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Journal of Clinical Oncology, Vol 23, No 7 (March 1), 2005: pp. 1420-1430 © 2005 American Society of Clinical Oncology. DOI: 10.1200/JCO.2005.08.140 Circulating Tumor Cells: A Novel Prognostic Factor for Newly Diagnosed Metastatic Breast CancerFrom The University of Texas M.D. Anderson Cancer Center, Houston, TX; The University of Michigan Comprehensive Cancer Center, Ann Arbor, MI; The Cleveland Clinic, Cleveland, OH; Washington University, St Louis, MO; University of Arizona, Phoenix, AZ; and Immunicon Corporation, Huntingdon Valley, PA Address reprint requests to Massimo Cristofanilli, MD, FACP, Department of Breast Medical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd, Box 424, Houston, TX 77030; e-mail: mcristof{at}mdanderson.org
PURPOSE: Metastatic breast cancer (MBC) is incurable; its treatment is palliative. We investigated whether the presence of circulating tumor cells (CTCs) predicts treatment efficacy, progression-free survival (PFS), and overall survival (OS) in patients with newly diagnosed MBC who were about to start first-line therapy. PATIENTS AND METHODS: One hundred seventy-seven patients with measurable MBC were enrolled onto a prospective study. Eighty-three of the 177 patients were entering first-line treatment, and these patients are the focus of this analysis. CTCs from 7.5 mL of whole blood drawn before treatment initiation (baseline) and monthly thereafter for up to 6 months were isolated and enumerated using immunomagnetics.
RESULTS: The mean (± standard deviation) follow-up time was 11.1 ± 4.4 months (median, 12.2 months). Forty-three patients (52%) had CONCLUSION: Detection of CTCs before initiation of first-line therapy in patients with MBC is highly predictive of PFS and OS. This technology can aid in appropriate patient stratification and design of tailored treatments.
Breast cancer remains the most frequent type of cancer in women, with approximately 212,600 new cases (1,300 male) diagnosed each year in the United States. Breast cancer is among the leading causes of cancer death in women (15% of all cancer deaths in women), with an estimated 40,200 cancer-related deaths (400 male) in 2003 (Surveillance, Epidemiology, and End Results Cancer Statistics Review, 1975-2000; http://seer.cancer.gov/csr/1975_2000). The vast majority of these deaths are a result of recurrent metastatic disease. Despite years of clinical research, the odds of achieving complete response for patients with metastatic breast cancer (MBC) are extremely low.1,2 Only a few patients who achieve a complete response after chemotherapy remain in this state for prolonged periods of time, with some patients remaining in remission beyond 20 years.2 These long-term survivors are usually young, have an excellent performance status, and, more importantly, have limited metastatic disease.3,4 The majority of patients with metastatic disease respond transiently to conventional treatments and develop evidence of progressive disease within 12 to 24 months of initiating treatment.1 For these patients, systemic treatment has not translated into a significant improvement in survival but has substantially improved their quality of life. Several clinical factors have been proposed but never prospectively validated that would help in the prediction of long-term outcome and efficacy of treatments.5,6 Circulating tumor cells (CTCs) can be detected in blood from patients with metastatic and primary carcinomas.7-11 Over the past several years, the development of immunomagnetic platforms has permitted accurate enumeration of CTCs at extremely low frequencies.11 In several case reports, the presence of CTCs has been associated with shortened survival times.12-15 We conducted a prospective, multicenter, double-blind study to determine the clinical significance of CTCs in patients with measurable MBC starting a new course of systemic therapy. The overall results of this study have been published elsewhere.16 This article represents the detailed analysis of only the cohort of patients with newly diagnosed MBC about to start first-line therapy. We believe this is an important analysis because patients who are newly diagnosed and about to start first-line therapy will derive the most benefit from appropriate risk stratification and treatment planning. Furthermore, an early prediction of treatment efficacy could have an impact in their quality of life.
Study Design A prospective, multi-institutional, clinical trial was conducted at 20 clinical centers throughout the United States to evaluate the potential role for CTCs in 177 patients being treated for MBC.16 The analyses described in this article focus only on the 83 women with newly diagnosed, measurable MBC who were about to start their first line of systemic therapy. All of these first-line therapy patients had an Eastern Cooperative Oncology Group performance status score of 0 to 2. The protocol included a centralized review of imaging studies to document objective response or progressive disease. The institutional review board at each center approved the study protocol, and all patients provided written informed consent. Before the initiation of therapy, patients had imaging evaluation (including computed tomography scans of chest and abdomen) of their metastatic sites and a baseline blood draw for enumeration of CTCs. Serial blood specimens were collected at roughly monthly intervals for a period of up to 6 months. Reassessments of disease status by the same modalities used at baseline were conducted every 9 to 12 weeks, depending on treatment type and schedule. Disease status was assessed using WHO criteria without knowledge of the patients’ CTC results.
Isolation and Enumeration of CTCs
CTC Definition
Statistical Analysis
Patient Characteristics The demographics of 83 newly diagnosed MBC patients are listed in Table 1. Sixty-one patients had initial diagnoses of infiltrating ductal carcinoma, including two patients with mixed histology (76%). Eleven patients (13%) had lobular histology. Hormone receptor positivity was detected in 53 patients (64%), whereas 21 patients (25%) had HER2/neu 2+, 3+ by immunohistochemical staining. Fifty-one patients (61%) had received previous adjuvant chemotherapy. Visceral metastases, which are defined here as lung, liver, adrenal gland, brain, kidney, pancreas, and/or peritoneal involvement with or without ascites and/or pleural effusions, were the predominant sites of disease recurrence and were found in 70 patients (84%). Nonvisceral metastases were defined as involvement of any of the following sites without visceral metastases: breast, lymph nodes, chest wall, bone, skin, and/or abdomen. Of the 59 patients (71%) who received cytotoxic chemotherapy (alone or in combination) as their first-line treatment, 37 received chemotherapy only (25 received single-agent cytotoxic treatment, and 12 received a combination regimen), six received combined hormonal therapy, 15 received combined trastuzumab therapy, and one received combined hormonal and trastuzumab-based therapy. Twenty-three patients were treated with hormonal therapy alone at diagnosis of MBC. The average time (± standard deviation [SD]) to response assessment was 9.1 ± 4.0 weeks (range, 3.0 to 23.0 weeks). Only baseline blood specimens were obtained from three patients because they died before any further follow-up. Blood draws were obtained from 60 of the 83 patients at the first follow-up after initiation of therapy. The time between baseline and first follow-up blood draws ranged from 2.4 to 13.9 weeks (mean ± SD, 3.9 ± 1.7 weeks). Additionally, blood draws from 79 of the 83 patients were obtained at the first reassessment of disease status (first imaging visit). Follow-up time for survival after the baseline blood draw ranged from 5.7 to 88.4 weeks (mean ± SD, 47.9 ± 18.7 weeks).
Prevalence of CTCs and Response to Therapy As Assessed by Imaging We have previously reported that detection of circulating epithelial cells using CellSearch (Veridex) is rare in healthy women (mean ± SD, 0.1 ± 0.2 per 7.5 mL of blood) and patients with benign disease (mean ± SD, 0.1 ± 0.9 per 7.5 mL of blood).16 Patients who were started on a chemotherapy regimen (alone or in combination, n = 59) as their first-line treatment had a higher percentage of CTCs detected at baseline compared with patients receiving hormone therapy (alone or in combination, n = 24; P = .015; Table 2). Patients who were started on chemotherapy alone (n = 37) as their first-line treatment had a higher percentage of CTCs detected at baseline compared with patients receiving hormone therapy alone (n = 23), although this difference was not statistically significant (P = .064). There was no significant difference in CTC levels at any time point between patients with or without visceral metastasis (P  .371) or between patients receiving hormone therapy alone (n = 23) or combined trastuzumab therapy (n = 17; P .108). However, patients who were started on chemotherapy alone (n = 37) had a higher percentage of CTCs detected at the first follow-up and first imaging visit blood draws compared with patients receiving combined trastuzumab therapy (n = 17; P  .064).
Patients treated with chemotherapy (alone or in combination, n = 59) showed a significant decrease in CTCs from baseline to the first follow-up (61% to 27%, P = .003) and first imaging visit blood draws (61% to 24%, P = .004). Patients treated with hormone therapy (alone or in combination with trastuzumab therapy, n = 24) also showed a significant decrease in CTCs from baseline to the first follow-up (29% to 19%, P = .018) and first imaging visit blood draws (29% to 17%, P = .003). Patients treated with chemotherapy alone (n = 37) showed a significant decrease in CTCs from baseline to the first follow-up (57% to 37%, P = .001) and first imaging visit blood draws (57% to 31%, P = .004). The largest decrease in CTCs from baseline to the first follow-up (59% to 7%, P = .600) and first imaging visit blood draws (59% to 0%, P = not applicable) was observed in patients receiving trastuzumab-combined regimens.
CTCs and Imaging to Assess Response to Therapy
At the first follow-up blood draw, the median PFS for patients with less than five CTCs was 9.5 months v 2.1 months for patients with five CTCs (P = .0057), and the median OS for patients with less than five CTCs was more than 18 months v 11.1 months for patients with five CTCs (P = .0012; Fig 1). At the first follow-up imaging visit, the median PFS for patients with less than five CTCs was 8.9 months v 1.8 months for patients with five CTCs (P = .0001), and the median OS for patients with less than five CTCs was 18 months v 11.1 months for patients with five CTCs (P = .0001; Fig 1). In summary, detection of CTCs 3 to 4 weeks after the initiation of therapy predicts treatment efficacy as determined by traditional imaging modalities 5 to 6 weeks later. The strong correlation between the presence of CTCs and poor prospects for survival suggests that the prognostic value of CTCs may be more relevant than the information obtained by imaging.
Prediction of PFS and OS Before Initiation of Therapy In all 83 patients, the median PFS time was approximately 7.2 months (95% CI, 4.9 to 9.4 months), and the median OS time was more than 18 months. Figure 1 shows the Kaplan-Meier plots for prediction of PFS and OS using the baseline CTC counts (Figs 1A and 1D, n = 83 patients), the first follow-up CTC counts (Figs 1B and 1E, n = 60 patients), and the CTC counts at restaging (Figs 1C and 1F, n = 79 patients). Forty-three of the patients (52%) had five CTCs per 7.5 mL of blood at baseline. These patients had a significantly shorter median PFS ( 4.9 months; 95% CI, 2.0 to 8.1 months) and median OS ( 14.2 months; 95% CI, 11.1 to > 18 months) compared with patients with less than five CTCs per 7.5 mL of blood (median PFS, 9.5 months; 95% CI, 6.1 to > 18 months; P = .0014; median OS, > 18 months; P < .0048). We further analyzed PFS and OS by patient characteristics (Table 4). Baseline CTC count was almost significantly associated with PFS in patients whose first-line therapy was chemotherapy (alone or with hormone therapy or trastuzumab therapy; P = .0464; Table 4). In patients with visceral disease, hormone receptor–positive tumors, or HER2/neu-negative tumors, a CTC count of less than five CTCs at baseline was significantly associated with longer PFS. In patients who underwent chemotherapy (alone or with hormone therapy or trastuzumab therapy) or who had nonvisceral disease, hormone receptor–positive tumors, or HER2/neu-negative tumors, a CTC count of less than five CTCs at baseline was significantly associated with longer OS.
Prediction of PFS and OS at First Visit After Initiation of Therapy Sixty patients had blood drawn at the first follow-up visit. Fifteen of these patients (25%) had five CTCs at this time. These patients had a significantly shorter median PFS compared with patients with less than five CTCs (2.1 months; 95% CI, 1.4 to 9.2 months, v 9.5 months; 95% CI, 6.7 to > 18 months, respectively; P = .0057) and a significantly shorter median OS (11.1 months; 95% CI, 6.2 to > 18 months, v > 18 months, respectively; P = 0.0012; Fig 1B and 1E). Further analyses revealed that a CTC count of less than five CTCs at the first follow-up visit was significantly associated with longer PFS in all subgroups except hormone receptor–positive disease and nonvisceral metastases (Table 4). Despite the large difference in the median PFS times, the lack of significance in the hormone receptor–positive disease group is largely a result of the small number of patients with five CTCs in this subgroup. Hormone receptor status remained the only factor not associated with improved prognosis in this analysis with regards to OS. Fifteen patients (25%) who demonstrated a reduction of CTCs to less than five showed improvement in their median PFS compared with patients with five CTCs at the first follow-up visit, although this improvement did not reach statistical significance (9.5 v 2.1 months, respectively; P = .1308; Fig 2).
Prediction of PFS and OS at First Reassessment of Disease Status by Imaging After Initiation of Therapy Seventy-nine patients had their blood drawn at the restaging visit. Seventeen of these patients (22%) had five CTCs at this time. These patients had a significantly shorter median PFS from initiation of therapy compared with patients with less than five CTCs (1.8 months; 95% CI, 1.2 to 2.2 months, v 8.9 months; 95% CI, 6.1 to 11.9, respectively; P = .0001) and a significantly shorter median OS from initiation of therapy (11.1 months; 95% CI, 4.6 to > 18 months, v > 18 months, respectively; P = .0001; Figs 1C and 1F). Further analyses showed that a CTC count of less than five CTCs at the restaging visit was significantly associated with longer PFS in all patients except those who received hormone therapy (alone or with trastuzumab) or those who had nonvisceral disease (Table 4). Furthermore, except for patients who received hormone therapy (alone or with trastuzumab therapy), a CTC count of less than five CTCs at the restaging visit was significantly associated with longer OS in all patients. Twenty-three patients (29%) who demonstrated a reduction of CTCs to below five showed improvement in PFS compared with patients with five CTCs at the restaging visit (8.1 v 1.8 months, respectively; P = .0332; Fig 2).
Univariate and Multivariate Analysis of Predictors of PFS and OS
We used stepwise Cox regression analysis at a stringency level of P < .05 to both include and exclude factors for the combination of the baseline CTC count, first follow-up CTC count, or restaging CTC count with the other factors to predict PFS and OS. Several of the clinical factors maintained their association in the multivariate analysis (Table 6). CTC level was the strongest predictor.
The results of this analysis demonstrated that the presence of five or more CTCs in 7.5 mL of blood at time of diagnosis of MBC and before initiation of first-line therapy is associated with short PFS and OS. Furthermore, the levels of CTCs at 3 to 4 weeks and at the time of restaging are predictive of treatment efficacy, PFS, and OS. The subset analysis, even if not statistically significant because of the small number of patients, suggests intriguing correlations. Interestingly, patients with detection of CTCs at the time of disease reassessment by imaging (22% of patients) who had visceral disease and HER2/neu-negative, estrogen receptor–negative, and progesterone receptor–negative disease and who received chemotherapy had the worse differences in PFS and OS compared with patients without detectable CTCs (median OS, 11.1 months for patients with visceral metastasis and 7.1 months if the patients were receiving chemotherapy). Moreover, these data strongly correlate with the results demonstrated at the time of first laboratory follow-up, suggesting that CTCs are a significant surrogate marker for treatment efficacy and prognosis, particularly in candidates for chemotherapy. In summary, these data suggest that detection of CTCs in MBC may correlate with prognosis at baseline and early in the treatment and may be more predictive than traditional measures of treatment efficacy (eg, partial remission or stable disease by Response Evaluation Criteria in Solid Tumors Group criteria). The data reported in two subsets of patients included in this analysis also indicate the need for future investigations using CTCs. First, the detection of CTCs at baseline was of prognostic significance in patients with hormone receptor–positive disease and without evidence of visceral disease (worse PFS and OS, respectively), which suggests that detection of CTCs is more than simply a marker of tumor burden. More than two thirds of breast cancer tumors express the estrogen receptor, and the majority of these tumors was estrogen dependent for growth.20 Several endocrine modalities are available for the management of hormone receptor–positive disease, in particular for postmenopausal women.21,22 Despite the superior efficacy demonstrated with aromatase inhibitors in postmenopausal women, the management of hormone-sensitive MBC remains disappointing, with an overall response rate of approximately 20% to 40% and, more importantly, a time to progression of approximately 9 to 11 months.21 For these patients, who are candidates for various endocrine treatments based on the expression of their hormone receptor status in the primary or metastatic tumor, there is no known prognostic marker that could be used for risk stratification and treatment selection. Furthermore, patients with hormone receptor–positive disease but with visceral disease sometimes are selected for treatment with cytotoxic agents based on the assumption of possible aggressive malignancy. The detection of CTCs at time of diagnosis may help predict which patients would most benefit from earlier initiation of chemotherapy.
Second, in this study, patients with HER2/neu-positive tumors who were treated with trastuzumab-based regimens had the highest proportional reduction in CTC levels at first follow-up and at the time of restaging, confirming the recognized efficacy of this treatment modality. These data indicate that the use of this technology during follow-up of patients with MBC receiving systemic therapy can provide extremely useful information by identifying two groups of patients. The first group is constituted of women who have a high probability of obtaining prolonged benefit from their treatments (disappearance of CTCs), and the other group is represented by patients in whom the treatment may produce a symptomatic improvement and/or an objective remission (or even stability of disease by imaging) but will not be associated with a significant prognostic improvement (persistent detection of In summary, this analysis demonstrates that the detection of CTCs in patients with MBC about to start first-line treatment is associated with significant prognostic information. Furthermore, the persistence of CTCs at 3 to 4 weeks after the treatment is started and at the time of restaging continues to be significantly associated with prognosis, particularly in women with hormone receptor–negative disease and women who are receiving chemotherapy. These data suggest the value of this technology in the identification of chemotherapy-resistant patients who could benefit from early treatment change and/or more investigational approaches.
The following authors or their immediate family members have indicated a financial interest. No conflict exists for drugs or devices used in a study if they are not being evaluated as part of the investigation. Employment: Gerald V. Doyle, Immunicon; Jeri Matera, Immunicon; W. Jeffrey Allard, Immunicon; M. Craig Miller, Immunicon; Leon W.M.M. Terstappen, Immunicon. Leadership Position: W. Jeffrey Allard, Immunicon; Leon W.M.M. Terstappen, Immunicon. Consultant/Advisory Role: Daniel F. Hayes, Immunicon; G. Thomas Budd, Novartis; Gerald V. Doyle, Immunicon. Stock Ownership: Gerald V. Doyle, Immunicon; Jeri Matera, Immunicon; W. Jeffrey Allard, Immunicon; M. Craig Miller, Immunicon; Leon W.M.M. Terstappen, Immunicon. Honoraria: Daniel F. Hayes, Veridex; G. Thomas Budd, Aventis, AstraZeneca, Genentech. Research Funding: Massimo Cristofanilli, Immunicon; Daniel F. Hayes, Immunicon; Mathew J. Ellis, Immunicon; Alison Stopeck, Immunicon; James M. Reuben, Immunicon. Expert Testimony: Daniel F. Hayes, Immunicon. Other Remuneration: Gerald V. Doyle, Immunicon. For a detailed description of these categories, or for more information about ASCO’s conflict of interest policy, please refer to the Author Disclosure Declaration and Disclosures of Potential Conflicts of Interest found in Information for Contributors in the front of each issue.
Supported by Immunicon Corporation, Huntingdon Valley, PA. Authors’ disclosures of potential conflicts of interest are found at the end of this article.
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21. Bonneterre J, Thurlimann B, Robertson JF, et al: Anastrozole versus tamoxifen as first-line therapy for advanced breast cancer in 668 postmenopausal women: Results of the Tamoxifen or Arimidex Randomized Group Efficacy and Tolerability study. J Clin Oncol 18:3748-3757, 2000
22. Mouridsen H, Gershanovich M, Sun Y, et al: Phase III study of letrozole versus tamoxifen as first-line therapy of advanced breast cancer in postmenopausal women: Analysis of survival and update of efficacy from the International Letrozole Breast Cancer Group. J Clin Oncol 21:2101-2109, 2003 Submitted August 26, 2004; accepted December 8, 2004. This article has been cited by other articles:
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ABSTRACT
INTRODUCTION
