PD-L1 CPS in gastroesophageal cancer: differences in routine care versus Checkmate 649 and implications for biopsy-site choice and assay standardisation. - Flanders L; Savy T; Ficial M; Al-Ghraibawi N; Barber L; Slater S; Pihlak R; Propper D; Begum S; Rodriguez-Justo M; Gerlinger M (British journal of cancer, 2026)