Kristine Burgess

Treatment of immune-mediated hemolytic anemia in dogs with cyclophosphamide.

A review of 60 cases of immune-mediated hemolytic anemia (IMHA) in the dog was performed in order to characterize the disease and to identify potential prognostic indicators. Dogs ranged in age from 1 to 13 years, with a mean age of 6.5 years. The 2 most commonly affected breeds were Cocker Spaniels and Labrador Retrievers. Fifty-two of the 60 dogs tested (87%) were autoagglutination positive and spherocytes were present in 45 (75%). Forty-one (89%) of 46 patients tested positive for the presence of immunoglobulin on the red blood cell surface (Coombs assay). The most common clinical signs at presentation were lethargy, weakness, pale mucous membranes, icterus, hemoglobinuria, and anorexia. PCV less than 25% was present in 59 (98%) dogs. At the time of presentation, 35 dogs (58%) had a nonregenerative anemia, whereas 25 patients (42%) had a regenerative response. Thrombocytopenia was seen in 41 (68%) dogs. Nine of 34 dogs (26%) had a prolonged prothrombin time, 19 of 34 (56%) had a prolonged activated partial thromboplastin clotting time, and 12 of 34 (35%) had abnormal fibrinogen concentrations. All dogs received prednisone at immunosuppressive doses (2.2-4.4 mg/kg PO as a single or divided dose every 24 hours) and cyclophosphamide as primary therapy. Forty-one dogs (63%) received cyclophosphamide at 50 mg/m2 q24h for 4 days, whereas 9 dogs (15%) received an initial high dose (200 mg/m2) followed by 3 days of a lower dose (50 mg/m2 q24h). No statistical difference in survival times was found for either protocol. Thirteen dogs were treated with azathioprine in addition to cyclophosphamide and prednisone. The median survival time of dogs that received all 3 drugs was 370 days as compared to 9 days for those dogs that were treated with cyclophosphamide and prednisone alone. Thirty-one (52%) dogs died from the disease, 13 (22%) dogs were alive, and 15 (25%) dogs were lost to follow-up. The median length of survival for all dogs was 21 days. Eight dogs that were discharged from the hospital suffered a relapse (PCV < 25%).

Refining tumor-associated aneuploidy through ‘genomic recoding’ of recurrent DNA copy number aberrations in 150 canine non-Hodgkin lymphomas

Identification of the genomic regions most intimately associated with non-Hodgkin lymphoma (NHL) pathogenesis is confounded by the genetic heterogeneity of human populations. We hypothesize that the restricted genetic variation of purebred dogs, combined with the contrasting architecture of the human and canine karyotypes, will increase the penetrance of fundamental NHL-associated chromosomal aberrations in both species. We surveyed non-random aneuploidy in 150 canine NHL cases, revealing limited genomic instability compared to their human counterparts and no evidence for CDKN2A/B deletion in canine B-cell NHL. ‘Genomic recoding’ of canine NHL data into a ‘virtual human’ chromosome format showed remarkably few regions of copy number aberration (CNA) shared between both species, restricted to regions of dog chromosomes 13 and 31, and human chromosomes 8 and 21. Our data suggest that gene discovery in NHL may be enhanced through comparative studies exploiting the less complex association between CNAs and tumor pathogenesis in canine patients.

Molecular Profiling Reveals Prognostically Significant Subtypes of Canine Lymphoma

We performed genomewide gene expression analysis of 35 samples representing 6 common histologic subtypes of canine lymphoma and bioinformatics analyses to define their molecular characteristics. Three major groups were defined on the basis of gene expression profiles: (1) low-grade T-cell lymphoma, composed entirely by T-zone lymphoma; (2) high-grade T-cell lymphoma, consisting of lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma not otherwise specified; and (3) B-cell lymphoma, consisting of marginal B-cell lymphoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Interspecies comparative analyses of gene expression profiles also showed that marginal B-cell lymphoma and diffuse large B-cell lymphoma in dogs and humans might represent a continuum of disease with similar drivers. The classification of these diverse tumors into 3 subgroups was prognostically significant, as the groups were directly correlated with event-free survival. Finally, we developed a benchtop diagnostic test based on expression of 4 genes that can robustly classify canine lymphomas into one of these 3 subgroups, enabling a direct clinical application for our results.

Response of Canine Cutaneous Epitheliotropic Lymphoma to Lomustine (CCNU): A Retrospective Study of 46 Cases (1999–2004)

BACKGROUND Epitheliotropic lymphoma (ELSA) is an uncommon cutaneous canine malignancy of T lymphocytes. A consensus regarding the therapeutic standard of care is lacking, warranting evaluation of chemotherapeutic agents traditionally employed against canine nodal lymphoma in the treatment of ELSA. HYPOTHESIS The purpose of this retrospective, multi-institutional study was to evaluate the efficacy of 1-(2-chloroethyl)-3-cyclohexyl-l-nitrosourea (CCNU) in the treatment of ELSA. ANIMALS Forty-six dogs with adequate follow-up and treatment response information. METHODS All cases were diagnosed histopathologically. Immunohistochemisty (CD3, CD79a) was performed on 42/46 samples. RESULTS Presenting skin lesions included generalized scales (25/46), plaques or nodules (22/46), mucocutaneous lesions (14/ 46), and corneal involvement (1/46). Lymph node involvement and Sézary syndrome were documented in 7 and 2 dogs, respectively. The median number of CCNU treatments was 4 (range, 1-11), with a median starting dose of 60 mg/m(2) (range, 30-95). Of the 46 dogs, 15 achieved complete remission, 23 achieved partial remission, 5 had stable disease, and 3 had progressive disease, for an overall response rate of 83%. The median number of treatments to achieve a response was 1 (range, 1-6). The overall median duration of response was 94 days (range, 22-282). Sixteen dose reductions were required because of neutropenia (10/46), thrombocytopenia (1/46), anemia (1/46), increased liver enzyme activity (3/46), or unspecified reasons (1/46). CONCLUSIONS AND CLINICAL IMPLICATIONS Given the high response rate and well tolerated protocol, prospective studies are warranted to investigate the utility of CCNU alone or in multi-agent protocols for the treatment of ELSA.

Genome-wide Association Study Identifies Shared Risk Loci Common to Two Malignancies in Golden Retrievers

Dogs, with their breed-determined limited genetic background, are great models of human disease including cancer. Canine B-cell lymphoma and hemangiosarcoma are both malignancies of the hematologic system that are clinically and histologically similar to human B-cell non-Hodgkin lymphoma and angiosarcoma, respectively. Golden retrievers in the US show significantly elevated lifetime risk for both B-cell lymphoma (6%) and hemangiosarcoma (20%). We conducted genome-wide association studies for hemangiosarcoma and B-cell lymphoma, identifying two shared predisposing loci. The two associated loci are located on chromosome 5, and together contribute ~20% of the risk of developing these cancers. Genome-wide p-values for the top SNP of each locus are 4.6×10-7 and 2.7×10-6, respectively. Whole genome resequencing of nine cases and controls followed by genotyping and detailed analysis identified three shared and one B-cell lymphoma specific risk haplotypes within the two loci, but no coding changes were associated with the risk haplotypes. Gene expression analysis of B-cell lymphoma tumors revealed that carrying the risk haplotypes at the first locus is associated with down-regulation of several nearby genes including the proximal gene TRPC6, a transient receptor Ca2+-channel involved in T-cell activation, among other functions. The shared risk haplotype in the second locus overlaps the vesicle transport and release gene STX8. Carrying the shared risk haplotype is associated with gene expression changes of 100 genes enriched for pathways involved in immune cell activation. Thus, the predisposing germ-line mutations in B-cell lymphoma and hemangiosarcoma appear to be regulatory, and affect pathways involved in T-cell mediated immune response in the tumor. This suggests that the interaction between the immune system and malignant cells plays a common role in the tumorigenesis of these relatively different cancers.

Toxicity, Dosage, and Efficacy of Vinorelbine (Navelbine) in Dogs with Spontaneous Neoplasia

The purpose of this study was to evaluate short-term adverse effects and determine a safe dosage for vinorelbine (Navelbine)--a new semisynthetic vinca alkaloid--in dogs with malignant tumors. Nineteen dogs were treated with vinorelbine as a 5-minute IV infusion every 7 days at starting dosages ranging from 10 to 20 mg/m2. The median number of treatments per dog was 7 (range, 1-11). The maximum tolerated dosage varied between 15 and 18 mg/m2, and a starting dosage of 15 mg/m2 is recommended. Neutropenia was the dose-limiting toxicity. Although efficacy was a secondary endpoint of this dosage-finding study, 2 dogs with metastatic bronchoalveolar carcinoma experienced a partial response for an overall response rate of 12.5% in 16 dogs with gross measurable disease. Three dogs with microscopic disease were treated (incompletely excised bronchoalveolar carcinoma or lymph node metastatic disease). Two died of pulmonary metastatic disease 113 and 196 days posttreatment, and 1 is still alive after at least 730 days. The well-tolerated toxicity profile and clinical activity observed in dogs with bronchoalveolar carcinoma warrants further investigation.

Survival time of dogs with splenic hemangiosarcoma treated by splenectomy with or without adjuvant chemotherapy: 208 cases (2001–2012)

OBJECTIVE To determine survival time for dogs with splenic hemangiosarcoma treated with splenectomy alone, identify potential prognostic factors, and evaluate the efficacy of adjuvant chemotherapy. DESIGN Retrospective case series. ANIMALS 208 dogs. PROCEDURES Medical records were reviewed, long-term follow-up information was obtained, and survival data were analyzed statistically. RESULTS 154 dogs were treated with surgery alone, and 54 were treated with surgery and chemotherapy. Twenty-eight dogs received conventional chemotherapy, 13 received cyclophosphamide-based metronomic chemotherapy, and 13 received both conventional and metronomic chemotherapy. Median survival time of dogs treated with splenectomy alone was 1.6 months. Clinical stage was the only prognostic factor significantly associated with survival time. When the entire follow-up period was considered, there was no significant difference in survival time between dogs treated with surgery alone and dogs treated with surgery and chemotherapy. However, during the first 4 months of follow-up, after adjusting for the effects of clinical stage, survival time was significantly prolonged among dogs receiving any type of chemotherapy (hazard ratio, 0.6) and among dogs receiving both conventional and metronomic chemotherapy (hazard ratio, 0.4). CONCLUSIONS AND CLINICAL RELEVANCE Clinical stage was strongly associated with prognosis for dogs with splenic hemangiosarcoma. Chemotherapy was effective in prolonging survival time during the early portion of the follow-up period. Combinations of doxorubicin-based conventional protocols and cyclophosphamide-based metronomic protocols appeared to be more effective than either type of chemotherapy alone, but prolongations in survival time resulting from current protocols were modest.

Efficacy of Maropitant in the Prevention of Delayed Vomiting Associated with Administration of Doxorubicin to Dogs

BACKGROUND Vomiting, nausea, inappetence, and diarrhea are common delayed adverse effects of doxorubicin. Maropitant, a neurokinin-1 receptor antagonist, is known to prevent acute vomiting in dogs receiving cisplatin. OBJECTIVE To evaluate the efficacy of maropitant in preventing delayed vomiting after administration of doxorubicin to dogs. ANIMALS Fifty-nine dogs with cancer. METHODS This randomized, double-blind, placebo-controlled study used a cross-over design. Dogs were randomized into 1 of 2 treatment groups. Group A received maropitant after the 1st doxorubicin, and placebo after the 2nd. Group B received placebo first, and maropitant second. Maropitant (2 mg/kg) or placebo tablets were administered PO for 5 days after doxorubicin treatment. Owners completed visual analog scales based on Veterinary Cooperative Oncology Group-Common Terminology Criteria for Adverse Events to grade their pets clinical signs during the week after administration of doxorubicin. Statistical differences in gastrointestinal toxicosis and myelosuppression between maropitant and placebo treatments were evaluated. RESULTS Significantly fewer dogs had vomiting (P=.001) or diarrhea (P=.041), and the severity of vomiting (P<.001) and diarrhea (P=.024) was less the week after doxorubicin when receiving maropitant compared with placebo. No differences were found between maropitant and placebo for other gastrointestinal and bone marrow toxicoses. CONCLUSIONS AND CLINICAL IMPORTANCE Maropitant is effective in preventing delayed vomiting induced by doxorubicin. Its prophylactic use might improve quality of life and decrease the need for dose reductions in certain dogs.

A tumor-related lymphoid progenitor population supports hierarchical tumor organization in canine B-cell lymphoma

BACKGROUND Tumors have heterogeneous properties, which could be explained by the existence of hierarchically and biologically distinct tumor cells such as tumor-initiating cells (TICs). This model is clinically important, as TICs are promising targets for cancer therapies. However, TICs in spontaneous B-cell lymphoma have not been conclusively identified. HYPOTHESIS/OBJECTIVES Tumor cells with a progenitor phenotype exist in B-cell lymphoma, reflecting a hierarchical organization. ANIMALS Twenty-eight client-owned dogs with previously untreated B-cell lymphoma and 6 healthy dogs. METHODS This was a prospective study. Flow cytometry was used to identify lymphoid progenitor cells (LPCs) that coexpressed hematopoietic progenitor antigens CD34, CD117, and CD133, with lymphoid differentiation markers CD21 and/or CD22 in B-cell lymphoma. The polymerase chain reaction for antigen receptor rearrangements was used to analyze clonality and relatedness of tumor populations. A xenograft model with NOD/SCID/IL-2Rγ(-/-) mice was adapted to expand and serially transplant primary canine B-cell lymphoma. RESULTS LPCs were expanded in lymph nodes from 28 dogs with B-cell lymphoma compared with 6 healthy dogs (P= .0022). LPCs contained a clonal antigen receptor gene rearrangement identical to that of the bulk of tumor cells. Canine B-cell lymphoma xenografts in recipient mice that maintained LPCs in the tumors were recurrently observed. CONCLUSIONS AND CLINICAL IMPORTANCE These results suggest the presence of a hierarchy of tumor cells in B-cell lymphoma as has been demonstrated in other cancers. These findings have the potential to impact not only the understanding of lymphoma pathogenesis but also the development of lymphoma therapies by providing novel targets for therapy.

IMAGING CHARACTERISTICS OF INTRATHORACIC HISTIOCYTIC SARCOMA IN DOGS

In this retrospective study, two observers independently reviewed thoracic imaging studies of 39 dogs with confirmed histiocytic sarcoma. The most common findings were intrathoracic lymphadenopathy, identified by the first and second observers in 82.1% and 87.2% of dogs, respectively, and pulmonary masses (74.4% and 82.1%). Right middle lung lobe masses were significantly more common than masses in any other lung lobe (P < 0.0013), with the majority having a ventral distribution. Sternal and tracheobronchial lymphadenopathy were significantly more common than cranial mediastinal lymphadenopathy (P-values of 0.0002 and 0.012, respectively). Interobserver agreement regarding distribution of lymphadenopathy and pulmonary masses was good (kappa = 0.64 and 0.75, respectively). Other findings included pulmonary nodules, pleural effusion, and abnormal pulmonary patterns. In patients with CT examinations, the majority of masses were mildly to moderately enhancing and heterogeneous, poorly marginated, and bronchocentric. Lymphadenopathy and pulmonary masses are the most common intrathoracic findings in dogs with histiocytic sarcoma, and the strong predilection for the ventral aspect of the right middle lung lube may help to differentiate it from other types of neoplasia.