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Journal of Clinical Oncology, Vol 22, No 17 (September 1), 2004: pp. 3646 © 2004 American Society of Clinical Oncology. DOI: 10.1200/JCO.2004.99.015
Testing for Epidermal Growth Factor Receptor in Lung Cancer: Have We Learned Anything From HER-2 Testing?Baptist Hospital of Miami, Miami, FL
PhenoPath Laboratories, Seattle, WA To the Editor: We read with interest the recently published study by Hirsch et al1 on the correlation between the expression of epidermal growth factor receptor (EGFR) and prognosis in non–small-cell lung carcinoma. A number of observations are worth mentioning. In the technical part of the study, the authors chose to use tissue microarrays (TMA). Given the real and perceived heterogeneity of EGFR distribution in tumor sections, as we routinely encounter in our practice, the use of an entire tissue section may have been more accurate in scoring the results, particularly because no study has yet validated the applicability of TMA for EGFR testing by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). This is especially relevant given that published studies already documented significant heterogeneity of EGFR expression when examined on tissue sections.2 Also, only a single antibody in this study was used on a relatively small number of specimens. The authors could have easily performed the studies on entire sections without significantly lengthening the interpretation time of IHC. In terms of the discussion of correlation with survival, a much larger cohort of patients is needed to address this point, especially given the uncertainty of IHC results on the TMA used in this study. This is critical given that no significant correlation has been previously found between the status of the EGFR gene and its protein product.3,4 Finally, the authors have misquoted a study that they claim shows superiority of FISH over IHC in predicting treatment response to trastuzumab. In fact, the quoted article is from a study done by Pauletti et al,5 in which trastuzumab was not even employed. Instead, that study addressed the question of outcome analysis on patients who largely received surgical treatment alone. Pauletti et al conclude that FISH predicts outcome better than IHC. Unfortunately, those authors used profoundly flawed IHC methodology that we discussed in detail elsewhere.6 Therefore, we warn that a potentially similar problem might present itself in EGFR testing unless investigators validate their methodology prior to conducting the study, and unless the studies are conducted on large cohorts of patients. Authors' Disclosures of Potential Conflicts of Interest The authors indicated no potential conflicts of interest. REFERENCES
1. Hirsch FR, Varella-Garcia M, Bunn PA Jr, et al: Epidermal growth factor receptor in non-small-cell lung carcinomas: Correlation between gene copy number and protein expression and impact on prognosis. J Clin Oncol 21:3798-3807, 2003 2. Goldstein NS, Armin M: Epidermal growth factor receptor immunohistochemical reactivity in patients with American Joint Committee on Cancer Stage IV colon adenocarcinoma: Implications for a standardized scoring system. Cancer 92:1331-1346, 2001[CrossRef][Medline] 3. Reissmann PT, Koga H, Figlin RA, et al: Amplification and overexpression of the cyclin D1 and epidermal growth factor receptor genes in non-small-cell lung cancer. Lung Cancer Study Group. J Cancer Res Clin Oncol 125:61-70, 1999[CrossRef][Medline] 4. Gorgoulis VG, Barbatis C, Poulias I, et al: Molecular and immunohistochemical evaluation of epidermal growth factor receptor and c-erb-B-2 gene product in transitional cell carcinomas of the urinary bladder: A study in Greek patients. Mod Pathol 8:758-764, 1995[Medline]
5. Pauletti G, Dandekar S, Rong H, et al: Assessment of methods for tissue-based detection of the HER-2/neu alteration in human breast cancer: A direct comparison of fluorescence in situ hybridization and immunohistochemistry. J Clin Oncol 18:3651-3664, 2000 6. Yaziji H, Gown AM: Testing for HER-2/neu in breast cancer: Is fluorescence in situ hybridization superior in predicting outcome? Adv Anat Pathol 9:338-344, 2002[CrossRef][Medline]
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Copyright © 2004 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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