations without standard paired white blood cell testing. However, its application for the detection of germline mutations remains relatively understudied. Here, we characterize the role of BRCA1&2 ctDNA mutant allele frequency (MAF) to identify underlying putative germline BRCA1&2 mutations.

Methods: Patient data were retrospectively obtained under an IRB-approved protocol to review ctDNA data at Northwestern University between 2015 and 2020. All ctDNA samples were analyzed using the Guardant360 next-generation sequencing (NGS) assay (Guardant Health). Patients with ctDNA alterations in the BRCA genes were identified at all mutant allele frequencies (MAF). Clinical data were collected including breast cancer subtype, prior lines of therapy, tissue-based NGS and germline testing information. Separate CLIA-approved testing performed per standard of care was used as the gold standard for germline testing. Statistical analysis was used to test the association of MAF cut-offs with the presence or absence of a germline alteration. Receiver operating characteristic (ROC) analysis was performed.

Results: We identified 127 patients with breast cancer who underwent ctDNA collection. There were 69 HR+ HER2-, 24 HER2+, and 34 triple negative breast cancer (TN) patients. Of these, 8 patients had known BRCA1 germline mutations, as confirmed with separate germline testing, and 9 patients had known BRCA2 germline mutations. BRCA1 germline mutations were significantly association with age &lt; 40 (p=0.016) and triple negative subtype (p=0.042). Mean ctDNA BRCA1 MAF was 2.27% (Standard Deviation {SD} 10.19%) and mean BRCA2 MAF was 2.04% (SD 9.51%). BRCA1/2 MAF was analyzed with respect to germline mutations through ROC analysis. For BRCA1 ctDNA MAF cut-off 32.4% was associated with confirmed putative germline mutation. This cutoff demonstrated sensitivity of 1 and specificity of 0.99. Area under the curve (AUC) was 1.00 at this cut-off. For BRCA2, ctDNA MAF cutoff of 28.5% was associated with confirmed putative germline mutations. This cutoff demonstrated sensitivity of 0.86, specificity of 0.99 and AUC of 0.93.

Discussion: ctDNA alterations of BRCA1 with MAF&gt;32.4% and BRCA2 with MAF&gt;28.5% in clinical ctDNA testing were useful criterion to identify germline BRCA mutations. The data suggest the potential to utilize ctDNA as a diagnostic tool to predict germline mutations based on MAF thresholds. Future prospective studies are needed to determine how ctDNA testing may be incorporated into existing clinical algorithms to refer patients for germline testing.

Citation Format: Saya Jacob, Andrew Davis, Paolo D'Amico, Lorenzo Gerratana, Michael Burns, Ami Shah, Neelima Katam, Firas Wehbe, Qiang Zhang, Elena Vagia, Lisa Flaum, Kalliopi Siziopikou, Leonidas Platanias, Amir Behdad, William Gradishar, Massimo Cristofanilli. Circulating tumor DNA (ctDNA) as a diagnostic tool to identify putative germline BRCA mutations [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 PS2-10.

Abstract PS2-05: Genetic profiling for circulating tumor cell clusters to unveil molecular drivers of metastasis

Introduction: Although CTCs display the same spatial and temporal heterogeneity as the primary tumor, they represent a privileged window to disclose mechanisms of metastases. A portion of CTCs may form clusters that contain two or more CTCs bound together which were reported to have up to 50-fold of potential of forming distant metastasis in MBC as compared to individual CTCs (Aceto N. Cell, 2015). However, genomic characterization of CTCs-clusters compared to single CTCs remain largely unknown. We previously reported single CTC sequencing for HER2+ CTCs (2020 AACR #3120). Herein, we report a new finding of heterogeneity profiling for CTC-clusters compared to single CTCs, which would be helpful to evaluate the MBC metastasis capability and treatment in clinic. Methods: Whole blood sample (7.5ml/each) was collected from stage III/IV MBC patients before therapy. CTC enumeration was performed using the FDA-cleared CellSearch™ System (Menarini) targeting the EpCAM antigen for capturing CTCs which were then stained by Anti-CK-PE, DAPI, anti-CD45-APC and anti-HER2-FITC. The CTC-clusters and single CTCs were isolated using DEPArrayTM System (Menarini). DNA was isolated from CTC-clusters and single CTCs by ArcturusTM PicoPureTM DNA Extraction kit. The initial library was prepared by SMARTer® PicoPLEX® Gold Single Cell DNA-Seq Kit, and the exome capture was performed by Twist Human Core Exome EF Multiplex Complete Kit. The sequencing was prepared by NextSeq 500 mid output V2.5 kit and was performed on the NextSeq 500 (Illumina). It was a paired end run, 75×75 bps run with dual indexing. Results: We identified 107 CTCs by CellSearch™, including 93 single CTCs, 14 CTC-clusters and 145 WBCs. Autologous CTC-clusters (CK+DAPI+CD45-, Group 1), single CTCs (CK+DAPI+CD45-, Group 2), and leukocytes (CK-DAPI+CD45+, Group 3) were sequenced respectively. The sequencing data was processed following the GATK pipeline and annotated using SnpEff. There were 60,638 counts (6.77%) and 70,334 counts (8.20%) for exon variants in CTC-clusters and single CTCs respectively, 507,595 counts (56.69%) and 486,119 counts (56.69%) for intron variants, 194,026 (21.67%) and 175,819 counts (20.51%) for intergenic variants, 54,174 counts (6.05%) and 50,370 counts (5.87%) for downstream genes, 51,716 counts (5.78%) and 45,915 counts (5.36%) for upstream genes, and 3.04% and 3.37% of others variants in CTC-clusters and single CTCs respectively. Meanwhile, there was 0 count for exon and intron variants found in Group 3. There were 60 and 79 gene variants (SNP and Ins-Del) identified to have the highest impact effect (≥20) on CTC-clusters and single CTC exons respectively, which affect significantly on the functional proteins coding. Among the top 50 high impact gene variants in each group, there were 25 gene alteration sites were similar in Group 1 and 2, including XYLB, RAN, QPCT, HPGDS, HDAC8, GABBR2, CYP11B2 and CHKA. Specific to Group 1, there were 25 gene alterations which were primarily related to cellular proliferation and tumor promotion (AMD1), liver drug clearance (CES1), tissue remodeling (CHI3L1), immune cytokine signaling (JAK1) and metabolism (ASRGL1). Meanwhile, there are 25 specific gene alterations in Group 2 compared to Group 1, which were associated with nucleotide-excision repair (DDB1 and FAN1) chromosome positioning (KIF11), cell growth, differentiation, mitotic cycle, oncogenic transformation (PTPN3 and MAPK14), apoptosis (CASP1) and cell growth (CTNNB1). Conclusion: Genomic characterization of CTC-clusters compared to autologous single CTCs and leukocytes elucidated new specific gene alterations in CTC-clusters associated with most aggressive disease metastasis in MBC, which will help to gain new insights on the molecular mechanisms associated with the metastasis and find new molecularly driven therapies for disease metastasis.

Citation Format: Qiang Zhang, Lorenzo Gerratana, Paolo D'Amico, Andrew A. Davis, Saya Liz Jacob, Xinkun Wang, Zhe Ji, Zheng Cai, Elena Vagia, Wenan Qiang, Ami Shah, Youbin Zhang, Lisa Flaum, Firas Wehbe, Amir Behdad, William Gradishar, Leonidas Platanias, Massimo Cristofanilli. Genetic profiling for circulating tumor cell clusters to unveil molecular drivers of metastasis [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 PS2-05.

Abstract PS2-06: The detection and enumeration of circulating tumor cells (CTCs) and circulating endothelial cells (CECs) in metastatic breast cancer

Introduction: Circulating tumor cells (CTCs) are the roots of metastasis which is the main cause for death in metastatic breast cancer (MBC). CTCs enumeration is strongly prognostic in advanced disease and can stratify patients in two distinct disease, Stage IV aggressive and Stage IV indolent. In the former disease, the detection of CTC clusters and HER2-expression increase prognostic and predictive value. The metastatic cascade is a complex, regulated process involving immune cells and endothelial cells for progression and neoangiogenesis. Circulating endothelial cells (CECs) from the inner wall of blood vessels are shed into the blood stream during formation of blood vessels which is considered a sensitive marker of endothelial damage in pathological conditions such as cancer. CECs have been also studied as a biomarker for tumor progression and monitoring anti-angiogenic therapeutic effects in MBC. We evaluated the concomitant detection of CTCs and CECs in MBC patients, along with expression of HER2 in CTCs that may offer an interesting clue to elucidate the metastasis mechanisms. Methods: Whole blood samples (7.5ml/each) were collected from 14 stage IV MBC patients before systemic therapy. CTCs enumeration was performed in FDA approved CELLTRACKS System (Menarini) by using CTC Kit contains specific antibodies targeting the EpCAM for capturing CTCs, anti-CK-PE (for epithelial cells), DAPI (for nucleus), anti-CD45-APC (for leukocytes), and anti-HER-2/neu-FLU. The CTCs were classified as CK+, EpCAM+, DAPI+ and CD45-. Meanwhile, the same patients’ blood samples (4.0ml/each) were processed for CEC analyzed by using CEC kit which immunomagnetically captures CD146+ cells, and then stains the cells for CD105-PE (specific for protein endolgin), CD45-APC, nucleus-DAPI. The positive CECs were classified as CD 146+, CD105+, DAPI+ and CD45-. The associations between CTCs, HER2 expression and CECs were evaluated. Results: The average age of patients was 53.1. Subtypes of Luminal, HER2 positive and TNBC were 64.2% 7.2% and 28.6% respectively. Distant metastasis were found in 13 out of 14 patients, including bone (7), liver (5), Lymph nodes (5) and Pleura (2). CTCs were found positive (≥5, Stage IV aggressive) in 5 patients (range: 5-47, mean=24), and HER expression was identified in all 5 of these cases with a range of numbers between 1 and 7 (mean=4.2). The ratios of HER+ CTC/total ratios were 8.51%, 17.95%, 20%, 30.77%, and 33.33%. HER2 expression were defined officially in our lab according to the percentile of positive HER2 CTCs/Total CTCs and the expression intensity as - (&lt;20%), + (20-39%), ++ (40-59%) and +++ (≥60%) respectively. There were 9 patients (%) were identified as CTCs negative (&lt;5, Stage IV indolent) with the mean=1, and HER+ CTCs were found in only 2 patients with Stage IV indolent. Meanwhile, CECs were found in all 14 patients with a range of numbers between 4 to 115. There were an average of 33 CECs in Stage IV aggressive disease, compared to 53 CECs in Stage IV indolent. The average of CECs were 53.44, 12 and 37.25 in Luminal, HER2 positive and TNBC groups respectively. On the other hand, patients with HER2+ CTCs had an average of 50 CECs which is significantly higher than average of 41 CECs in patients without HER2+ CTCs. Moreover, there were average of 94.5, 56 and 40.22 CECs were found in groups when HER2 expression was ++/+++, above + and - respectively. The results demonstrated that although CTC enumeration have a reverse correlation with CECs numbers, HER2 expression in CTCs was significantly related with high CECs numbers. Conclusions: Our data provides the first evidence of potential association between CTCs and CECs in metastatic breast cancer. The association between HER2 expression and CECs offers a potential new insight to mechanism connections between CECs and disease metastasis in MBC.

Citation Format: Qiang Zhang, Paolo D'Amico, Jeannine Donahue, Lorenzo Gerratana, Andrew A. Davis, Saya Liz Jacob, Zheng Cai, Elena Vagia, Wenan Qiang, Ami N. Shah, Katy Kerby, Lisa Flaum, Youbin Zhang, Firas Wehbe, Amir Behdad, William Gradishar, Leonidas Platanias, Massimo Cristofanilli. The detection and enumeration of circulating tumor cells (CTCs) and circulating endothelial cells (CECs) in metastatic 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 PS2-06.

Abstract PS2-20: Prognostic value of baseline circulating tumor cells (CTCs) enumerations is for stage III and stage IV breast cancer

Introduction: Prognosis of metastatic breast cancer (MBC) is initially predicted by the cancer’s characteristics based on AJCC TNM system, including the size of the cancer tumor, invasion into nearby tissue, lymph nodes and other parts of the body beyond the breast. Although additional information including hormone-receptor status, HER2 status, and possibly Oncotype DX score contributed to improve prognostic evaluation, predicting clinical outcomes and treatment benefit for MBC is still a challenge in clinic because of the clinical and biologically heterogeneous condition. We recently reported that CTCs enumeration can classify MBC in two distinct prognostic groups independently of clinical and molecular characteristics (Crit Rev Oncol Hematol. 2019). Moreover, our group reported that CTCs is associated with HER2 expression in MBC which may indicate more aggressive tumor (2019 AACR #1919). Here we compared CTCs enumeration of Stage III and Stage IV, which would be helpful to evaluate the MBC metastasis capability and treatment in clinic. Methods: The study included 38 specimens prospectively collected under IRB-approved protocol from 38 patients with Stage III MBC, and 254 specimens from 254 patients with stage IV MBC who received standard systemic treatments based on disease subtypes at NMH (2016-2020). Duplicate whole blood samples (7.5ml/each) were collected in EDTA tubes from these patients who were longitudinally characterized for CTCs before therapy (baseline). CTCs enrichment and enumeration were performed in FDA approved semi-automated fluorescence CELLTRACKS ANALYZERII® System (Menarini) by using CELLSEARCH® CXC Kit contains antibodies targeting the Epithelial Cell Adhesion Molecule (EpCAM) antigen for capturing CTCs, anti-CK-PE which is specific for the intracellular protein cytokeratin in epithelial cells, DAPI for staining the cell nucleus, anti-CD45-APC is specific for leukocytes (2019 ASCO #1036). The CTCs were classified based on morphology and correct phenotype as CK+, DAPI+ and CD45-. Kruskal-Wallis test was used for statistics. Results: Patients were classified as Luminal, HER2 positive and TNBC disease subtypes in 46.6%, 46.7% and 6.7% respectively in Stage III patients, and 54%, 18% and 28% respectively in Stage IV patients. The patients at age above 50 were 26.% in Stage III group and 68% in Stage IV group respectively. IBC patients represented 61.5% and 33.5% of Stage III and Stage IV patients respectively. Metastasis in liver, lung and bone were diagnosed in 40.7%, 40.2% and 62.8% in Stage IV patients. CTC negative (&lt;5 CTCs) and positive (≥5CTCs) patients were identified in 32/38 (84.22%, group 1) and 6/38 (15.78%, group 2) respectively in Stage III patients, and 149/254 (59%, Stage IV indolent ) and 105/254 (41%, Stage IV aggressive ) respectively in Stage IV patients. Patients in Group 1 have a significantly less recurrence probability than patients in Group 2 (p=0.015). Correspondingly, patients with Stage IV indolent also had significantly longer survival than patients with Stage aggressive disease (p=0.0021). When comparing the all population, Group 1 patients still have the highest survival probability (p=0.00057) within 47 months follow-up survey. More interesting, there was no any CTC-clusters found in all Stage III patients when there were 28 out of 254 stage IV patients (11.02%) were detected with CTC-clusters, who had the worst prognosis in compared to either Stage IV patients without CTC-clusters or Stage III patients (p=0.00035). Conclusions: In this study, we showed that enumeration of baseline CTC and CTC-clusters correlated with worse prognosis even the patients were pathologically diagnosed for the same stage, which provided an additional measure to predict disease recurrence after systemic therapies especially for Stage III MBC patients.

Citation Format: Qiang Zhang, Zheng Cai, Lorenzo Gerratana, Paolo D'Amico, Andrew A. Davis, Saya Liz Jacob, Elena Vagia, Ami N Shah, Lisa Flaum, Youbin Zhang, Wenan Qiang, Firas Wehbe, Amir Behdad, William Gradishar, Leonidas C Platanias, Massimo Cristofanilli. Prognostic value of baseline circulating tumor cells (CTCs) enumerations is for stage III and stage IV 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 PS2-20.

Abstract PS2-11: Ctc-her2+ a novel subset in stage IVaggressive: Molecular correlations, outcome and clinical characteristics in metastatic breast cancer

Background The enumeration of Circulating Tumor Cells (CTCs) in the peripheral blood of patients (pts) with metastatic breast cancer (MBC) showed prognostic value independent of clinic-pathological characteristics and proposed as a new tool for Stage IV stratification. Molecular characterization of CTCs with analysis of standard HER2 and estrogen-receptor (ER) status provides additional predictive value. The presence of HER2 positive CTCs (CTCs-HER2+) has been documented in pts with HER2 negative MBC and suggestive of tumor heterogeneity. The molecular features associated with the detection of these cells and the clinical significance of CTCs-HER2+ remains of unclear clinical significance. The lack of validated prospective trials limits the use of this immunophenotypic characterization as a prognostic and predictive factor. We conducted an analysis of a large cohort of patients with MBC evaluated for CTCs enumeration (CTCs+), molecular analysis of CTCs (CTCs-HER2+) and ctDNA. Methods The IRB-approved study prospectively analyzed blood samples of pts with MBC enrolled before starting a new line of therapy. Samples were collected from pts treated at Northwestern University (Chicago, IL) between 2016 and 2020. ctDNA was analyzed using the Guardant360 NGS assay (Guardant Health) with a specific focus on the detection of ERBB2 mutations. CTCs were enumerated through CellSearch™ (Menarini Silicon Biosystems, Bologna, Italy), and characterized for HER2 expression using the CellSearch CXC Kit. HER2+ CTCs were divided in 4 different categories (0,1+,2+,3+), leaning on fluorescence intensity, as previously reported by Riethdorf et al. Pts with &lt;5 CTCs (stage IV indolent ) were excluded from the analysis. The cHER2 ratio, defined as the sum of 2+ CTCs and 3+ CTCs divided by the total number of HER2+ CTCs was used to split the remaining pts in 2 different subgroups: cHER2 ratio&gt; 0.75 (cHER2high), cHER2 ratio&lt;0.75 (cHER2low). Pts' characteristics and genomic alterations were compared between these two subgroups and a long-rank test was performed to analyze the outcome (progression-free survival, PFS). Results A total of 247 pts with MBC about to start new therapy were enrolled. 136 patients (55%) demonstrated CTCs count ≥ 5 (stage IV aggressive). Of these, 111 pts had a blood sample bearing HER2+ CTCs. 88 pts were classified as cHER2low, while 32 were allocated in the second subgroup (cHER2high). The clinic subtype distribution of the two groups was as follows: 65% ER+, 19% HER2+ and 16% TNBC among cHER2low, compared to 55% ER+, 38% HER2+ and 7% TNBC among cHER2high pts. The HER2+ subtype was significantly more represented in the cHER2high group (p&lt;0.05), along with ERBB2 mutations (p&lt;0.05). We observed a total of 89 events (progression to treatment), 67 and 22 respectively. The median PFS was 87 days in the cHER2low and 209 days among cHER2high pts (log Rank test, p&lt;0.001). Conclusion This study shows a significant association between the cHER2 ratio and outcome in pts with Stage IV aggressive disease, suggesting a potential predictive/prognostic role of this biomarker among MBC pts bearing CTC-HER2+. cHER2high pts, in which blood was collected a prevalent number of CTC-HER2+ 2+ and 3+, were more likely to have a HER2 FISH amplification by tissue biopsy and ERBB2 gene alteration by ctDNA. These findings, taken together, suggest a potential role of these subsets of CTC-HER2+ in the characterization of the HER2+ metastatic disease. The cHER2low is intrinsically characterized by a higher percentage of CTC-HER2+ 1+. This CTC-HER2+ subset of cells is commonly detected among all subtypes but, more frequently in ER+ disease and their significance remains unclear. Exploring the underlying biological nature of the CTC-HER2+ 1+ could allow to better understand the role these cells in the natural evolution of the MBC.

Citation Format: Paolo D'Amico, Qiang Zhang, Lorenzo Gerratana, Youbin Zhang, Ami Shah, Carolina Reduzzi, Andrew Davis, Saya Jacob, Firas Wehbe, Amir Behdad, Giuseppe Curigliano, Massimo Cristofanilli. Ctc-her2+ a novel subset in stage IVaggressive: Molecular correlations, outcome and clinical characteristics in metastatic 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 PS2-11.

Pharmacological management of male breast cancer

INTRODUCTION

Despite its rarity, male breast cancer shows a steadily rising incidence. Given the absence of ad hoc prospective randomized clinical trials, treatment strategies are based on extrapolation from female breast cancer recommendations or solely on population-based data.

AREAS COVERED

This review discusses the current treatment landscape for male breast cancer in the adjuvant and in the metastatic setting. The authors also discuss the biology and genomic landscape of male breast cancer. Original research and review articles, relative to the period 2010-2019, were included in the review of the literature.

EXPERT OPINION

There is a major medical need to include male patients with breast cancer in prospective clinical trials. The call to equality in breast cancer care can be pursued via two divergent paths: (i) a gender-neutral delivery of breast cancer information and (ii) the creation of separate sections, for the more common female breast cancer and for the rare male ones. We propose to differentiate male breast cancer care, acknowledging unique onco-sexual and social needs that can be only partially shared.

Preclinical models of breast cancer: Two-way shuttles for immune checkpoint inhibitors from and to patient bedside

The Food and Drug Administration has lately approved atezolizumab, anti-programmed death ligand 1 (PD-L1), to be used together with nanoparticle albumin-bound (nab) paclitaxel in treating patients with triple negative breast cancer (BC) expressing PD-L1. Nonetheless, immune checkpoint inhibitors (ICIs) are still challenged by the resistance and immune-related adverse effects evident in a considerable subset of treated patients without conclusive comprehension of the underlying molecular basis, biomarkers and tolerable therapeutic regimens capable of unleashing the anti-tumour immune responses. Stepping back to preclinical models is thus inevitable to address these inquiries. Herein, we comprehensively review diverse preclinical models of BC exploited in investigating ICIs underscoring their pros and cons as well as the learnt and awaited lessons to allow full exploitation of ICIs in BC therapy.

Liver toxicity in the era of immune checkpoint inhibitors: A practical approach

Immune checkpoint inhibitors have revolutionized the cancer treatment with an approved efficacy in different solid tumors and hematologic malignancies. These agents are increasing the indication in cancer treatment, but can be associated with serious immune-related adverse effects (IRAEs). Dermatologic and gastrointestinal toxicities are the most common IRAE followed by endocrinopathies with a different time of occurrence. Rarely cases of gastrointestinal toxicities are observed almost 2 years after initiation of the therapy. In this review we focus on liver toxicity related to these immunotherapeutic agents for which the largest amount of safety data is available. The management of drug-induced liver toxicity is very complicated and in same cases may take a long period of time to be resolved. A prompt recognition of liver IRAEs and an appropriate management of this event, requiring close collaboration with other specialist figures, could improve its treatment with evident implication on the efficacy of the therapy.

Thyroid Function in Patients with Cancer of the Breast

In 47 patients with operable cancer of the breast the thyroid activity has been studied with the following tests: a) radioactive iodine uptake, 3 and 24 hours after the administration of 50 μc of I131; b) conversion rate; c) hormonal index, i. e. the quantity of protein bound radioiodine in 1 liter of plasma, evaluated as a percentage of the administered dose. The thyroid function was studied immediately before Halstead operation as well as one, three, and twelve months later. From the data obtained it appears that a) breast cancer patients show a thyroid radioiodine uptake higher than the controls, either at the 3rd or at the 24th hour, b) after the removal of the breast, the uptake decreases, reaching normal values 12 months after the operation, c) the conversion rate does not show any difference from the controls either before or after the operation, d) the hormonal index is considerably higher than normal values before operation, and in spite of a lowering after radical mastectomy, it is still higher one year later. The data seem to show that breast cancer patients have a higher metabolic activity of the thyroid gland, without clinical signs of hyperthyroidism. After removal of the carcerous breast the thyroid activity slowly decreases. However, the conversion rate is not modified as compared to the control patients. Further confirmation of the present preliminary results should be obtained by a comparative evaluation of the results either in patients with other types of tumors, or in patients subjected to surgical procedures for non-tumorous lesions.

Targeting the microenvironment in solid tumors

Tumorigenesis is a complex and dynamic process involving different cellular and non-cellular elements composed of tumor microenvironment (TME). The interaction of TME with cancer cells is responsible for tumor development, progression and drug resistance. TME consists of non malignant cells of the tumor such as cancer associated fibroblasts (CAFs), endothelial cells and pericytes composing tumor vasculature, immune and inflammatory cells, bone marrow derived cells, and the extracellular matrix (ECM) establishing a complex cross-talk with tumor. These interactions contribute towards proliferation and invasion of the tumor by producing growth factors, chemokines and matrix-degrading enzymes. ECM is a complex system containing macromolecules with distinctive physical, biochemical and biomechanical properties. During tumorigenesis this system is deregulated favoring the generation of tumorigenic microenvironment enhancing tumor-associated angiogenesis and inflammation. An important step of anticancer treatment is the identification of the biological alterations present in TME in order to target these key molecular players. Multitargeted approaches, providing a simultaneous inhibition of TME components, may offer a more efficient way to treat cancer. In this manuscript we overview the function of each components of TME and the treatments targeting the key players.

Clinical efficacy of ribociclib as a first-line therapy for HR-positive, advanced breast cancer

INTRODUCTION

Breast cancer (BC) remains the most frequently diagnosed cancer and the most common cause of cancer death among women of all races worldwide. Over 80% of BC cases are hormone receptor (HR)-positive, comprised of luminal A and luminal B per molecular subtypes, imposing an urgent need to fully understand the mechanisms behind progression. Ribociclib is a selective cycline-dependent kinase 4 and 6 inhibitor. A phase 1 and a phase 3 trial have established a definitive role of ribociclib as frontline in the treatment of endocrine-sensitive advanced BC. Areas covered: Herein, the authors provide an overview of the data on ribociclib covering all aspects of the drug from its pharmacokinetics to efficacy and safety. The authors also provide their perspectives for the future. Expert opinion: Ribociclib is offering an opportunity to explore a new compound at the crossroads of different molecular activity and cell targets, which focus on endocrine-resistance reversal in multiple settings including early BC. Moreover, its activity against different subtypes of BC is being studied as is its immune-modulating effect. One cautionary note is that, in a market of concomitant similar competitors, a financial discussion will be mandatory.

Orthofile®: a new approach for mechanical interproximal reduction : a scanning electron microscopic enamel evaluation

PURPOSE

The aim of this in vitro study was to evaluate the stripping achieved on different teeth (incisors, canines, and premolars) by two grades of abrasive strips used for the first and tenth time. Our second aim was to test the efficacy of these strips by calculating the time necessary to perform interproximal reductions of 0.10, 0.20, and 0.30 mm.

METHODS

Four models were constructed using extracted teeth affixed in wax. The upper and lower arches were set on plaster bases and fixed in wax, carefully creating contact points. All model mouths were treated with artificial saliva (Oral Balance®) in order to simulate the biological conditions in the oral cavity. We then tested specific air-rotor strips of different grades and degrees of wear (15-µm-grain and 25-µm-grain Orthofile® strips). Afterwards the teeth from all samples were cut lengthwise in half, and each mesial and distal portion was gold-plated and observed under SEM at incremental magnification (30, 60, and 100 µm).

RESULTS

The 25-µm-grain strip was more effective than the 15-µm-grain strip, irrespective of the tooth involved. Second, the finishing phase with specific polishing strips after interproximal reduction was fundamental in reducing the number of abrasions and irregularities created by stripping, in particular after using the 25-µm-grain strip. To achieve the best result, the entire abraded area must be polished.

CONCLUSION

This system permits a rapid and effective stripping procedure in direct proportion to the strip's grain and in inverse proportion to the wear from its use. Further research will enable us to compare this system with similar procedures.

MRI of the small-bowel: how to differentiate primary neoplasms and mimickers

MRI of the gastrointestinal tract is gaining clinical acceptance and is increasingly used to evaluate patients with suspected small-bowel diseases. MRI may be performed with enterography or enteroclysis, both of which combine the advantages of cross-sectional imaging with those of conventional enteroclysis. In this paper, MRI features of primary small-bowel neoplasms, the most important signs for differential diagnosis and the diseases that can be considered as mimickers of small-bowel neoplasms, are discussed.

Patient-oriented assessment of back pain in pregnancy

Back pain is a common symptom in women during the last period of pregnancy. Only a few studies using validated patient-oriented tools have been undertaken on this topic. We report on a multicenter study on back pain in women during the last period of pregnancy, which involved seven Italian institutions. Seventy-six women in their 8th and 9th months were studied using the Italian validated version of the Roland questionnaire -- a disease-specific patient-oriented tool for low back pain. Sixty-two percent of the women had gone through at least one previous pregnancy, and clinical data concerning both the period before all pregnancies and the period before the current pregnancy were acquired. The study found that 31% of the women had no back pain symptoms (Roland score 0), 40% scored from 1 to 4, 21% scored from 5 to 10, and 8% scored more than 10. With regard to the predictive factor, history of back pain and sciatica before the pregnancy were found to be associated with occurrence of back pain symptoms during pregnancy. Unexpectedly, our results showed that male sex of the fetus seems to be related to occurrence of back pain symptoms during pregnancy. However, back pain was not associated with having gone through previous pregnancies, nor was the Roland score related to the weight before pregnancy or to increment of weight during pregnancy. Evaluation of the patient's perspective made it possible to identify predictive factors for occurrence of back pain, thereby furnishing important information for the clinical approach to pregnancy.

Carpal tunnel syndrome: relationship between clinical and patient-oriented assessment

Clinical diagnosis of carpal tunnel syndrome usually is easy and sensitive, but frequently, it is based on history and referred symptoms when no motor or sensory deficits are observed during examination. In patients with carpal tunnel syndrome, a dissociation between the severity of the disease reported by the patient and the deficits clinically evaluated by the physician often are observed. The Italian Carpal Tunnel Syndrome Study Group did a multicenter study on 740 patients (1123 hands) with carpal tunnel syndrome to assess the aspects of dissociation between the patient's and the physician's quantification of the disease severity and the ability of the patients with carpal tunnel syndrome to do daily activities. Validated patient-oriented parameters assessing symptoms and hand functional status were used. The relationship between the physician's and the patient's measurements is strong with a linear significant correlation when analyzing the functional status of the hand but not so clear and simple when analyzing the symptoms. Patients with mild-to-moderate carpal tunnel syndrome seemed to function well, although severe symptoms may be reported by the patient; however, when nerve impairment becomes severe, the patient's hand function is extremely impaired although symptoms may be milder. The data show that the patient's point of view is reliable. Carpal tunnel syndrome seems to be an ideal model to evaluate the importance of patient-oriented measurements.

A new clinical scale of carpal tunnel syndrome: validation of the measurement and clinical-neurophysiological assessment

OBJECTIVE

To validate a new clinical scale of carpal tunnel syndrome (CTS). The scale is based on clinical history and physical examination findings and includes two figures. The first is a score determined by clinical history and objective findings. The second evaluates the presence/absence of pain as a dichotomous categorical score.

METHODS

One hundred and sixty-eight consecutive idiopathic CTS hands were studied in two centers (Rome, Siena). We compare the results of the historical-objective scale (Hi-Ob scale) with the results of other validated measurements of CTS severity: (1) the Italian version of the Boston Carpal Tunnel Questionnaire, (2) the neurophysiological classification adopted by the Italian CTS study group. Furthermore, for the Hi-Ob scale the intra-observer and inter-observer evaluations were assessed.

RESULTS

The main Hi-Ob parameter was positively related to the conventional validated measurements. Conversely, the category 'PAIN' of the Hi-Ob scale appeared unrelated to the other clinical and electrophysiological parameters. Intra- and inter-observer evaluation showed the reproducibility of the Hi-Ob assessment.

CONCLUSIONS

Our data show that the Hi-Ob scale is a reliable measurement which may be useful in CTS evaluation either for clinical or for scientific purposes.

Multiperspective assessment of peripheral nerve involvement in diabetic patients

To assess the relationship between peripheral nerve involvement and the patient's perception of his own quality of life, we studied 36 consecutive out-patients affected by insulin-dependent diabetes mellitus without other diabetic complications other than neuropathy (20 men, 16 women; mean age 39.1 years). We used clinical (Semmes-Weinstein, vibration perception threshold, muscle strength, osteotendinous reflexes), neurophysiological (sural, peroneal and ulnar nerves), metabolic (glycosylated haemoglobin) and patient-oriented (SF-36 and NASS questionnaires) measurements. Patient-oriented physical scores were significantly related to: (1) neurophysiological findings of the inferior limbs; (2) conventional measurements of sensitivity; (3) metabolic assessment. Conversely, patient-oriented mental scores were significantly related only to metabolic assessment. The patient-oriented measure provided an important perspective of the severity of the disease often closely related with the biological parameters and suggested new ways of interpreting conventional biological measurements. In particular, the peripheral nerve picture appeared strictly related with the physical aspects of the patients' quality of life, while the metabolic picture appeared related with both the mental and physical aspects of the quality of life.

A useful electrophysiological test for diagnosis of minimal conduction block

OBJECTIVE

To evaluate the usefulness, sensitivity and specificity of a new neurophysiological test for partial conduction block. METHODS. In 17 patients (17 nerves) with clinical pictures strongly suggesting the presence of motor conduction block and 20 healthy subjects (40 nerves), motor nerve conduction studies were performed with the conventional surface technique and with a new technique developed by us: the single fiber EMG (SFEMG) conduction block test. Moreover, we also evaluated patients with other neurological diseases. The recent American Association of Electrodiagnostic Medicine (AAEM) consensus criteria for partial conduction block were used for the standard conduction block tests.

RESULTS

According to AAEM consensus criteria, 5/17 cases presented 'definite' partial conduction block and 6 presented 'probable' partial conduction block. In contrast, 16/17 cases (94%) presented evidence of conduction block at the SFEMG conduction block test. The 5/6 cases that did not fulfill in the AAEM criteria and that presented abnormal findings at SFEMG nerve conduction test could be considered affected by minimal conduction block. The sensitivity of this new test was greater than conventional test. The specificity was 100% (no abnormal findings in healthy subjects or patients with diseases other than neuropathy).

CONCLUSIONS

The SFEMG conduction block test is a sensitive, complementary, technique for diagnosis of minimal conduction block in patients with normal findings in standard nerve conduction studies.