CPS-22C3

PD-L1 Testing in Gastric Cancer by the Combined Positive Score of the 22C3 PharmDx and SP263 Assay with Clinically Relevant Cut-offs

Results

The two assays showed a high correlation in both the CPS and TPS. At a CPS ≥ 1 cut-off, 219 (57.8%) and 231 (60.9%) GCs were positive for PD-L1 with the 22C3 and SP263 assays, and at ≥ 10 cut-off, 37 (9.8%) and 36 (9.5%) GCs were positive, respectively. The overall percent agreement (OPA) was greater than 90% with CPS ≥ 1 and ≥ 10 cut-offs, and TPS ≥ 1% and ≥ 10% cut-offs. There was higher OPA between the two assays with a CPS cut-off ≥ 10 (99.2%) than ≥ 1 (94.7%). The percent agreement between the CT and IM was higher with a CPS cut-off ≥ 10 (92.9%) than ≥ 1 (77.6%). Patient with positive expression at CPS ≥ 5 cut-off had a significantly better outcomes in both assays. Interobserver variability among five pathologists was higher than the assay variability.

Conclusion

Two assays for PD-L1 expression in GC showed high agreement. These results provide guidance for selecting eligible patients with GC for pembrolizumab treatment.

Keywords: Programmed cell death ligand 1, Immunohistochemistry, 22C3 pharmDx, SP263 assay, Gastric neoplasms

Pathologic Report for PD-L1 (22C3) Assay (Agilent/Dako)

The slides have sent to Taipei Institute of Pathology for PD-L1 study and the report read as below.

Tissue blocks/unstained slides received labeled as: S22-03853 Tumor type: cholangiocarcinoma Tumor location: liver Testing assay: 22C3 pharmDx Assay (Agilent/Dako) Testing platform: Autostainer Link 48 Detection system: EnVision FLEX visualization system Control slide result: [V] Pass, [ ] Fail Adequate tumor cells present (>=100 viable tumor cells): [V] Yes, [ ] No

Result:

1. Combined Positive Score (CPS) assessment [] CPS < 1 [v] CPS >=1 and <10 [] CPS >=10
2. Combined Positive Score (CPS): 4

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