Akademik Veri Yönetim Sistemi
Combined positive score to evaluate PD-L1 expression in gastric and gastroesophageal junction adenocarcinomas, Vienna, Avusturya, 6 - 10 Eylül 2025, cilt.487, ss.429, (Özet Bildiri)
Background & Objectives: PD-L1 expression has been investigated as a predictive biomarker of response to immunotherapy in several tumours, and is reported to be elevated in up to 40% to 65% of gastric or gastroesophageal junction adenocarcinoma (G/GEJ). There is a need to provide reliable, standardised training for pathologists to improve their accuracy of interpretation and scoring, as the results are used directly to inform clinical decisions. We present findings regarding reproducibility and improvement for scoring PD-L1 expression for GC using online training tool.
Methods: This study included 102 cases of G/GEJ adenocarcinoma. PD-L1 expression is scored using the combined positive score (CPS), which is calculated as the number of PD-L1–stained cells (tumour cells, lymphocytes, and macrophages) divided by the total number of viable tumour cells multiplied by 100. The CPS was categorized into a four-step score (0–3) based on clinical relevant thresholds: 0 (CPS < 1), 1 (CPS 1–4), 2 (CPS 5–9), 3 (CPS ≥ 10). Online training was led by qualified and trained pathologists from Targos Molecular Pathology.
Results: The positive rates of CPS with a cutoff value of 1 and 5 were 38,2% (39/102) and 20,5% (21/102), respectively. More than half of the cases was PD-L1 negative (CPS < 1; 61,8%), 17,6% showed low PD-L1 expression (CPS ≥ 1, < 5), 2,9% moderate (CPS ≥ 5 to < 10) and 17,6% strong expression (CPS ≥ 10). Positivity rate after online training according to 1> and 5> cutoff value were 53,3% (24/45) and 35.6% (16/45), increased in line with the literature.
Conclusion: Consistent, accurate, and reproducible scoring of PD-L1 expression, regardless of scoring method, remains a concern.The online training tool offers a means of standardised training for practising pathologists in a clinical setting and can help pathologists successfully learn techniques to confidently score PD-L1 CPS across histologic subtypes and cutoffs