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Short Communication |
1 Division of Surgical Oncology, School of Medicine and 2 Department of Biomathematics, University of California at Los Angeles, Los Angeles, California
Requests for reprints: Mai N. Brooks, Division of Surgical Oncology, School of Medicine, University of California at Los Angeles, 10833 Le Conte Avenue, P.O. Box 951782, Los Angeles, CA 90095. Phone: 310-206-2215; Fax: 310-825-7575. E-mail: maibrooks{at}mednet.ucla.edu
| Abstract |
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Experimental Design: In this study, we determined the levels of an angiogenic factor basic fibroblast growth factor (bFGF) in the nipple fluid of healthy subjects as well as patients with benign breast conditions, those at high risk for breast cancer, and patients with active breast cancer. ELISAs were used to measure bFGF.
Results: Nipple fluid bFGF levels were as follows (mean ± SE): 158 ± 17 pg/mL from benign breasts, 561 ± 277 pg/mL from high-risk breasts, and 1,343 ± 441 pg/mL from cancerous breasts. One-way ANOVA showed that the bFGF levels from cancerous breasts were significantly higher than those from benign and high-risk breasts (P = 0.0001 and P = 0.0193, respectively). After logarithmic transformation was applied to the data, high-risk breast bFGF levels were higher than those from benign breasts (P = 0.0028). With a cutoff level of 250 pg/mL, the sensitivity was 79.2%, specificity was 82.5%, and correct diagnosis was 66.4%. The area under the receiver operating characteristic curve was 0.86.
Conclusions: We conclude that nipple fluid bFGF levels are progressively elevated in high-risk and cancerous breasts compared with benign breasts. The sensitivity and specificity of this test are promising compared with current breast cancer screening methods, and this test deserves further studies with larger clinical trials. Potential areas of usefulness include the detection of breast cancer risk or breast cancer, as well as the monitoring and/or prediction of the antiangiogenic effect of preventive therapies. (Cancer Epidemiol Biomarkers Prev 2005;14(12):29958)
| Introduction |
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Breast cancer arises from epithelial cells that line the ductal/lobular systems of the milk ducts. Therefore, it makes sense that examination of this ductal system or analysis of its secretions may reveal signs of early cancer (4). We thus expect that the fluid secreted into the breast ducts would contain a much higher concentration of angiogenic factors than serum or urine (2, 3). Our preliminary data indicated that nipple fluid basic fibroblast growth factor (bFGF), a potent angiogenic factor, is significantly elevated in patients with breast cancer in comparison with benign controls (5). Here, we report our more recent results with a larger population of subjects.
| Materials and Methods |
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First, the nipple was wiped with an alcohol prep pad to remove any debris that may occlude the ductal openings. Then, nipple fluid was obtained with manual breast compression in the direction from the chest wall towards the areola. This procedure may be done by the investigator or the patient herself. The nipple-areolar complex may be squeezed manually or with a breast pump and suction syringe apparatus (Cytyc, Boxborough, MA), to encourage nipple fluid yield. Nipple fluids from any and all ductal openings from one nipple were collected with a Pipetman (Rainin Instrument, Emeryville, CA) and placed in Eppendorf tubes (Axygen Scientific, Union City, CA). The nipple fluids obtained were placed in the refrigerator at 4°C, and transported within 4 to 5 hours to be stored in a 70°C secured freezer.
ELISA
Measurement of bFGF was done by ELISA according to the manufacturers' instructions (R&D, Minneapolis, MN). We diluted 2 µL of nipple fluid in 98 µL of calibrator diluent (R&D), and this dilution was corrected during the subsequent calculations. The amount of protein in nipple fluid was determined by the Bio-Rad protein assay (Bio-Rad, Hercules, CA). Values of bFGF were expressed either as pg/mL directly, or as pg/mg protein.
Data Analysis
Group statistical analysis was done with the Kruskal-Wallis test, and pair-wise comparisons with Wilcoxon test. The nipple fluid bFGF test was also evaluated using measures such as sensitivity, specificity, and correct diagnostic rate.
| Results |
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Group bFGF Levels
We measured bFGF levels and calculated them as pg/mL or pg/mg protein (Fig. 1). In the benign group, bFGF levels were follows: mean 158 ± 17 pg/mL, median 120, range 0 to 1,715, or 0.61 ± 0.07 pg/mg, median 0.46, range 0 to 7.88. In the high-risk group, bFGF levels were as follows: mean 561 ± 277 pg/mL, median 184, range 3 to 17,282, or 2.26 ± 1.29 pg/mg, median 0.64, range 0 to 80.77. In the cancer group, bFGF levels were as follows: mean 1,343 ± 441 pg/mL, median 480, range 42 to 8,726, or 6.28 ± 2.33 pg/mg, median 1.17, range 0.23 to 46.12. One-way ANOVA of the pg/mL data showed a significant group difference (P = 0.0004). The bFGF levels from cancerous breasts were significantly higher than those from benign and high-risk breasts (P = 0.0001 and P = 0.0193, respectively). High-risk breast bFGF levels were higher than those from benign breasts with borderline significance (P = 0.0601). Statistical analysis using the pg/mg data set yielded similar results. Because the distribution of bFGF values were highly skewed, logarithmic transformation was applied to the data. One-way ANOVA of this transformed data showed an even greater significant group difference (P < 0.0001). The bFGF levels from cancerous breasts were significantly higher than those from benign and high-risk breasts (P < 0.0001 and P = 0.0007, respectively). High-risk breast bFGF levels were higher than those from benign breasts with statistical significance (P = 0.0028). In the benign group, we noted no significant influence on bFGF levels (both pg/mL and pg/mg) exerted by age (Spearman correlation coefficient 0.10; P = 0.2550), race (one-way ANOVA P = 0.06838), menopausal status (Wilcoxon rank sum test, P = 0.5930), or hormone use (Wilcoxon rank sum test; P = 0.1328).
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In the benign group, all had nipple aspirate fluid collection prior to any needle or surgical biopsy. We found no significant difference between the bFGF levels from the right versus left breast of the same woman (P = 0.74). For this analysis, we used the benign group subjects who had normal physical exams and normal radiological tests (if indicated). We analyzed the benign subgroups of cyst, fibroadenoma, papilloma, and other physiologically normal conditions. The mean ± SE were 187.56 ± 44.77, 238.71 ± 76.32, 424.90 ± 216.85, and 129.87 ± 10.97 pg/mL, respectively. One-way ANOVA showed that there was no significant difference among the three benign diagnosis groups (cyst, fibroadenoma, and papilloma; P = 0.41). However, the bFGF level in the papilloma group was significantly higher than the group with physiologically normal conditions (P = 0.01, Wilcoxon rank sum test). In the physiologically normal condition group, there were three cases of "usual type hyperplasia," two with apocrine metaplasia, and one with adenosis. For these six cases, the mean ± SE was 130.85 ± 43.33 pg/mL, which was not significantly different from that of the physiologically normal condition group (Table 1A).
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Analysis of a Nipple Fluid bFGF Test
We calculated sensitivity, specificity, and correct diagnosis variables for different bFGF cutoff levels. With a cutoff level of 250 pg/mL, the sensitivity was 79.2%, specificity was 82.5%, and correct diagnosis was 66.4%. With an equivalent cutoff of 1 pg/mg, the sensitivity was 66.7%, specificity was 81.2%, and correct diagnosis was 78.9%.
2 test revealed a statistical significance of P < 0.0001. As we adjusted the cutoff level to 132 pg/mL, the sensitivity reached 96% but specificity decreased to 54%, with correct diagnosis of 60.5%. Similarly, for a cutoff value of 0.30 pg/mg, the sensitivity reached 96% but specificity decreased to 36%, with correct diagnosis of 45.4%. Conversely, if the cutoff level was increased to 350 pg/mL, the specificity improved to 93.8% and correct diagnosis 86.4%, at the cost of a lower sensitivity of 54.2%. As the cutoff level was increased to 1.3 pg/mg, the specificity improved to 93.0% and correct diagnosis was 85.5%, at the cost of a lower sensitivity of 45.8%. These analyses are summarized in the receiver operating characteristic curve in Fig. 2, with an area under the receiver operating characteristic curve of 0.86.
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| Discussion |
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According to the guidelines set forth by the National Cancer Institute Early Detection Research Network, this bFGF nipple fluid test has completed phase 1, and is ready for phase 2 (9). Further studies are warranted, but it does seem that nipple fluid bFGF has the potential to be used to supplement the traditional methods of physical examination and mammogram to screen for breast cancer. A high level of nipple fluid bFGF in a patient with a normal physical exam and mammogram may indicate high risk for breast cancer, and may warrant a more intensive workup or follow-up or even consideration of preventive measures. In the future, we need to proceed to larger prospective studies using this particular method in certain specific populations of women. The validation questions are both scientific and practical. Is this new method statistically valid enough to diagnose or predict breast cancer? And if it is, does this method improve on existing standards of breast cancer diagnosis (physical exam and mammogram), and does it change current breast treatment algorithms? Nipple fluid bFGF aspirate must fulfill both criteria to be useful clinically to women. A possible second use for nipple fluid bFGF may be as a surrogate marker for chemoprevention clinical trials to provide some preliminary insight as to the antiangiogenic effect of the chemopreventive agent (10).
A current major challenge regarding studies of nipple fluid aspirate is the ability to obtain adequate samples. Depending on the investigators' experience and patience, nipple fluid may be elicited in 30% to 98% of eligible subjects. Thus, pharmacologic intervention may be needed in order to increase the sampling adequacy of nipple fluid studies. Normally, the breast fluid is prevented from escaping from the nipple because nipple ducts are occluded by constricting bands of smooth muscle. Various drugs including oxytocin, prolactin, kallikrein, bradykinin, and acetylcholine have been shown to have a relaxation effect on the breast duct smooth muscle (11). We have used nasal oxytocin in a pilot study involving volunteer women, and found that the drug can, in certain cases, increase the yield of nipple fluid aspiration (12). On the other hand, the emerging field of bionanotechnology may soon produce devices that can measure multiple and simultaneous fluid-based as well as cellular markers in the minute amounts derived from nipple fluid aspiration alone (13). Future studies of nipple fluids should use samples obtained from the breast prior to any invasive or semi-invasive biopsy, which is known to release multiple trauma-related factors leading to ambiguity in data interpretation. Furthermore, in premenopausal subjects, care should be taken to account for possible cyclical variability during the menstrual cycle (14).
A second major challenge is the identification of more specific tumor markers. We have observed that bFGF levels are elevated in nipple fluids from pregnant or lactating women (data not shown). There may be other confounding factors, that have yet been identified. Thus, we predict that a panel of multiple nipple fluid markers would be more reliable than one alone. In the near future, more novel breast tumor markers may be identified in the nipple fluid at the earliest stage of breast malignant transformation. Currently, we think that the following nipple fluid factors may prove promising: human glandular kallikreins including prostate-specific antigen (15, 16), insulin-like growth factor and insulin-like growth factorbinding protein (17), Her-2/neu (18), and epidermal growth factor (19). Cellular DNA mutations (20), promoter hypermethylation of important cancer genes (21, 22), and chromosomal changes (23) could also be useful.
In summary, we believe that the breast nipple fluid analysis should be further studied for its potential for adding another important diagnostic tool for breast cancer and for evaluating the antiangiogenic effect of chemoprevention agents (10, 24). This evolving field has promise for future impact on the clinical care of patients with breast cancer.
| Footnotes |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Note: M.R. Sartippour and L. Zhang contributed equally to this work.
Research was performed at the UCLA Medical Center, Los Angeles, CA 90095.
Received 6/ 3/05; revised 9/27/05; accepted 10/10/05.
| References |
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-difluoromethylornithine: breast tissue, imaging, and serum and urine biomarkers. Clin Cancer Res 2002;8:310517.This article has been cited by other articles:
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Y.-s. Zhao, D. Pang, F. Wang, Y.-w. Xue, D.-n. Gao, H. Li, K. Li, B.-y. Wang, D. Wang, and H.-y. Li Nipple Aspirate Fluid Collection, Related Factors and Relationship between Carcinoembryonic Antigen in Nipple Aspirate Fluid and Breast Diseases in Women in Harbin, PRC Cancer Epidemiol. Biomarkers Prev., March 1, 2009; 18(3): 732 - 738. [Abstract] [Full Text] [PDF] |
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