Lymphoma is the most common hematologic malignancy in dogs, with some subtypes being highly similar to their human counterparts in terms of molecular, pathologic, and biologic features. Despite the rapid growth in our understanding of canine lymphoma, tools for early detection, personalized therapy, and treatment monitoring are still lacking. Blood-based liquid biopsy using next-generation sequencing (NGS) of cell-free DNA is gaining adoption in human medicine and is now available for canine patients. This non-invasive tool affords new opportunities to profile the genomic landscape of naturally occurring canine lymphomas across large cohorts of patients, and given the high homology (>90%) between human and canine cancer genomes, findings in canine lymphomas may afford unique opportunities for comparative oncology studies for the benefit of both species. One hundred sixteen dogs diagnosed with lymphoma (63 intermediate to large B-cell, 21 intermediate to large T-cell, 6 T-zone, and 26 unphenotyped) were included in this analysis, enrolled as part of a larger liquid biopsy clinical validation study. Lymphomas with inconclusive immunophenotype or other types of indolent lymphomas were excluded. A blood sample was collected from each dog following diagnosis and prior to undergoing therapy to evaluate the ability of liquid biopsy to non-invasively detect the presence and characterize the genomic signature of the cancer. In a subset of patients, longitudinal blood samples and clinical outcomes were also collected. Of all lymphoma-diagnosed dogs, 56% were purebred (representing 32 distinct breeds); 57% were male; median age was 8 years; and median weight was 28.4kg. The overall detection rate for lymphoma by liquid biopsy was 92.2% (107/116); with detection rates of 57% for localized/regional disease (Stages I and II) and 95% for disseminated/metastatic disease (Stages III, IV, and V). By immunophenotype, the detection rate for B-cell lymphoma was 97%, T-cell 91%, T-zone 50%, and unphenotyped 92%. A variety of genomic alterations were identified in patients with positive liquid biopsy results, including single nucleotide variants in common oncogenes and tumor suppressor genes, and copy number variants across the genome (including CNVs previously described in tumor tissue of canine lymphoma patients). In patients with longitudinal samples, the presence or absence of cancer signal appeared to be closely related to remission status at corresponding time points. A novel NGS-based liquid biopsy tool has demonstrated the ability to identify genomic alterations in blood samples of dogs with lymphoma, including alterations previously described in human and canine lymphoma tissue. This technology may also provide a non-invasive method for longitudinal monitoring of treatment response in dogs with lymphoma. These findings, and the high degree of homology between the human and canine disease, support the utility of liquid biopsy for the study of canine lymphoma as a comparative oncology model for accelerated biomarker discovery and therapeutic development.
Citation Format: Angela L McCleary-Wheeler, Kristina M Kruglyak, Gilberto E Hernandez, Prachi Nakashe, Lisa M McLennan, Thuy Jennings, Jill M Rafalko, Lauren E Holtvoigt, Daniel S Grosu, Jason Chibuk, Susan C Hicks, John A Tynan, Ilya Chorny, Dana WY Tsui, Andi Flory. Liquid biopsy for the detection and characterization of canine lymphoma [abstract]. In: Proceedings of the Third AACR International Meeting: Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2022 Jun 23-26; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2022;3(5_Suppl):Abstract nr A16.