Definition: A scoring method for PD-L1 expression used to predict response to immune checkpoint inhibitors (e.g., pembrolizumab).
- Key points:
- CPS includes tumor cells + immune cells (lymphocytes, macrophages), unlike the Tumor Proportion Score (TPS) which counts only tumor cells.
- CPS can range from 0 to >100 (but reported as a whole number, max 100).
- A higher CPS indicates more PD-L1 expression and may predict greater benefit from immunotherapy.
Clinical Relevance by Tumor Type
- Gastric/GEJ adenocarcinoma: Pembrolizumab approved if CPS ≥ 1.
- Cervical cancer: Pembrolizumab approved if CPS ≥ 1.
- Head and Neck Squamous Cell Carcinoma (HNSCC): Pembrolizumab approved if CPS ≥ 1; stronger benefit if CPS ≥ 20.
- Triple-negative breast cancer (TNBC): Atezolizumab or pembrolizumab can be used if CPS ≥ 10.
- Endometrial cancer: Pembrolizumab may be used if CPS ≥ 1 (for certain settings).
Takeaway for oncology pharmacy:
- CPS is a biomarker guiding checkpoint inhibitor eligibility.
- It is different from TPS, and you’ll often see CPS cutoffs (≥1, ≥10, ≥20) in clinical trial inclusion criteria and drug labels.