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Background: The phenotypes of tumor cells change during disease progression, but invasive rebiopsies of metastatic lesions are not always feasible. Here we aimed to determine whether initially HER2-negative metastatic breast cancer (MBC) patients with HER2-positive circulating tumor cells (CTCs) benefit from a HER2-targeted therapy., Methods: The open-label, interventional randomized phase III clinical trial (EudraCT Number 2010-024238-46, CliniclTrials.gov Identifier: NCT01619111) recruited from March 2012 until September 2019 with a follow-up duration of 19.5 months. It was a multicenter clinical trial with 94 participating German study centers. A total of 2137 patients with HER2-negative MBC were screened for HER2-positive CTCs with a final modified intention-to-treat population of 101 patients. Eligible patients were randomized to standard therapy with or without lapatinib. Primary study endpoints included CTC clearance (no CTCs at the end of treatment) and secondary endpoints were progression-free survival, overall survival (OS), and safety., Results: In both treatment arms CTC clearance at first follow-up visit-although not being significantly different for both arms at any time point-was significantly associated with improved OS (42.4 vs 14.1 months; P = 0.002). Patients treated additionally with lapatinib had a significantly improved OS over patients receiving standard treatment (20.5 vs 9.1 months, P = 0.009)., Conclusions: DETECT III is the first clinical study indicating that phenotyping of CTCs might have clinical utility for stratification of MBC cancer patients to HER2-targeting therapies. The OS benefit could be related to lapatinib, but further studies are required to prove this clinical observation. ClinicalTrials.gov Registration Number: NCT01619111., (© Association for Diagnostics & Laboratory Medicine 2024. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Obesity and the presence of circulating tumor cells (CTCs) before and/or after chemotherapy are associated with poor outcome in breast cancer (BC) patients. The activation of oncogenic pathways in fatty tissue leads to cell proliferation, suggesting a possible link between obesity and CTCs., Materials and Methods: In the phase III SUCCESS A trial, 3754 patients with early BC were randomized to 3 cycles of fluorouracil, epirubicin and cyclophosphamide followed by 3 cycles of docetaxel with or without gemcitabine. Data of 1088 patients with CTC assessments (CellSearch-System; Menarini Silicon Biosystems, Italy) and body mass index (BMI) measurements both before and after chemotherapy were available. Patients were classified according to the WHO's international definitions as underweight, normal weight, overweight, or obese, and according to their weight-change during chemotherapy into a weight-loss group (> 5% decrease), stable-weight group (≤ 5% weight-change) or weight-gain group (>5% increase). Associations between CTC positivity and, BMI or weight-change group were analyzed using frequency-table methods., Results: At study entry, 47.4% patients were underweight or normal weight, 33.6% were overweight and 18.9% were obese. Before and after chemotherapy, CTCs were detected in 20.1% and 22.6% of patients, respectively. There was no association between CTC positivity and BMI before (P = 0.104) or after (P = 0.051) chemotherapy. Furthermore, there was no association between weight-change group and CTC status before/after chemotherapy (P = 0.332)., Conclusions: According to our analysis, the risk factors obesity and prevalence of CTCs are not associated and may represent independent prognostic factors., Competing Interests: Disclosure TWP: Personal fees from Lilly and Novartis. FS: Grants from AstraZeneca, Roche and Karyopharm. Personal fees from Roche, Pfizer, Novartis, AstraZeneca, GSK, MSD, Clovis and Eisai. TF: Personal fees from Medconcept, Onkowissen. KP: Grants from: EU/IMI CANCER-ID EFPIA, Personal fees from: BMS, Agena, Menarini, Novartis, Sanofi, Illumina, Abcam, MSD, Boehringer Ingelheim, Eppendorf and Hummingbird. AS: Grants from Celgene, Roche and AbbVie. Personal fees from Celgene, Roche, Pfizer, AstraZeneca, Novartis, MSD, Tesaro, Lilly, Seagen, Gilead, GSK, Bayer, Amgen and Pierre Fabre. HT: Personal fees from Novartis, Roche, GSK, Seagan, Pfizer, Lilly, Astra Zeneca, Daiichi, Exact Science, Vifor and Seagan. Shares/stocks from CHOP GmbH, VISION MED GmbH, Care and Coach GmbH, Onco Medical Consult GmbH. VA-F: Honoraria from Novartis. PF: Grants from Pfizer, Cepheid and Biontech. Personal fees from Novartis Daiichi-Sankyo, Pfizer Astra Zeneca, Eisai, Merck Sharp & Dohme, Lilly, Pierre Fabre, SeaGen, Roche, Agendia, Sanofi Aventis, Gilead, Mylan and Menarini., WJ: honoraria from Sanofi-Aventis, Novartis and Pfizer. BR: honoraria from AstraZeneca, Chugai, Lilly, Novartis, Sanofi-Aventis, and Jannssen-Cilag. All other authors have no conflicts of interest., (Copyright © 2023. Published by Elsevier Inc.)

Background: Circulating tumour cells (CTCs) are mainly enriched based on the epithelial cell adhesion molecule (EpCAM). Although it was shown that an EpCAM low-expressing CTC fraction is not captured by such approaches, knowledge about its prognostic and predictive relevance and its relation to EpCAM-positive CTCs is lacking., Methods: We developed an immunomagnetic assay to enrich CTCs from metastatic breast cancer patients EpCAM independently using antibodies against Trop-2 and CD-49f and characterised their EpCAM expression. DNA of single EpCAM high expressing and low expressing CTCs was analyzed regarding chromosomal aberrations and predictive mutations. Additionally, we compared CTC-enrichment on the CellSearch system using this antibody mix and the EpCAM based enrichment., Results: Both antibodies acted synergistically in capturing CTCs. Patients with EpCAM high-expressing CTCs had a worse overall and progression-free survival. EpCAM high- and low-expressing CTCs presented similar chromosomal aberrations and mutations indicating a close evolutionary relationship. A sequential enrichment of CTCs from the EpCAM-depleted fraction yielded a population of CTCs not captured EpCAM dependently but harbouring predictive information., Conclusions: Our data indicate that EpCAM low-expressing CTCs could be used as a valuable tumour surrogate material-although they may be prognostically less relevant than EpCAM high-expressing CTCs-and have particular benefit if no CTCs are detected using EpCAM-dependent technologies., (© 2023. The Author(s).)

Background: Circulating tumor cells (CTCs) have been reported to predict clinical outcome in metastatic breast cancer (MBC). Biology of CTCs may differ from that of the primary tumor and HER2-positive CTCs are found in some patients with HER2-negative tumors., Patients and Methods: Patients with HER2-negative MBC were screened for participation in DETECT III and IV trials before the initiation of a new line of therapy. Blood samples were analyzed using CELLSEARCH. CTCs were labeled with an anti-HER2 antibody and classified according to staining intensity (negative, weak, moderate, or strong staining)., Results: Screening blood samples were analyzed in 1933 patients with HER2-negative MBC. As many as 1217 out of the 1933 screened patients (63.0%) had ≥1 CTC per 7.5 ml blood; ≥5 CTCs were detected in 735 patients (38.0%; range 1-35 078 CTCs, median 8 CTCs). HER2 status of CTCs was assessed in 1159 CTC-positive patients; ≥1 CTC with strong HER2 staining was found in 174 (15.0%) patients. The proportion of CTCs with strong HER2 staining among all CTCs of an individual patient ranged between 0.06% and 100% (mean 15.8%). Patients with estrogen receptor (ER)- and progesterone receptor (PR)-positive tumors were more likely to harbor ≥1 CTC with strong HER2 staining. CTC status was significantly associated with overall survival (OS). Detection of ≥1 CTC with strong HER2 staining was associated with shorter OS [9.7 (7.1-12.3) versus 16.5 (14.9-18.1) months in patients with CTCs with negative-to-moderate HER2 staining only, P = 0.013]. In multivariate analysis, age, ER status, PR status, Eastern Cooperative Oncology Group performance status, therapy line, and CTC status independently predicted OS., Conclusion: CTC detection in patients with HER2-negative disease is a strong prognostic factor. Presence of ≥1 CTC with strong HER2 staining was associated with shorter OS, supporting a biological role of HER2 expression on CTCs., Competing Interests: Disclosure VM received speaker honoraria from Amgen, Astra Zeneca, Daiichi-Sankyo, Eisai, GSK, Pfizer, MSD, Novartis, Roche, Teva, and Seagen; consultancy honoraria from Genomic Health, Hexal, Roche, Pierre Fabre, Amgen, Clin Sol, Novartis, MSD, Daiichi-Sankyo, Eisai, Lilly, and Seagen; institutional research support from Novartis, Roche, Seagen, and Genentech; travel grants from Roche, Pfizer, and Daiichi Sankyo. MBP received honoraria for lectures and advisory role from Novartis, Roche, Pfizer, Eli Lilly, Eisai, Daiichi Sankyo, GSK, AstraZeneca, pfm, and Amgen; and study support from Endomag, Mammotome and Merit Medical. PW has received research funding from Amgen, AstraZeneca, MSD, GlaxoSmithKline, Novartis, Pfizer, PharmaMar, Roche Pharma, Clovis, and Lilly; honoraria from Amgen, AstraZeneca, MSD, GlaxoSmithKline, Novartis, Pfizer, Roche Pharma, Clovis, TEVA, Eisai, and Lilly; serves on the advisory board of Amgen, AstraZeneca, MSD, GlaxoSmithKline, Novartis, Pfizer, Roche Pharma, Clovis, TEVA, Eisai, and Lilly. NH reports honoraria for consulting and/or lectures from Astra Zeneca, Daiichi-Sankyo, Exact Sciences, Lilly, MSD, Novartis, Pierre Fabre, Pfizer, Roche, Sandoz, and Seagen. JH received research funding from Celgene, Novartis, and Hexal; honoraria from Lilly, Novartis, Roche, Pfizer, AstraZeneca, MSD, Celgene, Eisai, and AbbVie; honoraria for consulting/advisory relationship from Lilly, Novartis, Roche, Pfizer, Hexal, AstraZeneca, MSD, Celgene, and AbbVie; and travel expenses from Roche, Pfizer, Novartis, Celgene, and Daiichi. TF reports honoraria from Novartis, unrelated to this work. OH received honoraria for advisory boards, lectures, and congress and travel expense support from Roche, Novartis, MSD, Pfizer, Astra Zeneca, Daiichi Sankyo, Riemser Pharma, Celgene, and Seagen. FMS reports consulting fees from Amgen. TF received consulting fees (e.g. advisory boards) from Amgen, Daiichi Sankyo, Roche, AstraZeneca, MSD Oncology, Novartis, Pierre Fabre, and Pfizer Teva, and fees for non-CME services received directly from commercial interest or their agents (e.g. speakers’ bureaus): Daiichi Sankyo, Roche, and Novartis. All other authors have declared no conflicts of interest., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

In recent years, breast cancer treatment has become increasingly individualized. Circulating tumor cells (CTCs) have the potential to move personalized medicine another step forward. The prognostic relevance of CTCs has already been proven both in early and metastatic breast cancer. In addition, there is evidence that changes in CTC numbers during the course of therapy can predict treatment response. Thus, CTCs are a suitable tool for repeated treatment monitoring through noninvasive liquid biopsy. The next step is to evaluate how this information can be used for clinical decision making with regard to the extension, modification, or abandonment of a treatment regimen. This review will summarize the completed and ongoing clinical trials using CTC number or phenotype for treatment decisions. Based on current knowledge, CTCs can be regarded as a useful prognostic and predictive marker that is well suited for both risk stratification and treatment monitoring in breast cancer patients. However, there is still the need to provide sufficient and unequivocal evidence for whether CTCs may indeed be used to guide treatment decisions in everyday clinical practice. The results of the ongoing trials described in this review are eagerly awaited to answer these important questions., Competing Interests: Dr. Schochter: honoraria by Roche, Novartis and Pfizer; Dr. Friedl: honoraria by Novartis; Dr. deGregorio: honoraria from Roche, Pfizer, Novartis, Celgene, Tesaro, Daiichi; Dr. Krause: no relevant financial relationsships; Prof. Huober: research grants from Celgene, Novartis; Speaker fees by Lilly, Novartis, Roche, Pfizer, AstraZeneca, MSD, Celgene, Eisai; consultant by Lilly, Novartis, Roche, Pfizer, Hexal, AstraZeneca, MSD, Celgene; Travel expenses by Roche, Pfizer, Novartis, Celgene, Daiichi; Prof Rack: research grants and honoraria Aventis, Pharmacia, Amgen, Novartis, AstraZenica, Roche, Pfizer, Chugai; Prof. Janni has received research grants and honoraria from Menarini Silicon Biosystems, Johnson&Johnson. Institutional founding by the Deutsche Krebshilfe (German Cancer Aid), Menarini Silicon Biosystems, Roche, Novartis, GlaxoSmithKline, Amgen, Celgene, Eisai, and TEVA.

Background: The prognostic relevance of circulating tumor cells (CTCs) at the time of primary diagnosis has been well established. However, little information is available regarding their prognostic relevance to follow-up care., Methods: The multicenter, open-label, phase III SUCCESS A trial compared two adjuvant chemotherapy regimens followed by 2 vs 5 years of zoledronate for early-stage, high-risk breast cancer patients. The presence of CTCs was assessed before and 2 years after chemotherapy using the FDA-approved CellSearch System. Overall survival (OS) and disease-free survival (DFS) were analyzed using univariate log-rank tests and multivariable Cox regressions. OS and DFS were measured starting from an assessment of CTCs 2 years after the completion of chemotherapy. All statistical tests were two-sided., Results: The sample included 1087 patients who participated in the translational research program of the SUCCESS A trial and for whom sufficient translational data were available regarding CTC status at baseline and at the 2-year follow-up visit. Two years after chemotherapy, 198 (18.2%) patients were CTC-positive. The median follow-up after this timepoint was 37 months. Cox regressions that included CTC status at baseline revealed that CTC status 2 years after chemotherapy had statistically significant and independent prognostic relevance for OS (hazard ratio [HR] = 3.91, 95% confidence interval [CI] = 2.04 to 7.52, P < .001) and DFS (HR = 2.31, 95% CI = 1.50 to 3.55, P < .001)., Conclusion: The presence of CTCs 2 years after chemotherapy was associated with decreased OS and DFS. Based on these results, active individualized surveillance strategies for breast cancer survivors based on biomarkers should be reconsidered., (© The Author(s) 2018. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Purpose: Several studies have provided evidence on the prognostic relevance of circulating tumor cells (CTCs) detected before and after chemotherapy regarding overall survival (OS) and progression-free survival (PFS) in early breast cancer (EBC). We provide data on the prevalence of CTCs 2 and 5 years after primary diagnosis in a cohort of patients with EBC., Methods: The SUCCESS study is a multicenter, prospective, randomized trial comparing PFS in primary breast cancer patients undergoing one of two adjuvant chemotherapy regimens followed by 2 versus 5 years of treatment with zoledronate. CTCs from patients without signs of breast cancer recurrence were analyzed in peripheral blood using the FDA cleared CellSearch® System (Veridex, USA) 2 and 5 years after primary diagnosis., Results: CTCs were detected at 2 and 5 years after primary diagnosis in 96 (16.7%) and 47 (8.2%) of the 574 patients, respectively. There were no associations between CTC status and patient and tumor characteristics or treatment regimens. In 442 (77.0%) patients, no CTCs were detected at either of the two time points, and in 11 patients (1.9%), CTCs were found at both 2 and 5 years after primary diagnosis. In 85 (14.8%) patients, CTCs were present 2 years after primary diagnosis but not after 5 years, while 36 (6.3%) patients had CTCs in their blood only at the 5-year follow-up., Conclusions: In patients with EBC, CTCs can be detected even 5 years after primary diagnosis without clinical signs of disease recurrence.

Background: Little is known about the effect of granulocyte colony-stimulating factor (G-CSF) treatment during adjuvant chemotherapy on prognostic markers. The present study explored the association between G-CSF and changes in cancer antigen (CA)27.29 and circulating tumor cell (CTC) levels during therapy., Patients and Methods: A total of 3754 node-positive or high-risk node-negative early-stage breast cancer patients were treated within the SUCCESS-A trial (simultaneous study of gemcitabine-docetaxel combination adjuvant treatment, as well as extended bisphosphonate and surveillance-trial). CA27.29 and CTCs were determined before the start and within 6 weeks after the end of chemotherapy., Results: Overall, 1324 of the 2646 patients (50.0%) available for analysis had ≥ 1 G-CSF applications during chemotherapy. G-CSF application was significantly associated with CA27.29 status before and after chemotherapy (χ 2  = 30.6, df = 3; P < .001), because 238 patients (18.0%) with G-CSF treatment but only 146 (11.0%) without G-CSF treatment switched from a negative CA27.29 status before to a positive CA27.29 status after chemotherapy. In addition, patients with G-CSF application showed a significantly greater increase in CA27.29 levels after chemotherapy compared with patients without any G-CSF application during chemotherapy (Mann-Whitney U test; Z = -7.81, P < .001). No significant association was found between G-CSF application and CTC status before or after chemotherapy (χ 2  = 1.2, df = 3; P = .75)., Conclusion: Cautious interpretation is needed regarding elevated levels of MUC-1-derived tumor markers such as CA27.29 shortly after adjuvant chemotherapy when G-CSF has been given, because G-CSF treatment was associated with increased CA27.29 levels after chemotherapy., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Importance: Circulating tumor cells (CTCs) represent the liquid component of solid tumors and are a surrogate marker for residual cancer burden. Although CTC status is prognostic of recurrence and death in breast cancer, its role in guiding clinical management remains unknown., Objective: To determine whether CTC status is predictive of radiotherapeutic benefit in early-stage breast cancer., Design, Setting, and Participants: The cohort studies in the present analysis included patients with stages pT1 to pT2 and pN0 to pN1 breast cancer and known CTC status from the National Cancer Database (NCDB) and the multicenter phase 3 SUCCESS clinical trial. Multivariable parametric accelerated failure time models were used to evaluate the association of CTC status and radiotherapy (RT) with survival outcomes. Data were collected from January 1, 2004, through December 31, 2014, from the NCDB cohort. The SUCCESS trial collected data from September 1, 2005, through September 30, 2013. The analyses were completed from November 1, 2016, through December 17, 2017., Exposure: Adjuvant RT., Main Outcomes and Measures: Overall survival (OS), local recurrence-free survival (LRFS), and disease-free survival (DFS)., Results: A total of 1697 patients from the NCDB (16 men [0.9%] and 1681 women [99.1%]; median age, 63 years; interquartile range, 53-71 years) and 1516 patients from the SUCCESS clinical trial (median age, 52 years; interquartile range, 45-60 years) were identified. Circulating tumor cells were detected in 399 patients (23.5%) in the NCDB cohort and 294 (19.4%) in the SUCCESS cohort. The association of RT with survival was dependent on CTC status within the NCDB cohort (4-year OS, 94.9% for CTC-positive RT vs 88.0% for CTC-positive non-RT vs 93.9% for CTC-negative RT vs 93.4% for CTC-negative non-RT groups; P < .001) and 5-year DFS within the SUCCESS cohort (88.0% for CTC-positive RT vs 75.2% for CTC-positive non-RT vs 92.3% for CTC-negative RT vs 88.3% for CTC-negative non-RT; P = .04). In the NCDB cohort, RT was associated with longer OS in patients with CTCs (time ratio [TR], 2.04; 95% CI, 1.55-2.67; P < .001), but not in patients without CTCs (TR, 0.80; 95% CI, 0.52-1.25; P = .33). In the SUCCESS cohort, CTC-positive patients treated with RT exhibited longer LRFS (TR, 2.73; 95% CI, 1.62-4.80; P < .001), DFS (TR, 3.03; 95% CI, 2.22-4.13; P < .001), and OS (TR, 1.83; 95% CI, 1.23-2.72; P = .003). Among patients from both cohorts who underwent breast-conserving surgery, RT was associated with longer OS in patients with CTCs (TR, 4.37; 95% CI, 2.71-7.05; P < .001) but not in patients without CTCs (TR, 0.87; 95% CI, 0.47-1.62; P = .77). Radiotherapy was not associated with OS after mastectomy in CTC-positive or CTC-negative patients., Conclusions and Relevance: Treatment with RT was associated with longer LRFS, DFS, and OS in patients with early-stage breast cancer and detectable CTCs. These results are hypothesis generating; a prospective trial evaluating CTC-based management for RT after breast-conserving surgery in women with early-stage breast cancer is warranted.

Background: Optimal choice and sequence of endocrine treatment following adjuvant chemotherapy in postmenopausal early breast cancer patients are still under discussion and treatment stratification factors are missing., Patients and Methods: Postmenopausal women with HER2-negative, hormone receptor-positive tumors and persisting circulating tumor cells (CTCs; assessed using the FDA-approved CellSearch® System, Janssen Diagnostics, LLC) after chemotherapy were randomized to 2 years of tamoxifen followed by 3 years of exemestane (tamoxifen-exemestane group, n = 54) or 5 years of exemestane (exemestane-only group, n = 54). CTCs were again assessed after the first 2 years of endocrine treatment. In addition, safety data were compared between the 2 groups., Results: The 2 groups were well-balanced with regard to baseline characteristics. The CTC clearance rate after 2 years was 89% in the exemestane-only group and 97% in the tamoxifen-exemestane group (exact Fisher test, p = 0.36). The safety profile showed good tolerability with few grade 3 or 4 adverse events in both groups., Conclusion: The similar CTC clearance rate after 2 years of endocrine therapy with exemestane or tamoxifen, and the safety profiles obtained may indicate comparable efficacy and tolerability of both endocrine treatment regimens. However, these results have to be confirmed by final survival and safety analysis., (© 2018 S. Karger GmbH, Freiburg.)

During intravasation, circulating tumor cells (CTCs) detach from the epithelium of origin and begin the epithelial-to-mesenchymal transition (EMT) process, where they lose epithelial features and pass through the endothelium to enter circulation. Although detachment from the extracellular matrix is a strong source of metabolic stress, which induces anoikis, CTCs can survive. Recently, the tumor suppressor liver kinase B1 (LKB1) has gained attention for its role as a proto-oncogene in restoring the correct ATP/AMP ratio during metabolic stress. The aim of this study was to assess LKB1 expression in epithelial-negative CTCs isolated from patients with metastatic breast cancer and to characterize its possible association with EMT and stemness features. Transcriptome analysis of EpCAM-negative CTCs indicated that over 25% of patients showed enhanced LKB1 levels, while almost 20% of patients showed enhanced levels of an EMT transcription factor known as ZEB1. Transcriptome and immunofluorescence analyses showed that patients with enhanced LKB1 were correspondingly ZEB1 negative, suggesting complementary activity for the two proteins. Only ZEB1 was significantly associated with cancer stem cell (CSC) markers. Neither LKB1 nor ZEB1 upregulation showed a correlation with clinical outcome, while enhanced levels of stemness-associated CD44 correlated with a lower progression-free and overall survival. Ex vivo models showed that MDA-MB-231, a mesenchymal tumor cell line, grew in suspension only if LKB1 was upregulated, but the MCF-7 epithelial cell line lost its ability to generate spheroids and colonies when LKB1 was inhibited, supporting the idea that LKB1 might be necessary for CTCs to overcome the absence of the extracellular matrix during the early phases of intravasation. If these preliminary results are confirmed, LKB1 will become a novel therapeutic target for eradicating metastasis-initiating CTCs from patients with primary breast cancer., (© 2017 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.)

Background: Use of anthracycline-based chemotherapy in patients with early breast cancer (EBC) has been well-established but is often associated with cardiotoxicity. Based on data suggesting a limited benefit of anthracyclines in human epidermal growth factor receptor 2 (HER2)-negative patients, the Simultaneous Study of Docetaxel Based Anthracycline Free Adjuvant Treatment Evaluation, as well as Life Style Intervention Strategies (SUCCESS) C study randomized patients to either anthracycline-containing or anthracycline-free chemotherapy. Given the proven prognostic value of circulating tumor cells (CTCs) in EBC, we compared the prevalence of CTCs after chemotherapy between both treatment arms for a preliminary efficacy assessment., Methods: The SUCCESS C trial (NCT00847444) is an open-label, phase III study randomizing 3547 patients with HER2-negative EBC to either 3 cycles of epirubicin, 5-fluorouracil, and cyclophosphamide followed by 3 cycles of docetaxel (FEC-DOC) or 6 cycles of docetaxel and cyclophosphamide (DOC-C). CTC status was prospectively evaluated in hormone receptor-positive patients at the time of last chemotherapy cycle using the US Food and Drug Administration-approved CellSearch System (Janssen Diagnostics)., Results: Data on CTC status were available for 1766 patients. Overall, CTCs were found in 221 (12.5%) patients. Univariate analyses revealed that presence of CTCs at time of last chemotherapy cycle was not significantly associated with tumor or patient characteristics (all P > .1). There was no significant difference with respect to presence of CTCs between patients randomized to FEC-DOC or DOC-C (11.5% vs. 13.6%; P = .18)., Conclusions: The comparable prevalence of CTCs at the time of last chemotherapy cycle may indicate that anthracycline-free chemotherapy is equally effective to anthracycline-containing chemotherapy in HER2-negative, hormone receptor-positive EBC. However, efficacy data from the final survival analysis of SUCCESS C have to be awaited to confirm these preliminary findings., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: HER2 is one of the predominant therapeutic targets in breast cancer. The metastatic selection process may lead to discrepancies between the HER2 status of the primary tumor and circulating tumor cells (CTCs). This study analyzed the HER2 status of CTCs in patients with HER2-positive primary breast cancer at the time of diagnosis. Aim of the study was to assess potential discordance of HER2 status between primary tumor and CTCs, as this may have important implications for the use of HER2-targeted therapy., Methods: The number and HER2 status of CTCs out of 30ml peripheral blood were assessed in 642 patients using the CellSearch System (Janssen Diagnostics, USA). The cutoff for CTC positivity was the presence of at least 1 CTC, and the cutoff for HER2 positivity of CTCs was the presence of at least 1 CTC with a strong HER2 staining., Results: 258 (40.2%) of the 642 patients were positive for CTCs (median 2; range 1-1,689). 149 (57.8%) of these 258 patients had at least 1 CTC with strong HER2 staining. The presence of HER2-positive CTCs was not associated with tumor size (p = 0.335), histopathological grading (p = 0.976), hormone receptor status (ER: p = 0.626, PR: p = 0.263) or axillary lymph node involvement (p = 0.430). Overall, 83 (32.2%) of the CTC-positive patients exclusively had CTCs with strong HER2 staining, whereas 31 (12.0%) had only CTCs with negative HER2 staining. Within-sample variation in the HER2 status of CTCs was found in 86 (57.8%) of the 149 patients with more than 1 CTC., Conclusion: This study demonstrated that discordance between the HER2 expression of CTCs and that of the primary tumor frequently occurs in early breast cancer. Future follow-up evaluation will assess whether this discrepancy may contribute to trastuzumab resistance.