For patients diagnosed with gastric or gastroesophageal junction (G/GEJ) adenocarcinoma:
Learn more about testing for CLDN18.2 using standard IHC procedures in accordance with guidance from the College of American Pathologists Preanalytics for Precision Medicine Project Team (CAP PPMPT).1,2
Learn more about testing for CLDN18.2 using standard IHC procedures in accordance with guidance from the College of American Pathologists Preanalytics for Precision Medicine Project Team (CAP PPMPT).1,2
CLDN18 antibodies can identify both major isoforms — CLDN18.1 and CLDN18.2. But when evaluating G/GEJ tumor tissue, the staining observed is reflective of CLDN18.2 expression because2:
CLDN18.2 is normally present in gastric epithelium and is often retained in malignant gastric tissue3
CLDN18.1 is primarily expressed in
adenocarcinoma lung tissue; its expression is negligible in G/GEJ cancers3
Appropriate specimen handling and preparation are essential to ensure the accuracy of biomarker results.1 Expand the following section for key recommendations.
CAP PPMPT recommends daily tissue processor
maintenance per the manufacturer
recommendations and rigorous quality maintenance of processor fluids, including formalin pH/purity and water contamination of alcohols.1
Cold ischemic time should be limited to ≤60 minutes according to CAP PPMPT.1
CAP PPMPT provides recommendations regarding dimensions and duration involved in sample fixation.1
Specimen thickness should not exceed 4 mm-5
mm
Tissue should be completely submerged in fixative
Ensure a fixative volume to tissue mass ratio of no less than 4:1, with an optimal ratio of 10:1
Paraffin should be melted at <60°C
As part of stabilization, tissue should be
fixed in 10% neutral phosphate-buffered
formalin (pH 7.0) for at least 6 hours and
no longer than 24 to 36 hours
If the tissue has high fat content, fixation
may require up to 48 hours
Routinely processed, formalin-fixed, paraffin-embedded (FFPE) tissues are suitable for use with IHC testing
Tissue sections can be cut at 3 µm-6 µm*
Before staining, the cut slides should be dried completely either at room temperature (air dried)
or by offline baking (baked in oven) at 60°C for 60 minutes*
CLDN18 specific.
≤1 freeze-thaw cycle: for nucleic acids
and proteins use aliquots
A number of assays, antibodies, and platforms are
available for the assessment of CLDN18.2 expression.
Select assays and antibodies include the VENTANA
CLDN18 (43-14A) Class I IVD Assay, the LSBio
PathPlus™ CLDN18 Antibody, and the Novus
Biologicals Claudin-18 Antibody. Options for
platforms can include BenchMark ULTRA, Dako
Autostainer, and Leica Bond.4
The list of antibodies/assays and platforms is not
exhaustive and the tests mentioned above are not
FDA-approved companion diagnostics. Please use
the appropriate test to guide in clinical decision-
making.
Appropriate controls are essential for the detection of
CLDN18.2 in G/GEJ tumor samples. Here are some
key points on their selection and use.2,5
CAP guidelines recommend that laboratories validate
and/or verify immunohistochemical tests before
placing them into clinical service and should include
positive, negative, and borderline tissue, reflecting
the intended use of the assay.5
CLDN18 specific.
In a study to assess the reproducibility and
comparability of three CLDN18 antibodies and IHC
staining platforms across a cohort of 27 global
laboratories4,*,†:
Antibodies in the study comprised the VENTANA CLDN18 (43-14A) Class I IVD
Assay from Roche Tissue Diagnostics, the PathPlus™ CLDN18 Antibody from
LSBio, and the Claudin-18 Antibody from Novus Biologicals. Platforms
comprised BenchMark ULTRA, Dako Autostainer, and Leica Bond.4
Consensus reference scores from all antibodies for each sample were
determined by central pathology review. CLDN18.2 positivity was defined with a
threshold of ≥75% of tumor cells expressing membranous CLDN18 with
moderate-to-strong (≥2+) staining intensity. Accordingly, participating
pathologists were required to submit a binary positive/negative call as well as
an estimation of the percent of cells stained. Laboratory-submitted IHC scores
were compared to the reference consensus score and considered discordant if
the positive/negative binary result differed. Statistical analysis was performed
for comparison and an acceptance criteria of 85% (≥0.85) was applied.4
CAP PPMPT, College of American Pathologists Preanalytics for Precision
Medicine Project Team; CLDN, claudin; CLDN18.1, claudin 18 isoform 1; CLDN18.2,
claudin 18 isoform 2; FDA, US Food and Drug Administration; G/GEJ, gastric/
gastroesophageal junction; IHC, immunohistochemistry; IVD, in vitro diagnostic.
Appropriate controls are essential for the detection of
CLDN18.2 in G/GEJ tumor samples. Here are some
key points on their selection and use.2,5
CAP guidelines recommend that laboratories validate
and/or verify immunohistochemical tests before
placing them into clinical service and should include
positive, negative, and borderline tissue, reflecting
the intended use of the assay.5
CLDN18 specific.
References: 1. Compton CC, Robb JA, Anderson MW, et al. Preanalytics and precision pathology: pathology practices to enure molecular integrity of cancer patient biospecimens for precision medicine. Arch Pathol Lab Med 2019;143(11):1346-63. 2. Ventana CLDN18 (43-14A) assay [package insert]. Mannheim, Germany: Roche Diagnostics GmbH. 3. Sahin U, Koslowski M, Dhaene K, et al. Claudin-18 splice variant 2 is a pan-cancer target suitable for therapeutic antibody development. Clin Cancer Res 2008;14(23):7624-34. 4. Jasani B, Schildhaus HU, Taniere P, et al. Global ring study determining reproducibility and comparability of CLDN18 testing in gastric cancer. Poster presented at: ESMO Targeted Anticancer Therapies Congress; March 6-8, 2023; Paris, France. 5. College of American Pathologists. IHC assays—New evidence-based guideline for analytic validation (04-01-2004). https://documents.cap.org/documents/ihc-validation-webinar-handout.pdf. Accessed 03-30-2023.