Search

OBJECTIVE To review ordering patterns, positivity rates, and outcome data for a subset of consecutive samples submitted for a commercially available, blood-based multicancer early-detection liquid biopsy test for dogs using next-generation sequencing at 1 laboratory. SAMPLE 1,500 consecutively submitted blood samples from client-owned dogs with and without clinical suspicion and/or history of cancer for prospective liquid biopsy testing between December 28, 2021, and June 28, 2022. PROCEDURES We performed a retrospective observational study, reviewing data from 1,500 consecutive clinical samples submitted for liquid biopsy testing. Outcome data were obtained via medical record review, direct communication with the referring clinic, and/or a patient outcome survey through October 16, 2022. RESULTS Sixty-four percent (910/1,419) of reportable samples were submitted for cancer screening, 26% (366/1,419) for aid in diagnosis, and 10% (143/1,419) for other indications. The positivity rate was 25.4% (93/366) in aid-in-diagnosis patients and 4.5% (41/910) in screening patients. Outcome data were available for 33% (465/1,401) of patients, and outcomes were classifiable for 428 patients. The relative observed sensitivity was 61.5% (67/109) and specificity was 97.5% (311/319). The positive predictive value was 75.0% (21/28) for screening patients and 97.7% (43/44) for aid-in-diagnosis patients, and the time to diagnostic resolution following a positive result was < 2 weeks in most cases. CLINICAL RELEVANCE Liquid biopsy using next-generation sequencing represents a novel tool for noninvasive detection of cancer in dogs. Real-world clinical performance meets or exceeds expectations established in the test’s clinical validation study.

Age-related somatic genomic alterations in hematopoietic cell lines have been well characterized in humans; however, this phenomenon has not been well studied in other species. Next-generation sequencing-based liquid biopsy testing for cancer detection was recently developed for dogs and has been used to study the genomic profiles of blood samples from thousands of canine patients since 2021. In this study, 4870 client-owned dogs with and without a diagnosis or suspicion of cancer underwent liquid biopsy testing by this method. Copy number variants detected exclusively in genomic DNA derived from white blood cells (WBC gDNA-specific CNVs) were observed in 126 dogs (2.6%; 95% CI: 2.2–3.1); these copy number variants were absent from matched plasma cell-free DNA, and from tumor tissue in dogs with concurrent cancer. These findings were more common in older dogs and were persistent in WBC gDNA in over 70% of patients, with little to no change in the amplitude of the signal across longitudinal samples. Many of these alterations were observed at recurrent locations in the genome across subjects; the most common finding was a partial loss on CFA25, typically accompanied by a partial gain on the same chromosome. These early findings suggest that age-related somatic alterations may be present at an appreciable frequency in the general canine population. Further research is needed to determine the clinical significance of these findings.

Genotype-matched therapeutics have become widely adopted in the management of human cancers and can be guided by testing tumor tissue or cell-free DNA from plasma. OncoKB (Oncology Knowledge Base) is the first FDA-recognized database that contains information about these targetable somatic variants and corresponding therapeutic agents, including levels of evidence. Many of the human OncoKB variants have orthologs in the canine genome. This study was conducted to determine the feasibility of detecting these orthologs in dogs using liquid biopsy. This study involved two cohorts: The first was a cohort of 619 client-owned dogs with a variety of cancer diagnoses across all disease stages enrolled in a clinical validation study for a liquid biopsy test (herein the “research cohort”). All dogs had pre-treatment plasma samples collected at enrollment, and a subset of dogs also had matched tumor tissue collected. The second cohort comprised 457 client-owned dogs that had testing as part of the clinical deployment of the above-mentioned liquid biopsy test (herein the “clinical cohort”); 31% of these dogs had samples submitted as an aid in diagnosis (for dogs in which cancer was suspected clinically), and 69% had samples submitted for screening (in dogs with no a priori suspicion of cancer). Blood samples (and tumor samples, when available) were subjected to DNA extraction, proprietary library preparation, and next-generation sequencing. Sequencing data were analyzed using an internally developed bioinformatics pipeline to detect genomic alterations associated with the presence of cancer. Only canine orthologs of variants in the OncoKB database were evaluated in this study. Variants were called if they were observed in plasma at an allele frequency of at least 0.5%, with at least 6 unique supporting reads. Variants identified from plasma were subsequently genotyped in tissue without additional variant-level filtering. Analysis of plasma identified canine orthologs of OncoKB variants in ~8% of dogs in the research cohort, and ~4% of dogs in the clinical cohort. The higher percentage observed in the research cohort is likely due to the higher percentage of patients with confirmed cancer diagnosis. In the patients with an OncoKB ortholog in the research cohort, the dog had a cancer type that matched the human indication for the detected variant in 15% of cases. Of dogs in which an ortholog was identified in plasma, 44% had matched tumor tissue; and the variant observed in plasma was confirmed in tissue in >50% of these subjects. This study demonstrates the feasibility of detecting canine orthologs of targetable human cancer somatic variants in the blood of dogs using next-generation sequencing. Although it is currently unclear how human databases can be used to inform targeted treatment decisions in dogs, these findings may have relevance for comparative oncology studies and future precision therapeutics development for both species. Citation Format: Daniel S. Grosu, Ilya Chorny, Kristina M. Kruglyak, John A. Tynan, Susan C. Hicks, Todd A. Cohen, Allison L. O'Kell, Jill M. Rafalko, Jason Chibuk, Angela L. McCleary-Wheeler, Andi Flory, Dana W. Tsui. Liquid biopsy analysis reveals orthologs of actionable human cancer variants in dogs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3377.

The goal of cancer screening is to detect disease at an early stage when treatment may be more effective. Until recently, cancer screening in dogs has relied upon annual physical examinations and routine laboratory tests, which are largely inadequate for detecting preclinical disease. With the introduction of non-invasive “liquid biopsy” cancer detection methods, the discussion is shifting from “How to screen dogs for cancer” to “When to screen dogs for cancer”. To address this question, data from 3,452 cancer-diagnosed subjects were analyzed to determine the age at which dogs of certain breeds and weights are typically diagnosed with cancer. In the study population, the median age at cancer diagnosis was 8.8 years, with males diagnosed at younger ages than females, and spayed/neutered dogs diagnosed at significantly later ages than intact dogs. Overall, weight was inversely correlated with age at cancer diagnosis, and purebred dogs were diagnosed at significantly younger ages than mixed-breed dogs. For breeds with 10 or more subjects, a breed-based median age at diagnosis was calculated. A weight-based linear regression model was developed to predict the median age at diagnosis for breeds represented by fewer than 10 subjects and for mixed-breed dogs. The study findings support a general recommendation to start cancer screening for all dogs at the age of 7, and as early as 4 years of age for breeds with a lower median age at cancer diagnosis, in order to increase the chances of early detection and treatment.

Background Differentiation of lymphocytic-plasmacytic enteropathy (LPE) from small cell lymphoma (SCL) in cats can be challenging. Hypothesis/objective Histology-guided mass spectrometry (HGMS) is a suitable method for the differentiation of LPE from SCL in cats. Animals Forty-one cats with LPE and 52 cats with SCL. Methods This is a retrospective clinicopathologic study. Duodenal tissue samples of 17 cats with LPE and 22 cats with SCL were subjected to HGMS, and the acquired data were used to develop a linear discriminate analysis (LDA) machine learning algorithm. The algorithm was subsequently validated using a separate set of 24 cats with LPE and 30 cats with SCL. Cases were classified as LPE or SCL based on a consensus by an expert panel consisting of 5-7 board-certified veterinary specialists. Histopathology, immunohistochemistry, and clonality testing were available for all cats. The panel consensus classification served as a reference for the calculation of test performance parameters. Results Relative sensitivity, specificity, and accuracy of HGMS were 86.7% (95% confidence interval [CI]: 74.5%-98.8%), 91.7% (95% CI: 80.6%-100%), and 88.9% (95% CI: 80.5%-97.3%), respectively. Comparatively, the clonality testing had a sensitivity, specificity, and accuracy of 85.7% (95% CI: 72.8%-98.7%), 33.3% (95% CI: 14.5%-52.2%), and 61.5% (95% CI: 48.3%-74.8%) relative to the panel decision. Conclusions and clinical importance Histology-guided mass spectrometry was a reliable technique for the differentiation of LPE from SCL in duodenal formalin-fixed paraffin-embedded samples of cats and might have advantages over tests currently considered state of the art.

The concept of age-related somatic alterations in the blood or bone marrow of humans, commonly referred to as clonal hematopoiesis of indeterminate potential (CHIP) or age-related clonal hematopoiesis (ARCH), has been well characterized. In humans, these abnormalities tend to be associated with advanced age, often exhibit consistent signal over time, and typically involve recurrent locations in the genome. Though these somatic alterations may be associated with an increased risk of cancer, they do not originate from the tumor when cancer is concurrently present in the body. This study describes early findings that suggest similar age-related somatic alterations may also be present in dogs. Recently, next-generation sequencing-based liquid biopsy testing was developed for cancer detection in dogs. The clinical validation of this test involved 1,100 cancer-diagnosed and presumably cancer-free client-owned dogs. The test has also been performed commercially in thousands of additional dogs since 2021. This recent ability to test large numbers of dogs using liquid biopsy affords an unprecedented opportunity to study the genomic profiles of a broad population of canine subjects. Blood samples from over three thousand dogs ranging in age from 1 to >15 years were used in this analysis. Cell-free DNA (cfDNA) was extracted from the plasma, and genomic DNA (gDNA) was extracted from the white blood cells present in the buffy coat. Both cfDNA and gDNA were analyzed using next-generation sequencing to identify somatic genomic alterations. In a subset of patients, tumor tissue was also available for evaluation. Recurrent variants (e.g., involving CFA6 and CFA25, among others) were identified in the gDNA of a small fraction of patients. These findings occurred more commonly in older dogs and were typically persistent in gDNA across subsequent timepoints (when available) with no significant change in signal over time. When a clinical cancer evaluation was pursued, the majority of dogs with these findings had no evidence of cancer. For those in which cancer was identified, and tumor tissue was available for testing, the genomic profiles of the tumor tissue and gDNA were uncorrelated in almost all cases, suggesting the concomitant presence of age-related somatic alterations was incidental to the patient’s cancer. Additionally, regardless of whether cancer was present in the patient, the variants detected in gDNA were typically not encountered in cfDNA. These findings may be early evidence for the existence of age-related somatic alterations in dogs that potentially resemble the phenomenon of CHIP/ARCH previously observed in humans. Additional studies are ongoing to determine if these incidental findings may represent a risk factor for cancer development in dogs. Citation Format: Dana W.Y. Tsui, Allison L. O'Kell, Todd A. Cohen, Katherine M. Lytle, Kristina M. Kruglyak, Maggie A. Marshall, Carlos A. Ruiz-Perez, John A. Tynan, Susan C. Hicks, Jill M. Rafalko, Daniel S. Grosu, Jason Chibuk, Ilya Chorny, Angela L. McCleary-Wheeler, Andi Flory. Incidental detection of age-related somatic genomic alterations in blood samples from dogs with and without cancer [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr A028.

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.

This proof-of-concept study demonstrates that blood-based liquid biopsy using next generation sequencing of cell-free DNA can noninvasively detect multiple classes of genomic alterations in dogs with cancer, including alterations that originate from spatially separated tumor sites.Eleven dogs with a variety of confirmed cancer diagnoses (including localized and disseminated disease) who were scheduled for surgical resection, and 5 presumably cancer-free dogs, were enrolled. Blood was collected from each subject, and multiple spatially separated tumor tissue samples were collected during surgery from 9 of the cancer subjects.All samples were analyzed using an advanced prototype of a novel liquid biopsy test designed to noninvasively interrogate multiple classes of genomic alterations for the detection, characterization, and management of cancer in dogs.In 5 of the 9 cancer patients with matched tumor and plasma samples, pre-surgical liquid biopsy testing identified genomic alterations, including single nucleotide variants and copy number variants, that matched alterations independently detected in corresponding tumor tissue samples. Importantly, the pre-surgical liquid biopsy test detected alterations observed in spatially separated tissue samples from the same subject, demonstrating the potential of blood-based testing for comprehensive genomic profiling of heterogeneous tumors. Among the 3 patients with post-surgical blood samples, genomic alterations remained detectable in one patient with incomplete tumor resection, suggesting utility for noninvasive detection of minimal residual disease following curative-intent treatment.Liquid biopsy allows for noninvasive profiling of cancer-associated genomic alterations with a simple blood draw and has potential to overcome the limitations of tissue-based testing posed by tissue-level genomic heterogeneity.

Human and canine cancers share a high level of homology. Characterizing their respective genomic landscapes can expand the knowledge base of comparative oncology and support biomarker discovery and therapeutic development for the benefit of both species. Genomic profiling via tumor biopsy infers risk to the patient in both human and veterinary medicine and is often complicated by tumor heterogeneity. Blood-based liquid biopsy has been shown to open new opportunities to profile the cancer genome noninvasively in both species. The goal of this study was to benchmark the occurrence of homologous genomic variants in a variety of canine cancers that have a counterpart in humans, including lymphoma (B-cell and T-cell), soft-tissue sarcoma, osteosarcoma, and melanoma, among others, utilizing tumor and liquid biopsy profiling. The study was performed in a prospective cohort of over 300 client-owned dogs that received a confirmed cancer diagnosis either at the time of enrollment or after sample collection. A blood sample was collected prior to biopsy or surgical resection of the tumor to evaluate the use of liquid biopsy to noninvasively profile the cancer genome. Tumor tissue samples were collected at the time of surgical resection. In a subset of the subjects, blood samples were collected 3 to 30 days following surgical removal of the tumor, and longitudinally during cancer therapy and monitoring. The Cancer Gene Census (CGC) and COSMIC databases were interrogated, and a high degree of homology (>90%) between human and canine oncogenes and tumor suppressor genes was observed. A custom panel was designed encompassing 95 of the top 100 human DNA single nucleotide variants from COSMIC that had a canine orthologue, and targeted sequencing was performed on all tissue and blood samples. A large number of these variants—many of which are actionable in human cancer— were detected in the tumor samples and pre-surgical plasma samples. In some patients, tumor-derived variants were detected in the post-surgical plasma that confirmed the presence of residual disease after surgery. As disease progressed, an increase in the variant allele fraction (VAF) of the tumor-derived mutations was observed and tracked with the patient’s clinical course. Additionally, the presence of variants that may be targetable by human cancer drugs were identified in a subset of patients. These findings demonstrate the potential of liquid biopsy to characterize the genomic landscape of canine cancers at diagnosis and throughout treatment, similar to observations reported in human cancers. This builds the foundation for comparative oncology to translate the knowledge of precision medicine between humans and dogs, to facilitate biomarker discovery, and to track emergence of potential actionable biomarkers in various therapeutic contexts to the benefit of both species. Citation Format: Ilya Chorny, Kristina M. Kruglyak, John A. Tynan, Gilberto E. Hernandez, Prachi Nakashe, Susan Hicks, Rita Motalli-Pepio, Lisa McLennan, Lauren E. Holtvoigt, Jill M. Rafalko, Jason Chibuk, Angela L. McCleary-Wheeler, Andi Flory, Daniel S. Grosu, Dana W. Tsui. Comparative oncology analysis of canine cancer by tumor and liquid biopsy testing for biomarker and therapeutic discovery in humans and dogs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1612.

e15012 Background: Targeted therapies offer great potential for cancer treatment in humans; however, enrollment in clinical trials may be slow, particularly for rare cancer types. The high homology between human and canine cancer genomes provides an opportunity for comparative oncology analyses that can inform the development of therapeutics for the benefit of both species. Currently, there is no well-established canine cancer genomic database. This study presents preliminary findings from an ongoing initiative aimed at building a foundational database of canine cancer genomic variants and their human orthologs via tissue and liquid biopsy profiling of multiple cancer types. Methods: Matched blood and tissue samples were collected from an all-comers cohort of over 150 cancer-diagnosed, client-owned dogs undergoing surgical resection or tissue sampling by biopsy. Cancer types included those found in both humans and dogs, such as lymphoma, osteosarcoma, mammary gland tumors and melanoma. Blood samples were processed to obtain plasma and white blood cells, and all samples were subjected to DNA extraction, library preparation, and next-generation sequencing. Somatic variants detected by liquid biopsy and tissue testing were mapped to human orthologs targeted by therapeutic agents approved by the FDA or listed in NCCN guidelines, and to orthologs with therapeutic or prognostic levels of evidence annotated in human oncology databases. Results: Somatic alterations were identified in over half of the tissue and/or liquid biopsy samples tested. Results from tissue and liquid biopsy showed high concordance, and liquid biopsy revealed additional alterations that may have been missed in single-site tissue biopsies due to tumor heterogeneity. Of the mutations identified in plasma and/or tissue but absent in matched white blood cells, 10% mapped to a human ortholog listed as a biomarker targeted by either an approved therapeutic agent or a therapeutic currently undergoing clinical trials; examples include NRAS, HRAS and AKT1 mutations. Over 10% of canine cancer patients also harbored orthologs of somatic TP53 mutations reported to be prognostic in multiple human cancers. In particular, TP53 mutations were found in > 20% of canine osteosarcoma patients, which aligns with prior findings in human osteosarcoma and highlights the potential of comparative oncology for cancer types that are rare in humans but common in dogs. Conclusions: The results confirm the homology between canine and human cancers and emphasize the potential to translate genomic knowledge for biomarker discovery and therapeutic development between species. The high concordance between tumor and liquid biopsy findings support the prospect of using a noninvasive blood test to expand the genomic characterization effort to much larger cohorts of cancer-diagnosed dogs.

Cancer is the leading cause of death in dogs, in part because many cases are identified at an advanced stage when clinical signs have developed, and prognosis is poor. Increased understanding of cancer as a disease of the genome has led to the introduction of liquid biopsy testing, allowing for detection of genomic alterations in cell-free DNA fragments in blood to facilitate earlier detection, characterization, and management of cancer through non-invasive means. Recent discoveries in the areas of genomics and oncology have provided a deeper understanding of the molecular origins and evolution of cancer, and of the “one health” similarities between humans and dogs that underlie the field of comparative oncology. These discoveries, combined with technological advances in DNA profiling, are shifting the paradigm for cancer diagnosis toward earlier detection with the goal of improving outcomes. Liquid biopsy testing has already revolutionized the way cancer is managed in human medicine – and it is poised to make a similar impact in veterinary medicine. Multiple clinical use cases for liquid biopsy are emerging, including screening, aid in diagnosis, targeted treatment selection, treatment response monitoring, minimal residual disease detection, and recurrence monitoring. This review article highlights key scientific advances in genomics and their relevance for veterinary oncology, with the goal of providing a foundational introduction to this important topic for veterinarians. As these technologies migrate from human medicine into veterinary medicine, improved awareness and understanding will facilitate their rapid adoption, for the benefit of veterinary patients.

The purpose of this report is to offer a consensus opinion of ACVIM oncology diplomates and technicians on the safe use of cytotoxic chemotherapeutics in veterinary practice. The focus is on minimizing harm to the personnel exposed to the drugs: veterinary practitioners, veterinary technicians, veterinary staff, and pet owners. The safety of the patient receiving these drugs is also of paramount importance, but is not addressed in this statement. Much of the information presented is based on national recommendations by Occupational Safety and Health Administration, National Institute for Occupational Safety and Health, United States Pharmacopeia, and other published regulations. These directives reflect an abundance of caution to minimize exposure to medical personnel, but large-scale studies about the consequences of long-term occupational exposure are not available in veterinary medicine. Challenges in the delivery of optimal treatment safely and economically to veterinary patients in general practice without access to a veterinary oncologist or other specialist, because of costs or proximity, remain.

Objectives Gastrointestinal (GI) perforation is a well described complication of GI lymphoma in people, commonly occurring within days of initiation of chemotherapy. There are no studies documenting the prevalence of GI perforation in cats with intermediate- or large-cell GI lymphoma or whether it is associated with induction of chemotherapy. The objectives of this study were to document the prevalence and timing of post-chemotherapy perforation in cats with discrete GI masses caused by intermediate- or large-cell lymphoma. Methods Cats with a diagnosis of intermediate- or large-cell lymphoma based on cytologic or histopathologic examination of a mass lesion of the GI tract and treated with chemotherapy were identified by searching the patient record database of three large specialty referral hospitals. Cats undergoing surgical resection of a GI mass prior to chemotherapy were excluded from the study. A clinical diagnosis of GI perforation was made using ultrasound findings and analysis of abdominal fluid. Results Twenty-three cats with intermediate- (n = 3) or large-cell (n = 20) lymphoma were included in the study. GI perforation was confirmed in 4/23 cats (17%), and occurred at 23, 56, 59 and 87 days after induction. There was no association between tumor size, the presence of hypoproteinemia or suppurative inflammation within the mass at the time of diagnosis and subsequent perforation. Post-hoc analysis revealed that the magnitude of weight loss within 15–28 days of diagnosis was greater in cats with perforation. Conclusions and relevance In this pilot study, we found that post-chemotherapy GI perforation in cats with intermediate- or large-cell GI lymphoma occurs. Acute perforation after induction of chemotherapy was not documented. Larger prospective studies are needed to determine risk factors associated with perforation and whether surgical excision would reduce the risk of subsequent GI perforation in these patients.