HER2 status of circulating tumor cells in patients with metastatic breast cancer: a prospective, multicenter trial

Clinical challenges in the molecular characterization of circulating tumour cells in breast cancer

Blood testing for circulating tumour cells (CTC) has emerged as one of the hottest fields in cancer research. CTC detection and enumeration can serve as a 'liquid biopsy' and an early marker of response to systemic therapy, whereas their molecular characterisation has a strong potential to be translated to individualised targeted treatments and spare breast cancer (BC) patients unnecessary and ineffective therapies. Different analytical systems for CTC detection and isolation have been developed and new areas of research are directed towards developing novel assays for CTC molecular characterisation. Molecular characterisation of single CTC holds considerable promise for predictive biomarker assessment and to explore CTC heterogeneity. The application of extremely powerful next-generation sequencing technologies in the area of CTC molecular characterisation in combination with reliable single CTC isolation opens new frontiers for the management of patients in the near future. This review is mainly focused on the clinical potential of the molecular characterisation of CTC in BC.

Presence of EpCAM-positive circulating tumor cells as biomarker for systemic disease strongly correlates to survival in patients with hepatocellular carcinoma

Current imaging technologies do not sufficiently detect micrometastasis and therefore do not allow adequate stratification of patients with hepatocellular carcinoma (HCC) for curative or systemic therapy. In HCC, presence of stem cell-like, epithelial cell adhesion molecule (EpCAM)-positive cells correlates with tumor aggressiveness and formation of metastasis. Therefore, we investigated the prognostic relevance of EpCAM-positive circulating tumor cells (CTCs) in patients with HCC. Blood from 78 patients (19 patients in the control cohort and 59 patients with HCC) was tested for CTCs with the CellSearch™ system. Correlation analysis to overall survival (OS), the Barcelona Clinic Liver Cancer (BCLC) staging system, macroscopic and microscopic vascular invasion and alpha-fetoprotein (AFP) levels were performed. We detected ≥1 CTC in 18/59 HCC patients and in 1/19 patients with cirrhosis or benign hepatic tumor (p = 0.026). OS was significantly shorter (460 vs. 746 days) in the CTC-positive cohort (p = 0.017). Comparing BCLC stages, significant differences in CTC detection rates were also observed: BCLC stages A 1/9, B 6/31 and C 11/19 (p = 0.006). Ten of 18 patients with macroscopic and 10/16 patients with microscopic vascular invasion exhibited positive findings in CTC testing (p = 0.004 and p = 0.006). Furthermore, CTC results correlated to AFP (cutoff > 400 ng/mL) levels (p = 0.050). Our study demonstrates frequent presence of EpCAM-positive CTC in patients with intermediate or advanced HCC and its prognostic value for OS with possible implications for future treatment stratification.

Microcavity array system for size-based enrichment of circulating tumor cells from the blood of patients with small-cell lung cancer

In this study, we present a method for efficient enrichment of small-sized circulating tumor cells (CTCs) such as those found in the blood of small-cell lung cancer (SCLC) patients using a microcavity array (MCA) system. To enrich CTCs from whole blood, a microfabricated nickel filter with a rectangular MCA (10(4) cavities/filter) was integrated with a miniaturized device, allowing for the isolation of tumor cells based on differences in size and deformability between tumor and blood cells. The shape and porosity of the MCA were optimized to efficiently capture small tumor cells on the microcavities under low flow resistance conditions, while allowing other blood cells to effectively pass through. Under optimized conditions, approximately 80% of SCLC (NCI-H69 and NCI-H82) cells spiked in 1 mL of whole blood were successfully recovered. In clinical samples, CTCs were detectable in 16 of 16 SCLC patients. In addition, the number of leukocytes captured on the rectangular MCA was significantly lower than that on the circular MCA (p < 0.001), suggesting that the use of the rectangular MCA diminishes a considerable number of carryover leukocytes. Therefore, our system has potential as a tool for the detection of CTCs in small cell-type tumors and detailed molecular analyses of CTCs.

Monitoring apoptosis and Bcl-2 on circulating tumor cells in patients with metastatic breast cancer

BACKGROUND

Enumeration of circulating tumor cells (CTC) from whole blood permits monitoring of patients with breast carcinoma. Analysis of apoptosis & Bcl-2 expression in CTC might add additional prognostic and predictive information. We estimated the degree of these markers in CTC from patients being treated for metastatic breast cancer.

METHODS

Eighty-three evaluable patients initiating a new therapy for metastatic breast cancer were enrolled. Whole blood was collected at baseline, at one of three short term time windows (24, 48, or 72 h) after initiating treatment, and at first follow-up (3-5 weeks). CTC were isolated, enumerated, and expression of M30 and Bcl2 was determined using the CellSearch(®) System.

RESULTS

At baseline, window, and 3-5 weeks post-treatment, 41/80 (51%), 40/80 (50%) and 21/75 (28%) patients had ≥5 CTC, respectively. At baseline, the proportion of CTC-apoptosis (M30) was inversely correlated with CTC number, and modestly inversely correlated with CTC-Bcl-2. As expected, higher CTC levels at baseline or first follow-up were associated with worse prognosis. Surprisingly, in patients with elevated CTC, higher levels of CTC-apoptosis were associated with worse prognosis, while higher CTC-Bcl-2 levels correlated with better outcomes.

CONCLUSIONS

CTC apoptosis and expression of Bcl-2 can be analytically determined in patients with metastatic breast cancer and may have biological and clinical implications. Characterization of CTC for these and other markers could further increase the utility of CTC monitoring patients in clinical investigations of new anti-neoplastic agents.

Clinical application of circulating tumor cells in breast cancer: overview of the current interventional trials

In 2004, circulating tumor cells (CTC) enumeration by the CellSearch® technique at baseline and during treatment was reported to be associated with prognosis in metastatic breast cancer patients. In 2008, the first evidence of the impact of CTC detection by this technique on survival of cM0(i+) patients were reported. These findings were confirmed by other non-interventional studies, whereas CTC were also investigated as a surrogate for tumor biology, mainly for HER2 expression/amplification. The aim of this report is to present the current prospective large interventional studies that have been specifically designed to demonstrate that CTC enumeration/characterization may improve the management of breast cancer patients: STIC CTC METABREAST (France) and Endocrine Therapy Index (USA) assess the CTC-guided hormone therapy vs chemotherapy decision in M1 patients; SWOG0500 (USA) and CirCe01 (France) assess the CTC count changes during treatment in metastatic patients; DETECT III (M1 patients, Germany) and Treat CTC (cM0(i+) patients, European Organization for Research and Treatment of Cancer/Breast International Group) assess the use of anti-HER2 treatments in HER2-negative breast cancer patients selected on the basis of CTC detection/characterization. These trials have different designs in various patient populations but are expected to be the pivotal trials for CTC implementation in the routine management of breast cancer patients.

Circulating tumour cells and cell-free DNA as tools for managing breast cancer

Circulating blood biomarkers promise to become non-invasive real-time surrogates for tumour tissue-based biomarkers. Circulating biomarkers have been investigated as tools for breast cancer diagnosis, the dissection of breast cancer biology and its genetic and clinical heterogeneity, prognostication, prediction and monitoring of therapeutic response and resistance. Circulating tumour cells and cell-free plasma DNA have been analysed in retrospective studies, and the assessment of these biomarkers is being incorporated into clinical trials. As the scope of breast cancer intratumour genetic heterogeneity unravels, the development of robust and standardized methods for the assessment of circulating biomarkers will be essential for the realization of the potentials of personalized medicine. In this Review, we discuss the current status of blood-born biomarkers as surrogates for tissue-based biomarkers, and their burgeoning impact on the management of patients with breast cancer.

Noninvasive detection of HER2 amplification with plasma DNA digital PCR

PURPOSE

Digital PCR is a highly accurate method of determining DNA concentration. We adapted digital PCR to determine the presence of oncogenic amplification through noninvasive analysis of circulating free plasma DNA and exemplify this approach by developing a plasma DNA digital PCR assay for HER2 copy number.

EXPERIMENTAL DESIGN

The reference gene for copy number assessment was assessed experimentally and bioinformatically. Chromosome 17 pericentromeric probes were shown to be suboptimal, and EFTUD2 at chromosome position 17q21.31 was selected for analysis. Digital PCR assay parameters were determined on plasma samples from a development cohort of 65 patients and assessed in an independent validation cohort of plasma samples from 58 patients with metastatic breast cancer. The sequential probability ratio test was used to assign the plasma DNA digital PCR test as being HER2-positive or -negative in the validation cohort.

RESULTS

In the development cohort, the HER2:EFTUD2 plasma DNA copy number ratio had a receiver operator area under the curve (AUC) = 0.92 [95% confidence interval (CI), 0.86-0.99, P = 0.0003]. In the independent validation cohort, 64% (7 of 11) of patients with HER2-amplified cancers were classified as plasma digital PCR HER2-positive and 94% (44 of 47) of patients with HER2-nonamplified cancers were classified as digital PCR HER2-negative, with a positive and negative predictive value of 70% and 92%, respectively.

CONCLUSION

Analysis of plasma DNA with digital PCR has the potential to screen for the acquisition of HER2 amplification in metastatic breast cancer. This approach could potentially be adapted to the analysis of any locus amplified in cancer.

Circulating tumor cells in HER2-positive metastatic breast cancer patients: a valuable prognostic and predictive biomarker

BACKGROUND

This study was initiated to investigate the prognostic significance of circulating tumor cell (CTC) enumeration and the predictive value of CTC HER2 expression for efficient anti-HER2 therapy in HER2-positive metastatic breast cancer (MBC) patients.

METHODS

Sixty HER2-positive MBC patients were enrolled in the present study. Before the initiation of systemic treatment, CTCs from 7.5 ml of blood were analyzed using the CellSearch system. The progression-free survival (PFS) of the patients was estimated using Kaplan-Meier survival curves.

RESULTS

CTCs were detected in 45% (27/60) of the patients, who had shorter median PFS than those without CTCs (2.5 vs. 7.5 months, P=0.0125). Furthermore, referring to the standard HER2 testing that uses immunohistochemistry (IHC), we proposed a CTC HER2-positive criterion, defined as >30% of CTCs over-expressing HER2. Among patients undergoing anti-HER2 therapy, those with HER2-positive CTCs had longer PFS (8.8 vs. 2.5 months, P=0.002). Among patients with HER2-positive CTCs, the median PFS for those receiving anti-HER2 therapy was significantly longer than those who were not (8.8 vs. 1.5 months, P=0.001). Notably, up to 52% (14/27) of the HER2-positive patients were CTC HER2-negative, and anti-HER2 therapy did not significantly improve the median PFS in these patients (2.5 vs. 0.9 months, P=0.499).

CONCLUSIONS

Our findings underscore the necessity of a comprehensive CTC analysis, which may provide valuable prognostic and predictive information for optimizing individually tailored therapies in HER2-positive MBC patients. To test this idea, additional large cohort, multi-center and prospective clinical trials are needed.

Progress in using circulating tumor cell information to improve metastatic breast cancer therapy

Circulating tumor cells (CTCs) were discovered nearly 150 years ago but have only recently been recognized as a feature of most solid tumors due to their extremely low concentration in the peripheral circulation. Several technologies have been developed to isolate and analyze CTCs, which can now be routinely accessed for clinical information. The most mature of these (the CELLSEARCH system) uses immunomagnetic selection of epithelial cell adhesion molecule to isolate CTCs for analysis. Studies using this system have demonstrated that categorization of patients into high and low CTC groups using a validated decision point is prognostic in patients with metastatic breast, colorectal, or prostate cancer. Initial attempts to use CTC counts to guide therapeutic decisions appeared to yield positive results and key concepts in clinical application of CTC information, including the CTC cutoff, predictive value in disease subtypes, and comparison to current evaluation methods, have been demonstrated. Clinical studies of the impact of CTC counts in routine clinical practice are ongoing; however, recent published evidence on the clinical use of CTCs in metastatic breast cancer continues to support these concepts, and experience in the community oncology setting also suggests that CTC enumeration can be useful for therapy management.

The HER2 status of disseminated tumor cells in the bone marrow of early breast cancer patients is independent from primary tumor and predicts higher risk of relapse

Overexpression of the HER2-receptor in early breast cancer (EBC) patients is associated with aggressive tumor behavior. However, women suffering from HER2-positive EBC benefit from trastuzumab treatment. As the HER2 status of the primary tumor may differ from that of disseminated tumor cells (DTC) in bone marrow (BM), the aim of this study was (1) to compare the HER2 status of the primary tumor (prim-HER2-status) with that of DTC (DTC-HER2-status) and (2) to analyze the influence of the DTC-HER2-status on patient survival. For this purpose, BM aspirates from 569 EBC patients were analyzed for the presence of DTC. The DTC-HER2-status was identified by a double-staining procedure against cytokeratin and the HER2-receptor. DTC were detected in 151 (27 %) patients. The concordance between the HER2 status of DTC and the primary tumor was 51 %. In patients with detectable DTC, mean disease-free survival was 77.44 (95 % CI 74.72-80.17) months for DTC-HER2-negative and 55.15 (95 % CI 48.57-61.79) months for DTC-HER2-positive patients (p = 0.044). The multivariate analysis showed that the DTC-HER2-status was an independent predictor of disease-free survival. In conclusion, the presence of HER2-positive DTC in EBC patients is associated with an increased risk of relapse. Due to the low concordance between the HER2 status of the primary tumor and DTC, only a minority (13 %) of the DTC-HER2-positive patients was treated with trastuzumab. These patients might, however, benefit from HER2-directed therapy.

Comparison of three molecular assays for the detection and molecular characterization of circulating tumor cells in breast cancer

Introduction

Comparison studies between different analytical methodologies for circulating tumor cells (CTC) detection and molecular characterization are urgently needed, since standardization of assays is essential before their use in clinical practice.

Methods

We compared three different CTC molecular assays. To avoid discrepancies due to pre-analytical errors we used the same cDNAs throughout our study. CTC were isolated using anti-EpCAM and anti-MUC1 coated magnetic beads from 2 × 5 ml of peripheral blood of 254 early and 51 metastatic breast cancer patients and 30 healthy individuals. The same cDNAs were analyzed by: a) singleplex RT-qPCR assay for CK-19; b) multiplex RT-qPCR for CK-19, HER-2, MAGE- A3, and PBGD; and c) a commercially available molecular assay (AdnaTest BreastCancer) for GA733-2, MUC-1, HER-2 and beta-actin.

Results

In early breast cancer, CK-19 RT-qPCR, multiplex RT-qPCR and the AdnaTest, were positive for the presence of CTC in 14.2%, 22.8% and 16.5% subjects, respectively. The concordance between the AdnaTest and CK-19 RT-qPCR was 72.4% while between the AdnaTest and multiplex RT-qPCR was 64.6%. In patients with overt metastasis, CK-19 RT-qPCR, multiplex RT-qPCR and the AdnaTest were positive in 41.2%, 39.2% and 54.9% patients, respectively. The concordance between the AdnaTest and CK-19 RT-qPCR was 70.6% while between the AdnaTest and multiplex RT-qPCR was 68.6%.

Conclusions

All CTC assays gave similar results in about 70% of cases. Better agreement was found in the metastatic setting, possibly explained by the higher tumor load in this group. Discordances could be attributed to the different gene transcripts used to evaluate CTC positivity. Our results indicate the importance of CTC heterogeneity for their detection by different analytical methodologies.

Discordance in HER2 gene amplification in circulating and disseminated tumor cells in patients with operable breast cancer

Human epidermal growth factor receptor 2 (HER2) gene amplification in circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) might be useful for modifying Herceptin therapy in breast cancer. In the process of investigating the utility of a microfluidic platform for detecting HER2 gene amplification in these cells, we observed novel results on discordance of HER2 status. Peripheral blood (8.5 mL) and bone marrow (BM) (7.5-10 mL) were collected prospectively from patients with clinical stages I-IV breast cancer. Mononuclear cells were recovered, stained with cytokeratin (CK), CD45, and DAPI, and processed through microfluidic channels for fluorescence in situ hybridization (FISH). A ratio of HER2:CEP17 >2 in any CK+/CD45 or CK-/CD45 cell was regarded as positive for HER2 gene amplification. Peripheral blood from 95 patients and BM from 78 patients were studied. We found CK+/CD45-/DAPI+ CTCs in 27.3% of patients. We evaluated HER2 gene amplification by FISH in 88 blood and 78 BM specimens and found HER2+ CTCs in 1 of 9 (11.1%) and HER2+ DTCs (27.2%) in 3 of 11 patients with HER2+ primary tumor. Among patients with a HER2- primary tumor, 5 of 79 had HER2+ CTCs (6.3%) and 14 of 67 had HER2+ DTCs (20.8%). The overall rate of discordance in HER2 status was 15% between primary tumor and CTCs and 28.2% between primary tumor and DTCs. HER2 was amplified in CTCs and DTCs in a portion of both HER2+ and HER2- primary tumors. HER2 discordance was more frequent for DTCs. The clinical implications of evaluating HER2 status in CTCs and DTCs in breast cancer needs to be established in prospective clinical trials. The cell enrichment and extraction microfluidic technology provides a sensitive platform for evaluation of HER2 gene amplification in CTCs and DTCs.

Detection and recovery of circulating colon cancer cells using a dielectrophoresis-based device: KRAS mutation status in pure CTCs

The characterization of circulating tumor cells (CTCs) could substantially improve the management of cancer patients. However, their study is still a matter of debate, often due to lymphocyte contamination. In the present paper, an investigation of CTCs was carried out for the first time using DEPArray, a dielectrophoresis-based platform able to detect and sort pure CTCs. Analyses were conducted on peripheral blood (PB) samples from patients with metastatic colon cancer. After 100% pure cell recovery and whole genome amplification, KRAS gene mutation of CTCs was screened and compared to gene status in the primary tumor tissue. CTCs were found in 21 colon cancer patients (52.5%), with more than three tumor cells per 7.5 ml. KRAS gene mutation analysis, showed a mutational concordance between CTCs and primary tumor in 50% of matched cases. The present study demonstrates for the first time the feasibility of analyzing at the molecular level pure CTCs avoiding lymphocyte contamination using an innovative instrumentation, and a KRAS discordance between CTCs and primary tissue. Our results present dielectrophoresis-based procedures as a new standard in single cell analysis and recovery and invite careful reflection on the value of CTCs characterization.

The prognostic impact of circulating tumor cells in subtypes of metastatic breast cancer

The detection of circulating tumor cells (CTCs) in the peripheral blood of metastatic breast cancer (MBC) patients is an independent marker of prognosis. This large prospective multicenter study aimed to assess the impact of CTCs on overall survival (OS) and progression free survival (PFS) in patients with predefined molecular subgroups of MBC. To this end, 468 MBC patients were divided into three subgroups based on immunohistochemical staining of the primary tumor: (1) hormone receptor-positive/HER2-negative (HorR+/HER2-), (2) HER2-positive (HER2+), and (3) HorR-negative/HER2-negative (HorR-/HER2-) patients. CTC status (<5 CTCs/7.5 ml blood (CTC-negative) vs. ≥5 CTCs/7.5 ml blood (CTC-positive)) was determined using the CellCearch(®) system before patients started a new line of therapy. At baseline, 205 (42 %) patients were CTC-positive. On multivariate analysis, CTC-positivity was an independent prognostic factor for shorter PFS and OS. In HorR+/HER2- patients, median PFS [95 % CI] of CTC-negative versus CTC-positive patients was 8.60 [5.93-11.27] versus 4.33 [3.29-5.38] months (p < 0.001), in HER2+ patients 7.60 [5.40-9.79] versus 6.60 [4.20-9.00] months (p = 0.477) and in HorR-/HER2- patients 5.83 [5.09-6.78] versus 3.05 [1.81-4.29] months (p < 0.001), respectively. Median OS [95 % CI] of CTC-negative versus CTC-positive patients was as follows: not reached by either in the HorR+/HER2- subgroup (p < 0.001), not reached versus 18.07 [11.10-25.05] months (p = 0.001) in the HER2+ subgroup, and not reached versus 8.57 [4.07-13.07] months in the HorR-/HER2- subgroup (p = 0.001). In conclusion, our results strongly confirm the independent prognostic value of CTC enumeration in MBC patients. In contrast to recent reports, there was no association between primary tumor-based molecular subgroups and the impact of CTC status on OS. Hence, CTC status may help to identify patients who require aggressive therapy, especially among those with triple-negative MBC.

Change of HER2 status in metastatic esophageal adenocarcinoma: heterogeneity of the disease? Case report and review of literature

A case report is presented of a patient diagnosed with esophageal adenocarcinoma with an extremely aggressive clinical course. Discordant expression of HER2 in longitudinally-collected biopsies was noted, with the original biopsy testing negative and a follow up biopsy testing positive. Upon retest of the original biopsy however, heterogeneity of HER2 expression was found among tumor clones across three distinct fields. The patient did not survive long enough to receive chemotherapy with trastuzumab, which has shown efficacy in tumors with HER2 positive expression. Understanding of the biological heterogeneity of HER2 expression in the primary tumor is crucial to detect HER2 positive clones, which may yield improved patient outcomes.

Heterogeneity of ERα and ErbB2 Status in Cell Lines and Circulating Tumor Cells of Metastatic Breast Cancer Patients

Hormone therapy and anti-ErbB2 therapies are prescribed according to the hormone receptor [estrogen receptor α (ERα)/progesterone receptor] and ErbB2 status of the initial tumor, but it appears that circulating tumor cells (CTCs) and, consequently, the metastatic cells may have a different receptor status. As an attempt to meet the crucial need for identification of the subpopulation of patients that will benefit from more individualized therapies, rapidly evolving therapies should allow a profiling of the tumors and/or of the CTCs. We established a triple fluorescence staining using eight cell lines to visualize the CTCs (cytokeratin detection) and then to define their individual ERα and ErbB2 status. Afterward, we used this method for blood samples from 26 metastatic breast cancer patients. We identified major differences of ERα levels between the cell lines and even within one cell line. For the metastatic patients, we detected and characterized CTCs in 38.5% of the patients with a total of 92 CTCs. We could demonstrate that at least 69.6% of the CTCs exhibit an ERα and/or ErbB2 status different from the status of the primary tumor and that the CTCs from only 30% of the patients had no change of receptor status. Strikingly, heterogeneities of the status, aggregation, and size clearly appear within the CTCs. The data we generated outline the importance of a profiling not only of tumors but also of CTCs to establish individualized treatments. CTCs may then appear as new prognosis and treatment marker for both metastatic and adjuvant breast cancers.

Prognostic value of circulating tumor cells in primary and metastatic breast cancer

In patients with breast cancer, there is evidence correlating the presence of circulating tumor cells (CTCs) with disease-free survival, progression-free survival and overall survival. The detection of CTCs may be useful in gaining a better understanding of the mechanisms of tumor growth and in the improvement of patient management. This review analyzes the prognostic and predictive relevance of CTCs through the principal published studies, cytometric techniques and nucleic acid-based approaches to detect CTCs, phenotypic expression of specific receptors, molecular pathways and genetic signatures for potential tailored therapies.

Prognostic impact of circulating tumor cells assessed with the CellSearch System™ and AdnaTest Breast™ in metastatic breast cancer patients: the DETECT study

Introduction

There is a multitude of assays for the detection of circulating tumor cells (CTCs) but a very limited number of studies comparing the clinical relevance of results obtained with different test methods. The DETECT trial for metastatic breast cancer patients was designed to directly compare the prognostic impact of two commercially available CTC assays that are prominent representatives of immunocytochemical and RT-PCR based technologies.

Methods

In total, 254 metastatic breast cancer patients were enrolled in this prospective multicenter trial. CTCs were assessed using both the AdnaTest Breast Cancer and the CellSearch system according to the manufacturers' instructions.

Results

With the CellSearch system, 116 of 221 (50%) evaluable patients were CTC-positive based on a cut-off level at 5 or more CTCs. The median overall survival (OS) was 18.1 months in CTC-positive patients. (95%-CI: 15.1-22.1 months) compared to 27 months in CTC-negative patients (23.5-30.7 months; p<0.001). This prognostic impact for OS was also significant in the subgroups of patients with triple negative, HER2-positive and hormone receptor-positive/HER2-negative primary tumors. The progression free survival (PFS) was not correlated with CTC status in our cohort receiving different types and lines of systemic treatment (p = 0.197). In multivariate analysis, the presence of CTCs was an independent predictor for OS (HR: 2.7, 95%-CI: 1.6-4.2). When the AdnaTest Breast was performed, 88 of 221 (40%) patients were CTC-positive. CTC-positivity assessed by the AdnaTest Breast had no association with PFS or OS.

Conclusions

The prognostic relevance of CTC detection in metastatic breast cancer patients depends on the test method. The present results indicate that the CellSearch system is superior to the AdnaTest Breast Cancer in predicting clinical outcome in advanced breast cancer.

Trial registration

Current Controlled Trials Registry number ISRCTN59722891.

Considerations in the development of circulating tumor cell technology for clinical use

This manuscript summarizes current thinking on the value and promise of evolving circulating tumor cell (CTC) technologies for cancer patient diagnosis, prognosis, and response to therapy, as well as accelerating oncologic drug development. Moving forward requires the application of the classic steps in biomarker development–analytical and clinical validation and clinical qualification for specific contexts of use. To that end, this review describes methods for interactive comparisons of proprietary new technologies, clinical trial designs, a clinical validation qualification strategy, and an approach for effectively carrying out this work through a public-private partnership that includes test developers, drug developers, clinical trialists, the US Food & Drug Administration (FDA) and the US National Cancer Institute (NCI).

Final results of a multicenter phase II clinical trial evaluating the activity of single-agent lapatinib in patients with HER2-negative metastatic breast cancer and HER2-positive circulating tumor cells. A proof-of-concept study

This multicenter phase II trial was designed to evaluate the activity of lapatinib in metastatic breast cancer patients with HER2-negative primary tumors and HER2-positive circulating tumor cells (CTCs). In this study MBC patients with HER2-negative primary tumors and HER2-positive CTCs previously treated with at least a first-line therapy for metastatic disease received lapatinib 1500 mg/day. The CellSearch System® was used for CTCs isolation and bio-characterization. HER2 status was assessed on CTCs by immunofluorescence. A case was defined as CTCs positive if ≥2 CTC/7.5 ml of blood were isolated and HER2-positive if ≥50% of CTCs were HER2-positive. 139 HER2-negative patients were screened, 96 patients were positive for CTCs (mean number of CTCs: 85; median number of CTCs: 19; range 2-1637). Seven of the 96 patients (7%) had ≥50% HER2-positive CTCs and were eligible for treatment with lapatinib. No objective tumor responses occurred in this population. In one patient, disease stabilization lasting 254 days (8.5 months) was observed. From the findings of this study, we concluded that a subset of patients with a HER2-negative primary tumor presents HER2-positive CTCs during disease progression, although the HER2 shift rate seems to be lower than previously reported. Despite the lack of objective response, the durable disease stabilization observed in one patient cannot rule out the hypothesis that lapatinib may have some activity in this patient population. However, considering that only 1/139 screened patients may potentially have derived benefit from this approach, future trials designed according to the presented strategy cannot be recommended.

Strategies for the discovery and development of therapies for metastatic breast cancer

Nearly all deaths caused by solid cancers occur as a result of metastasis--the formation of secondary tumours in distant organs such as the lungs, liver, brain and bone. A major obstruction to the development of drugs with anti-metastatic efficacy is our fragmented understanding of how tumours 'evolve' and metastasize, at both the biological and genetic levels. Furthermore, although there is significant overlap in the metastatic process among different types of cancer, there are also marked differences in the propensity to metastasize, the extent of metastasis, the sites to which the tumour metastasizes, the kinetics of the process and the mechanisms involved. Here, we consider the case of breast cancer, which has some marked distinguishing features compared with other types of cancer. Considerable progress has been made in the development of preclinical models and in the identification of relevant signalling pathways and genetic regulators of metastatic breast cancer, and we discuss how these might facilitate the development of novel targeted anti-metastatic drugs.

Single cell profiling of circulating tumor cells: transcriptional heterogeneity and diversity from breast cancer cell lines

Background

To improve cancer therapy, it is critical to target metastasizing cells. Circulating tumor cells (CTCs) are rare cells found in the blood of patients with solid tumors and may play a key role in cancer dissemination. Uncovering CTC phenotypes offers a potential avenue to inform treatment. However, CTC transcriptional profiling is limited by leukocyte contamination; an approach to surmount this problem is single cell analysis. Here we demonstrate feasibility of performing high dimensional single CTC profiling, providing early insight into CTC heterogeneity and allowing comparisons to breast cancer cell lines widely used for drug discovery.

Methodology/Principal Findings

We purified CTCs using the MagSweeper, an immunomagnetic enrichment device that isolates live tumor cells from unfractionated blood. CTCs that met stringent criteria for further analysis were obtained from 70% (14/20) of primary and 70% (21/30) of metastatic breast cancer patients; none were captured from patients with non-epithelial cancer (n = 20) or healthy subjects (n = 25). Microfluidic-based single cell transcriptional profiling of 87 cancer-associated and reference genes showed heterogeneity among individual CTCs, separating them into two major subgroups, based on 31 highly expressed genes. In contrast, single cells from seven breast cancer cell lines were tightly clustered together by sample ID and ER status. CTC profiles were distinct from those of cancer cell lines, questioning the suitability of such lines for drug discovery efforts for late stage cancer therapy.

Conclusions/Significance

For the first time, we directly measured high dimensional gene expression in individual CTCs without the common practice of pooling such cells. Elevated transcript levels of genes associated with metastasis NPTN, S100A4, S100A9, and with epithelial mesenchymal transition: VIM, TGFß1, ZEB2, FOXC1, CXCR4, were striking compared to cell lines. Our findings demonstrate that profiling CTCs on a cell-by-cell basis is possible and may facilitate the application of ‘liquid biopsies’ to better model drug discovery.

Circulating tumor cells in immunohistochemical subtypes of metastatic breast cancer: lack of prediction in HER2-positive disease treated with targeted therapy

BACKGROUND

Circulating tumor cells (CTCs) are associated with inferior prognosis in metastatic breast cancer (MBC). We hypothesized that the relationship between CTCs and disease subtype would provide a better understanding of the clinical and biologic behavior of MBC.

PATIENTS AND METHODS

We retrospectively analyzed 517 MBC patients treated at a single institution. Subtypes of primary tumors were analyzed by immunohistochemical (IHC) or fluorescent in situ hybridization analyses and CTCs were enumerated by CellSearch(®) at starting a new therapy. Overall survival (OS) and progression-free survival durations for each IHC subtype were determined.

RESULTS

At a median follow-up of 24.6 months, 276 of 517 (53%) patients had died. The median OS for patients with <5 and ≥ 5 CTCs were 32.4 and 18.3 months, respectively (P < 0.001). Except in HER2+ patients, the prognostic value of CTCs was independent of disease subtype and disease site.

CONCLUSIONS

In this large retrospective study, CTCs were strongly predictive of survival in all MBC subtypes except HER2+ patients who had been treated with targeted therapy. Our results clearly demonstrate the value of enumerating CTCs in MBC and strongly suggest an interesting biological implication in the HER2+ subset of patients that need to be further explored.

Evaluation of circulating tumor cells and circulating tumor DNA in non-small cell lung cancer: association with clinical endpoints in a phase II clinical trial of pertuzumab and erlotinib

PURPOSE

Elevated levels or increases in circulating tumor cells (CTC) portend poor prognosis in patients with epithelial cancers. Less is known about CTCs as surrogate endpoints or their use for predictive biomarker evaluation. This study investigated the utility of CTC enumeration and characterization using the CellSearch platform, as well as mutation detection in circulating tumor DNA (ctDNA), in patients with advanced non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Forty-one patients were enrolled in a single-arm phase II clinical trial of erlotinib and pertuzumab. Peripheral blood was analyzed for CTC enumeration, EGFR expression in CTCs, and detection of oncogenic mutations in CTCs and ctDNA. Changes in CTC levels were correlated with 2[18F]fluoro-2-deoxy-D-glucose-positron emission tomographic (FDG-PET) and computed tomographic (CT) imaging and survival endpoints.

RESULTS

CTCs were detected (≥ 1 CTC) at baseline in 78% of patients. Greater sensitivity for mutation detection was observed in ctDNA than in CTCs and detected mutations were strongly concordant with mutation status in matched tumor. Higher baseline CTC counts were associated with response to treatment by Response Evaluation Criteria in Solid Tumors (RECIST, P = 0.009) and decreased CTC counts upon treatment were associated with FDG-PET and RECIST response (P = 0.014 and P = 0.019) and longer progression-free survival (P = 0.050).

CONCLUSION

These data provide evidence of a correlation between decreases in CTC counts and radiographic response by either FDG-PET or RECIST in patients with advanced NSCLC. These findings require prospective validation but suggest a potential role for using CTC decreases as an early indication of response to therapy and ctDNA for real-time assessment of mutation status from blood.

Concepts of metastasis in flux: the stromal progression model

The ability of tumor cells to leave a primary tumor, to disseminate through the body, and to ultimately seed new secondary tumors is universally agreed to be the basis for metastasis formation. An accurate description of the cellular and molecular mechanisms that underlie this multistep process would greatly facilitate the rational development of therapies that effectively allow metastatic disease to be controlled and treated. A number of disparate and sometimes conflicting hypotheses and models have been suggested to explain various aspects of the process, and no single concept explains the mechanism of metastasis in its entirety or encompasses all observations and experimental findings. The exciting progress made in metastasis research in recent years has refined existing ideas, as well as giving rise to new ones. In this review we survey some of the main theories that currently exist in the field, and show that significant convergence is emerging, allowing a synthesis of several models to give a more comprehensive overview of the process of metastasis. As a result we postulate a stromal progression model of metastasis. In this model, progressive modification of the tumor microenvironment is equally as important as genetic and epigenetic changes in tumor cells during primary tumor progression. Mutual regulatory interactions between stroma and tumor cells modify the stemness of the cells that drive tumor growth, in a manner that involves epithelial-mesenchymal and mesenchymal-epithelial-like transitions. Similar interactions need to be recapitulated at secondary sites for metastases to grow. Early disseminating tumor cells can progress at the secondary site in parallel to the primary tumor, both in terms of genetic changes, as well as progressive development of a metastatic stroma. Although this model brings together many ideas in the field, there remain nevertheless a number of major open questions, underscoring the need for further research to fully understand metastasis, and thereby identify new and effective ways of treating metastatic disease.

FISH-based determination of HER2 status in circulating tumor cells isolated with the microfluidic CEE™ platform

Determination of HER2 status in breast cancer patients is considered standard practice for therapy selection. However, tumor biopsy in patients with recurrent and/or metastatic disease is not always feasible. Thus, circulating tumor cells (CTCs) are an alternative source of tumor cells for analysis of HER2. An antibody cocktail for recovery of variable, high- and low-, EpCAM-expressing tumor cells was developed based on FACS evaluation and then verified by CTC enumeration (based on CK and CD45 staining) with comparison to EpCAM-only and with CellSearch® (n=19). HER2 fluorescence in situ hybridization (FISH) on all (CK+ and CK-) captured cells was compared to HER2 status on the primary tumors (n=54) of patients with late stage metastatic/recurrent breast cancer. Capture of low EpCAM-expressing tumor cells increased from 27% to 76% when using the cocktail versus EpCAM alone, respectively. Overall, CTC detection with the OncoCEE™ platform was better compared to CellSearch® (68% vs. 89%, respectively), and a 93% concordance in HER2 status was observed. HER2 FISH analysis of CK+ and CK- CTCs is feasible using the CEE™ platform. Although larger clinical studies are warranted, the results demonstrate adequate sensitivity and specificity as needed for incorporation into laboratory testing.

Challenges and opportunities in the use of CTCs for companion diagnostic development

Circulating tumor cells offer promise as a surrogate source of cancer cells that can be obtained in real time and may provide opportunities to evaluate predictive biomarkers that can guide treatment decisions. In this review, we consider some of the technical hurdles around CTC numbers and suitability of various CTC capture and analysis platforms for biomarker evaluation. In addition, we consider the potential regulatory hurdles to development of CTC-based diagnostics. Finally, we suggest a path for co-development of anticancer therapeutics with CTC-based diagnostics that could enable clinical validation and qualification of CTC-based assays as companion diagnostics.

DTCs/CTCs in breast cancer: five decades later

Since circulating tumor cells were first reported in 1955, the field has seen major advances in their detection and has established their prognostic impact. Here we review the current evidence for the prognostic and predictive value of circulating tumor cells in metastatic breast cancer. We then evaluate the role of CTCs and DTCs in early stage breast cancer. The weight of the evidence supports the role of CTCs and DTCs as prognostic indicators, however their role in therapy prediction remains unclear. Ongoing trials may provide answers and newer detection methods which improve sensitivity and specificity may have greater impact. At this point, the data does not support incorporation into clinical practice for early breast cancer patients.

HER2-positive DTCs/CTCs in breast cancer

The presence of circulating tumor cells (CTCs) in the blood as well as disseminated tumor cells (DTCs) in the bone marrow of breast cancer patients is associated with a worsened prognosis in the primary as well as in the metastatic situation. Next to their detection, evaluation of human epidermal growth factor receptor (HER2) expression is a valuable feature of CTCs/DTCs. As the HER2 status may change during disease progression CTCs/DTCs might (1) characterize the phenotype of minimal residual disease in the adjuvant setting and (2) serve as a "real time biopsy" of metastatic breast cancer. Phenotyping of CTCs/DTCs will thus help to understand mechanism of resistance to HER2-directed therapy. Moreover, patients that are likely to benefit from HER2-directed therapy despite a HER2-negative primary tumor might be identified. 

Molecular assays for the detection and characterization of CTCs

Molecular characterization for circulating tumor cells (CTCs) can be used to better understand the biology of metastasis, to improve patient management and help to identify novel targets for biological therapies aimed to prevent metastatic relapse. New areas of research are directed towards developing novel sensitive assays for CTC molecular characterization. Towards this direction, molecular detection technologies that take advantage of the extreme sensitivity and specificity of PCR, offer many advantages, such as high sensitivity, specificity, and significant flexibility in the clinical lab setting, in terms of high-throughput analysis, multiplexing, and quality control issues. Using molecular assays, a variety of molecular markers such as multiple gene expression, DNA methylation markers, DNA mutations, and miRNAs have been detected and quantified in CTCs in various cancer types, enabling their molecular characterization. Here, we present the main molecular detection technologies currently used for CTC analysis and molecular characterization.

Circulating tumour cells, their role in metastasis and their clinical utility in lung cancer

Circulating tumour cells (CTCs) have attracted much recent interest in cancer research as a potential biomarker and as a means of studying the process of metastasis. It has long been understood that metastasis is a hallmark of malignancy, and conceptual theories on the basis of metastasis from the nineteenth century foretold the existence of a tumour "seed" which is capable of establishing discrete tumours in the "soil" of distant organs. This prescient "seed and soil" hypothesis accurately predicted the existence of CTCs; microscopic tumour fragments in the blood, at least some of which are capable of forming metastases. However, it is only in recent years that reliable, reproducible methods of CTC detection and analysis have been developed. To date, the majority of studies have employed the CellSearch™ system (Veridex LLC), which is an immunomagnetic purification method. Other promising techniques include microfluidic filters, isolation of tumour cells by size using microporous polycarbonate filters and flow cytometry-based approaches. While many challenges still exist, the detection of CTCs in blood is becoming increasingly feasible, giving rise to some tantalizing questions about the use of CTCs as a potential biomarker. CTC enumeration has been used to guide prognosis in patients with metastatic disease, and to act as a surrogate marker for disease response during therapy. Other possible uses for CTC detection include prognostication in early stage patients, identifying patients requiring adjuvant therapy, or in surveillance, for the detection of relapsing disease. Another exciting possible use for CTC detection assays is the molecular and genetic characterization of CTCs to act as a "liquid biopsy" representative of the primary tumour. Indeed it has already been demonstrated that it is possible to detect HER2, KRAS and EGFR mutation status in breast, colon and lung cancer CTCs respectively. In the course of this review, we shall discuss the biology of CTCs and their role in metastagenesis, the most commonly used techniques for their detection and the evidence to date of their clinical utility, with particular reference to lung cancer.

Highly sensitive proximity mediated immunoassay reveals HER2 status conversion in the circulating tumor cells of metastatic breast cancer patients

Background

The clinical benefits associated with targeted oncology agents are generally limited to subsets of patients. Even with favorable biomarker profiles, many patients do not respond or acquire resistance. Existing technologies are ineffective for treatment monitoring as they provide only static and limited information and require substantial amounts of tissue. Therefore, there is an urgent need to develop methods that can profile potential therapeutic targets with limited clinical specimens during the course of treatment.

Methods

We have developed a novel proteomics-based assay, Collaborative Enzyme Enhanced Reactive-immunoassay (CEER) that can be used for analyzing clinical samples. CEER utilizes the formation of unique immuno-complex between capture-antibodies and two additional detector-Abs on a microarray surface. One of the detector-Abs is conjugated to glucose oxidase (GO), and the other is conjugated to Horse Radish Peroxidase (HRP). Target detection requires the presence of both detector-Abs because the enzyme channeling event between GO and HRP will not occur unless both Abs are in close proximity.

Results

CEER was able to detect single-cell level expression and phosphorylation of human epidermal growth factor receptor 2 (HER2) and human epidermal growth factor receptor 1 (HER1) in breast cancer (BCa) systems. The shift in phosphorylation profiles of receptor tyrosine kinases (RTKs) and other signal transduction proteins upon differential ligand stimulation further demonstrated extreme assay specificity in a multiplexed array format. HER2 analysis by CEER in 227 BCa tissues showed superior accuracy when compared to the outcome from immunohistochemistry (IHC) (83% vs. 96%). A significant incidence of HER2 status alteration with recurrent disease was observed via circulating tumor cell (CTC) analysis, suggesting an evolving and dynamic disease progression. HER2-positive CTCs were found in 41% (7/17) while CTCs with significant HER2-activation without apparent over-expression were found in 18% (3/17) of relapsed BCa patients with HER2-negative primary tumors. The apparent 'HER2 status conversion' observed in recurrent BCa may have significant implications on understanding breast cancer metastasis and associated therapeutic development.

Conclusion

CEER can be multiplexed to analyze pathway proteins in a comprehensive manner with extreme specificity and sensitivity. This format is ideal for analyzing clinical samples with limited availability.

'Omic approaches to preventing or managing metastatic breast cancer

Early detection of metastasis-prone breast cancers and characterization of residual metastatic cancers are important in efforts to improve management of breast cancer. Applications of genome-scale molecular analysis technologies are making these complementary approaches possible by revealing molecular features uniquely associated with metastatic disease. Assays that reveal these molecular features will facilitate development of anatomic, histological and blood-based strategies that may enable detection prior to metastatic spread. Knowledge of these features also will guide development of therapeutic strategies that can be applied when metastatic disease burden is low, thereby increasing the probability of a curative response.

A novel platform for detection of CK+ and CK- CTCs

Metastasis is a complex, multistep process that begins with the epithelial-mesenchymal transition (EMT). Circulating tumor cells (CTC) are believed to have undergone EMT and thus lack or express low levels of epithelial markers commonly used for enrichment and/or detection of such cells. However, most current CTC detection methods target only EpCAM and/or cytokeratin (CK) to enrich epithelial CTCs, resulting in failure to recognize other, perhaps more important, CTC phenotypes that lack expression of these markers. Here, we describe a population of complex aneuploid CTCs that do not express CK or CD45 antigen in patients with breast, ovarian, or colorectal cancer. These cells were not observed in healthy subjects. We show that the primary epithelial tumors were characterized by similar complex aneuploidy, indicating conversion to an EMT phenotype in the captured cells. Collectively, our study provides a new method for highly efficient capture of previously unrecognized populations of CTCs.

SIGNIFICANCE

Current assays for CTC capture likely miss populations of cells that have undergone EMT. Capture and study of CTCs that have undergone EMT would allow a better understanding of the mechanisms driving metastasis.

Circulating tumor cells and circulating tumor DNA

Solid tumors derived from epithelial tissues (carcinomas) are responsible for 90% of all new cancers in Europe, and the main four tumor entities are breast, prostate, lung, and colon cancer. Present tumor staging is mainly based on local tumor extension, metastatic lymph node involvement, and evidence of overt distant metastasis obtained by imaging technologies. However, these staging procedures are not sensitive enough to detect early tumor cell dissemination as a key event in tumor progression. Many teams have therefore focused on the development of sensitive assays that allow the specific detection of single tumor cells or small amounts of cell-free tumor DNA in the peripheral blood of cancer patients. These methods allow the detection and characterization of early metastatic spread and will provide unique insights into the biology of metastatic progression of human tumors, including the effects of therapeutic interventions.

Clinical relevance and biology of circulating tumor cells

Most breast cancer patients die due to metastases, and the early onset of this multistep process is usually missed by current tumor staging modalities. Therefore, ultrasensitive techniques have been developed to enable the enrichment, detection, isolation and characterization of disseminated tumor cells in bone marrow and circulating tumor cells in the peripheral blood of cancer patients. There is increasing evidence that the presence of these cells is associated with an unfavorable prognosis related to metastatic progression in the bone and other organs. This review focuses on investigations regarding the biology and clinical relevance of circulating tumor cells in breast cancer.

Organ-specific markers in circulating tumor cell screening: an early indicator of metastasis-capable malignancy

Circulating tumor cells (CTCs) represent an important biological link in the spread of primary solid tumors to the metastatic disease responsible for most cancer mortality. Their detection in the peripheral blood of patients with many different carcinomas has shown that tumor-cell dissemination can proceed at an early stage of tumor development and their presence is associated with poor clinical outcomes, particularly in metastatic disease. In this article we describe how the increasingly sensitive isolation and detailed molecular characterization of CTCs has greatly improved our understanding of metastatic proliferation. We focus on how CTC detection and knowledge of the molecular architecture of these cells can serve as biomarkers to signal metastasis-capable disseminating cells and predict therapy-specific response. This has marked clinical utility for improved selection of systemic therapies to the individual needs of a cancer patient, real-time monitoring of metastatic disease treatments and the development of new targeted therapies.

Minimal residual disease and circulating tumor cells in breast cancer

Tumor cell dissemination in bone marrow or other organs is thought to represent an important step in the metastatic process. The detection of bone marrow disseminated tumor cells is associated with worse outcome in early breast cancer. Moreover, the detection of peripheral blood circulating tumor cells is an adverse prognostic factor in metastatic breast cancer, and emerging data suggest that this is also true for early disease. Beyond enumeration, the characterization of these cells has the potential to improve risk assessment, treatment selection and monitoring, and the development of novel therapeutic agents, and to advance our understanding of the biology of metastasis.

The human epidermal growth factor receptor 2 (HER2)

The declared "war on cancer" aimed to eradicate this disease using our knowledge of cancer cell biology to develop novel therapeutics. One such target of these novel therapies has been the human epidermal growth factor receptor 2 (HER2) gene. Unique in the approach to abolishing function of this gene coded receptor, it was the first target of new monoclonal antibody therapy targeting the extracellular receptor and now also a target of small molecule drugs against the intracellular tyrosine kinase domain. In this instance, it was also one of the first applications of personalized medicine requiring companion diagnostics. In this manuscript, we review the biology and clinical applications of HER2 as a biomarker of disease and as a therapeutic target.

Circulating tumor cell isolation and diagnostics: toward routine clinical use

From February 7-11, 2011, the multidisciplinary Lorentz Workshop Circulating Tumor Cell (CTC) Isolation and Diagnostics: Toward Routine Clinical Use was held in Leiden (The Netherlands) to discuss progress and define challenges and potential solutions for development of clinically useful circulating tumor cell (CTC) diagnostics. CTCs, captured as "liquid biopsy" from blood, for counting and characterization using pathology and molecular assays, are expected to replace metastatic tissue biopsies to be used to predict drug response and resistance and to monitor therapy response and cancer recurrence. CTCs are highly heterogeneous; therefore, cancer type-specific isolation technologies, as well as complex clinical interpretation software, are required.

Circulating tumor cells in breast cancer: detection systems, molecular characterization, and future challenges

BACKGROUND

Circulating tumor cell (CTC) analysis is a promising new diagnostic field for estimating the risk for metastatic relapse and metastatic progression in patients with cancer.

CONTENT

Different analytical systems for CTC isolation and detection have been developed as immunocytochemical and molecular assays, most including separation steps by size or biological characteristics, such as expression of epithelial- or cancer-specific markers. Recent technical advancements in CTC detection and characterization include methods based on multiplex reverse-transcription quantitative PCR and approaches based on imaging and microfilter and microchip devices. New areas of research are directed toward developing novel assays for CTC molecular characterization. QC is an important issue for CTC analysis, and standardization of micrometastatic cell detection and characterization methodologies is important for the incorporation of CTCs into prospective clinical trials to test their clinical utility. The molecular characterization of CTCs can provide important information on the molecular and biological nature of these cells, such as the status of hormone receptors and epidermal and other growth factor receptor family members, and indications of stem-cell characteristics. This information is important for the identification of therapeutic targets and resistance mechanisms in CTCs as well as for the stratification of patients and real-time monitoring of systemic therapies.

SUMMARY

CTC analysis can be used as a liquid biopsy approach for prognostic and predictive purposes in breast and other cancers. In this review we focus on state-of-the-art technology platforms for CTC isolation, imaging, and detection; QC of CTC analysis; and ongoing challenges for the molecular characterization of CTCs.

Diagnostic applications of cell-free and circulating tumor cell-associated miRNAs in cancer patients

Recently, miRNA-expression profiling in primary tumors has yielded promising results. However, establishing miRNA expression in the circulation probably has advantages over determination in primary tumor tissue, further augmenting the potential applications of miRNA determination in oncology. Circulating tumor cells (CTCs) have rapidly developed as important prognostic and therapy-monitoring biomarkers in metastatic breast, colorectal and prostate cancer when enumerated, and their isolation enables subsequent analysis using various molecular applications, including miRNA-expression analysis. In addition to CTC-associated miRNAs, free circulating miRNAs have been identified in whole blood, plasma and serum. Determination of miRNAs in peripheral blood, either cell-free or CTC-associated, is expected to become important in oncology, especially when linked to and interpreted together with epithelial CTCs. In this article, we will discuss miRNA-expression profiling in primary tumors, depict the potential applications of measuring miRNA in the circulation and review the literature on cell-free circulating miRNAs, as well as offering some methodological and technical considerations on the measurement of circulating miRNAs.

Prospective evaluation of serum tissue inhibitor of metalloproteinase 1 and carbonic anhydrase IX in correlation to circulating tumor cells in patients with metastatic breast cancer

INTRODUCTION

Circulating tumor cells (CTCs) reflect aggressive tumor behavior by hematogenous tumor cell dissemination. The tissue inhibitor of metalloproteinase 1 (TIMP-1) plays a role in tissue invasion and is also involved in angiogenesis, abrogation of apoptosis and in chemoresistance. Carbonic anhydrase IX (CAIX) is a metalloenzyme involved in cell adhesion, growth and survival of tumor cells. The aim of the study was to investigate whether serum concentrations of TIMP-1 and CAIX are associated with the detection of CTC in metastatic breast cancer.

METHODS

Blood was obtained in a prospective multicenter setting from 253 patients with metastatic breast cancer at the time of disease progression. Serum TIMP-1 and CAIX were determined using commercial ELISA-kits (Oncogene Science). CTC were detected with the CellSearch system (Veridex).

RESULTS

Five or more CTCs were detected in 122 patients out of 245 evaluable patients (49.8%). Out of 253 metastatic patients 70 (28%) had serum TIMP-1 levels above 454 ng/mL. Serum CAIX was elevated above 506 ng/mL in 90 (35%) patients. Both serum markers had prognostic significance. Median progression free survival (PFS) was 7.2 months with elevated TIMP-1 vs. 11.4 months with non-elevated levels (p < 0.01). OS was 11.5 vs. 19.1 months (p < 0.01). Median PFS was 7.5 months with elevated CAIX vs. 11.7 months with non-elevated levels (p < 0.01), overall survival (OS) was 13.4 months vs. 19.1 months (p < 0.01). In patients with five or more CTCs, serum levels were above the cut-off for CAIX in 47% vs. 25% in those with less than five CTCs (p = 0.01). For TIMP-1, 37% patients with five or more CTCs had elevated serum levels and 17% of patients with less than five CTCs (p = 0.01). Including TIMP-1, CAIX, CTC and established prognostic factors in the multivariate analysis, the presence of CTCs, the therapy line and elevated CAIX remained independent predictors of OS.

CONCLUSIONS

Elevated serum levels of the invasion markers TIMP-1 and CAIX in metastatic breast cancer are prognostic markers and are associated with the presence of CTCs. Whether increased secretion of TIMP-1 and/or CAIX might directly contribute to tumor cell dissemination remains to be elucidated in further investigations.

TRIAL REGISTRATION

Current Controlled Trials: ISRCTN59722891.

Trastuzumab clears HER2/neu-positive isolated tumor cells from bone marrow in primary breast cancer patients

PURPOSE

Isolated tumor cells (ITC) in the bone marrow of breast cancer patients increase the risk of recurrence and decrease survival, both at primary diagnosis and during follow-up. We tested the efficacy of trastuzumab in clearing HER2/neu-positive ITC from the marrow of patients completing primary treatment.

METHODS

Ten recurrence-free patients with persistent HER2/neu-positive ITC after routine adjuvant treatment received trastuzumab 6 mg/kg q3w for 12 months in a non-randomized pilot phase II interventional study. Bone marrow ITC HER2/neu status was evaluated at baseline, after treatment for 3, 6 and 12 months, and yearly thereafter, in combination with clinical follow-up. Median follow-up was 23 (15-64) months after baseline bone marrow aspiration.

RESULTS

Trastuzumab for 12 months eradicated HER2/neu-positive ITC from bone marrow in all patients (P = 0.002) and significantly reduced the number of ITC-positive patients (P = 0.031). However, HER2/neu-negative ITC persisted in three patients immediately after treatment and were detected at yearly bone marrow aspiration in five patients. Two patients with ITC counts ≥5 at yearly follow-up developed metastases and one died.

CONCLUSION

This is the first evidence that trastuzumab is effective in clearing HER2/neu-positive cells from bone marrow during recurrence-free follow-up in breast cancer patients. It also suggests, thanks to the antigen shift phenomenon, an important prognostic role for HER2/neu expression on marrow ITC as a real-time biopsy. However, treatment was mainly effective in patients with HER2/neu-positive ITC. Given the heterogeneity of minimal residual disease, these patients might benefit from a combination of targeted treatment approaches.