Epithelial-to-mesenchymal transition of tumor cells: cancer progression and metastasis

Detection and characterization of circulating tumor cells (CTCs) with an epithelial-to-mesenchymal transition (EMT) phenotype is very important, as it can contribute to the identification of high-risk for relapse and death patients. However, most methods underestimate CTC numbers, owing to their dependence on epithelial markers. In the current study, we evaluated the EMT phenotype in CTCs isolated from breast cancer (BC) patients, using the CellSearch system. Spiking experiments for the evaluation of the specificity and sensitivity of our method were performed using HeLa cells. Sixty-five breast cancer (BC) patients (47 early and 18 metastatic) were enrolled in the study. Vimentin is a mesenchymal marker that indicates tumoral cells acquiring invasive and malignant properties. We studied vimentin (VIM) expression using the extra channel of the CellSearch system and an anti-vimentin antibody conjugated with FITC. In our present results, we reported the percentage of circulating tumor cells that expressed vimentin in early and in metastatic breast cancer patients. Interestingly, the incidence of cells with a CK-VIM+CD45- phenotype was detected in both settings. These cells were detected in 31.4% of CK-negative (11/35) and 82.3% of CK-positive (10/12) early BC patients. The corresponding numbers for metastatic disease were 15.4% (2/13) and 100% (5/5), respectively. Our results suggest that in CTC-negative patients, potentially undetectable tumor cells could be identified using the FDA-approved CellSearch system, based on the (CK-VIM+CD45-)-phenotype, offering additional information regarding metastatic dissemination in cancer patients. Further experiments evaluating more biomarkers are necessary to elucidate the mechanisms that regulate tumorigenesis and metastasis.

A Comprehensive Molecular Analysis of in Vivo Isolated EpCAM-Positive Circulating Tumor Cells in Breast Cancer

BACKGROUND

Circulating tumor cell (CTC) analysis is highly promising for liquid biopsy-based molecular diagnostics. We undertook a comprehensive molecular analysis of in vivo isolated CTCs in breast cancer (BrCa).

METHODS

In vivo isolated CTCs from 42 patients with early and 23 patients with metastatic breast cancer (MBC) were prospectively collected and analyzed for gene expression, DNA mutations, and DNA methylation before and after treatment. 19 healthy donor (HD) samples were analyzed as a control group. In identical blood draws, CTCs were enumerated using CellSearch® and characterized by direct IF staining.

RESULTS

All 19 HD samples were negative for CK8, CK18, CK19, ERBB2, TWIST1, VEGF, ESR1, PR, and EGFR expression, while CD44, CD24, ALDH1, VIM, and CDH2 expression was normalized to B2M (reference gene). At least one gene was expressed in 23/42 (54.8%) and 8/13 (61.5%) CTCs in early BrCa before and after therapy, and in 20/23 (87.0%) and 5/7 (71.4%) MBC before and after the first cycle of therapy. PIK3CA mutations were detected in 11/42 (26.2%) and 3/13 (23.1%) in vivo isolated CTCs in early BrCa before and after therapy, and in 11/23 (47.8%) and 2/7 (28.6%) MBC, respectively. ESR1 methylation was detected in 5/32 (15.7%) and 1/10 (10.0%) CTCs in early BrCa before and after therapy, and in 3/15(20.0%) MBC before the first line of therapy. The comprehensive molecular analysis of CTC revealed a higher sensitivity in relation to CellSearch or IF staining when based on creatine kinase selection.

CONCLUSIONS

In vivo-CTC isolation in combination with a comprehensive molecular analysis at the gene expression, DNA mutation, and DNA methylation level comprises a highly powerful approach for molecular diagnostic applications using CTCs.

Dynamic changes of CTCs in patients with metastatic HR(+)/HER2(-) breast cancer receiving salvage treatment with everolimus/exemestane

PURPOSE

Detection of CTCs represents a poor prognostic factor in patients with early and metastatic breast cancer (mBC) and treatment with everolimus-exemestane (E/E) is an established effective treatment in hormone receptor-positive/HER2-negative mBC patients. The effect of E/E on CTCs in mBC patients was prospectively investigated.

METHODS

CTCs from 50 pre-treated patients with mBC receiving E/E were analyzed using the CellSearch (CS) platform and triple immunofluorescence (IF) staining for cytokeratin, M30 and Ki67 expression to assess their proliferative and apoptotic status.

RESULTS

CTCs (by CS) were detected in 64% of patients before treatment and E/E administration resulted in their decreased prevalence [(n = 18; 36%, p = 0.004) and (n = 7; 19.4%, p = 0.019) post-1st and post-3rd treatment cycle, respectively] whereas it was significantly increased at disease progression (PD: 61%) compared to post-1st and post-3rd cycle (p = 0.049 and p = 0.021, respectively). Ki67-positive CTCs were detected in 60%, 60%, 17% and 50% of patients before treatment, post-1st, post-3rd cycle and at PD, respectively, while the opposite was observed for M30-positive CTCs (0% at baseline, 10% after the 1st cycle, 50% after the 3rd cycle and 0% at PD). The detection of even ≥ 1 CTC/5 ml after one cycle was associated with decreased PFS (3.3 vs 9.0 months, p = 0.025) whereas the detection of even ≥ 2 CTCs at PD was associated with decreased OS (32.4 vs 19.5 months; p = 0.009).

CONCLUSIONS

The combination of E/E resulted in early elimination of proliferating CTCs in mBC patients and this effect was associated with a favorable clinical outcome.

PIK3CA hotspot mutations in circulating tumor cells and paired circulating tumor DNA in breast cancer: a direct comparison study

Liquid biopsy analysis, mainly based on circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), provides an extremely powerful tool for the molecular profiling of cancer patients in real time. In this study, we directly compared PIK3CA hotspot mutations (E545K, H1047R) in EpCAM‐positive CTCs and paired plasma‐ctDNA in breast cancer (BrCa). PIK3CA hotspot mutations in CTCs and ctDNA were analyzed using our previously developed highly sensitive (0.05%), specific, and validated assay in plasma‐ctDNA from 77 early and 73 metastatic BrCa patients and 40 healthy donors. We further analyzed and directly compared PIK3CA hotspot mutations in DNAs isolated from CellSearch^® cartridges (CTCs) and paired plasma‐ctDNA, in 56 cases of early and 27 cases of metastatic breast cancer, and 16 corresponding primary tumors. In plasma‐ctDNA,PIK3CA hotspot mutations were identified in 30/77(39.0%) early and 35/73(47.9%) metastatic BrCa cases; none (0/40, 0%) of the healthy donors’ plasma‐ctDNA samples were positive. Our direct comparison study in DNAs isolated from CellSearch^® cartridges (CTCs) and paired plasma‐ctDNA from the same blood draws has shown a lack of concordance in early BrCa (27/56, 48.2%), while the concordance in the metastatic setting was higher (18/27, 66.6%). Our results were validated by ddPCR methodology, and the concordance between our assay and ddPCR for PIK3CA E545K hotspot mutation was 30/37 (81.1%). In many cases, PIK3CA hotspot mutations were detected in samples found to be negative for CTCs in CellSearch^®. Our data demonstrated for the first time that (a) PIK3CA hotspot mutations are present at high frequencies in CTCs isolated from CellSearch^® cartridges and paired plasma‐ctDNA both in early and metastatic BrCa, (b) the detection and concordance of PIK3CA hotspot mutations between plasma‐ctDNA and CTCs are higher in the metastatic setting, (c) PIK3CA mutational status significantly changes after therapeutic intervention, and (d) PIK3CA mutation detection in CTCs and plasma‐ctDNA provides complementary information.

PIK3CA hotspot mutations in circulating tumor cells and paired circulating tumor DNA in breast cancer: a direct comparison study

Liquid biopsy analysis, mainly based on circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), provides an extremely powerful tool for the molecular profiling of cancer patients in real time. In this study, we directly compared PIK3CA hotspot mutations (E545K, H1047R) in EpCAM-positive CTCs and paired plasma-ctDNA in breast cancer (BrCa). PIK3CA hotspot mutations in CTCs and ctDNA were analyzed using our previously developed highly sensitive (0.05%), specific, and validated assay in plasma-ctDNA from 77 early and 73 metastatic BrCa patients and 40 healthy donors. We further analyzed and directly compared PIK3CA hotspot mutations in DNAs isolated from CellSearch^® cartridges (CTCs) and paired plasma-ctDNA, in 56 cases of early and 27 cases of metastatic breast cancer, and 16 corresponding primary tumors. In plasma-ctDNA, PIK3CA hotspot mutations were identified in 30/77(39.0%) early and 35/73(47.9%) metastatic BrCa cases; none (0/40, 0%) of the healthy donors' plasma-ctDNA samples were positive. Our direct comparison study in DNAs isolated from CellSearch^® cartridges (CTCs) and paired plasma-ctDNA from the same blood draws has shown a lack of concordance in early BrCa (27/56, 48.2%), while the concordance in the metastatic setting was higher (18/27, 66.6%). Our results were validated by ddPCR methodology, and the concordance between our assay and ddPCR for PIK3CA E545K hotspot mutation was 30/37 (81.1%). In many cases, PIK3CA hotspot mutations were detected in samples found to be negative for CTCs in CellSearch^® . Our data demonstrated for the first time that (a) PIK3CA hotspot mutations are present at high frequencies in CTCs isolated from CellSearch^® cartridges and paired plasma-ctDNA both in early and metastatic BrCa, (b) the detection and concordance of PIK3CA hotspot mutations between plasma-ctDNA and CTCs are higher in the metastatic setting, (c) PIK3CA mutational status significantly changes after therapeutic intervention, and (d) PIK3CA mutation detection in CTCs and plasma-ctDNA provides complementary information.

Characterization of DLL3-positive circulating tumor cells (CTCs) in patients with small cell lung cancer (SCLC) and evaluation of their clinical relevance during front-line treatment

OBJECTIVES

The aim of the study was to characterize and evaluate the presence of DLL3-positive Circulating Tumor Cells (CTCs) in SCLC patients receiving front-line chemotherapy and assess their clinical relevance.

MATERIALS AND METHODS

Peripheral blood was obtained from treatment-naïve patients with SCLC (n = 108 patients), after one etoposide/platinum cycle (n = 68 patients) and on disease progression (n = 48 patients). Immunofluorescence staining using antibodies against the DLL3, cytokeratins (CK), CD45 and vimentin (Vim) was used for the detection and characterization of CTCs.

RESULTS

Before treatment, 74.1% of patients had detectable DLL3⁺/CD45^- CTCs. One-treatment cycle significantly decreased both the detection rate (p < 0.001) and the absolute number (p < 0.001) of DLL3⁺/CD45^- CTCs. Triple immunofluorescence staining using anti-CK, anti-Vim and anti-DLL3 antibodies revealed an important CTC heterogeneity since DLL3 could be detected in Vim⁺, Vim^-, CK⁺ and CK^- CTCs. On disease progression, both the detection rate and the absolute number of DLL3⁺/CD45^- CTCs were significantly increased compared to post-1^st cycle values (p < 0.001 and p = 0.002, respectively). In addition, 22.7% of patients had detectable DLL3⁺/CD45^- cells which could not be captured by the CellSearch assay. In multivariate analysis, the detection of DLL3+/CD45- CTCs at baseline was significantly associated with decreased progression-free survival (HR = 10.8; p = 0.005) whereas their detection on disease progression was associated with decreased overall survival (HR: 28.2; p = 0.016).

CONCLUSIONS

These findings demonstrate an important heterogeneity of CTCs, based on the expression of CK, Vim and DLL3, in patients with SCLC and the changes of DLL3⁺/CD45^- CTCs during treatment seem to be a dynamic biomarker associated with patients' clinical outcome.

Characterization of DLL3-positive circulating tumor cells (CTCs) in patients with small cell lung cancer (SCLC) and evaluation of their clinical relevance during front-line treatment

e20086

Background: The aim of the study was to characterize and evaluate the presence of DLL3-positive Circulating Tumor Cells (CTCs) in SCLC patients receiving front-line chemotherapy and assess their clinical relevance. Methods: Peripheral blood was obtained from treatment-naïve patients with SCLC (n = 108 patients), after one-etoposide/platinum cycle (n = 68 patients) and on disease progression (n = 48 patients). CTCs were detected after immunofluorescence staining using antibodies against the DLL3, cytokeratins (CK), CD45 and vimentin (Vim). Results: Before treatment, 74.1% of patients had detectable CTCs (DLL3+/CD45-). One-treatment cycle significantly decreased both the detection rate of DLL3+/CD45- CTCs ( p< 0.001) and their absolute number ( p< 0.001). Triple immunofluorescence staining using anti-CK, anti-Vim and anti-DLL3 antibodies revealed an important CTC heterogeneity since DLL3 could be detected in Vim+, Vim-, CK+ and CK- CTCs. On disease progression, both the detection rate of DLL3+/CD45- CTCs as well as their number were significantly increased compared to post-1st cycle values ( p< 0.001 and p= 0.002, respectively). In addition, 22.7% of patients had detectable DLL3+/CD45- cells which could not be captured by the CellSearch assay. In multivariate analysis, the detection of DLL3+/CD45- CTCs at baseline was significantly associated with decreased progression-free survival (HR = 10.8; p= 0.005) whereas their detection on disease progression was associated with decreased overall survival (HR: 28.2; p= 0.016). Conclusions: These findings demonstrate an important heterogeneity of CTCs, based on the expression of CK, Vim and DLL3, in patients with SCLC and the changes of DLL3+/CD45- CTCs during treatment seem to be a dynamic biomarker associated with treatment efficacy and patients’ clinical outcome.

The clinical use of circulating tumor cells (CTCs) enumeration for staging of metastatic breast cancer (MBC): International expert consensus paper

BACKGROUND

The heterogeneity of metastatic breast cancer (MBC) necessitates novel biomarkers allowing stratification of patients for treatment selection and drug development. We propose to use the prognostic utility of circulating tumor cells (CTCs) for stratification of patients with stage IV disease.

METHODS

In a retrospective, pooled analysis of individual patient data from 18 cohorts, including 2436 MBC patients, a CTC threshold of 5 cells per 7.5 ml was used for stratification based on molecular subtypes, disease location, and prior treatments. Patients with ≥ 5 CTCs were classified as Stage IVaggressive, those with < 5 CTCs as Stage IVindolent. Survival was analyzed using Kaplan-Meier curves and the log rank test.

RESULTS

For all patients, Stage IVindolent patients had longer median overall survival than those with Stage IVaggressive (36.3 months vs. 16.0 months, P < 0.0001) and similarly for de novo MBC patients (41.4 months Stage IVindolent vs. 18.7 months Stage IVaggressive, p < 0.0001). Moreover, patients with Stage IVindolent disease had significantly longer overall survival across all disease subtypes compared to the aggressive cohort: hormone receptor-positive (44 months vs. 17.3 months, P < 0.0001), HER2-positive (36.7 months vs. 20.4 months, P < 0.0001), and triple negative (23.8 months vs. 9.0 months, P < 0.0001). Similar results were obtained regardless of prior treatment or disease location.

CONCLUSIONS

We confirm the identification of two subgroups of MBC, Stage IVindolent and Stage IVaggressive, independent of clinical and molecular variables. Thus, CTC count should be considered an important tool for staging of advanced disease and for disease stratification in prospective clinical trials.

Bcl-2 expression in circulating tumor cells (CTCs) of patients with small cell lung cancer (SCLC) receiving front-line treatment

INTRODUCTION

To investigate the presence of Bcl-2⁺CTCs in chemotherapy-naïve SCLC patients and their clinical relevance during front-line treatment.

METHODS

Peripheral blood was obtained from 66 consecutive-patients before chemotherapy administration, after one-cycle and at relapse. CTCs were detected by CellSearch and immunofluorescence using anti-Bcl-2, anti-M30, anti-cytokeratins(CK), anti-CD45 and anti-vimentin(Vim) antibodies.

RESULTS

Before treatment, CTCs were detected in 62.1% and 72.7% of patients using the CellSearch and immunofluorescence (Bcl-2⁺/CD45^-), respectively. One-treatment cycle significantly decreased both CTCs' detection rate(p < 0.001) and their absolute number (p < 0.001). On relapse, both the number of positive-patients and the absolute number of CTC subpopulations were significantly increased, compared to post-1st cycle (CellSearch: p = 0.002 and immunofluorescence: p < 0.001). Immunofluorescence revealed an important CTC heterogeneity (Bcl2⁺/Vim⁺, Bcl2⁺/Vim^-, Bcl2⁺/CK⁺, Bcl2⁺/CK^- and Bcl2⁺/M30^- CTCs). Moreover, 50.0% of patients without detectable CTCs by CellSearch had detectable Bcl-2⁺/CD45^- cells. Multivariate analysis revealed a significant association between Bcl-2⁺/CD45^-cells at baseline and PFS (HR = 4.5;p = 0.005) and OS (HR: 4.3; p = 0.001). Bcl-2⁺/CD45^-cells after one-treatment cycle were significantly associated with shorter OS (HR: 13.9; p = 0.007).

CONCLUSIONS

These results demonstrate an important phenotypic CTCs heterogeneity based on the co-expression of Bcl-2, CK, Vim and M30 in SCLC patients. The changes of Bcl-2⁺/CD45^- CTCs during treatment seem to be a dynamic biomarker associated with treatment efficacy and patients' clinical outcome.

Abstract 4577: ESR1 methylation: A liquid biopsy-based epigenetic assay for the follow up of patients with metastatic breast cancer receiving endocrine treatment

Introduction: Liquid biopsy provides real-time monitoring of tumor evolution and response to therapy through analysis of CTCs and plasma-ctDNA. ESR1 epigenetic silencing potentially affects response to endocrine treatment. We evaluated ESR1 methylation in CTCs and paired plasma-ctDNA. We evaluated ESR1 methylation in CTCs and paired plasma-ctDNA as a potential biomarker for response to everolimus/exemestane treatment. Materials and methods: A highly sensitive and specific real-time MSP assay for ESR1 methylation was developed and validated in: a) 65 primary breast tumors (FFPEs), b) EpCAM+ CTC-fractions (122 patients and 30 healthy donors; HD), c) plasma-ctDNA (108 patients and 30HD), d) in CTCs (CellSearch®) and in paired plasma-ctDNA for 58 BrCa patients. ESR1 methylation status was investigated in CTCs isolated from serial peripheral blood samples of 19 patients with ER+/ HER2- advanced BrCa receiving everolimus/exemestane. Results: ESR1 methylation was detected in: a) 25/65(38.5%) FFPEs, b) EpCAM+ CTC-fractions: 26/112(23.3%) patients and 1/30(3.3%) HD, c) plasma-ctDNA: 8/108(7.4%) patients and 1/30(3.3%) HD. ESR1 methylation was highly concordant in 58 paired DNA samples, isolated from CTCs (CellSearch®) and corresponding plasma. In serial peripheral blood samples of patients treated with everolimus/exemestane, ESR1 methylation was observed in 10/36(27.8%) CTC-positive samples, and was associated with lack of response to treatment (p=0.023 Fisher's Exact Test). Conclusions: We report for the first time the detection of ESR1 methylation in CTCs and a high concordance with paired plasma-ctDNA. ESR1 methylation in CTCs was associated with lack of response to everolimus/exemestane regimen. ESR1 methylation should be further evaluated as a potential liquid biopsy-based biomarker.

Citation Format: Sofia Mastoraki, Areti Strati, Eleni Tzanikou, Maria Chimonidou, Eleni Politaki, Alexandra Voutsina, Amanda Psyrri, Vassilis Georgoulias, Evi S. Lianidou. ESR1 methylation: A liquid biopsy-based epigenetic assay for the follow up of patients with metastatic breast cancer receiving endocrine treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4577.

Dynamic changes of phenotypically different circulating tumor cells sub-populations in patients with recurrent/refractory small cell lung cancer treated with pazopanib

The aim of the study was to investigate the effect of 2^nd-line pazopanib on the different CTCs subpopulations in SCLC patients and evaluate the clinical relevance of their changes. Different CTCs subpopulations were evaluated before pazopanib initiation (n = 56 patients), after one-cycle (n = 35) and on disease progression (n = 45) by CellSearch and double immunofluorescence using anti-CKs and anti-Ki67, anti-M30 or anti-Vimentin antibodies. Before treatment, CTCs were detected in 50% of patients by CellSearch whereas 53.4%, 15.5% and 74.1% patients had CK⁺/Ki67⁺, CK⁺/M30⁺ and CK⁺/Vim⁺ CTCs, respectively. One pazopanib cycle significantly decreased the number of CTCs as detected by CellSearch (p = 0.043) as well as the number of CK⁺/Ki67⁺ (p < 0.001), CK⁺/M30⁺ (p = 0^.015) and CK⁺/Vim⁺ (p < 0^.001) cells. On disease progression, both the incidence and CTC numbers were significantly increased (CellSearch, p = 0.027; CK⁺/Ki67⁺, p < 0.001; CK^+/M30⁺, p = 0.001 and CK⁺/Vim⁺, p < 0^.001)^. In multivariate analysis, the detection of CK⁺/Vim⁺ CTCs after one treatment cycle (HR: 7.9, 95% CI: 2.9–21.8; p < 0.001) and CTCs number on disease progression, as assessed by CellSearch, (HR: 2.0, 95% CI: 1.0–6.0; p = 0.005) were emerged as independent factors associated with decreased OS. In conclusion, pazopanib can eliminate different CTC subpopulations in patients with relapsed SCLC. The analysis of CTCs could be used as a dynamic biomarker of treatment efficacy.

ESR1 Methylation: A Liquid Biopsy-Based Epigenetic Assay for the Follow-up of Patients with Metastatic Breast Cancer Receiving Endocrine Treatment

Purpose: Liquid biopsy provides real-time monitoring of tumor evolution and response to therapy through analysis of circulating tumor cells (CTCs) and plasma-circulating tumor DNA (ctDNA). ESR1 epigenetic silencing potentially affects response to endocrine treatment. We evaluated ESR1 methylation in CTCs and paired plasma ctDNA. We evaluated ESR1 methylation in CTCs and paired plasma ctDNA as a potential biomarker for response to everolimus/exemestane treatment.Experimental Design: A highly sensitive and specific real-time MSP assay for ESR1 methylation was developed and validated in (i) 65 primary breast tumors formalin-fixed paraffin-embedded (FFPE), (ii) EpCAM⁺ CTC fractions (122 patients and 30 healthy donors; HD), (iii) plasma ctDNA (108 patients and 30HD), and (iv) in CTCs (CellSearch) and in paired plasma ctDNA for 58 patients with breast cancer. ESR1 methylation status was investigated in CTCs isolated from serial peripheral blood samples of 19 patients with ER⁺/HER2^- advanced breast cancer receiving everolimus/exemestane.Results:ESR1 methylation was detected in: (i) 25/65 (38.5%) FFPEs, (ii) EpCAM⁺ CTC fractions: 26/112 (23.3%) patients and 1/30 (3.3%) HD, and (iii) plasma ctDNA: 8/108 (7.4%) patients and 1/30 (3.3%) HD. ESR1 methylation was highly concordant in 58 paired DNA samples, isolated from CTCs (CellSearch) and corresponding plasma. In serial peripheral blood samples of patients treated with everolimus/exemestane, ESR1 methylation was observed in 10/36 (27.8%) CTC-positive samples, and was associated with lack of response to treatment (P = 0.023, Fisher exact test).Conclusions: We report for the first time the detection of ESR1 methylation in CTCs and a high concordance with paired plasma ctDNA. ESR1 methylation in CTCs was associated with lack of response to everolimus/exemestane regimen. ESR1 methylation should be further evaluated as a potential liquid biopsy-based biomarker. Clin Cancer Res; 24(6); 1500-10. ©2017 AACR.

A Comparison of Three Methods for the Detection of Circulating Tumor Cells in Patients with Early and Metastatic Breast Cancer

BACKGROUND

We directly compared CTC detection rates and prognostic significance, using three different methods in patients with breast cancer (BC).

METHODS

Early (n=200) and metastatic (n=164) patients were evaluated before initiating adjuvant or first-line chemotherapy, using the CellSearchTM System, an RT-qPCR for CK-19 mRNA detection and by double immunofluorescence (IF) microscopy using A45-B/B3 and CD45 antibodies.

RESULTS

Using the CellSearchTM System, 37% and 16.5% of early BC patients were CTC-positive (at ≥1 and ≥2 CTCs/23 ml of blood), 18.0% by RT-qPCR and 16.9% by IF; no agreement was observed between methods. By the CellSearchTM 34.8% and 53.7% (at≥ 5 and ≥ 2 CTCs/7.5 ml) of metastatic patients were CTC-positive, 37.8% by RT-qPCR and 28.5% by IF. A significant agreement existed only between the CellSearchTM and RT-qPCR. In 60.8% of cases, differential EpCAM and CK-19 expression on CTCs by IF could explain the discrepancies between the CellSearchTM and RT-qPCR. CTC-positivity by either method was associated with decreased overall survival in metastatic patients.

CONCLUSION

A significant concordance was observed between the CellSearchTM and RT-qPCR in metastatic but not in early BC. Discordant results could be explained in part by CTC heterogeneity. CTC detection by all methods evaluated had prognostic relevance in metastatic patients.

Abstract 1730: ESR1 methylation in circulating tumor cells, ctDNA and primary tumors of breast cancer patients

Background: Estrogen receptor (ER) is an important prognostic biomarker in breast cancer. Epigenetic silencing of ESR1 could be of important clinical significance especially for its potential impact on endocrine treatment efficacy. Liquid biopsy provides real-time monitoring of tumor evolution and response to therapy through analysis of CTCs and ctDNA. Our group has evaluated for the first time epigenetic silencing of tumor and metastasis suppressor genes in CTCs and corresponding ctDNA. In this study, we evaluated for the first time ESR1 methylation in CTCs, paired ctDNA and primary tumors of breast cancer patients.

Methods: We developed and validated a highly sensitive and specific real-time MSP assay for ESR1 methylation. We further applied the developed assay in sodium bisulfite (SB) treated DNA samples from: a) FFPEs from 40 patients with operable breast cancer, 25 patients with metastasis, 30 mammoplasties and 15 fibroadenomas, b) EpCAM+ immunomagnetically isolated CTCs fractions, from 74 early breast cancer patients, 48 patients with metastasis and 30 healthy donors, c) CellSearch® cartridges from 36 early breast cancer patients, 22 patients with metastasis, d) ctDNA isolated from plasma of matched samples and 54 healthy donors as a control group.

Results: By using this highly specific and sensitive assay (sensitivity 0.1%) we detected methylation of ESR1 in: a) FFPEs: 16/40(40%) early breast cancer patients, 9/25(36%) patients with verified metastasis, 7/30(23.3%) mammoplasties and 5/15(33.3%) fibroadenomas. A statistically significant negative correlation was observed between ESR1 methylation status and ER protein expression (56/65 samples, 86%, p&lt;0.001). b) In EpCAM+ CTCs fraction samples: ESR1 was found methylated in 16/74(21.6%) operable breast cancer patients, 10/48(20.8%) patients with metastasis, but only in 1/30(3.3%) healthy donors. c) CTC+ CellSearch® cartridges: 3/13(23.1%) in early breast cancer and 2/7(28.6%) in patients with metastasis. d) In ctDNA: ESR1 methylation was observed in 3/36(8.3%) early breast cancer patients, 3/22(13.6%) patients with metastasis and 2/54(3.7%) samples in the control group. ESR1 methylation status was highly correlated when paired DNA from CellSearch® cartridges and corresponding ctDNA samples were compared; 36/36 (100%, p&lt;0.001) in early breast cancer and 21/22 (95.5%, p&lt;0.001) in metastasis.

Conclusions: ER expression and ESR1 methylation were found 100% inversely correlated in primary tissues. The EpCAM+ CTC fraction of patients with breast cancer was found methylated for ESR1. Interestingly, ESR1 methylation was detected exclusively in CTC+ samples as analyzed from CellSearch® cartridges but in none of CTC- samples. In paired plasma samples, ESR1 methylation showed a high concordance (p&lt;0.001) with ESR1 methylation in CTCs. Additional studies are needed to further evaluate the clinical significance of our findings.

Citation Format: Sophia Mastoraki, Areti Strati, Eleni Tzanikou, Eleni Politaki, George Koutsodontis, Loukas Kaklamanis, Nikolaos Malamos, Amanda Psyrri, Vassilis Georgoulias, Evi Lianidou. ESR1 methylation in circulating tumor cells, ctDNA and primary tumors of breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1730. doi:10.1158/1538-7445.AM2017-1730

Abstract 1725: Detection of ESR1 D538G mutation in circulating tumor cells (CTCs) and paired circulating tumor DNA (ctDNA) samples of breast cancer patients

AIMS: Molecular characterization of CTCs and ctDNA analysis holds promise as an extremely powerful tool for the molecular profiling of cancer patients in real time. Estrogen receptor alpha (ERα) is expressed in approximately 70% of all breast cancers and endocrine therapy represents a major treatment modality in ERα-positive disease. Recently, somatic mutations in the ERα gene (ESR1) were linked to acquired resistance to endocrine therapies in breast cancer. In this study, we analyzed the most frequent ERS1 mutation (D538G) in CTCs (DNA samples isolated from CellSearch cartridges), corresponding ctDNA from early and metastatic breast cancer patients and healthy donors.

METHODS: We first developed a highly sensitive and specific methodology for the detection of ESR1 D538G hotspot mutation, based on a combination of allele-specific PCR, asymmetric rapid PCR and high resolution melting analysis. We analyzed DNAs isolated from CTCs (CellSearch) and the corresponding ctDNA before and/or after therapy in: a) 25 patients with ER+ operable breast cancer, b) 11 patients with ER+ metastatic breast cancer, c) 13 patients with ER- early breast cancer, d) 5 patients with ER- metastatic breast cancer and e) 80 healthy female volunteers. In all cases ctDNA (extracted from 2 ml plasma) and DNA from CTCs were first examined for their DNA quality before analysis.

RESULTS: The assay is highly sensitive (analytical sensitivity: 0.05%) and specific (0/80 healthy donors). ERS1 D538G hotspot mutation was identified in ctDNA in 4/18 (22.2%) of ER+ metastasis-verified and in 5/33 (15.2%) of ER+ early breast cancer. In CTCs, ERS1 D538G mutation was identified in 6/18 (33.3%) of ER+ metastasis-verified and 5/33 (15.2%) of ER+ early breast cancer. In ER-pos metastasis-verified breast cancer, the concordance for D538G mutation between CTCs and ctDNA was 10/18 (55.6%), whereas the corresponding concordance for ER+ operable breast cancer was 25/33 (75.8%). Moreover, ERS1 D538G hotspot mutation was identified in ctDNA in 2/9 (22.2%) of ER- metastasis-verified breast cancer and 2/16 (12.5%) of ER- early breast cancer. ERS1 D538G hotspot mutation was identified in CTCs in 3/16 (18.8%) of ER- operable breast cancer, whereas none of ER- metastasis-verified breast cancer patients (0/9) were positive. In ER- metastasis-verified breast cancer patients, the concordance between CTCs and ctDNA for D538G mutation was 7/9(77.8%), whereas the corresponding concordance for ER- early breast cancer was 15/16 (93.8%).

CONCLUSIONS: We developed and validated an ultrasensitive and highly specific methodology for the detection of ERS1 D538G hotspot mutation. This mutation was detected not only in the ER+ group, but also in the ER- group of breast cancer patients. We will further evaluate our findings in a large cohort of patients before and after treatment, to evaluate response to endocrine therapies in breast cancer.

Citation Format: Eleni Tzanikou, Athina Markou, Eleni Politaki, Giorgos Koytsodontis, Amanda Psyrri, Vassileios Georgoulias, Evi Lianidou. Detection of ESR1 D538G mutation in circulating tumor cells (CTCs) and paired circulating tumor DNA (ctDNA) samples of breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1725. doi:10.1158/1538-7445.AM2017-1725

Prognostic value of circulating tumor cells in non-small cell lung cancer

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Background: Quantitative analysis of circulating tumor cells (CTCs) is increasingly investigated as a novel predictor of prognosis in non-small cell lung cancer (NSCLC). The primary aim of this study was to further investigate the prognostic value of CTCs enumeration in patients with advanced NSCLC. Methods: The medical records of patients with chemotherapy-naïve, advanced NSCLC and at least one available measurement of CTCs were retrospectively reviewed. The presence of CTCs was evaluated using the CellSearch system. A cut-off point of 2 CTCs ( < 2 vs ≥2 ) was used to discriminate between negative and positive samples, respectively. The detection of CTCs was correlated with the clinicopathological features of patients and outcome. Results: Our study population comprised a total of 43 patients (mean age 67.1±9.9 years; male/female ratio: 39/4). Eight out of 43 patients (18.6%) harbored CTCs. No significant associations were found between treatment response and baseline count of circulating tumor cells (CTCs) (p = 0.067). Positive CTC count was associated with the presence of five or more metastatic sites (p = 0.018). Neither PFS nor OS were found to differ significantly between CTC-positive and CTC-negative cases (log-rank p = 0.079 and 0.549, respectively). The presence of five or more metastatic sites and worse PS were recognized as independent predictors of reduced PFS [HR = 2.9, p = 0.042 and HR = 2.7, p = 0.035, respectively], and reduced OS [HR = 7.8, p = 0.003 and HR = 16.9, p < 0.001, respectively]. Conclusions:CTCs were detected in a relatively small percentage of our patient population and their presence was associated with increased metastatic burden. In contrast, we failed to observe any significant associations between baseline CTC count and the prognostic variables evaluated. Our results support the suggested role of CTCs in the metastatic dissemination of cancer and underline the need for more efficient methods of CTCs detection.

TTF-1- and/or CD56-positive Circulating Tumor Cells in patients with small cell lung cancer (SCLC)

The aim of the study was to evaluate the phenotypic CTCs heterogeneity (TTF-1⁺ and/or CD56⁺) in SCLC patients and correlate it with the CellSearch. Peripheral blood was obtained from 108 consecutive patients. CTCs were detected by CellSearch and double-immunofluorescence using anti-CD45, anti-TTF-1 and anti-CD56 antibodies. Before chemotherapy TTF-1⁺/CD45⁻, CD56⁺/CD45⁻ and TTF-1⁺/CD56⁺ CTCs were detected in 66(61.1%), 55(50.9%) and 46(42.6%) patients, respectively; 60.2% of patients were CellSearch⁺. Among the 22 patients with 0 CTCs/7.5 ml on CellSearch, TTF-1⁺/CD45⁻, CD56⁺/CD45⁻ and TTF-1⁺/CD56⁺ CTCs were detected in 8(36.4%), 6(27.3) and 6(27.3%) patients, respectively; no CK⁺/EpCAM⁺ or TTF1⁺/EpCAM⁺ CTCs were detected in these patients. One-chemotherapy cycle decreased both the number of positive patients (p < 0.001) and their CTC number (p < 0.001), irrespectively of their phenotype and the detection method. The incidence and number of the different CTC subpopulations on PD, was significantly increased at their baseline levels. Multivariate analysis revealed that the increased number of CTCs at baseline and on PD were significantly associated with decreased PFS (p = 0.048) and OS (p = 0.041), respectively. There is an important CTC heterogeneity in such patients according to the expression of TTF-1 and CD56 which could detect EpCAM⁻ CTC subpopulations and, thus, undetectable by CellSearch. These CTC subpopulations are dynamically correlated with treatment efficacy and disease-progression.

Abstract P1-01-06: Ki67-positive CTCs are associated with early disease relapse in patients with early breast cancer undergoing adjuvant chemotherapy

Background: The determination of Ki67 in the primary tumor has prognostic value in early breast cancer (BC). We evaluated Ki67 expression in circulating tumor cells (CTCs) from patients with early BC undergoing adjuvant chemotherapy and correlated Ki67 positivity with patient outcome.

Methods: Ki67 expression in CTCs was evaluated by immunofluorescent analysis in paired blood samples of patients with early BC (n=166) obtained before and after adjuvant chemotherapy. Ki67 expression was also evaluated in CTC-positive patients at 6 - 24 months after the end of chemotherapy (n=31). Cytospins of peripheral blood mononuclear cells were double stained with A45-B/B3 cytokeratin and Ki67 antibodies. The proliferation index (PI) of CTCs was defined as the ratio of Ki67-positive CTCs/total CTCs.

Results: CTCs were detected in 53 (32%) patients before and/or after chemotherapy. Ki67-positive [Ki67(+)] CTCs were identified in 79% of CTC-positive patients, 25% presenting exclusively Ki67(+) CTCs and 21%, exclusively Ki67(-) CTCs. The mean value of Ki67(+) CTCs/patient remained unchanged pre- and post-chemotherapy [(mean±SE): pre- vs post-chemotherapy 2.5±0.7 vs 4.2±2, respectively; p= 0.900]. Similarly, the PI among the total CTCs detected pre- and post-chemotherapy was 59% and 60%, respectively. Ten (19%) of 53 CTC-positive and 9 (8%) of 113 CTC-negative patients relapsed (p = 0.039). In addition, all CTC-positive patients who relapsed harbored Ki67(+) CTCs before and/or after chemotherapy. Interestingly, 70% of them experienced early disease recurrence, ranging from 6-29 months after the initiation of adjuvant chemotherapy. Furthermore, 38.5% of patients with exclusively Ki67(+) CTCs relapsed compared to none among patients with exclusively Ki67(-) CTCs (p = 0.041). Of the 31 CTC-positive patients evaluated during follow-up, 39% remained CTC-positive. However, only 33.3% of them harbored Ki67(+) CTCs, 8.3% had exclusively Ki67(+) CTCs and 66.7% exclusively Ki67(-) CTCs. The mean value of Ki67(+) CTCs/patient was significantly reduced on the follow-up samples [(mean±SE): follow-up vs pre-chemotherapy, 1.35±1.3 vs 2.5±0.7, respectively; p=0.014 and follow-up vs post-chemotherapy, 1.35±1.3 vs 4.2±2, respectively; p= 0.026].

Conclusions: Ki67 expression on CTCs is predictive of early relapse in patients with early BC. Ki67 expression is not decreased by adjuvant chemotherapy, whereas it is reduced early during follow-up, possibly due to adjuvant hormone therapy and/or anti-HER2 therapy. The above results suggest that additional therapy is needed for patients with early BC and Ki67(+) CTCs to prevent early disease recurrence.

Citation Format: Agelaki S, Spiliotaki M, Politaki E, Spanaki A, Kassiou L, Koinis F, Georgoulias V, Mavroudis D. Ki67-positive CTCs are associated with early disease relapse in patients with early breast cancer undergoing adjuvant chemotherapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-01-06.

Evaluation of Isolation Methods for Circulating Tumor Cells (CTCs)

Background: Detection of CTCs is a poor prognostic factor for many cancer types; however, their very low frequency represents an obstacle for their detection. The objective of the current study was to compare the performance of commonly used methods for CTCs isolation. Methods: The evaluated methods using spiking experiments of MCF7, SKBR3 and MDA MB-231 breast cancer cell lines were (i) ficoll density gradient separation (DGS), (ii) red blood cell lysis (Erythrolysis) isolation, (iii) positive immunomagnetic selection (EpCAM Dynal beads), (iv) two different negative immunomagnetic separation systems (Dynal vs Miltenyi CD45 beads) as well as (v) the Cell Search platform and (vi) the ISET system. Results: The recovery rates of Erythrolysis and DGS were 39% and 24%, respectively. Magnetic isolations are ranked from the worse to the best recovery rate as follows:, Myltenyi-anti-CD45 microbeads (24%); Dynal-anti-EpCAM beads (75%); Dynabeads-anti-CD45 (97%). CTCs isolation from blood samples using the CellSearch and ISET systems revealed that the recovery rate for Cell Search and ISET was 52% and 95%, respectively. Conclusions: Dynal-anti-CD45 beads have the best recovery rate compared to other magnetic methods. Furthermore the recovery rate of ISET was higher compared to Cell Search, especially for the more aggressive MDA-MB 231 cell line.

Abstract 503: Molecular characterization of in vivo isolated EpCAM-positive circulating tumor cells in breast cancer

Introduction: In the early stages of cancer, the chance to detect rare CTCs is increasing by increasing the sample volume. The aim of our study was to evaluate the diagnostic sensitivity of a novel clinical device for the in-vivo isolation of EpCAM-positive CTCs (CellCollectorTM, GILUPI, GmBH), by using highly sensitive RT-qPCR molecular assays.

Patients and methods: 29 breast cancer patients without overt metastases before the beginning of adjuvant chemotherapy (M0), 26 breast cancer patients with overt metastases before starting of therapy (M1) and 12/26 of them before the second cycle of therapy (M2), as well as 18 healthy donors participated in the study. After in-vivo isolation, total RNA was extracted from captured cells, lysed in Trizol, followed by cDNA synthesis. RT-qPCR was used for the molecular characterization of captured cells, for: CK-19, HER-2, TWIST1, VEGF, ER, PR, EGFR, CD44, CD24, and ALDH1, while B2M was used as a reference gene. Peripheral blood was also collected for CTC analysis by the FDA cleared CellSearchTM system. In addition, immunofluorescence staining of cytospins was performed and screened for CTCs using the ARIOL system, using ER, HER2, CK (8, 18, 19) and CD45 for CTC identification.

Results: Results are shown in Table 1. At least one gene was expressed in 10(34.5%) of M0, 15(57.7%) of M1 and 4(33.3%) of M2 patient groups, but in none of healthy donors 0/18(0%). CellSearchTM gave positive results in 5(17.2%) of M0, 10(38.5%) of M1 and 0(0%) of M2. Immunofluorescence (Ariol system) was positive for ER, HER2, CK (8, 18, 19) in 5/15(33.3%) M0, in 4/12(33.3%) M1 and in 1/7(14.3%) M2 groups. Table 1.Gene expression in CTCHealthy N = 18M0 N = 29M1 N = 26M2 N = 12CK-190 (0%)6(20.7%)6 (23.1%)2 (16.7%)HER20 (0%)2 (6.9%)0 (0%)0 (0%)ER0 (0%)2 (6.9%)0 (0%)0 (0%)PR0 (0%)0 (0%)0 (0%)0 (0%)EGFR0 (0%)0 (0%)0 (0%)0 (0%)TWIST10 (0%)1 (3.4%)0 (0%)2 (16.7%)VEGF0 (0%)3 (10.3%)5 (19.2%)1 (8.3%)CD44+/CD24−,0 (0%)4 (13.8%)3 (11.5%)1 (8.3%)ALDH1high/CD24−,0 (0%)2 (6.9%)8 (30.8%)1(8.3%)

Conclusions: In-vivo isolation of CTC is minimally invasive, and in combination with high specific and sensitive RT-qPCR assays for CTC detection and molecular characterization seems promising. Comparison studies with the CellSearch and immunofluorescence have shown poor agreement. These results should be validated in large patient cohorts, and in respect to the clinical outcome.

Citation Format: Areti D. Strati, Martha Zavridou, Galateia Kallergi, Eleni Politaki, Tobias Gorges, Andra Kuske, Anna-Lena Bohnen, George Koutsodontis, Amanda Psyrri, Klaus Lucke, Vasilis Georgoulias, Klaus Pantel, Evi Lianidou. Molecular characterization of in vivo isolated EpCAM-positive circulating tumor cells in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 503.

Abstract P2-08-08: Circulating tumor cells count-based nomograms to predict survival of metastatic breast cancer patients: Results from the European pooled analysis

Background: The European Pooled Analysis of CTC (EPAC) in metastatic breast cancer, based on 1,944 individual data from patients with various tumor types and clinical settings (Bidard et al, Lancet Oncol 2014), has established CTC count (CellSearch) at baseline and during therapy as a level of evidence 1 independent prognostic biomarker and demonstrated its superiority over serum blood markers. As part of the study pre-planned objectives, we sought to establish nomograms allowing accurate individual survival predictions.

Methods: Using individual data from 17 centers, we built simplified multivariate prognostic models taking into account the independent prognostic clinico-pathological (CP) characteristics including CTC count, dichotomized using the 5CTC/7.5ml threshold, at baseline and at 3-5 weeks after the start of a new treatment regimen, and derived nomograms for progression-free survival (PFS) and overall survival (OS) prediction at baseline and after 3-5 weeks of treatment. We report here the internal validation of these nomograms. Discrimination of the models was assessed using the c-index estimated by a jackknife procedure and the calibration was visually assessed through 10-fold crossvalidated calibration plots at 1,2,3 years for OS and 1,2 years for PFS.

Results: Multivariate models at baseline for PFS and OS were fitted on 1501 and 568 individual patient data with CTC count at baseline and CTC count at baseline and after 3-5 weeks, respectively. Models include tumor subtype, the number of previous chemotherapy lines (0/1/≥2), PS, age (&lt;=50/&gt;50-65/&gt;65 years), metastasis-free intervals (0/&gt;0-3/&gt;3 years), metastatic sites (liver and CNS) and CTC count at baseline and eventually at 3-5 weeks of treatment. The C-index increased from 0.722 to 0.755 (increase in C-index:0.033, 95% CI [0.019;0.045]) when adding baseline CTC to the CP only model for OS (n=1501). For those patients with CTC values at 3-5 weeks (n=568), there was an additional increase in the C-index when adding CTC at 3-5 weeks to a model with already CP and baseline CTC from 0.731 to 0.743 (increase in C-index 0.013, 95% CI [-0.004;0.025]). The model with CP and baseline CTC counts showed a good calibration for OS at 1,2,3 years and the model with CP, baseline CTC and CTC count at 3-5 weeks a moderately good calibration. Similar results were obtained for PFS.

Conclusion: From the largest database with individual CTC data, we were able to build PFS and OS survival nomograms, with satisfactory discrimination and calibration. Our planned next step is to validate the nomogram in an additional cohort.

Citation Format: Bidard F-C, Peeters D, Fehm T, Nole F, Gisbert-Criado R, Mavroudis D, Grisanti S, Generali D, Garcia-Saenz JA, Stebbing J, Caldas C, Gazzaniga P, Manso L, Zamarchi R, Fernandez de Lascoiti A, de Mattos-Arruda L, Ignatiadis M, van Laere SJ, Meier-Stiegen F, Sandri M-T, Vidal-Martinez J, Politaki E, Consoli F, Bottini A, Diaz-Rubio E, Krell J, Dawson S-J, Raimondi C, Rutten A, Janni W, Munzone E, Carañana V, Agelaki S, Almici C, Dirix L, Solomayer E, Zorzino L, Reis-Filho JS, Squifflet P, Pantel K, Beije N, Sleijfers S, Pierga J-Y, Michiels S. Circulating tumor cells count-based nomograms to predict survival of metastatic breast cancer patients: Results from the European pooled analysis. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-08-08.

Variable expression levels of keratin and vimentin reveal differential EMT status of circulating tumor cells and correlation with clinical characteristics and outcome of patients with metastatic breast cancer

Background

CTCs expressing variable levels of epithelial and mesenchymal markers in breast cancer have previously been reported. However, no information exists for keratin expression levels of CTCs in association with disease status, whereas assays for the characterization of transitional EMT phenotypes of CTCs in breast cancer are rather lacking. We investigated the correlation between keratin expression of CTCs and patients’ outcome and characterized the EMT status of CTCs via the establishment of a numerical “ratio” value of keratin and vimentin expression levels on a single cell basis.

Methods

Keratin expression was evaluated in 1262 CTCs from 61 CTC-positive patients with metastatic breast cancer, using analysis of images obtained through the CellSearch System. For the determination of vimentin/keratin (vim/K) ratios, expression levels of keratin and vimentin were measured in cytospin preparations of luminal (MCF-7 and T47D) and basal (MDA.MB231 and Hs578T) breast cancer cell lines and 110 CTCs from 5 CTC-positive patients using triple immunofluorescence laser scanning microscopy and image analysis.

Results

MCF-7 and T47D displayed lower vim/K ratios compared to MDA.MB231 and Hs578T cells, while MCF-7 cells that had experimentally undergone EMT were characterized by varying intermediate vim/K ratios. CTCs were consisted of an heterogeneous population presenting variable vim/K values with 46% of them being in the range of luminal breast cancer cell lines. Keratin expression levels of CTCs detected by the CellSearch System correlated with triple negative (p = 0.039) and ER-negative (p = 0.025) breast cancer, and overall survival (p = 0.038).

Conclusions

Keratin expression levels of CTCs correlate with tumor characteristics and clinical outcome. Moreover, CTCs display significant heterogeneity in terms of the degree of EMT phenotype that probably reflects differential invasive potential. The assessment of the vim/K ratios as a surrogate marker for the EMT status of CTCs merits further investigation as a prognostic tool in breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1386-7) contains supplementary material, which is available to authorized users.

Abstract P4-01-13: CTC enumeration and characterization has predictive and prognostic implications in patients with metastatic breast cancer treated with exemestane plus the mTOR inhibitor everolimus

Background: The utility of CTC enumeration in predicting patient (pt) outcome has been demonstrated in metastatic breast cancer (MBC) treated with chemotherapy or endocrine therapy. In this study we evaluated the clinical impact of CTC assessment in terms of both enumeration and characterization in breast cancer pts treated with exemestane plus everolimus. Patients and methods: Thirty-nine pts with hormone receptor (HR)-positive, HER2-negative MBC, received exemestane plus everolimus. CTC enumeration in peripheral blood (7.5 ml) was performed before treatment (n=39), post cycles 1 (n=39) and 3 (n=29), on disease re-evaluation and on relapse, whichever occurred first, using the CellSearch System. CTC characteristics were determined at the same time points by immunofluorescence (IF) analysis of PBMC cytospins (106 cells), triple stained with pancytokeratin (CK) antibody along with Ki67 and M30 as proliferation and apoptosis markers, respectively, using the Ariol System. Patients were assessed by CT scans and bone scan, every 3 months or as clinically indicated. Results: At the cut-off of ≥ 1 CTC, 25 of 39 (64%) pts had detectable CTCs at baseline, 12 (31%) of 39 post-1st and 10 (34.5%) of 29 post-3rd cycle. Ten (25.6%) pts remained CTC(+) and 12 (30.8%) CTC(-) both at baseline and post-1st cycle; 15 (38.5%) CTC(+) pts turned to CTC(-) and 2 (5%) CTC(-) turned to (+). CTC positivity after the first cycle was associated with shorter median progression-free survival (PFS) compared to CTC(-) status (3.9 vs 8 mo, p=0.031). Shorter PFS was also recorded for pts that remained CTC(+) at both time points compared to all other (p=0.02). At the cut-offs of ≥ 2 and ≥ 5 CTCs, 16 (41%) and 9 (23%) pts were CTC(+) at baseline, respectively; post-1st cycle, 7 (18%) and 4 (10%) pts were CTC(+) (at ≥ 2 and ≥ 5 CTCs, respectively). Post-3rd cycle the positivity rate was 17% for both cut-offs and these pts had significantly shorter PFS compared to CTC(-) pts (3.7 vs 8.7 months, p=0.048). Efficacy assessment revealed partial response in 3 (7.7%) pts, stable disease in 27 (69.23%) and progressive disease (PD) in 8 (20.5%); 1 pt was non-evaluable for response. Among pts determined CTC(+) post-1st cycle (cut-off ≥ 2 CTCs), 57% progressed compared to 13% of CTC(-) pts (p=0.02). In addition, at the post-3rd cycle evaluation, pts with PD had significantly higher CTC counts compared to non-progressors (mean ± SEM; 10 ± 5.78/pt vs 1.62±0.83/pt, p=0.027). By the use of IF 43%, 44% and 40% of CTC(+) pts had proliferative [Ki67(+)/M30(-)] CTCs at baseline, post -1st and -3rd cycles, respectively (cut-off ≥ 1 CTC); 67%, 50% and 50% of those pts, respectively, experienced PD. Apoptotic [Ki67(-)/M30(+)] CTCs were detected in 14%, 22% and 60% of CTC(+) pts at baseline, post -1st and -3rd cycles, respectively; none of the pts with apoptotic CTCs experienced PD. Conclusions: CTC enumeration and characterization in terms of proliferation and apoptosis during the course of treatment has significant predictive and prognostic implications in patients with MBC receiving the combination of exemestane plus everolimus.

Citation Format: Sofia Agelaki, Dimitris Mavroudis, Maria Spiliotaki, Eleni Politaki, Maria A Papadaki, Stella Apostolaki, Christos Nikolaou, Vassilis Georgoulias. CTC enumeration and characterization has predictive and prognostic implications in patients with metastatic breast cancer treated with exemestane plus the mTOR inhibitor everolimus [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-01-13.

Effect of front-line chemotherapy on circulating CK-19 mRNA-positive cells in patients with metastatic breast cancer

PURPOSE

To evaluate the effect of front-line chemotherapy on CK-19mRNA+ circulating tumor cells (CTCs) and their relevance in patients with metastatic breast cancer (MBC).

PATIENTS AND METHODS

The presence of CK-19mRNA+ CTCs was assessed using a real-time RT-PCR assay in 298 previously untreated patients with MBC before and after the administration of front-line chemotherapy.

RESULTS

CK-19mRNA+ CTCs were detected in the blood of 199 (66.8 %) and 148 (49.7 %) patients before and after chemotherapy, respectively. There was no correlation between the detection of CK-19mRNA+ CTCs after chemotherapy and the various known clinicopathologic parameters except with HER2 status. The incidence of detection of CK-19mRNA+ CTCs was significantly decreased after the administration of 3 (47.8 %; p < 0.001) or 6 (44.3 %; p = 0.001) chemotherapy cycles. The persistent detection of >2.25 CK-19mRNA+ CTCs both before and after chemotherapy (persistently high group) was associated with a significantly (p = 0.003) decreased overall survival. In addition, chemotherapy-induced decrease of CK-19mRNA+ CTCs (≤2.25 CTCs) was associated with a better survival (47 vs 34 months; p < 0.001). Failure of chemotherapy to decrease the CK-19mRNA+ CTCs ≤2.25 was associated with decreased overall survival (HR 1.405, 95 % CI 1.044-1.891; p = 0.025) whereas in multivariate analysis the persistence of >2.25 CTCs both before and after chemotherapy was emerged as an independent prognostic factor (HR 1.661, 95 % CI 1.070-2.579; p = 0.024).

CONCLUSION

Detection of CK-19mRNA+ CTCs after the completion of front-line chemotherapy in patients with MBC is associated with poor survival and may be a useful tool for the evaluation of front-line chemotherapy.

International study on inter-reader variability for circulating tumor cells in breast cancer

Introduction

Circulating tumor cells (CTCs) have been studied in breast cancer with the CellSearch® system. Given the low CTC counts in non-metastatic breast cancer, it is important to evaluate the inter-reader agreement.

Methods

CellSearch® images (N = 272) of either CTCs or white blood cells or artifacts from 109 non-metastatic (M0) and 22 metastatic (M1) breast cancer patients from reported studies were sent to 22 readers from 15 academic laboratories and 8 readers from two Veridex laboratories. Each image was scored as No CTC vs CTC HER2- vs CTC HER2+. The 8 Veridex readers were summarized to a Veridex Consensus (VC) to compare each academic reader using % agreement and kappa (κ) statistics. Agreement was compared according to disease stage and CTC counts using the Wilcoxon signed rank test.

Results

For CTC definition (No CTC vs CTC), the median agreement between academic readers and VC was 92% (range 69 to 97%) with a median κ of 0.83 (range 0.37 to 0.93). Lower agreement was observed in images from M0 (median 91%, range 70 to 96%) compared to M1 (median 98%, range 64 to 100%) patients (P < 0.001) and from M0 and <3CTCs (median 87%, range 66 to 95%) compared to M0 and ≥3CTCs samples (median 95%, range 77 to 99%), (P < 0.001). For CTC HER2 expression (HER2- vs HER2+), the median agreement was 87% (range 51 to 95%) with a median κ of 0.74 (range 0.25 to 0.90).

Conclusions

The inter-reader agreement for CTC definition was high. Reduced agreement was observed in M0 patients with low CTC counts. Continuous training and independent image review are required.

Clinical validity of circulating tumour cells in patients with metastatic breast cancer: a pooled analysis of individual patient data

BACKGROUND

We aimed to assess the clinical validity of circulating tumour cell (CTC) quantification for prognostication of patients with metastatic breast cancer by undertaking a pooled analysis of individual patient data.

METHODS

We contacted 51 European centres and asked them to provide reported and unreported anonymised data for individual patients with metastatic breast cancer who participated in studies between January, 2003, and July, 2012. Eligible studies had participants starting a new line of therapy, data for progression-free survival or overall survival, or both, and CTC quantification by the CellSearch method at baseline (before start of new treatment). We used Cox regression models, stratified by study, to establish the association between CTC count and progression-free survival and overall survival. We used the landmark method to assess the prognostic value of CTC and serum marker changes during treatment. We assessed the added value of CTCs or serum markers to prognostic clinicopathological models in a resampling procedure using likelihood ratio (LR) χ(2) statistics.

FINDINGS

17 centres provided data for 1944 eligible patients from 20 studies. 911 patients (46·9%) had a CTC count of 5 per 7·5 mL or higher at baseline, which was associated with decreased progression-free survival (hazard ratio [HR] 1·92, 95% CI 1·73-2·14, p<0·0001) and overall survival (HR 2·78, 95% CI 2·42-3·19, p<0·0001) compared with patients with a CTC count of less than 5 per 7·5 mL at baseline. Increased CTC counts 3-5 weeks after start of treatment, adjusted for CTC count at baseline, were associated with shortened progression-free survival (HR 1·85, 95% CI 1·48-2·32, p<0·0001) and overall survival (HR 2·26, 95% CI 1·68-3·03) as were increased CTC counts after 6-8 weeks (progression-free survival HR 2·20, 95% CI 1·66-2·90, p<0·0001; overall survival HR 2·91, 95% CI 2·01-4·23, p<0·0001). Survival prediction was significantly improved by addition of baseline CTC count to the clinicopathological models (progression-free survival LR 38·4, 95% CI 21·9-60·3, p<0·0001; overall survival LR 64·9, 95% CI 41·3-93·4, p<0·0001). This model was further improved by addition of CTC change at 3-5 weeks (progression-free survival LR 8·2, 95% CI 0·78-20·4, p=0·004; overall survival LR 11·5, 95% CI 2·6-25·1, p=0·0007) and at 6-8 weeks (progression-free survival LR 15·3, 95% CI 5·2-28·3; overall survival LR 14·6, 95% CI 4·0-30·6; both p<0·0001). Carcinoembryonic antigen and cancer antigen 15-3 concentrations at baseline and during therapy did not add significant information to the best baseline model.

INTERPRETATION

These data confirm the independent prognostic effect of CTC count on progression-free survival and overall survival. CTC count also improves the prognostication of metastatic breast cancer when added to full clinicopathological predictive models, whereas serum tumour markers do not.

FUNDING

Janssen Diagnostics, the Nuovo-Soldati foundation for cancer research.

Abstract PD6-5: Pooled analysis of circulating tumor cells in metastatic breast cancer: Findings from 1944 individual patients data

Background: Clinical validity of CTCs (CellSearch®) in metastatic breast cancer (MBC) patients has previously been assessed in studies with limited statistical power. We aimed to pool all European studies to obtain high-level evidence on the prognostic value of CTCs, to investigate their effects across different clinico-pathological characteristics and therapies and to further validate the MD Anderson/Institut Curie/Fox Chase CTC-based prognostic nomogram established in first-line treated MBC patients (Giordano et al, Clin Cancer Res 2013).

Material and methods: Methods were predefined in a written protocol. In December 2012, we searched for eligible studies that accrued patients in 2003-2012. We contacted all European laboratories using CellSearch®. We used likelihood ratio tests (LR) in Cox regression models stratified by study to assess the independent prognostic value of CTC when added to a clinicopathological (CP) model for progression-free (PFS) and overall survival (OS). Landmark analyses were used to assess the prognostic effect of early changes in CTC. The CTC-based nomogram (http://cancernomograms.com/CTCOnline.html) score was retrieved for every patient; we calculated C-indices, drew calibration plots and Kaplan-Meier curves according to quintiles of the nomogram score.

Results: We collected individual data of 1944 MBC patients, from 20 different studies (some unpublished), from 17 centers in 7 European countries. We observed 1507 PFS events and 929 deaths. Baseline CTC count was significantly associated with several patient characteristics, such as performance status (PS, p&lt;10-4), synchronous metastasis (p&lt;10- 2) tumor subtype (p&lt;10-4), liver & bone metastases (p&lt;10-4), CEA & CA15-3 levels (p&lt;10-4). The CP model for OS included PS, MBC subtypes, number of previous lines of treatment, patient's age, metastasis-free interval, metastatic sites (p&lt;0.01 for all). In a multivariate analysis containing the CP model parameters and CTC count at baseline, elevated CTC count (≥5) was a significant independent predictor of OS (n = 1444, HR = 2.7, 95%CI [2.2-3.2], LR p&lt;10-4). Baseline serum markers added either no or marginal effect to the CP plus baseline CTC model for OS. In contrast, early changes in CTC status at week 3-5 significantly added prognostic information for OS to the model with CP factors and baseline CTC+ (n = 569, HR = 1.8 [2.2-3.2], LR p&lt;0.001). In the population of interest (MBC treated by first line chemotherapy, n = 402 patients, 176 deaths), the CTC-based nomogram exhibited a good C-index for OS (0.69), was well calibrated and showed clear separation of the survival curves. Additional results, including subgroup analyses by tumor subtype and treatments will be presented at the meeting.

Conclusions: This pooled analysis is the largest study ever reported on CTC in MBC, with a previously unreached statistical power. It provides a clear level-of-evidence 1 on the independent prognostic value of CTCs before and during treatment in MBC. Also, the CTC-based prognostic nomogram is independently validated.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD6-5.

Abstract P1-04-12: Prognostic value of CTC detection by RT-PCR and the CellSearch system before first-line chemotherapy in metastatic breast cancer

Background: CTCs have significant prognostic role in patients with breast cancer. Several techniques developed for CTC detection might help in monitoring treatment efficacy. The CellSearch System is the only clinically validated for use in patients with metastatic breast cancer (MBC). We have previously shown a concordance between RT-PCR for cytokeratin 19 (CK-19) and CellSearch System in the detection of CTCs in MBC. In this study we aimed to evaluate the prognostic value of CTC detection using these assays in the same cohort of patients. Methods: Blood was obtained from patients with MBC before the initiation of first-line chemotherapy. Different aliquots of the same blood sample were evaluated for the presence of CTCs by RT-PCR for CK-19 mRNA and by the CellSearch System. Disease progression and response to treatment were determined using standard clinical and imaging criteria. Results: In 142 patients with available clinical data, CTC evaluation was performed using both methods. Median age was 60.7 years (range, 23-82), 74.6% were post-menopausal and 16.9% were HER2-positive. CTCs were detected in 52.1% and 36.6% of patients by the CellSearch System (cut-offs ≥2 and ≥5 CTCs/7.5 ml, respectively) and in 38.7% by RT-PCR; 27.5% (cut-off ≥2) and 20.4% (cut-off ≥5) of patients were CTC-positive by both methods. Response rate was 40% in patients with CTCs detected by CellSearch (cut-off ≥2) vs 62% in CTC-negative patients; there was no difference in objective responses using the ≥5 cut-off, or using RT-PCR for CTC detection. Median PFS was 9.0 (cut-off ≥2) and 7.5 months (cut-off ≥5) for CTC-positive versus 20.0 (cut-off ≥2) and 18.7 months (cut-off ≥5) for CTC-negative patients using the CellSearch System (p = 0.0001). No significant difference in PFS was evident according to CTC detection by RT-PCR (10.0 vs 13.1 months, p = 0.253). Median survival was 24.7 vs 57.3 (cut-off ≥2) and 18.5 vs 53.7 (cut-off ≥5) months for CTC-positive vs CTC-negative patients using the CellSearch System (p = 0.0001); by RT-PCR, median survival was 30.3 and 50.1 months for CTC-positive and CTC-negative patients, respectively (p = 0.021). Conclusions: The detection of CTCs before first-line chemotherapy using either the CellSearch System or RT-PCR for CK-19 mRNA has significant prognostic value in patients with MBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-04-12.

A multicenter phase I-II study of docetaxel plus epirubicin plus bevacizumab as first-line treatment in women with HER2-negative metastatic breast cancer

PURPOSE

To assess the efficacy and toxicity of docetaxel (D) plus epirubicin (E) in combination with bevacizumab (B) [DEB regimen] as front-line treatment in patients with metastatic breast cancer (MBC).

PATIENTS AND METHODS

Women with previously untreated HER2-negative MBC received B (15 mg/kg), E (75 mg/m2) and D (75 mg/m2) with prophylactic G-CSF support every 3 weeks (q3w) for up to 9 cycles followed by B (15 mg/kg q3w) until disease progression. Primary endpoint was the overall response rate (ORR). Circulating tumor cells (CTCs) were evaluated using the CellSearch system at different time points during therapy.

RESULTS

Eighty-three women were enrolled with median age 62 years, performance status 0-1 in 93%, triple negative disease in 12% and liver metastases in 47%. In an intention to treat analysis, complete response was achieved in 13 (15.7%) and partial response in 42 (50.6%) (overall response rate 66.3%; 95% CI 56.09-76.44%). The median time to progression was 20.1 months and the 1-year overall survival rate 82.3%. Grade 3-4 neutropenia occurred in 37%, febrile neutropenia in 10%, anemia in 4%, thrombocytopenia in 2% and diarrhea in 2% of patients. There were two deaths possibly related to study treatment (sigmoid perforation n = 1; sudden death n = 1). Moreover, one patient developed pulmonary embolism and another one myocardial infarction while on treatment. Although DEB administration significantly reduced the proportion of patients presenting CTCs, the detection of ≥5 or ≥1 CTCs before treatment initiation was significantly associated with worse progression-free survival (p = 0.001 and p = 0.004) and overall survival (p = 0.001 and p = 0.027), respectively.

CONCLUSIONS

The DEB regimen is a very active but also potentially toxic combination in MBC. Detection of CTCs before treatment is associated with worse outcome.

CLINICALTRIALSGOV

NCT00705315.

P4-07-21: A Comparison of Two Methods for the Detection of Circulating Tumor Cells (CTCs) in Patients (pts) with Early and Metastatic Breast Cancer (BC): RT-PCR for Cytokeratin (CK) −19 mRNA Versus the CellSearch System

Background: Different methods are available for the detection of CTCs in pts with BC, however, the variable performance of these assays, the heterogeneity of CTCs, and the possible treatment-induced alteration of the markers evaluated, imply that no ideal method currently exists. We compared the efficiency of two methods to detect CTCs in pts with BC.

Patients and Methods: Blood was obtained from 200 pts with early and 164 with metastatic BC before the start of adjuvant or first-line chemotherapy, respectively. Different aliquots of the same sample were evaluated by RT-PCR for CK-19 mRNA and by the CellSearch System. Blood samples were available after the end of adjuvant or first-line therapy in 99 and 93 pts, respectively. CTCs in 23 and 7.5 ml of blood were enumerated by CellSearch, in adjuvant and metastatic pts, respectively. Cut-off values of ≥1 and ≥2 CTCs/23 ml and ≥2 and ≥5 CTCs/7.5 ml were used. Twenty ml of blood were obtained for mRNA extraction in all RT-PCR experiments.

Results: In early BC, 18.0% of samples were positive prior to therapy by RT-PCR and 37.0% (CTC≥1) and 16.5% (CTC≥2) by CellSearch. No significant correlation was shown for the detection of CTCs between methods. Overall (positive and negative) concordance was 62% for CTC≥1 and 73.5% for CTC≥2 (Chi-Square, p=0.161 and p=0.307). Post-chemotherapy, the positivity rate was 33.6% (CTC≥1) and 18.8% (CTC≥2) by CellSearch and 11.6% by RT-PCR (Spearman, R=-0.031, p=0.761). Overall agreement was 60.6% (CTC≥1) and 71.4% (CTC≥2) (Chi-Square, p=0.771 and p=0.708). In the metastatic setting, 37.8% of the samples were positive by RT-PCR, and 50% (CTC≥2) or 32.3% (CTC≥5), by CellSearch (Spearman, R=0.373, p=0.0001). Overall agreement was 70.0% for CTC≥5 (Chi-Square, p=0.0001). Post-chemotherapy, 21% were positive by RT-PCR and 13.7% and 8.4% by CellSearch for CTC≥2 and ≥5, respectively (Spearman, R=0.194, p=0.063). Overall concordance for CTC≥5 was 79.6% (Chi-Square, p=0.017). Agreement was also observed for CTC≥2, pre-and post-chemotherapy (Chi-Square, p=0.0001 and p=0.010). The concordance rates in the adjuvant and metastatic settings are shown in Table 1.

Gene expression profile of circulating tumor cells in breast cancer by RT-qPCR

Background

Circulating tumor cells (CTCs) have been associated with prognosis especially in breast cancer and have been proposed as a liquid biopsy for repeated follow up examinations. Molecular characterization of CTCs is difficult to address since they are very rare and the amount of available sample is very limited.

Methods

We quantified by RT-qPCR CK-19, MAGE-A3, HER-2, TWIST1, hTERT α+β+, and mammaglobin gene transcripts in immunomagnetically positively selected CTCs from 92 breast cancer patients, and 28 healthy individuals. We also compared our results with the CellSearch system in 33 of these patients with early breast cancer.

Results

RT-qPCR is highly sensitive and specific and can detect the expression of each individual gene at the one cell level. None of the genes tested was detected in the group of healthy donors. In 66 operable breast cancer patients, CK-19 was detected in 42.4%, HER-2 in 13.6%, MAGE-A3 in 21.2%, hMAM in 13.6%, TWIST-1 in 42.4%, and hTERT α+β+ in 10.2%. In 26 patients with verified metastasis, CK-19 was detected in 53.8%, HER-2 in 19.2%, MAGE-A3 in 15.4%, hMAM in 30.8%, TWIST-1 in 38.5% and hTERT α⁺β⁺in 19.2%. Our preliminary data on the comparison between RT-qPCR and CellSearch in 33 early breast cancer patients showed that RT-qPCR gives more positive results in respect to CellSearch.

Conclusions

Molecular characterization of CTCs has revealed a remarkable heterogeneity of gene expression between breast cancer patients. In a small percentage of patients, CTCs were positive for all six genes tested, while in some patients only one of these genes was expressed. The clinical significance of these findings in early breast cancer remains to be elucidated when the clinical outcome for these patients is known.

Epithelial to mesenchymal transition markers expressed in circulating tumour cells of early and metastatic breast cancer patients

Introduction

Epithelial to mesenchymal transition (EMT) is considered an essential process in the metastatic cascade. EMT is characterised by upregulation of vimentin, Twist, Snail, Slug and Sip1 among others. Metastasis is also associated with the presence of circulating tumour cells (CTCs) and disseminated tumour cells in the blood and bone marrow, respectively, of breast cancer patients, but the expression of EMT markers in these cells has not been reported so far.

Methods

The expression of Twist and vimentin in CTCs of 25 metastatic and 25 early breast cancer patients was investigated by using double-immunofluorescence experiments in isolated peripheral blood mononuclear cell cytospins using anti-cytokeratin (anti-CK) anti-mouse (A45-B/B3) and anti-Twist or anti-vimentin anti-rabbit antibodies.

Results

Among early breast cancer patients, vimentin-and Twist-expressing CK⁺ CTCs were identified in 77% and 73% of the patients, respectively, and in 100% of the patients with metastatic breast cancer for both markers (P = 0.004 and P = 0.037, respectively). Among patients with early disease, 56% and 53% of the CK⁺ CTCs were double-stained with vimentin and Twist, and the corresponding values for metastatic patients were 74% and 97%, respectively (P = 0.005 and P = 0.0001, respectively). The median expression of CK⁺vimentin⁺ and CK⁺Twist⁺ cells per patient in metastatic patients was 98% and 100%, and in an adjuvant chemotherapy setting the corresponding numbers were 56% and 40.6%, respectively. Triple-staining experiments revealed that all CK⁺Twist⁺ or CK⁺vimentin⁺ cells were also CD45^-, confirming their epithelial origin. Immunomagnetic separation of CTCs and triple-immunofluorescence with anti-CK/anti-Twist/anti-vimentin antibodies demonstrated that both mesenchymal markers could be coexpressed in the same CK⁺ cell, since 64% of the total identified CTCs were triple-stained. There was a significant correlation (P = 0.005) between the number of CTCs expressing Twist and vimentin within the same setting.

Conclusions

CTCs expressing Twist and vimentin, suggestive of EMT, are identified in patients with breast cancer. The high incidence of these cells in patients with metastatic disease compared to early stage breast cancer strongly supports the notion that EMT is involved in the metastatic potential of CTCs.

Abstract 2040: Gene expression profile of circulating tumor cells in breast cancer by RT-qPCR

Background: Circulating tumor cells (CTCs) are associated with prognosis and can be used as a liquid biopsy for repeated follow up examinations. Molecular characterization of CTCs is difficult to address since they are very rare and the amount of available sample is very limited.

Patients and methods: We quantified by RT-qPCR CK-19, MAGE-A3, HER-2, TWIST1, hTERT α+β+, and mammaglobin gene transcripts in immunomagnetically positively selected CTCs from 92 breast cancer patients, and 28 healthy individuals. We compared our results with the CellSearch system in 33 patients with early breast cancer.

Results: RT-qPCR is highly sensitive and specific and can detect the expression of each individual gene at the one cell level. None of the genes tested was detected in the group of healthy donors. In 66 operable breast cancer patients, CK-19 was detected in 42.4%, HER-2 in 13.6%, MAGE-A3 in 21.2%, hMAM in 13.6%, TWIST-1 in 42.4%, and hTERT α+β+ in 10.2%. In 26 patients with verified metastasis, CK-19 was detected in 53.8%, HER-2 in 19.2%, MAGE-A3 in 15.4%, hMAM in 30.8%, TWIST-1 in 38.5% and hTERT α+β+in 19.2%. The comparison between RT-qPCR and CellSearch, showed that RT-qPCR was more sensitive than CellSearch.

Discussion: Molecular characterization of CTCs has revealed a remarkable heterogeneity of gene expression between breast cancer patients. In a small percentage of patients, CTCs were positive for all six genes tested, while in some patients only one of these genes was expressed. The clinical significance of these findings in early breast cancer remains to be elucidated when the clinical outcome for these patients is known.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2040. doi:10.1158/1538-7445.AM2011-2040

Abstract PD04-04: Cytokeratin-19 mRNA Positive Circulating Tumor Cells during Follow-Up of Patients with Early Breast Cancer: Prognostic Relevance for Late Relapse

PURPOSE: We reported previously that the detection of CK-19 mRNA-positive circulating tumor cells (CTCs) after adjuvant chemotherapy in patients with early breast cancer is associated with poor clinical outcome. Reliable prognostic markers for late disease relapse are not available. In this study we investigated the prognostic value of CTCs’ detection during the first 5 years of follow-up in predicting late disease relapse. PATIENTS AND METHODS: Blood was obtained from 281 patients with early breast cancer who had not experienced disease relapse during the first two years of follow up. CTCs were detected using a real-time reverse transcriptase polymerase chain reaction for CK 19 mRNA after the completion of adjuvant chemotherapy and every six months thereafter for a 5-year follow up period. Patients were classified into four groups based on the CTCs’ status during the first two years and the subsequent three years of follow up (persistently negative, persistently positive, negative turned to positive and the opposite).

RESULTS: The vast majority of patients (92.9%) received some kind of hormonal therapy in addition to chemotherapy. Sixty-nine (24.6%) patients remained CTCs-free throughout the 5-year period. A change in CK-19 mRNA status was observed in 126 (44.9%) patients; 60 (21.4%) patients with initially CK-19 mRNA-positive CTCs during the first 24 months turned CTC-negative afterwards while 66 (23.5%) patients who were initially CTC-negative became CTC-positive. Eighty-six (30.6%) patients remained persistently CK-19 mRNA-positive for the entire 5 years. After 94 months of median follow up (range: 51-147), the relapse rate for each of the above groups of patients is illustrated in the following table.

Table 1: CTCs’ detection status and risk of late disease repapse.

Compared to the persistently negative, only the group of CK-19 mRNA-persistently positive patients had a statistically significant higher risk of relapse (38.4% versus 7.2%, p&lt; 0.001), shorter progression-free survival (not reached vs 135 months, P&lt;0.001) and significant difference in overall survival (not reached vs 146 months, p=0.045).

CONCLUSION: Persistent detection of CK-19 mRNA-positive CTCs in the blood during the first 5 years of follow up after adjuvant chemotherapy is associated with an increased risk of late disease relapse indicating the presence of chemotherapy-and hormonetherapy-resistant residual disease. This prognostic evaluation may be useful when deciding on subsequent adjuvant systemic therapy.

Different prognostic value of cytokeratin-19 mRNA positive circulating tumor cells according to estrogen receptor and HER2 status in early-stage breast cancer

PURPOSE

To examine the prognostic value of cytokeratin-19 (CK-19) mRNA-positive circulating tumor cells (CTCs) in early-stage breast cancer patients focusing on clinically relevant subgroups based on estrogen receptor (ER) and HER2 expression.

PATIENTS AND METHODS

CK-19 mRNA-positive CTCs were detected by real-time reverse transcriptase polymerase chain reaction in the blood of 444 consecutive, stage I-III, breast cancer patients before initiation of adjuvant chemotherapy. The association between detection of CK-19 mRNA-positive CTCs and clinical outcome was analyzed for patients with ER-positive, ER-negative, triple-negative, HER2-positive, and ER-positive/HER2-negative tumors.

RESULTS

CK-19 mRNA-positive CTCs were detected in 181 (40.8%) of 444 patients; 109 (41.9%) of 260 patients with ER-positive tumors; 71 (40.6%) of 175 patients with ER-negative tumors; 27 (35%) of 77 patients with triple-negative tumors; 35 (39.8%) of 88 patients with HER2-positive tumors; and 82 (44.1%) of 186 patients with ER-positive/HER2-negative tumors. After a median follow-up of 53.5 months, patients with CK-19 mRNA-positive CTCs experienced reduced disease-free survival (DFS; P < .001) and overall survival (OS; P < .001); this was mainly observed in patients with ER-negative (P < .001 and P < .001, respectively) but not ER-positive tumors (P = .172 and P = .425, respectively) and in patients with triple-negative (P = .008 and P = .001, respectively) and HER2-positive (P = .023 and P = .040, respectively) but not ER-positive/HER2-negative tumors (P = .210 and P = .578, respectively). In multivariate analysis, the interaction between CK-19 mRNA-positive CTCs and ER status was the strongest independent prognostic factor for reduced DFS (hazard ratio [HR], 3.808; 95% CI, 2.415 to 6.003; P < .001) and OS (HR, 4.172; 95% CI, 2.477 to 9.161; P < .001).

CONCLUSION

Detection of CK-19 mRNA-positive CTCs before adjuvant chemotherapy predicts poor clinical outcome mainly in patients with ER-negative, triple-negative, and HER2-positive early-stage breast cancer.

Different prognostic value of cytokeratin-19 mRNA-positive circulating tumor cells according to estrogen receptor status in early breast cancer

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Background: We have previously shown that the detection of cytokeratin-19 (CK-19) mRNA-positive circulating tumor cells (CTCs) predicts poor clinical outcome in node-negative breast cancer patients. Here, we examined the prognostic value of CK-19 mRNA-positive CTCs in early breast cancer patients focusing on clinically relevant subgroups based on estrogen receptor (ER) status. Methods: We analysed peripheral blood from 448 consecutive patients with stage I-III breast cancer after surgery and before the initiation of any adjuvant treatment for the presence of CK-19 mRNA-positive CTCs using a real-time RT-PCR assay. The effect of CK-19 mRNA-positive CTCs on clinical outcome of patients with ER-positive, ER-negative, and triple-negative (ER/PR/HER2-negative) tumors was investigated. Results: CK-19 mRNA-positive CTCs were detected in 181 (40.4%) of the 448 patients; 109 (41.5%) of 263 patients with ER-positive, 71 (40.6%) of 175 patients with ER-negative and 27 (35%) of 77 patients with triple-negative tumors. There was no significant difference in the proportion of patients with detectable CK-19 mRNA-positive CTCs in the ER-negative and ER-positive subgroups (p=0.856). After a median follow-up of 53 months, patients with CK-19 mRNA-positive CTCs experienced reduced disease-free survival (DFS) (p<0.0005) and overall survival (OS) (p<0.0005); this was mainly observed in patients with ER-negative (p<0.0005 and p<0.0005, respectively) and triple-negative (p=0.008 and p=0.001, respectively) but not with ER-positive (p=0.174 and p=0.364, respectively) tumors. In multivariate analyses, detection of CK-19 mRNA-positive CTCs was the strongest independent prognostic factor associated with reduced DFS and OS in the entire cohort (p<0.0005 and p=0.009, respectively), in ER-negative (p<0.0005 and p=0.003, respectively) and triple-negative (p=0.020 and p=0.022, respectively) but not in ER-positive tumors (p=0.350 and p=0.621, respectively). Conclusions: Detection of CK-19 mRNA-positive CTCs predicts poor clinical outcome at five years follow-up, only in patients with ER-negative and triple-negative, but not with ER-positive, early breast cancer.

No significant financial relationships to disclose.

Circulating HER2 mRNA-positive cells in the peripheral blood of patients with stage I and II breast cancer after the administration of adjuvant chemotherapy: evaluation of their clinical relevance

BACKGROUND

The purpose of this study was to evaluate the prognostic value of circulating tumor cells (CTCs) expressing HER2 messenger RNA (mRNA) after the administration of adjuvant chemotherapy in women with operable breast cancer.

PATIENTS AND METHODS

HER2 mRNA-positive CTCs were detected by nested RT-PCR in the peripheral blood of 214 patients with stage I and II breast cancer after the completion of adjuvant chemotherapy.

RESULTS

HER2 mRNA-positive CTCs were detected in 45 (21%) patients. Adjuvant chemotherapy could eliminate HER2 mRNA-positive CTCs in 16 (30.2%) prechemotherapy-positive patients. Moreover, HER2 mRNA-positive CTCs were detected in eight (5%) of 161 prechemotherapy-negative patients. The detection of HER2 mRNA-positive CTCs after chemotherapy was associated with reduced disease-free interval (DFI) (P = 0.006) but not with overall survival (P = 0.2); this effect was mainly observed in node-negative patients (P = 0.04) and to a lesser extent in node-positive (P = 0.06). Multivariate analysis revealed that the detection of HER2 mRNA-positive CTCs was an independent predictive factor for DFI (hazard ratio 3.238, P < 0.0005).

CONCLUSIONS

The detection of HER2 mRNA-positive CTCs after the completion of adjuvant chemotherapy may provide clinically useful information concerning the efficacy of treatment and the prognosis of patients with operable breast cancer.