OncoCan: a liquid biopsy assay for cell-free DNA quantification in canine plasma to support cancer prognosis

Early cancer detection remains a major challenge in veterinary medicine. Cell-free DNA (cfDNA), released into the bloodstream through apoptosis, necrosis, or circulating tumor cells, can be quantified non-invasively via liquid biopsy and is already established in human oncology. In this study, we evaluated OncoCan, a targeted plasma cfDNA assay, by analyzing samples from 83 dogs with various neoplasms and 47 healthy controls to assess diagnostic and prognostic utility. Wilcoxon rank-sum testing revealed significantly higher cfDNA concentrations in neoplastic versus healthy samples (p = 4.45e-07). ROC curve analysis demonstrated high accuracy for lymphomas/leukemias (AUC = 0.95) and moderate accuracy for carcinomas (AUC = 0.75), sarcomas (AUC = 0.76), and melanomas (AUC = 0.69). Stratification by histological grade and clinical stage further supported cfDNA's predictive capability. Three practical thresholds were established: <50 pg/μL to distinguish healthy from neoplastic cases; ≥100 pg/μL as a "high positive" threshold indicating aggressive disease; and ≥300 pg/μL as a "very high positive" threshold strongly associated with systemic dissemination, high-grade histology, and poor survival. The <50 pg/μL cut-off showed robust diagnostic performance (AUC = 0.808, sensitivity = 82%, specificity = 73%), confirmed by survival analysis and hazard ratio modeling. These findings suggest that OncoCan provides a noninvasive, clinically applicable tool for cancer prognosis in dogs. Validation in larger cohorts is warranted to support its integration into routine veterinary oncology practice.