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Current Laboratory Testing Practices for Assessment of ERBB2/HER2 in Endometrial Serous Carcinoma and Colorectal
Ian S Hagemann1, Julia A Bridge2,3, Laura J Tafe4
1From the Department of Pathology and Immunology, Washington University School of Medicine, St Louis, Missouri (Hagemann).
Context.—:
Therapy targeted at human epidermal growth factor receptor 2 (HER2; also known as ERBB2) was used initially for breast and gastroesophageal carcinoma and has more recently been adopted for endometrial serous carcinoma (ESC) and colorectal carcinoma (CRC). There is evidence that predictive biomarker testing algorithms for HER2 must be tumor type specific and that an algorithm validated for one tumor type cannot be applied to another.
Objective.—:
To describe current laboratory practices for HER2 assessment in ESC and CRC.
Design.—:
We surveyed laboratories participating in the 2021 College of American Pathologists (CAP) HER2 immunohistochemistry proficiency testing program.
Results.—:
The survey was distributed to 1548 laboratories and returned by 1195, of which 83.5% (998) were in the United States. For ESC, 24.0% (287) of laboratories reported performing in-house testing for HER2 by immunohistochemical staining and/or in situ hybridization; of these, 44.3% (127) performed it reflexively on all cases of ESC. The most common criterion for evaluating HER2 was the American Society of Clinical Oncology/CAP 2018 guideline for breast carcinoma (69.0%; 194 of 281), whereas only 16.0% (45) of laboratories used guidelines specific to ESC. For CRC, 20.2% (239 of 1185) of laboratories performed in-house HER2 testing, and 82.0% of these (196) did the test only at the clinician's request. A plurality (49.4%; 115 of 233) used gastroesophageal cancer guidelines when scoring CRC, 30.0% (70) used the CRC scoring system from the HERACLES trial, and 16.3% (38) used the American Society of Clinical Oncology/CAP 2018 guideline for breast carcinoma.
Conclusions.—:
Laboratories vary in their approach to HER2 testing in ESC and CRC. Most laboratories did not report using tumor type-specific recommendations for HER2 interpretation. The lack of standardization could present a challenge to evidence-based practice when considering targeted therapy for these diseases.
Insights
Laboratory practices for human epidermal growth factor receptor 2 (HER2) testing in endometrial serous carcinoma (ESC) and colorectal carcinoma (CRC) lack standardization. Most labs do not use tumor-specific guidelines, potentially impacting targeted therapy decisions.
Area of Science:
- Oncology
- Pathology
- Biomarker Testing
Background:
- Targeted therapy for human epidermal growth factor receptor 2 (HER2) is expanding beyond breast and gastroesophageal cancers to include endometrial serous carcinoma (ESC) and colorectal carcinoma (CRC).
- HER2 predictive biomarker testing algorithms must be tumor-type specific, as algorithms validated for one cancer type are not applicable to others.
Purpose of the Study:
- To describe current laboratory practices for HER2 assessment in ESC and CRC.
- To identify variations in HER2 testing methodologies and interpretation guidelines across different laboratories for these cancer types.
Main Methods:
- A survey was distributed to laboratories participating in the 2021 College of American Pathologists (CAP) HER2 immunohistochemistry proficiency testing program.
- The survey collected data on in-house HER2 testing practices, including staining, in situ hybridization, and the guidelines used for interpretation in ESC and CRC.
Main Results:
- Significant variation exists in HER2 testing approaches for ESC and CRC among surveyed laboratories.
- A majority of laboratories did not utilize tumor type-specific recommendations for HER2 interpretation, with many applying breast or gastroesophageal cancer guidelines.
- In-house HER2 testing was reported by 24.0% of labs for ESC and 20.2% for CRC, with differing frequencies of reflexive testing or clinician-requested testing.
Conclusions:
- Current laboratory practices for HER2 testing in ESC and CRC are not standardized.
- The predominant use of non-specific guidelines for HER2 interpretation poses a challenge to evidence-based practice for targeted therapies.
- Lack of standardization may hinder optimal patient care and treatment decisions in ESC and CRC patients eligible for HER2-targeted therapies.
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