Fredrick L. Kiechle, MD, PhD
Q. Oncologists have been requesting HER2/neu testing on gastric and gas-tro-esophageal carcinomas. Are the testing parameters different from those for breast cancer?
A. The Food and Drug Administration recently approved trastuzumab (Herceptin) for treatment of metastatic gastric and gastroesophageal junction adenocarcinoma (G-GE), based on data from an international phase three randomized study of Trastuzumab for GAstric Cancer, or ToGA,1 demonstrating a 2.7-month survival benefit of trastuzumab (Herceptin) plus chemotherapy in HER2+ advanced G-GE adenocarcinoma, as compared with chemotherapy alone.
An accompanying study investigated HER2 testing parameters, and proposed modified HER2 scoring schema for G-GE carcinoma (Table 1).1-4 Analysis of the ToGA pathologic material showed that strong basolateral HER2 membrane staining by immunohistochemistry (IHC) correlates with HER2 amplification by fluorescence in situ hybridization (FISH); additionally, G-GE carcinoma has a greater tendency toward HER2 heterogeneity as compared with breast carcinoma (~five percent heterogeneous G-GE cases1). These data have been incorporated into the consensus recommendations for G-GE HER2 scoring (Table 1), which differ from breast cancer scoring. In G-GE carcinoma, basolateral (incomplete) membrane staining is scored, and circumferential staining is not required. For biopsy specimens, amplification or strong basolateral staining in a small cluster of cells is reported as positive, while the 10 percent threshold is maintained for resection specimens.
These studies have provided useful benchmarks regarding expected rates of positivity (Table 2), and they have highlighted technical and interpretive pitfalls, including antibody reactivity with benign gastric epithelium and occasional strong cytoplasmic staining precluding interpretation (Fig. 1).2,3 Interestingly, G-GE carcinoma has a greater fraction (up to 20 percent) of HER2 FISH-amplified but IHC-negative cases (0, 1+) (ToGA trial1) as compared with breast carcinoma. A ToGA subgroup analysis found that HER2 FISH-amplified but IHC-negative (0, 1+) cases derive little benefit from trastuzumab, while the survival benefit excluding these cases was longer, at 4.2 months.1 On the other hand, a subgroup analysis of heterogeneously HER2- positive cases has not been published.
The FDA approved Dako’s HER2 IHC and FISH assays for use in gastric cancer testing concurrently with its approval of trastuzumab for treatment of advanced gastric cancer. European data demonstrated excellent concordance using two different HER2 IHC kits, and two FISH kits, as well as other brightfield in situ hybridization methods.4 At present, HER2 assays for gastric carcinoma should be validated as appropriate for predictive markers (see CAP checklist ANP.22969 and ANP.22970); further guidelines may be forthcoming. A CAP Survey for HER2 immunohistochemistry in G-GE carcinoma will be available soon (GHER2) specifically for G-GE carcinoma. Further details and illustrations can be found in the references.
- Bang YJ, Van Cutsem E, Feyereislova A, et al. Trastuzumab in combination with chemotherapy versus chemotherapy alone for treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA): a phase 3, open-label, randomised controlled trial. Lancet. 2010;376:687–697.
- Hofmann M, Stoss O, Shi D, et al. Assessment of a HER2 scoring system for gastric cancer: results from a validation study. Histopathology. 2008;52:797–805.
- Rüschoff J, Nagelmeier I, Baretton G, et al. HER2-Diagnostik beim magenkarzinom: was ist anders im vergleichzum mammakarzinom? Pathologe. 2010;31:208–217.
- Rüschoff J, Dietel M, Baretton G, et al. HER2 diagnostics in gastric cancer–guideline validation and development of standardized immunohistochemical testing. Virchows Archiv. 2010;457(3): 299–307.
- Bang Y, Chung H, Sawaki A, et al. HER2-positivity rates in advanced gastric cancer (GC): results from a large international phase III trial. J Clin Oncol. 2008 ASCO Annual Meeting Proceedings. Vol. 26, No 15S (May 20 Supplement); 2008:4526.
- Kunz PL, Mojtahed A, Fisher GA, et al. HER2 expression in gastric and gastroesophageal junction adenocarcinoma in a U.S. population: clinicopathologic analysis with proposed approach to HER2 assessment. Appl Immunohistochem Mol Morphol. 2011 May 25. [Epub ahead of print] PMID:21617522.
Megan L. Troxell, MD, PhD
Oregon Health & Science University
Q. Every newborn in the United States is checked for metabolic diseases through a comprehensive newborn screening system. Why then is there a need to do alternative tests for reducing substances in the urine specimens of young children?
A. Detection of reducing substances in urine is a laboratory procedure that has been used for decades because it is easy to perform, results can be reported rapidly, and, historically, it was an early method of detecting serious inborn errors of metabolism. The reducing substance assay involves adding a reagent tablet to urine for detection of reducing substances (glucose and other carbohydrate metabolites), using the classic Benedict’s copper reduction reaction. If the reducing test is positive and the enzymatic dipstick assay for urinary glucose is negative, the presence of substances other than glucose is suggested. A positive test requires additional urine and blood testing and clinical evaluation to diagnose the actual inborn error of metabolism.
Some hospitals, especially pediatric facilities, perform a urine reducing substance assay on all children under age 5 whenever a urinalysis is ordered. Many states began performing blood tandem mass spectrometry (MS/MS) as early as 1998 as a part of their newborn screening panels. Tandem mass spectrometry is an excellent method for detecting numerous inborn errors of metabolism. Now nearly all states follow the American College of Medical Genetics’ recommendation to screen for 29 metabolic disorders and perform tandem mass spectrometry on newborns. With the success of newborn screening, the question is raised whether it is still necessary to perform urine tests for reducing substances on all children.1 In some pediatric hospitals, the urine reducing substance assay is now performed only when the clinician orders it and not as a routine part of urinalysis. In the case of a sick newborn in whom the newborn screening results are not yet available, the urine reducing substance assay may be useful; the rapid result could help support a diagnosis of an inborn error of metabolism such as fructosemia or galactosemia. Because there are no current national recommendations on the performance of urine reducing substance assays, each laboratory should review its patient population and determine the best utility and ordering options for this assay.
- Naumova NN, Schappert J, Kaplan LA. Reducing substances in urine: a paradigm for changes in a standard test. Ann Clin Lab Sci. 2006;36:447–448.
Deborah A. Perry, MD
Department of Pathology
Children’s Hospital and Medical Center
Member, CAP Point of Care Testing Committee
Dr. Kiechle is medical director of clinical pathology, Memorial Healthcare, Hollywood, Fla.