Abstract
Programmed death ligand 1 (PD-L1) expression as a predictive biomarker for programmed cell death 1 (PD-1) inhibitor efficacy in gastric cancer (GC) remains controversial. We hypothesised that the conflicting results may be due to the inaccurate assessment of PD-L1 expression using biopsy samples. A total of 191 patients with GC who received radical resection were enrolled. PD-L1 expressions in biopsy and paired resected samples by immunohistochemistry staining were compared according to the number of biopsies. The numbers of PD-L1-positive patients determined by biopsy and resected samples were 89 (46.6%) and 135 (70.1%), respectively. The accordance rate was 64.4% (κ = 0.31). Single biopsy showed a lower accordance rate compared with multiple biopsies. Our study revealed that single biopsy cannot fully reflect PD-L1 expression in the whole tumour in GC. Multiple biopsies are recommended for accurate diagnosis of PD-L1 expression in GC.
Highlights
Immune therapy targeting programmed cell death 1 (PD-1) and its ligand programmed death ligand 1 (PD-L1) demonstrated favourable therapeutic effects in gastric cancer (GC) in several clinical trials.[1,2] PD-L1 expression has been considered a potential biomarker for treatment efficacy in several types of cancer, including melanoma and non-small-cell lung carcinoma (NSCLC).[3]
Our results showed that biopsy could not fully reflect PD-L1 expression of the whole tumour in GC
PD-L1 positivity in biopsy samples was observed in 46.6% of the GC patients, which was consistent with previous reports.[2]
Summary
Immune therapy targeting programmed cell death 1 (PD-1) and its ligand programmed death ligand 1 (PD-L1) demonstrated favourable therapeutic effects in gastric cancer (GC) in several clinical trials.[1,2] PD-L1 expression has been considered a potential biomarker for treatment efficacy in several types of cancer, including melanoma and non-small-cell lung carcinoma (NSCLC).[3]. GC shows a strong histological heterogeneity in primary lesions, as various histological and differentiation types are frequently observed in the same samples. Intratumoural heterogeneity is often an obstacle for accurate assessment of tumour profiles and determining treatment strategy.[5] We hypothesised that PD-L1 expression evaluated by biopsy samples might differ from PD-L1 expression in the whole tumour because of intratumoural heterogeneity. To confirm whether PD-L1 expression evaluated by biopsy specimen accurately reflects its expression in the whole tumour, we compared PD-L1 expression of biopsy samples with those of matched resected samples and examined the correlations between the number of biopsies and accurate diagnosis of PD-L1 expression
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