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Journal of Clinical Oncology, Vol 26, No 20 (July 10), 2008: pp. 3338-3345 © 2008 American Society of Clinical Oncology. DOI: 10.1200/JCO.2007.14.0665 Novel Intraoperative Molecular Test for Sentinel Lymph Node Metastases in Patients With Early-Stage Breast Cancer
From the Department of Human Oncology, Allegheny General Hospital/Allegheny Cancer Center, Pittsburgh; Department of Surgery, Jefferson University Hospital, Philadelphia, PA; Department of Surgery, Morton Plant Mease Healthcare, Clearwater; Department of Surgery, Lakeland Regional Medical Center, Lakeland, FL; Department of Surgery, South Orange County Surgical Medical Group, Laguna Hills; Department of Surgery, John Wayne Cancer Institute, Santa Monica, CA; Nashville Breast Center, Nashville, TN; Berry Consultants LLC, Houston; Department of Surgery, Dallas Surgical Group, Dallas, TX; Department of Surgery, University of Louisville, Louisville, KY; Department of Surgery, Weill-Cornell Breast Center, New York, NY; Department of Surgery, McLaren Regional Medical Center, Flint, MI; and Department of Surgery, Aultman Hospital, Canton, OH Corresponding author: Thomas B. Julian, MD, Allegheny Breast Care Center, Allegheny General Hospital, 320 E North Ave, Pittsburgh, PA 15212; e-mail: tjulian{at}wpahs.org
Purpose An accurate, intraoperative sentinel lymph node (SLN) test could decrease delayed axillary dissections. Molecular tests may be more sensitive than current intraoperative tests but historically have not been rapid enough and have not been properly validated. We present the results from a large, prospective evaluation of the first rapid molecular SLN test, the Breast Lymph Node (BLN) Assay. Methods A beta trial (n = 304) to determine the threshold levels of mammaglobin and cytokeratin 19 correlating with metastasis greater than 0.2 mm and a validation trial (n = 416) to validate the threshold cutoffs were conducted. Alternating portions from each SLN were processed for histology and the BLN Assay. Results BLN Assay performance against extensive permanent-section histology verified by central pathology review was similar to that expected of standard permanent-section histology: sensitivity, 87.6%; specificity, 94.2%; positive predictive value, 86.2%; and negative predictive value (NPV), 94.9%. In 319 patients with both frozen-section hematoxylin and eosin results and BLN Assay results, the BLN Assay had higher sensitivity (95.6%) and NPV (98.2%) than frozen section (sensitivity, 85.6%; NPV, 94.5%). The assay can be performed in approximately 36 to 46 minutes for one to three nodes. Conclusion The BLN Assay allows a rapid evaluation of 50% of each SLN. Comparison with permanent-section histology on adjacent node pieces evaluated by expert pathologists indicated that the BLN Assay was more sensitive than current intraoperative techniques while maintaining high specificity. These data indicate that the assay may be clinically useful for intraoperative or postoperative axillary lymph node dissection decisions.
Sentinel lymph node biopsy (SLNB) provides accurate axillary staging while sparing node-negative patients the morbidity associated with axillary lymph node dissection (ALND).1-5 Current intraoperative sentinel lymph node (SLN) tests have reportedly high false-negative rates,6,7 leading to second operations when metastases are identified postoperatively by permanent-section hematoxylin and eosin (HE) or immunohistochemistry (IHC). This generates additional cost, time, and patient anxiety. Furthermore, the second operation may be difficult to perform because of edematous healing and difficult identification of anatomic landmarks.8 A rapid molecular test has been developed to reduce second-surgery ALNDs. The GeneSearch Breast Lymph Node (BLN) Assay (Veridex LLC, Raritan, NJ) is a real-time reverse-transcriptase polymerase chain reaction (RT-PCR) assay for detection of nodal metastases greater than 0.2 mm.9-14 Results from two consecutive, independent, prospective, blinded clinical trials of the BLN Assay are presented here.
The BLN Assay evaluation consisted of (1) a beta (cutoff) trial (n = 304 patients) to determine the threshold between normal and cancer-related levels of the markers mammaglobin (MG) and cytokeratin-19 (CK-19), and (2) a validation trial (n = 416 patients) to verify the chosen assay threshold cutoffs. Both trials were completed between July 2004 and December 2005 (United States Food and Drug Administration Pre-IDE I040002).
Male or female patients
Node Processing Tissue sections reserved for histology were processed for intraoperative cytopathology and/or frozen section, and for permanent-section HE (site slides) according to the standard procedures of each site. Patient management was based on the analysis of these slides. Additional HE slides (three levels, approximately 150 µm apart; central slides) were prepared and sent to the central study pathologists for evaluation. Sections were also stained for IHC, either on-site or by an outside laboratory (Albany Medical College, Department of Pathology, Albany, New York), and evaluated by either the site pathologist or the central pathologists.
Histologic Evaluation
BLN Assay Testing Alternating sections from the same node were combined and immediately processed as fresh tissue as per the BLN Assay instructions for use.
BLN Assay Result Interpretation
Additional Molecular Testing
Analysis The validation study design was Bayesian, which incorporates preplanned interim analyses and offers the potential benefit of ending a study earlier if predetermined success or futility criteria are met. The predetermined decision criteria for the validation study were as follows:
Type I error was controlled at Patients with invalid BLN Assay results were considered assay negative for performance calculations and were included in the primary analysis because, in clinical use, invalid results would not provide conclusive evidence of metastases. Second-surgery ALND would be required if nodal metastases were found later by histology. Invalid results can arise from inappropriate sampling (eg, all adipose tissue or no nodal tissue) or processing, operator error, or equipment malfunction. Bayesian statistical study design and analysis were performed by Berry Consultants, LLC (Houston, TX). Other statistical analyses and all data validation were performed by the sponsor.
Final Statistical Results Final analysis included 416 total patients (four patients did not have full data sets for the first interim analysis), with an observed sensitivity of 0.876 (95% credible interval, 0.811 to 0.928) and an observed specificity of 0.942 (95% credible interval, 0.913 to 0.966).
Patients
Overall GeneSearch BLN Assay Performance BLN Assay performance was high for both trials when compared with OHR (Table 2). Results of the validation study confirmed the cutoff choices from the beta study. Regardless of the subanalyses performed, results were nearly identical in the two studies.
Permanent-Section Histologic Analyses Of the 416 patients in the validation study, 121 patients (29.1%) were OHR positive. Discrepancies were seen in evaluations of site slides versus central slides, which contained different permanent sections (samplings) from the same node pieces. When comparing HE site slide results from site pathologists to the HE central slide results from consensus review by central pathologists, the sensitivity of site pathology was 94.1% (95% CI, 87.6 to 97.8), specificity was 95.8% (95% CI, 92.8 to 97.7), positive predictive value was 88.1%, and negative predictive value was 98.0%.
Difficult-to-Detect Metastases The OHR of only one patient in the validation study was negative by HE but positive (micrometastasis) by IHC. This patient was found negative by the BLN Assay.
BLN Assay Performance and Size of Metastases The majority (nine of 15) of BLN Assay false-negative results were observed in patients with only one OHR-positive node, and that node contained micrometastases. Eight of these same 15 patients had nodes that were confirmed positive on one set of histology slides (site or central), but not both. Similarly, the majority (15 of 17) of BLN Assay–positive/OHR-negative patients were BLN Assay–positive for only one node.
Histologic Intraoperative Test Performance
Detailed Histologic Analysis and BLN Assay Ct Values A high correlation was found between assay MG and CK-19 Ct values and size of metastases identified by histology (validation study, n = 383 with conclusive OHR and valid BLN Assay results), with Spearman correlation coefficients of 0.77 for MG and 0.74 for CK-19 Ct values versus six categories of histologic involvement (Fig 1). Correlations were similar in the beta study. Table 4 lists the number of assay results by histologic category that were positive by one, both, or neither assay marker.
Number of Positive Nodes Identified In the validation study, the mean and median number of nodes removed was 2.8 and two, respectively (range, one to 11 nodes). The number of positive nodes per patient reported by the BLN Assay versus OHR was in high agreement (Kappa = 0.75; 95% CI, 0.68 to 0.8; Table 5).
Additional Molecular Testing Independent molecular testing of residual assay samples from the validation study supported the BLN Assay results that were not in agreement with the OHR. As a control, residual assay samples from a total of 11 nodes were tested from 11 patients that were negative by both the BLN Assay and OHR. All 11 nodes tested negative with the independent molecular test. Of 15 nodes that tested BLN Assay–positive and OHR-negative, 11 nodes (73%) were confirmed positive by the independent molecular test, similar to the percentage confirmed positive that were both BLN Assay–positive and OHR-positive (15 of 23 nodes; 65%). Beta study results were similar.
Assay Time to Result
Our validation trial used an innovative Bayesian methodology to monitor the results, stopping accrual when the goal of the trial was achieved. In comparison with the maximum sample size of 700 patients, the trial's actual size of 416 patients represented a savings of 284 patients and approximately 9 months. The BLN Assay's true performance evaluation is limited by the intrinsic necessity of different tissue sections being tested by the BLN Assay and by histology with the practical limitations of histologic sampling. Despite these limitations, the results of the present study demonstrate high sensitivity and specificity of the BLN Assay for the molecular detection of SLN metastases greater than 0.2 mm. The Assay's agreement with moderately extensive permanent-section histology performed on adjacent node portions was similar to the agreement between central and site histology slides in the present study. The BLN Assay demonstrated higher sensitivity than intraoperative histologic techniques, despite the disadvantage of sampling different node sections than permanent-section histology. Specificities for the histologic/cytologic intraoperative tests were slightly, but not statistically, higher than that of the BLN Assay. Because of limited sampling, intraoperative histologic tests rarely identify metastases that are later missed by adjacent and more thorough permanent-section histology.17 In terms of false positives, nevi found in SLNs rarely can be mistaken on frozen section for metastases from infiltrating lobular carcinoma. In current practice, when the permanent-section HE result is negative and the intraoperative frozen-section test result is positive, it is more likely that intraoperative sampling exhausted the metastasis, not that the intraoperative result was incorrect. In the present study, it is likely that at least some BLN Assay–positive/OHR-negative results were due to the metastases being restricted to the portion of the node tested by the assay. Evidence for this supposition is provided by the independent molecular test analyses on the residual BLN Assay samples. For most (73%) BLN Assay–positive/OHR-negative samples, the independent test confirmed positivity, suggesting that the node portions tested by the BLN Assay did contain metastases. Thus the sensitivity and specificity of the BLN Assay reported here against histology on adjacent node pieces is likely an underestimation of the assay's true performance. Although permanent-section HE histology is the current standard, the number of histologic disagreements reported in the literature18-21 and observed in the present study between site slide and central slide results illustrate the limitations of histology owing to imperfect node analysis. These results point out the importance of more thorough evaluation of the node to detect metastases. Use of the BLN Assay would minimize the effect of sampling because a greater portion (50%) of the node is evaluated.
Other sources contribute to the generation of histologic false positives, which may or may not be sources of false positives with molecular tests. In a recent study, one source of false positives in IHC analysis was the presence of benign epithelial cells in the SLNs that test positive for cytokeratin.22 The authors suggested that these displaced cells originate in intraductal papillomas and are transported into the SLNs. Because the BLN Assay is designed not to recognize tumor cell deposits The BLN Assay and histologic results were in high agreement for the number of SLNs positive in a given patient, providing evidence that the Assay cutoff values are appropriately chosen to detect only clinically relevant metastases. The present study's results indicate several potential clinical uses for the BLN Assay. It can be used as an accurate intraoperative test for metastatic spread to the SLNs and can also provide valuable postoperative information as an adjunct to permanent-section histology by testing more of the node than is practical by histology alone. A patient found negative by both histology and the BLN Assay is more likely to have an accurate diagnosis than one found negative only by histology. This is supported by the data shown in this article for those cases when histology was negative and the BLN Assay was positive. Additional molecular testing supported the positive BLN Assay result, suggesting that the negative histologic result was not representative of the entire node's status. When both histology and the assay results are negative, the surgeon could feel more confident that the entire node is likely negative. An added advantage of the BLN Assay is that it can be performed by trained technicians and thus may be more easily adopted by clinical sites with limited pathology support. In summary, the combined data from two, large, prospective, multisite studies indicate that the BLN Assay is more sensitive than current intraoperative assays. The Assay's performance is similar to the current standard of care, permanent histologic analysis. It is an objective and reproducible assay and can easily be performed in most clinical laboratories, as shown by the high performance in this study where the assay was conducted soon after SLNB on fresh tissue at 12 different laboratories by a variety of personnel from histotechnologists to experienced pathologists. Using this new molecular pathology technique allows for a more thorough node evaluation and, when used intraoperatively, is likely to reduce the number of patients returning for a second operation for additional node removal because of delayed diagnosis.
Although all authors completed the disclosure declaration, the following author(s) indicated a financial or other interest that is relevant to the subject matter under consideration in this article. Certain relationships marked with a "U" are those for which no compensation was received; those relationships marked with a "C" were compensated. For a detailed description of the disclosure categories, or for more information about ASCO's conflict of interest policy, please refer to the Author Disclosure Declaration and the Disclosures of Potential Conflicts of Interest section in Information for Contributors. Employment or Leadership Position: None Consultant or Advisory Role: Thomas B. Julian, Veridex (C); Peter Blumencranz, Veridex (C); Pat Whitworth, Veridex (C); Donald A. Berry, Veridex (C); Scott M. Berry, Veridex (C); Rache Simmons, Veridex (C) Stock Ownership: None Honoraria: Thomas B. Julian, Veridex; Peter Blumencranz, Veridex; Pat Whitworth, Veridex Research Funding: Thomas B. Julian, Veridex; Peter Blumencranz, Veridex; Kenneth Deck, Veridex; Pat Whitworth, Veridex; Anne Rosenberg, Veridex; Anees B. Chagpar, Veridex; Douglas Reintgen, Veridex; Peter Beitsch, Veridex; Rache Simmons, Veridex; Sukamal Saha, Veridex; Eleftherios P. Mamounas, Veridex; Armando Giuliano, Veridex Expert Testimony: None Other Remuneration: None
Provision of study materials or patients: Thomas B. Julian, Peter Blumencranz, Kenneth Deck, Pat Whitworth, Anne Rosenberg, Anees B. Chagpar, Douglas Reintgen, Peter Beitsch, Rache Simmons, Sukamal Saha, Eleftherios P. Mamounas, Armando Giuliano Collection and assembly of data: Thomas B. Julian, Peter Blumencranz, Kenneth Deck, Pat Whitworth, Donald A. Berry, Scott M. Berry, Anne Rosenberg, Anees B. Chagpar, Douglas Reintgen, Peter Beitsch, Rache Simmons, Sukamal Saha, Eleftherios P. Mamounas, Armando Giuliano Data analysis and interpretation: Donald A. Berry, Scott M. Berry Manuscript writing: Thomas B. Julian, Peter Blumencranz, Kenneth Deck, Pat Whitworth, Donald A. Berry, Scott M. Berry, Anne Rosenberg, Anees B. Chagpar, Douglas Reintgen, Peter Beitsch, Rache Simmons, Sukamal Saha, Eleftherios P. Mamounas, Armando Giuliano Final approval of manuscript: Thomas B. Julian, Peter Blumencranz, Kenneth Deck, Pat Whitworth, Donald A. Berry, Scott M. Berry, Anne Rosenberg, Anees B. Chagpar, Douglas Reintgen, Rache Simmons, Sukamal Saha, Eleftherios P. Mamounas, Armando Giuliano
Supported by Veridex LLC. Presented in part at the 12th Annual Meeting of the Association for Molecular Pathology, November 16-19, 2006, Orlando, FL; 8th Annual Meeting of the American Society of Breast Surgeons, May 2-6, 2007, Phoenix, AZ; 43rd Annual Meeting of the American Society of Clinical Oncology, June 1-5, 2007, Chicago, IL; American Society of Clinical Oncology Breast Cancer Symposium, September 7-8, 2007, San Francisco, CA; Annual Meeting of the College of American Pathology, September 9-13, 2006,San Diego, CA; 6th Biennial Meeting of International Sentinel Node Society, November 1-4, 2006, Rome, Italy; 29th Annual Meeting of the San Antonio Breast Cancer Symposium, December 14-17, 2006, San Antonio, TX; Annual Meeting of the Society of Surgical Oncology, March 15-18, 2007, Washington, DC; 30th Annual Meeting of the San Antonio Breast Cancer Symposium, December 13-16, 2007, San Antonio, TX. Terms in blue are defined in the glossary, found at the end of this article and online at www.jco.org. Authors disclosures of potential conflicts of interest and author contributions are found at the end of this article.
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Copyright © 2008 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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