PD-L1 emerges as key prognostic marker in canine gastric carcinoma, promising advances in immunotherapy

A recent study indicates that PD-L1 may serve as the most reliable marker of prognosis in dogs with gastric carcinoma, offering potential for improved diagnostic and therapeutic strategies in veterinary medicine.

A study in Veterinary Oncology suggests that PD-L1 may be the clearest marker of outcome in canine gastric carcinoma, a rare and often rapidly fatal cancer in dogs. Researchers at the Royal Veterinary College analysed full-thickness gastric biopsies from 40 dogs and found PD-L1 expression in every tumour, usually in the cytoplasm of malignant cells. Higher PD-L1 scores were linked to shorter survival, while other measures of aggressiveness, including depth of invasion, stromal content and tumour-infiltrating lymphocytes, were less informative on their own.

The work matters because routine endoscopic biopsies often miss the full extent of disease. Using complete wall sections, the team documented extensive invasion, with many tumours reaching the serosa or omentum and more than half showing vascular invasion. Tumour budding was also common, reinforcing the impression of an aggressively metastatic disease.

The findings fit a broader pattern in veterinary oncology. Separate studies in canine urothelial and mammary carcinomas have also tied PD-L1 expression to poor prognosis and distinct immune microenvironments, suggesting the checkpoint pathway may be clinically relevant across several canine cancers.

The authors argue that, if validated in larger prospective cohorts, PD-L1 could help stratify prognosis and support future immunotherapy trials in dogs with gastric cancer.

Reference: Lean, F.Z., Tibbles, M.L., Hulme, B. et al. Histomorphological features and PD-L1 expression in canine gastric carcinoma using full thickness biopsy. Vet. Oncol. 3, 20 (2026). https://doi.org/10.1186/s44356-026-00074-3

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