Background: The detection of cell-free DNA (cfDNA) from plasma (e.g. liquid biopsy) is an emerging technique with many potential applications to facilitate cancer diagnosis and disease monitoring. Liquid biopsy approaches have been studied in canine cancer, but it is unknown if similar approaches can be used to facilitate staging and diagnosis of feline cancers. Hypothesis/
Objectives: It was hypothesized that liquid biopsy could be used to differentiate plasma samples originating from cats with and without cancer. Animals: 19 client owned cats with oral squamous cell carcinoma (n = 5), gastrointestinal lymphoma (n = 9), or cats with no clinical evidence of cancer (n = 5).
Methods: Blood samples (< 5ml) were collected from cats into an EDTA or Streck cell-free collection tube. Isolated cfDNA underwent ultra-low-pass whole genome sequencing with the resultant fastq files aligned with the feline genome (felis_catus_9.0). Copy number alterations and tumor fraction was determined using ichorCNA.
Results: cfDNA yield is variable, but not statistically different across diagnoses (p >0.5). Somatic copy number changes were detected in samples taken from cats with known cancer, but not in the non-cancer group. Conclusions and Clinical Importance: cfDNA can reliably be isolated from feline plasma, and exhibits biologic variability consistent with other species. Tumor fraction was higher in cats with known cancer, supporting further optimization of liquid biopsy approaches in cats with cancer.
