Circulating Tumor Cells, Disease Progression, and Survival in Metastatic Breast Cancer

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Circulating Tumor Cells, Disease
Progression, and Survival in Metastatic Breast Cancer
Massimo Cristofanilli

                      Metastatic breast cancer (MBC) is considered incurable; therefore, palliative treatment is
                      the only option. The biologic heterogeneity of the disease is reflected in its somewhat
                      unpredictable clinical behavior. The presence of circulating tumor cells (CTCs) in patients
                      with MBC about to start a new line of treatment has been shown to predict progression-free
                      and overall survival. This prognostic value is independent of the line of therapy (eg, first or
                      second line). Moreover, a multivariate analysis has shown the prognostic value of CTCs to
                      be superior to that of site of metastasis, type of therapy, and length of time to recurrence
                      after definitive primary surgery. These data suggest that the presence of CTCs may be used
                      to modify the staging system for advanced disease. Larger studies are needed to confirm these
                      data and evaluate the use of CTC detection in monitoring treatment and furthering our
                      understanding of breast cancer biology when combined with other diagnostic technologies.
                      Semin Oncol 33(suppl 9):S9-S14 © 2006 Elsevier Inc. All rights reserved.

B    reast cancer is one of the most frequently diagnosed types
     of cancer and a leading cause of cancer death in women.1
The vast majority of these deaths are caused by recurrent
                                                                            tastasis is a highly selective competition favoring the survival
                                                                            of a minor subpopulation of metastatic tumor cells. These
                                                                            findings suggest that the use of novel, sophisticated diagnos-
metastatic disease. Occult dissemination of tumor cells is the              tic technologies can allow early identification of micrometa-
main cause of recurrent metastatic breast cancer (MBC) in                   static foci, providing an opportunity for early intervention in
patients who have undergone resection of their primary tu-                  patients at high risk, and a better risk stratification in patients
mor.2 Approximately 5% of patients with breast cancer have                  with metastatic disease, leading to appropriate treatment de-
clinically detectable metastases at the time of initial diagnosis.          velopment and patient selection.
A further 30% to 40% of patients who appear clinically free of                 The detection of microscopic disease in breast cancer has
metastases harbor occult metastases.3,4                                     been evaluated in lymph nodes, bone marrow (primary
   The formation of metastatic colonies is a continuous pro-                breast cancer), and peripheral blood (metastatic disease).3-6
cess, commencing early during the growth of the primary                     Most of these studies have shown that the detection of mi-
tumor. Metastasis occurs through a cascade of linked sequen-                croscopic disease in patients with breast cancer contributes
tial steps involving multiple host-tumor interactions. To suc-              prognostic information and, in selected cases, can predict the
cessfully create a metastatic deposit, a cell or group of cells             efficacy of treatments.6 In primary breast cancer, the detec-
must be able to leave the primary tumor, invade the local host              tion of microscopic disease in lymph nodes and bone marrow
tissue, and survive to proliferate. This complex process re-                has led to a better understanding of the role of minimal re-
quires the cells to enter the circulation, arrest at the distant            sidual disease. The detection of tumor cells in the locore-
vascular bed, extravasate into the organ interstitium and pa-               gional lymph nodes of women with early breast cancer using
renchyma, and proliferate as a secondary colony. Several ex-                immunohistochemical analysis is technically feasible, and the
perimental studies suggest that during each stage of the pro-               presence of these cells has been shown to have a negative
cess only the most fit tumor cells survive.2 A very small                   effect on long-term prognosis.7 In this review, we specifically
percentage (less than .01%) of circulating tumor cells (CTCs)               discuss the detection of microscopic disease in the peripheral
ultimately initiate successful metastatic colonies. Thus, me-               blood, and the prognostic implication and clinical use of
                                                                            determining the presence of CTCs.

Department of Breast Medical Oncology, The University of Texas M. D.
   Anderson Cancer Center, Houston, TX.                                     Detection of CTCs in MBC
Address reprint requests to Massimo Cristofanilli, MD, FACP, Department
   of Breast Medical Oncology, Unit 1354, The University of Texas M. D.     The first report on tumor cells in the peripheral circulation
   Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030-           was attributed to Ashworth in 1869.8 Since then, the exis-
   4009. E-mail: mcristof@mdanderson.org                                    tence, origin, and clinical significance of CTCs have been

0093-7754/06/$-see front matter © 2006 Elsevier Inc. All rights reserved.                                                                   S9
doi:10.1053/j.seminoncol.2006.03.016
S10                                                                                                                       M. Cristofanilli

debated. The introduction of more sensitive and specific im-        value of CTCs in patients with MBC who were about to start
munohistochemical techniques in the late 1970s led to re-           a new systemic treatment. The 177 enrolled patients under-
newed interest in the detection of CTCs and their possible          went blood collection at monthly intervals for up to 6 months
association with minimal residual disease in solid malignan-        after enrollment (Table 1). A cutoff of 5 CTCs/7.5 mL was
cies.9,10 But, despite evidence of the prognostic value of CTCs     used to stratify patients into positive and negative groups
in some studies, the detection of micrometastases was never         (positive, ⱖ5 CTCs/7.5 mL; negative, ⬍5 CTCs/7.5 mL).
incorporated into cancer staging protocols or considered a          Patients classified as positive had shorter progression-free
valuable tool for clinical use. This may be the result of a         survival times (2.7 v 7.0 months; P ⫽ .0001) and shorter
combination of factors, such as variable antigen expression in      overall survival times (10.9 v 21.9 months; P ⬍.0001) than
poorly differentiated tumors and reports of cytokeratin and         did those classified as negative (Fig 1). At first follow-up after
epithelial membrane antigen positivity in nonepithelial cells,      initiation of therapy (3 weeks) there was an increased differ-
which showed a need for more sensitive and specific methods         ence between CTC-positive and -negative patients in terms of
of detection than were available at the time. This need was         progression-free survival time (2.1 v 7.0 months; P ⬍.0001)
fulfilled to some degree by more sensitive polymerase chain         and overall survival time (8.2 v ⬎18 months; P ⬍.0001). On
reaction (PCR) techniques in the late 1980s, which greatly          multivariate Cox hazards regression analysis, CTC levels,
facilitated the detection of occult tumor cells through the use     both at baseline and at first follow-up, were the most signif-
of nucleic acid analysis.11-13 In the past decade, a few studies    icant predictors of progression-free survival and overall sur-
                                                                    vival.6
have shown that the detection of occult disease by PCR has
                                                                       These data suggest several important considerations. First,
prognostic significance in some solid tumors.14 However, be-
                                                                    and more relevant to clinical practice, is the demonstration
cause these PCR-based assays for the detection of occult tu-
mor cells have limitations, particularly contamination of
samples, sensitivity and specificity of the assay, and inability
                                                                    Table 1 Demographics of Patients With Metastatic Breast
to quantify tumor cells, they cannot be used to perform func-
                                                                    Cancer Before Undergoing New Systemic Treatment
tional assays. These factors have precluded the widespread
use of PCR in in vitro diagnostic applications.                                                                     N                  %
   Over the past few years, immunomagnetic separation tech-         All patients                                  177
nology, with its higher level of sensitivity and specificity, has   Age at baseline (yrs)                     58.5 ⴞ 13.4
been used to improve the detection of CTCs.15-17 In this tech-      Median (yrs)                                   59
nique, the specimen is incubated with magnetic beads coated         Race
                                                                      White                                        152                86
with antibodies directed against epithelial cells. The epithelial
                                                                      Black                                         14                 8
cells are then isolated using a powerful magnet. The magnetic         Hispanic                                       7                 4
fraction can be used for downstream reverse-transcriptase PCR,        Unknown                                        4                 2
flow cytometry, or immunocytochemical analysis.18,19 Using          ER/PR
this approach, Austrup et al reported the prognostic signifi-         ER/PRⴙ                                       120                68
cance of genomic alterations (eg, c-erbB2 overexpression)             ER/PRⴚ                                        55                31
present in circulating cells purified from the blood of patients      Unknown                                        2                 1
with breast cancer.20 The authors investigated genomic im-          HER2 status
balances such as mutation, amplification, and loss of het-            HER2ⴚ (0ⴚ2ⴙ)                                 122                69
                                                                      HER2ⴙ (3ⴙ) 26                                 15
erozygosity of 13 tumor suppressor genes and two proto-
                                                                      Unknown                                       29                16
oncogenes using DNA from isolated minimal residual cancer           Line of chemotherapy for
cells. The presence and number of genomic imbalances mea-                metastases
sured in disseminated tumor cells were significantly associated       1st                                            83               47
with worse prognosis.20 More recently, advances in technology         2nd                                            25               14
have facilitated the detection of extremely rare CTCs. The            >3rd                                           67               38
CellSearch system (Veridex, LLC, Warren, NJ) was designed             Unknown                                         2                1
to detect circulating epithelial cells in whole blood. This sys-    Site of metastasis
                                                                      Visceral                                     145                82
tem is based on the principle of immunomagnetic isolation of
                                                                      Non-visceral                                  32                18
epithelial cells, with subsequent counting provided by im-          Survival status
munofluorescent analysis of cytokeratin expression.21,22              Alive                                        74             42
                                                                      Dead                                        103             58
                                                                    Average [mean] follow-up                    19.5 ⴞ 5.7 (median,
Prognostic Role of CTCs                                                  Time alive (mos)                          20.9 months)
The predictive and prognostic roles of CTCs were recently                (N ⴝ 74)
investigated in a prospective multicenter clinical trial led by     Average [mean] dead ⴞ SD                    10.3 ⴞ 6.9 (median,
researchers at The University of Texas M. D. Anderson Can-               (mos) (N ⴝ 103)                            8.8 months)
cer Center (Houston, TX).6 In this study, CellSearch was used       Abbreviations: ER, estrogen receptor; HER, human epidermal growth
to prospectively determine the prognostic and predictive               factor receptor; PR, progesterone receptor; SD, standard deviation.
CTCs, disease progression, and survival                                                                                                 S11

that detection of CTCs is superior to known factors, such as
site of metastasis (visceral versus non-visceral) and estrogen-
receptor status, that have been previously considered impor-
tant variables for prognostic evaluation. Furthermore, these
results showed that CTCs are detectable in MBC irrespective
of the site of metastasis, the line of therapy (eg, patients who
are newly diagnosed versus those undergoing second- or
third-line therapy), and, more importantly, initial hormone
receptor status. Of note was the fact that the proportion of
patients with newly diagnosed metastatic disease about to
undergo first-line treatment who were CTC-positive (ⱖ5
CTCs/7.5 mL) was similar to the proportion of patients un-
dergoing at least second-line treatment who were CTC-pos-
itive (52% v 48%, respectively).6 The detection of CTCs pre-
dicted overall survival independently of the number of
previous treatments, but the association was particularly
strong for patients undergoing first-line treatment for meta-
static disease (Fig 2).23 The data at first follow-up supported
the predictive value of CTCs. As expected, the CTC detection           Figure 2 Kaplan-Meier plots of overall survival in first-line therapy
rate in the group tested at first follow-up was lower than the         MBC patients with ⬍5 CTCs or ⱖ5 CTCs (per 7.5 mL) at baseline.
baseline, particularly in patients undergoing first-line treat-        The analysis includes 94 patients with measurable and evaluable
ment (25% v 52%) and those with visceral disease (28% v                (bone only) disease. Overall survival was calculated from the time of
                                                                       the baseline blood draw. Coordinates of dashed lines indicate me-
                                                                       dian survival time. CTCs, circulating tumor cells; CI, confidence
                                                                       interval; HR, hazard ratio; OS, overall survival.

                                                                       50%).6 These data indicate that patients with newly diag-
                                                                       nosed disease who are about to start first-line therapy may
                                                                       have detectable CTCs, and the changes in these detection
                                                                       rates at 3 to 4 weeks may indicate benefit from the use of
                                                                       systemic treatment (particularly chemotherapy). However,
                                                                       this short follow-up testing might be less useful in patients
                                                                       who presumably have more indolent disease (eg, patients
                                                                       undergoing hormonal treatment). A recent update and re-
                                                                       analysis of the data from this pivotal study, which included
                                                                       data from an additional 46 patients with bone-only MBC,
                                                                       confirmed the observation in the initial report indicating that
                                                                       the detection of CTCs at baseline was associated with a sig-
                                                                       nificant cumulative hazard risk of death (53% v 19% with
                                                                       and without CTCs, respectively; P ⫽ .0001) in patients with
                                                                       measurable as well as ‘nonmeasurable’ MBC.24
                                                                          In summary, the detection of CTCs in patients with MBC is
                                                                       associated with important prognostic implications, allowing
                                                                       for a defined stratification of risk of death. These findings
                                                                       suggest that CTC detection can be used for a stage subclassi-
                                                                       fication of MBC that would modify our approach to treatment
                                                                       planning and, more importantly, allow for more sophisti-
                                                                       cated design of efficacy trials.

                                                                       Staging Classification
                                                                       for MBC Using CTCs
Figure 1 Kaplan-Meier plots of (A) progression-free survival and
(B) overall survival in MBC patients with ⬍5 CTCs or ⱖ5 CTCs (per      The American Joint Committee on Cancer (AJCC) classifica-
7.5 mL) at baseline. Progression-free survival and overall survival    tion system includes much of the traditional prognostic in-
were calculated from the time of the baseline blood draw. Coordi-      formation used by clinicians when developing a comprehen-
nates of dashed lines indicate median survival time. CTCs, circulat-   sive treatment plan. This system was based on a schema
ing tumor cells.                                                       developed by the Union Internationale Contre le Cancer
S12                                                                                                                        M. Cristofanilli

(UICC).25-27 In brief, the AJCC system attempts to define the
disease by incorporating all aspects of cancer distribution in
terms of the primary tumor (T), lymph nodes (N), and distant
metastasis (M). A ‘stage’ group (0, I, II, III, or IV) is then
assigned on the basis of the possible TNM permutations, with
0 reflecting minimal involvement and IV either the most tu-
mor involvement or distant metastasis. This basic TNM stag-
ing is then further subdivided according to the time the eval-
uation is performed: c ⫽ clinical (before surgical treatment)
and p ⫽ pathologic (after surgical specimen analysis).7,28            Figure 3 Schematic representation of the prospective International
   Over the past 45 years, the AJCC has regularly updated its         Stage IV Stratification Study. Six hundred sixty patients with newly
staging standards to incorporate advances in prognostic tech-         diagnosed MBC will be enrolled and, after having blood drawn at
nology. The committee’s current work concerns the develop-            baseline, will be receiving treatments. Patients will have follow-up
ment of prognostic indices based on molecular markers. But            of their condition until death. There is no planned interim analysis
until these changes are incorporated, TNM staging quantifies          or additional blood evaluation. Dx, diagnosed; MBC, metastatic
only the physical extent of disease and, although it includes         breast cancer; Tx, treatment.
the approximately 2% of women who initially present with
primary metastatic disease (stage IV), the prognostic infor-
mation is only applicable to in situ, local, and regional pri-
                                                                      Thus, the main goal in the management of this entity is pal-
mary breast cancers. This is somewhat problematic in that
                                                                      liation.29,30 Only a few patients who experience a complete
because of the heterogeneity of the disease, the potential for
                                                                      response after chemotherapy remain in this state for pro-
continued mutation, and the variety of treatment options
                                                                      longed periods, with some remaining in remission for more
available, the information acquired at the time of the primary
                                                                      than 20 years.30 These long-term survivors are usually young,
diagnosis of breast cancer may not be as relevant to planning
                                                                      have an excellent performance status, and, more importantly,
the treatment of the approximately 30% of women with
                                                                      have limited metastatic disease.31,32 Most patients with met-
breast cancer who present with recurrent MBC years after
                                                                      astatic disease respond transiently to conventional therapies
their initial diagnosis.
                                                                      and develop evidence of progressive disease within 12 to 24
   The recent demonstration that the presence of CTCs pre-
                                                                      months of starting treatment.29 For these patients, systemic
dicted the prognoses of two subgroups of patients with MBC
raises the possibility that this method will allow for a true         treatment does not result in a significant improvement in
‘biologic staging’ of breast cancer (eg, stages IVA and IVB).6        survival time but substantially improves their quality of life.
The main limitations of the previous completed study were                At the present time, clinicians can use three different
the sample size (only 177 patients), the inclusion of measur-         systemic treatment modalities for advanced breast cancer:
able-disease-only patients, which did not reflect the real clin-      endocrine therapy, chemotherapy, and biologic targeted
ical heterogeneity of MBC, the inclusion of patients at differ-       therapy.33-35 Appropriate selection of patients for these mo-
ent points in treatment, and those who have newly diagnosed           dalities is based mostly on tissue assessment of hormone
disease versus those undergoing second- or third-line treat-          receptor status (estrogen and progesterone receptors) and
ment, whose benefit from further therapy could have been              c-erbB2 status. In patients who lack expression of hormone
limited by the advanced status of their disease. To overcome          receptors or who show no amplification of c-erbB2, cytotoxic
these limitations, a larger international validation trial, the       chemotherapy is used. However, no standard therapeutic
International Stage IV Stratification Study, has recently be-         regimen has been defined. For example, the optimal schedule
gun (Fig 3). The objective of this study is to confirm the            of chemotherapy administration in MBC (ie, concurrent v
prognostic value of CTC detection in a larger and more ho-            sequential) remains controversial, and the decision must be
mogeneous cohort of patients with newly diagnosed MBC.                individualized. Sledge et al36 addressed this issue in a pro-
The study aims to enroll 660 patients and will enable a more          spective study that included 739 chemotherapy-naive pa-
detailed analysis of the association between CTC detection            tients who were randomly assigned to receive, at progression,
and other factors, such as ethnicity (black compared with             doxorubicin, paclitaxel, or a combination of both. Although
white and Hispanic groups) and specific disease sites (vis-           the response rates and times to treatment failure were im-
ceral v non-visceral disease). Accrual is expected to be com-         proved with the combination regimen, the overall survival
pleted by November 2006, which will allow completion of               rate was comparable between the groups. Other trials have
data analysis by late 2007. This study may well help provide          shown a survival advantage for combination regimens, but all
definitive information on the subclassification of stage IV disease   of these studies have reported differences in median overall
for the revised 7th edition of the AJCC’s Cancer Staging Manual.      survival time, suggesting that even with comparable inclu-
                                                                      sion criteria the heterogeneity typical of MBC cannot be elim-
                                                                      inated.37,38 This is indeed one of the major limitations to the
Clinical Application of CTCs                                          development of more personalized treatments for patients.
Despite years of clinical research, the odds of patients with         Therefore, although the data show that patients can benefit
MBC achieving a complete response remain extremely low.               from combination therapy, they do not clearly identify the
CTCs, disease progression, and survival                                                                                                        S13

subsets of patients who most benefit or who experience only          tional, with decreased levels of major histocompatibility
additional toxicity.                                                 complex class II, CD86 (B7) expression, and interleukin-12
   In this context, the use of CTCs to stratify patients at the      secretion.49
time of disease recurrence may be appropriate. CTC detec-               The inherent and dynamic phenotypic instability of breast
tion may allow a more rational selection of treatments for           tumor cells complicates these issues of breast cancer biology.
patients with newly recurred disease, and this approach              Because tumors arise endogenously and progress, a continual
could maximize the chance of a particular combination or             dialogue between the tumor phenotype and the immune re-
single new drug showing clinical benefit and, eventually,            sponse ensues, with each influencing the other to evolve.50
prolonging survival. In essence, it is possible that CTC detec-      Therefore, being able to evaluate both the phenotype of CTCs
tion could be used in the design of efficacy trials of different     and the related immune response is a critical step in under-
therapeutic approaches. The efficacy of these treatments will        standing the complexity of tumor immunity in patients with
be more easily assessed when patients have been stratified by        breast cancer, and will enable more effective vaccine strate-
their prognosis, leading to more tailored treatment strategies.      gies to be designed. A recently developed glycan array has
We believe that the challenge for the next generation of clin-       shown the capacity to detect a particular profile of antibodies
ical trials, and the responsibility for both clinical investigator   directed against cancer-specific carbohydrate antigens.51,52
and the pharmaceutical industry, will be to incorporate these        The further development of this novel technology in combi-
concepts into the process of drug development.                       nation with CTC detection will represent a new frontier in
                                                                     breast cancer microdiagnostics.
Future Uses of CTCs
The process of sorting cancer cells from other cellular com-         Conclusion
ponents (eg, blood and stromal cells) in clinical samples is         The detection of microscopic disease in the peripheral blood
fundamentally important for the future of genomic and pro-           of patients with MBC is associated with prognostic informa-
teomic analysis.39-42 Indeed, the feasibility of evaluating the      tion. These data will allow appropriate risk stratification and
gene expression profiles of cancer cells depends mostly on           modification of the current staging system for advanced dis-
the quality of the specimen (relative proportion of cancer           ease. Moreover, it is expected that investigators and the phar-
cells) and the amount of nucleic acid that can be extracted          maceutical industry will derive benefit from these technolo-
from the appropriate cells to provide mRNA suitable for anal-        gies that will contribute to more tailored treatments and
ysis.41,42 Fine-needle aspiration biopsy of malignant lesions is     sophisticated trial designs. Using a combination of CTC de-
frequently used for diagnostic purposes, but the percentage          tection and other diagnostic technologies will help us further
of malignant cells recovered with this procedure ranges              understand the complex and heterogeneous tumor pheno-
widely (60% to 90%).41,42 Pusztai et al42 showed that single-        type and its relationship with tumor-related immunity.
pass fine-needle aspiration biopsies can provide samples con-
sisting of approximately 79% cancer cells (range, 25% to
100%).
                                                                     References
                                                                      1. National Cancer Institute: SEER Cancer Statistics Review (1975-2000).
   Collecting representative tissue in the metastatic setting            Available at: http://seer.cancer.gov/csr/1975_2000 Accessed Septem-
from solid tumors is more complex and usually requires                   ber 2005
more invasive procedures that increase the risk of complica-          2. Folkman J: Tumor angiogenesis: Therapeutic implications. N Engl
tions and discomfort. Furthermore, these procedures may                  J Med 285:1182-1186, 1971
not provide an adequate specimen for detailed analysis and            3. Clare SE, Sener SF, Wilkens W, et al: Prognostic significance of occult
                                                                         lymph node metastases in node-negative breast cancer. Ann Surg Oncol
typically cannot be repeated for a dynamic evaluation of the             4:447-451, 1997
biologic changes during treatments. Theoretically, CTC de-            4. Braun S, Pantel K, Müller P, et al: Cytokeratin-positive cells in the bone
tection would allow specific genes (eg, c-erbB2, EGFR, and               marrow and survival of patients with stage I, II or III breast cancer.
MGB) or more global gene expression to be analyzed while                 N Engl J Med 342:525-533, 2000
using specific targeted treatments in metastatic disease.43-46        5. Cristofanilli M, Budd GT, Ellis M, et al: Circulating tumor cells, disease
                                                                         progression, and survival in metastatic breast cancer. N Engl J Med
This information could then be used to design specific treat-            351:781-791, 2004
ments that more appropriately reflect the dynamics and het-           6. Reed W, Bohler PJ, Sandstad B, et al: Occult metastases in axillary
erogeneity of MBC.43                                                     lymph nodes as a predictor of survival in node-negative breast carci-
   The prognostic value of CTCs in the setting of MBC raises             noma with long-term follow-up. Breast J 10:174-180, 2004
                                                                      7. Singletary SE, Allred C, Ashley P, et al: Staging system for breast cancer:
the possibility that their presence or absence could be indic-
                                                                         revisions for the 6th edition of the AJCC Cancer Staging Manual. Surg
ative of the complex interplay between the host and the dis-             Clin North Am 83:803-819, 2003
ease, providing some indirect information on tumoral immu-            8. Ashworth TR: A case of cancer in which cells similar to those in the
nity. Substantial evidence exists for immune defects in                  tumours were seen in the blood after death. Aust Med J 14:146-149,
patients with breast cancer, demonstrated particularly by in-            1869
                                                                      9. Roberts S, Watne A, McGrath R, et al: Technique and results of isolation
creased numbers of functionally suppressive CD4⫹CD25⫹
                                                                         of cancer cells from the circulating blood. AMA Arch Surg 76:334-346,
T-regulatory cells in the peripheral blood.47,48 Furthermore,            1958
dendritic cells obtained from the peripheral blood and lymph         10. Long L, Jonasson O, Roberts S, et al: Cancer cells in blood. Results of
nodes of patients with operable breast cancer are dysfunc-               simplified isolation technique. Arch Surg 80:910-919, 1960
S14                                                                                                                                            M. Cristofanilli

11. Bossolasco P, Ricci C, Farina G, et al: Detection of micrometastatic cells    33. Swenerton KD, Legha SS, Smith L, et al: Prognostic factors in metastatic
    in breast cancer by RT-PCR for the mammaglobin gene. Cancer Detect                breast cancer treated with combination chemotherapy. Cancer Res 39:
    Prev 26:60-63, 2002                                                               1552-1562, 1979
12. Hawes D, Neville AM, Cote RJ: Occult metastasis. Biomed Pharmaco-             34. Hortobagyi GN, Smith TL, Legha SS, et al: Multivariate analysis of
    ther 55:229-242, 2001                                                             prognostic factors in metastatic breast cancer. J Clin Oncol 1:776-786,
13. Hu XC, Chow LW: Detection of circulating breast cancer cells with                 1983
    multiple-marker RT-PCR assay. Anticancer Res 21:421-424, 2001                 35. Bernard-Marty C, Cardoso F, Piccart MJ: Facts and controversies in
14. An XY, Egami H, Hayashi N, et al: Clinical significance of circulating            systemic treatment of metastatic breast cancer. Oncologist 9:617-632,
    cancer cells in peripheral blood detected by reverse transcriptase-poly-          2004
    merase chain reaction in patients with breast cancer. Tohoku J Exp Med        36. Sledge GW, Neuberg D, Ingle J, et al: Phase III trial of doxorubicin,
    193:153-162, 2001                                                                 paclitaxel and the combination of doxorubicin and paclitaxel as front-
15. Gross HJ, Verwer B, Houck D, et al: Model study detecting breast                  line chemotherapy for metastatic breast cancer (MBC): An Intergroup
    cancer cells in peripheral blood mononuclear cells at frequencies as low          trial (E1193). J Clin Oncol 21:588-592, 2003
                                                                                  37. O’Shaughnessy J, Miles D, Vukelja S, et al: Superior survival with cape-
    as 10(-7). Proc Natl Acad Sci U S A 92:537-541, 1995
                                                                                      citabine plus docetaxel combination therapy in anthracycline-pre-
16. Martin KJ, Graner E, Li Y, et al: High-sensitivity array analysis of gene
                                                                                      treated patients with advanced breast cancer: Phase III trial results.
    expression for the early detection of disseminated breast tumor cells in
                                                                                      J Clin Oncol 20:2812-2823, 2002
    peripheral blood. Proc Natl Acad Sci U S A 98:2646-2651, 2001
                                                                                  38. O’Shaughnessy J, Nag S, Calderillo-Ruiz G, et al: Gemcitabine plus
17. Racila E, Euhus D, Weiss AJ, et al: Detection and characterization of
                                                                                      paclitaxel versus paclitaxel as first-line treatment for anthracycline pre-
    carcinoma cells in the blood. Proc Natl Acad Sci U S A 95:4589-4594,
                                                                                      treated metastatic breast cancer: Interim results of a global phase III
    1998                                                                              study. Proc Am Soc Clin Oncol 22:7, 2003 (abstr)
18. Witzig TE, Bossy B, Kimlinger T, et al: Detection of circulating cytok-       39. Hancock W, Apffel A, Chakel J, et al: Integrated genomic/proteonomic
    eratin-positive cells in the blood of breast cancer patients using immu-          analysis. Anal Chem 71:742-748, 1999
    nomagnetic enrichment and digital microscopy. Clin Cancer Res                 40. Marshall A, Hodgson J: DNA chips: An array of possibilities. Nat Bio-
    8:1085-1091, 2002                                                                 technol 16:27-31, 1998
19. Pachmann K, Heiss P, Demel U, et al: Detection and quantification of          41. Page MJ, Amess B, Townsend RR, et al: Proteonomic definition of
    small numbers of circulating tumour cells in peripheral blood using               normal human luminal and myoepithelial breast cells purified from
    laser scanning cytometer (LSC). Clin Chem Lab Med 39:811-817, 2001                reduction mammoplasties. Proc Natl Acad Sci U S A 96:12589-12594,
20. Austrup F, Uciechowski P, Eder C, et al: Prognostic value of genomic              1999
    alterations in minimal residual cancer cells purified from the blood of       42. Pusztai L, Ayers M, Stec J, et al: Gene expression profiles obtained from
    breast cancer patients. Br J Cancer 83:1664-1673, 2001                            fine-needle aspirations of breast cancer reliably identify routine prog-
21. Kagan M, Howard D, Bendele T, et al: A sample preparation and anal-               nostic markers and reveal large-scale molecular differences between
    ysis system for identification of circulating tumor cells. J Clin Ligand          estrogen-negative and estrogen-positive tumors. Clin Cancer Res 9:
    Assay 25:104-110, 2002                                                            2406-2415, 2003
22. Terstappen LW, Rao C, Gross S, et al: Peripheral blood tumor cell load        43. Meng S, Tripathy D, Frenkel EP, et al: Circulating tumor cells in pa-
    reflects the clinical activity of the disease in patients with carcinoma of       tients with breast cancer dormancy. Clin Cancer Res 10:8152-8162,
    the breast. Int J Oncol 17:573-578, 2000                                          2004
23. Cristofanilli M, Hayes DF, Budd GT, et al: Circulating tumor cells: A         44. Lin DW, Holcomb I, Arfman EW, et al: Detection, isolation and initial
    novel prognostic factor for newly diagnosed metastatic breast cancer.             characterization of disseminated tumor cells following enrichment in
    J Clin Oncol 23:1420-1430, 2005                                                   patients with prostate cancer. Proc Am Assoc Cancer Res 46:97, 2005
24. Cristofanilli M, Budd GT, Ellis MJ, et al: Presence of circulating tumor          (abstr 419)
    cells (CTC) in metastatic breast cancer (MBC) predicts rapid progres-         45. Kimura H, Fukumoto H, Park S, et al: Deletional mutant EGFR de-
    sion and poor prognosis. J Clin Oncol 23:16S, 2003 (abstr)                        tected in circulating tumor-derived DNA from lung cancer patients
25. Denoix PF, Baclesse F: Proposed clinical classification of breast cancers;        treated with gefitinib. Proc Am Assoc Cancer Res 46:112, 2005 (abstr
    Statement of the International Cancer Union. Bull Assoc Fr Etud Can-              479)
                                                                                  46. Smirnov DA, Zweitzig DR, Foulk BW, et al: Global gene expression
    cer 42:433-440, 1955
                                                                                      profiling of circulating tumor cells. Cancer Res 65:4993-4997, 2005
26. International Union Against Cancer (UICC): TMN Classification of
                                                                                  47. Wolf AM, Wolf D, Steurer M, et al: Increase of regulatory T cells in the
    Malignant Tumours. Geneva, UICC, 1968
                                                                                      peripheral blood of cancer patients. Clin Cancer Res 9:606-612, 2003
27. Berndt H, Titze U: TNM clinical stage classification of breast cancer. Int
                                                                                  48. Liyanage UK, Moore TT, Joo H-G, et al: Prevalence of regulatory T cells
    J Cancer 4:837-844, 1969
                                                                                      is increased in peripheral blood and tumor microenvironment of pa-
28. Greene FL, Page DI, Fleming ID, et al: AJCC Cancer Staging Manual.
                                                                                      tients with pancreas or breast adenocarcinoma. J Immunol 169:2756-
    (ed 6). New York, NY, Springer, 2002                                              2761, 2002
29. Ellis M, Hayes DF, Lippman ME: Treatment of metastatic disease, in            49. Pockaj BA, Basu GD, Pathangey LB, et al: Reduced T-cell and dendritic
    Harris J, Lippman M, Morrow M, et al (eds): Diseases of the Breast.               cell function is related to cyclooxygenase-2 overexpression and prosta-
    (ed 2). Philadelphia, PA, Lippincott-Raven, 2000, pp 749-799                      glandin E2 secretion in patients with breast cancer. Ann Surg Oncol
30. Greenberg PA, Hortobagyi GN, Smith TL, et al: Long-term follow-up of              11:328-339, 2004
    patients with complete remission following combination chemother-             50. Dunn GP, Old LJ, Schreiber RD: The three Es of cancer immunoediting.
    apy for metastatic breast cancer. J Clin Oncol 14:2197-2205, 1996                 Annu Rev Immunol 22:329-360, 2004
31. Nieto Y, Cagnoni PJ, Shpall EJ, et al: Phase II trial of high-dose chemo-     51. Blixt O, Head S, Mondala T, et al: Printed covalent glycan array for
    therapy with autologous stem cell transplant for stage IV breast cancer           ligand profiling of diverse glycan binding proteins. Proc Natl Acad Sci
    with minimal metastatic disease. Clin Cancer Res 5:1731-1737, 1999                U S A 101:17033-17038, 2004
32. Rivera E, Holmes FA, Buzdar AU, et al: Fluorouracil, doxorubicin, and         52. Huflejt M, Cristofanilli M, Shaw L, et al: Detection of neoplasia-specific
    cyclophosphamide followed by tamoxifen as adjuvant treatment for                  clusters of anti-glycan antibodies in sera of breast cancer patients using
    patients with stage IV breast cancer who have no evidence of disease.             a novel glycan array. Proc Am Assoc Cancer Res 46:1312, 2005 (abstr
    Breast J 8:2-9, 2002                                                              5578)
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