Introduction
Which gastric cancers should be tested for HER2?
Consensus
Background/rationale
Staining intensity: IHC-Score | Surgical specimen staining pattern | Biopsy specimen staining pattern | HER2 status |
---|---|---|---|
0 | No reactivity or membranous reactivity in <10% of tumor cells | No reactivity or membranous reactivity in any (or <5) tumor cell(s) |
Negative
|
1+ | Very weak membranous reactivity in ≥10% of tumor cells | Tumor cell cluster with a very weak membranous reactivity irrespective of percentage of tumor cells stained (at least 5 tumor cells) |
Negative
|
2+ | Weak to moderate complete, basolateral or lateral only membranous reactivity in at least 10% of tumor cells | Tumor cell cluster with a weak to moderate complete, basolateral or only lateral membranous reactivity irrespective of percentage of tumor cells stained (at least 5 tumor cells) |
Equivocal (ISH assessment required) |
3+ | Strong complete, basolateral or lateral only membranous reactivity in at least 10% of tumor cells | Tumor cell cluster with a strong complete, basolateral or lateral only membranous reactivity irrespective of percentage of tumor cells stained (at least 5 tumor cells) |
Positive
|
Submission of at least 5 tumor-containing biopsies collected from different tumor sites to allow for valid testing |
When requesting the report, active communication as to whether HER2 testing is required |
Full clinical data (precise description of the sampling point, patient history, initial diagnosis, relapse, treatment etc.) |
Sample quality and quantity, and their impact on HER2 testing
Consensus
Background/rationale
Comments on the availability (acquisition) of tumor blocks
Specific considerations for HER2 testing and treatment decisions from the clinician’s perspective
Consensus
Consensus
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Various findings were discussed
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In case of a HER2-negative primary finding, a rebiopsy should be carried out if anti-HER2 targeted therapy may be indicated in case of relapse (i.e. where metastases have occurred) (consensus).
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If the metastasis is accessible, rebiopsy should be performed provided this can be tolerated by the patient (consensus).
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If the metastasis is not accessible for biopsy, any additional archived material (biopsy, surgical specimens) should also be accessed if available, and the primary finding should be confirmed by testing of this additional material (consensus).
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In case of a HER2-positive primary finding and a HER2-negative metastasis, the positive finding remains valid, and there is the option for treatment with trastuzumab.