CAP/ASCP/ASCO Guideline on HER2 Testing and Clinical Decision-Making in Gastroesophageal Adenocarcinoma

As reported by Angela N. Bartley, MD, of St Joseph Mercy Hospital, Ann Arbor, and colleagues in the Journal of Clinical Oncology, the College of American Pathologists (CAP), the American Society for Clinical Pathology (ASCP), and ASCO have released a guideline on HER2 testing and clinical decision-making in gastroesophageal adenocarcinoma. The guideline was developed by an expert panel, consisting of practicing pathologists, oncologists, and a gastroenterologist with expertise and experience in gastroesophageal adenocarcinoma, based on a systematic review of the literature. Panel co-chairs were Dr. Bartley; Mary Kay Washington, MD, PhD, of Vanderbilt University Medical Center; and Jaffer A. Ajani, MD, of The University of Texas MD Anderson Cancer.

Guideline questions were: What is the optimal testing algorithm for the assessment of HER2 status in patients with gastroesophageal adenocarcinoma? What strategies can help ensure optimal performance, interpretation, and reporting of established assays in patients with gastroesophageal adenocarcinoma? Key recommendations are summarized/reproduced here. The type of recommendation, quality of evidence, and strength of recommendation are shown in parentheses.

Recommendations for Clinicians

1.1: In patients with advanced gastroesophageal adenocarcinoma who are potential candidates for HER2-targeted therapy, the treating clinician should request HER2 testing on tumor tissue (type: evidence based; quality of evidence: high; strength of recommendation: strong).

1.2: Treating clinicians or pathologists should request HER2 testing on tumor tissue in the biopsy or resection specimens (primary or metastasis) preferably prior to the initiation of trastuzumab [Herceptin] therapy if such specimens are available and adequate. HER2 testing on fine-needle aspiration specimens (cell blocks) is an acceptable alternative (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: recommendation/moderate).

1.3: Treating clinicians should offer combination chemotherapy and HER2-targeted therapy as the initial treatment for appropriate patients with HER2-positive tumors who have advanced gastroesophageal adenocarcinoma (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: strong).

Recommendations for Pathologists

2.1: Laboratories/pathologists must specify the antibodies and probes used for the test and ensure that assays are appropriately validated for HER2 immunohistochemistry and in situ hybridization on gastroesophageal adenocarcinoma specimens (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: strong).

2.2: When gastroesophageal adenocarcinoma HER2 status is being evaluated, laboratories/pathologists should perform/order immunohistochemistry testing first, followed by in situ hybridization when immunohistochemistry result is 2+ (equivocal). Positive (3+) or negative (0 or 1+) HER2 immunohistochemistry results do not require further in situ hybridization testing (type: evidence based; quality of evidence: high; strength of recommendation: strong).

2.3: Pathologists should use the Ruschoff/Hofmann method in scoring HER2 immunohistochemistry and in situ hybridization results for gastroesophageal adenocarcinoma (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: strong).

2.4: Pathologists should select the tissue block with the areas of lowest-grade tumor morphology in biopsy and resection specimens. More than one tissue block may be selected if different morphologic patterns are present (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: moderate).

2.5: Laboratories should report HER2 test results in gastroesophageal adenocarcinoma specimens in accordance with the CAP “Template for Reporting Results of HER2 (ERBB2) Biomarker Testing of Specimens From Patients With Adenocarcinoma of the Stomach or Esophagogastric Junction” (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: strong).

2.6: Pathologists should identify areas of invasive adenocarcinoma and also mark areas with the strongest intensity of HER2 expression by immunohistochemistry in gastroesophageal adenocarcinoma specimen for subsequent in situ hybridization scoring when required (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: strong).

2.7: Laboratories must incorporate gastroesophageal adenocarcinoma HER2 testing methods into their overall laboratory quality improvement program, establishing appropriate quality improvement monitors as needed to ensure consistent performance in all steps of the testing and reporting process. In particular, laboratories performing gastroesophageal adenocarcinoma HER2 testing should participate in a formal proficiency testing program, if available, or an alternative proficiency assurance activity (type: evidence based; quality of evidence: moderate/intermediate; strength of recommendation: strong).

2.8: There is insufficient evidence to recommend for or against genomic testing in gastroesophageal adenocarcinoma patients at this time.

The guideline is jointly published in Archives of Pathology & Laboratory Medicine, American Journal of Clinical Pathology, and Journal of Clinical Oncology.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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