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Oncologists, Pathologists Issue HER2 Testing Guidance for Gastroesophageal Cancer Patients

NEW YORK (GenomeWeb) – The College of American Pathologists (CAP), the American Society for Clinical Pathology (ASCP), and the American Society of Clinical Oncology (ASCO) have issued new guidelines for clinicians using HER2 amplification or mutation testing to inform treatment of advanced gastroesophageal adenocarcinoma, a form of cancer that originates near the junction of the esophagus and stomach.

As they reported today in the Journal of Clinical Oncology, members of the three associations worked together to come up with 11 recommendations for HER2 testing in individuals with gastroesophageal adenocarcinoma, along with validated algorithms for assessing HER2 and using the test results to guide clinical decision-making. The recommendations are being concurrently published in the Archives of Pathology & Laboratory Medicine and the American Journal of Clinical Pathology.

The guidance urges HER2 testing on tumor biopsy, resection, or fine needle aspirate samples from individuals with advanced forms of the disease to determine eligibility for treatments that target the gene. The team also suggests that those with HER2 alterations should be offered the option of combining chemotherapy with HER2-targeting treatment such as trastuzumab (marketed as Herceptin by Genentech) as a first line treatment, among other recommendations.

"As cancer care evolves to be increasingly personalized, this new guideline helps establish standards for when and how to accurately perform HER2 testing to guide treatment for gastroesophageal adenocarcinoma patients," MD Anderson Cancer Center medical oncologist Jaffer Ajani, an author on the study and co-chair of the panel developing the recommendations, said in a statement.

The HER2 gene (also known as ERBB2) is already used as a biomarker for selecting treatment strategies for individuals with advanced gastroesophageal adenocarcinoma — a phase III trial reported in the Lancet in 2010 by members of the Trastuzumab for Gastric Cancer, or ToGA, consortium funded by Hoffman-La Roche pointed to enhanced survival in HER2-positive gastroesophageal adenocarcinoma patients treated with both trastuzumab and chemotherapy, the team explained. But evidence-based strategies for routinely testing HER2 in this context have been lacking.

Using information from more than 100 published studies or meta-analyses, the CAP-, ASCP-, and ASCO-led group set out to establish a concrete clinical framework for considering HER2 status in individuals with gastroesophageal adenocarcinoma, which is often diagnosed at an advanced stage. The investigators graded the quality of the evidence behind each of their recommendations, sharing these ratings along with the guidance.

Among their other guidelines, the researchers argued in favor of sufficient validation for antibodies used for the immunohistochemistry and/or in situ hybridization assays used to test for HER2 over-expression or mutation. The former method is recommended as a first step, they noted, followed by in situ hybridization testing for cases with ambiguous HER2 immunohistochemistry results.

Results of such tests would then be returned using a CAP reporting template developed for HER2 biomarker testing in individuals with esophageal-stomach junction adenocarcinoma. The team also highlighted the potential benefits of delineating parts of the tumor with high HER2 expression or enhanced invasiveness, when such information is available from pathologists. 

Based on the data available so far, the authors noted that there is "insufficient evidence to recommend for or against genomic testing in [gastroesophageal adenocarcinoma] patients at this time." However, they added, "as the fields of genomics, proteomics, and biotechnology continue to evolve, novel and more accurate methods of assessing HER2 status may become available. Similarly, as more clinical trials are conducted on HER2-directed therapy in [gastroesophageal adenocarcinoma], changes in treatment algorithms may necessitate updates to these recommendations in the future."