CHOP chemotherapy for the treatment of canine multicentric T-cell lymphoma

Prognostic role of the updated Kiel classification in canine high-grade T-cell lymphomas

BACKGROUND

The aim of this study was to determine and describe the prognostic role of the morphological subtype determined according to the updated Kiel classification in dogs with high-grade T-cell lymphomas (HGTCLs) depending on the treatment applied.

OBJECTIVES

The HGTCLs were classified into three subtypes according to the updated Kiel classification: pleomorphic mixed (PM), lymphoblastic lymphoma/acute lymphoblastic leukaemia and plasmacytoid (P). The treatment was divided into a palliative therapy (PlT) group and a chemotherapy (ChT) group.

METHODS

The study was conducted between 2009 and 2017, and it enrolled 58 dogs in which cytomorphological and immunocytochemistry diagnoses were HGTCL.

RESULTS

Overall survival (OS) was significantly longer in the ChT group (median OS-4 months, interquartile range [IQR] from 2 to 8 months) than in the PlT group (median OS-6 weeks, IQR from 1 week to 3 months). In the PlT group, PM subtype and glucocorticosteroids (GCSs) treatment proved significantly and independently linked to longer OS and approximately three-fold lower risk of death during the study period (adjusted hazard ratio [HRadj] = 0.26, confidence interval [CI] 95%: 0.08-0.81; p = 0.020 and HRadj = 0.30, CI 95%: 0.11-0.77; p = 0.013, respectively), although due to small group size, precision of estimations was poor (wide CI 95%). In the ChT group, >7 days elapsing between diagnosis and the beginning of chemotherapy and GCS treatment prior to chemotherapy were significantly associated with lower chance of complete remission (CR; p = 0.034 for both); GCS treatment prior to chemotherapy was significantly associated with shorter OS (p = 0.016); chemotherapy based on the modified CHOP protocol was significantly associated with higher chance of CR (p = 0.034) and longer OS (p = 0.039); and CR was significantly linked to longer OS (p = 0.001).

CLINICAL SIGNIFICANCE

The morphological subtype of HGTCL has some prognostic value in dogs treated palliatively (with PM subtype associated with longer OS than P subtype); however, this effect is no longer visible when a dog is treated with chemotherapy.

Novel Treatments for Lymphoma

Lymphoma is a common disease in companion animals. While conventional chemotherapy has the potential to induce remission and prolong life, relapse is common and novel treatments are needed to improve outcome. This review discusses recent modifications/adjustments to conventional standard of care therapy for canine and feline lymphoma, options for treatment or relapsed/refractory disease, and cutting-edge immunotherapy and small molecule-based approaches that are in varying stages of regulatory approval.

Canine T zone lymphoma is a tumor of mature, previously activated αβ T cells

T cell lymphomas are a diverse group of tumors found in both dogs and humans, originating from various normal T cell types. Identifying the origin of neoplastic lymphocytes can offer valuable insights into the pathogenesis and clinical behavior of these tumors. T zone lymphoma (TZL) in dogs is characterized by the absence of CD45 expression, a strong breed predilection, and its association with adult-onset demodicosis-a condition believed to be linked to immunosuppression. In this study, our aim was to employ transcriptomic and functional data to determine the normal counterpart of TZL. Identifying the normal counterpart may help us understand both how these tumors arise and explain their clinical behavior. Gene expression profiling using NanoString and RNA seq was used to compare the transcriptome between neoplastic T zone cells, normal canine T cells and publicly available gene sets using Gene Set Enrichment Analysis. Mitogen, anti-CD3 stimulation and PMA/ionomycin stimulation were used to assess T cell proliferation in vitro, and intracellular cytokine production was measured by flow cytometry. Gene expression profiling revealed that TZL is most likely derived from an activated or memory alpha-beta T cell but the cells do not fall cleanly into an effector subtype. TZL cells express CD4-specific transcription factors GATA3 and THPOK, even though TZL cells more commonly express CD8, or neither CD4 nor CD8. TZL cells produce high levels of interferon gamma and tumor necrosis factor alpha when stimulated, further supporting the hypothesis that they are derived from an antigen experienced T cell. TZL cells do not proliferate when stimulated through the T cell receptor but will divide when the T cell receptor is bypassed with PMA and ionomycin. The observation that these cells are derived from a mature, previously activated T cell is the first step in understanding the genesis of this unique T cell tumor.

The gene expression profile and cell of origin of canine peripheral T-cell lymphoma

BACKGROUND

Peripheral T-cell lymphoma (PTCL) refers to a heterogenous group of T-cell neoplasms with poor treatment responses and survival times. Canine PTCL clinically and immunophenotypically resembles the most common human subtype, PTCL-not otherwise specified (PTCL-NOS), leading to interest in this canine disease as a naturally occurring model for human PTCL. Gene expression profiling in human PTCL-NOS has helped characterize this ambiguous diagnosis into distinct subtypes, but similar gene expression profiling in canine PTCL is lacking.

METHODS

Bulk RNA-sequencing was performed on tumor samples from 33 dogs with either CD4+ (26/33), CD8+ (4/33), or CD4-CD8- (3/33) PTCL as diagnosed by flow cytometry, and sorted CD4+ and CD8+ lymphocytes from healthy control dogs. Following normalization of RNA-seq data, we performed differential gene expression and unsupervised clustering methods. Gene set enrichment analysis was performed to determine the enrichment of canine CD4+ PTCL for human PTCL-NOS, oncogenic pathways, and various stages of T-cell development gene signatures. We utilized gene set variation analysis to evaluate individual canine CD4+ PTCLs for various human and murine T-cell and thymocyte gene signatures. Cultured canine PTCL cells were treated with a pan-PI3K inhibitor, and cell survival and proliferation were compared to DMSO-treated controls. Expression of GATA3 and phosphorylated AKT was validated by immunohistochemistry.

RESULTS

While the canine CD4+ PTCL phenotype exhibited a consistent gene expression profile, the expression profiles of CD8+ and CD4-CD8- canine PTCLs were more heterogeneous. Canine CD4+ PTCL had increased expression of GATA3, upregulation of its target genes, enrichment for PI3K/AKT/mTOR signaling, and downregulation of PTEN, features consistent with the more aggressive GATA3-PTCL subtype of human PTCL-NOS. In vitro assays validated the reliance of canine CD4+ PTCL cells on PI3K/AKT/mTOR signaling for survival and proliferation. Canine CD4+ PTCL was enriched for thymic precursor gene signatures, exhibited increased expression of markers of immaturity (CD34, KIT, DNTT, and CCR9), and downregulated genes associated with the T-cell receptor, MHC class II associated genes (DLA-DQA1, DLA-DRA, HLA-DQB1, and HLA-DQB2), and CD25.

CONCLUSIONS

Canine CD4+ PTCL most closely resembled the GATA3-PTCL subtype of PTCL-NOS and may originate from an earlier stage of T-cell development than the more conventionally posited mature T-helper cell origin.

Evaluation of the clinical outcome of hypercalcemia of malignancy and concurrent azotemia in dogs with lymphoma

BACKGROUND

Hypercalcemia of malignancy (HM) secondary to lymphoma in dogs has the potential to cause renal injury.

HYPOTHESIS/OBJECTIVES

Characterize outcomes related to acute kidney injury (AKI) secondary to HM. We hypothesized that dogs do suffer AKI regardless of HM severity at the time of lymphoma diagnosis or relapse.

ANIMALS

Retrospective study. Twenty-nine dogs with lymphoma, HM, and azotemia (International Renal Interest Society [IRIS] grade II or higher AKI) that underwent chemotherapy were identified at 2 veterinary institutions.

METHODS

Logistic regression and descriptive statistical analysis were performed to evaluate data for potential prognostic factors.

RESULTS

After initiating treatment, resolution of hypercalcemia and azotemia occurred in 100% (29/29) and 79.3% (23/29) of dogs, respectively. Resolution of azotemia was influenced by serum creatinine concentration (odds ratio [OR], 0.148; Confidence interval [CI], 0.03-0.734; P = .02) and total hypercalcemia (OR, 0.36; CI, 0.14-0.93; P = .04) at diagnosis, whereas blood urea nitrogen concentration, IRIS grade, sex, and whether or not dogs were hospitalized were not significant factors. At data analysis, 13.8% (4/29) of dogs were alive or lost to follow-up. Of those dead, 4 dogs (15%) had renal disease at the time of death, 2/4 having concurrent lymphoma progression.

CONCLUSIONS AND CLINICAL IMPORTANCE

Although AKI may be of clinical concern in dogs with HM secondary to lymphoma at diagnosis, death secondary to renal impairment appears to be infrequent.

Review of Canine Lymphoma Treated with Chemotherapy-Outcomes and Prognostic Factors

While canine lymphoma is a relatively common and important disease seen by veterinarians, there are limited comprehensive reviews of the literature regarding the remission and survival times following chemotherapy, and the associated prognostic factors. This comprehensive thematic review covers the available veterinary literature covering treatment outcomes and identified prognostic factors. A lack of standardised approaches to evaluate and report the outcomes was identified, including factors that would alter the duration of responses by weeks, or occasionally months. After publication of the suggested reporting criteria, this has improved but is still not uniformly applied. The prognostic factors included for evaluation varied from as few as three to seventeen, with over 50 studies using only univariate analysis. Individual papers reported much longer outcomes than others, but assessing the outcomes overall, there has been minimal change over the last 40 years. This supports the belief that novel approaches for lymphoma therapy will be required to substantively improve outcomes.

Fractionated oral dosing and its effect on cyclophosphamide pharmacokinetics in dogs with high-grade multicentric lymphoma

Cyclophosphamide (CP) is an alkylating agent commonly included in multi-drug treatment protocols for canine cancer. As a prodrug, CP requires hepatic metabolism for activation to the intermediate compound 4-hydroxycyclophosphamide (4-OHCP) which then spontaneously forms alkylating phosphoramide mustard. CP is frequently administered in a fractionated manner, with the total dose given over multiple days. CP is reported to cause auto-induction of metabolism in humans, with faster CP clearance and relatively increased 4-OHCP formation following fractionated versus bolus dosing, however canine pharmacokinetic studies of CP dose fractionation are lacking. The study objective was to evaluate the pharmacokinetics of fractionated oral CP dosing at a dose of 200-250 mg/m² over 3 to 4 days in a prospectively identified population of cancer-bearing dogs. Plasma concentrations of CP and 4-OHCP were measured by ultra-high performance liquid chromatography tandem-mass spectrometry in eight dogs following the first and last doses to assess for auto-induction of CP metabolism. No significant difference in the rate of CP elimination between first and last doses were detected (0.73 ± 0.46 vs. 1.22 ± 0.5 h^-1 ; p = .125). Additionally, no significant difference in dose-normalized 4-OHCP exposure was identified between first and last doses (5.9 ± 2.1 vs. 7.9 ± 6.4 h × ng/ml; p = .936). These results suggest that fractionated dosing may not increase exposure to the active metabolite of CP in dogs as it does in humans. As such, standard bolus dosing and fractionated dosing may be equivalent in terms of bio-activation of CP in dogs administered a dose of 200-250 mg/m² .

Efficacy and tolerability of a 12-week combination chemotherapy followed by lomustine consolidation treatment in canine B- and T-cell lymphoma

BACKGROUND

High-grade lymphoma in dogs is a chemotherapy-responsive neoplasia with remission rates exceeding 80% under combination chemotherapy protocols. Usually these protocols are intensive and 24 + weeks. The objective of the present study was to investigate if a shorter protocol combined with an oral lomustine maintenance treatment (3 × in 8 weeks) would present an acceptable result, both for B- and T-cell lymphomas, and for the different types of lymphomas normally encountered in private veterinary practice.

RESULTS

144 dogs entered the study. Lymphoma types included multicentric (n = 123), alimentary (n = 13), miscellaneous (n = 7), and mediastinal lymphoma (n = 1). Overall response rate was 83.3% (B-cell: 86.6%, T-cell: 79.4%). Complete remission (CR) was achieved in 72.2% (B-cell: 77.3%, T-cell: 67.6%) and partial remission (PR) in 11.1% (B-cell: 9.3%, T-cell: 11.8%) of the dogs. Median duration of first CR amounted to 242 days (B-cell: 263 d, T-cell: 161 d). Median survival in dogs with CR was 374 days (B-cell: 436 d, T-cell: 252 d), and median overall survival time was 291 days (B-cell: 357d, T-cell: 210d). Immunophenotype demonstrated an independent significant influence on duration of remission and survival in the whole group. Findings of splenic and hepatic cytology were not significant associated with patient outcome. Treatment was well tolerated; the majority of adverse events were classified as grade 1 or 2.

CONCLUSIONS

Short-term chemotherapy followed by lomustine consolidation leads to compara-ble remission and survival times compared to conventional protocols with cyclophosphamide, doxorubicin, vincristine and prednisolone with acceptable toxicosis in dogs with both B-cell and T-cell lymphoma.

Randomised trial evaluating chemotherapy alone or chemotherapy and a novel monoclonal antibody for canine T-cell lymphoma: A multicentre US study

Background

Canine peripheral nodal T‐cell lymphoma is considered chemotherapy resistant and carries a relatively poor prognosis. Prospective evaluations reporting the impact of chemotherapy on progression‐free survival (PFS) and overall survival time for dogs with T‐cell lymphoma are lacking. This study examined the impact of L‐CHOP (L‐asparaginase, doxorubicin, cyclophosphamide, vincristine, prednisone) chemotherapy or L‐CHOP in combination with AT‐005, a US Department of Agriculture‐licensed caninised monoclonal antibody, on PFS and response rates in dogs with clinical intermediate‐ and high‐grade peripheral nodal T‐cell lymphoma.

Methods

A prospective, randomised, placebo‐controlled, investigator‐ and owner‐blinded, multicentre study was completed. All dogs received a 19‐week L‐CHOP chemotherapy protocol with randomisation (1:1) into placebo or AT‐005 groups. Response was evaluated via the Veterinary Cooperative Oncology Group criteria for canine lymphoma.

Results

Forty‐nine dogs were enrolled (25 received placebo and 24 received AT‐005). Most demographic factors were similar between the two groups, with the exception that more dogs with stage IV and V disease were treated with AT‐005 (34% vs. 8%; p = 0.03). Median PFS was 103 days (95% confidence interval [CI], 56–118) in the placebo group versus 64 days (95% CI, 36–118) in the AT‐005 group. The overall response rate (ORR) for all dogs was 98% (48 of 49); complete response rate in the placebo group (64%) was not different from the AT‐005 group (67%).

Conclusions

To the best of the authors’ knowledge, this is the first prospective study to document that treatment with L‐CHOP chemotherapy, with or without AT‐005, may result in a high ORR, but relatively brief PFS in dogs with clinical intermediate‐ and high‐grade T‐cell lymphoma.

Procarbazine, prednisolone and cyclophosphamide (PPC) oral combination chemotherapy protocol for canine lymphoma

Orally administered daily chemotherapy offers a novel treatment approach for canine lymphoma in a population of dogs that have failed or not tolerated maximum tolerable dose chemotherapy. A multidrug oral chemotherapy protocol was designed and implemented for the treatment of fifty dogs with multicentric lymphoma with minimal side effects. The protocol consisted of oral procarbazine, prednisolone and cyclophosphamide (PPC) administered daily. Efficacy and toxicity were evaluated by clinical and laboratory evaluation. An overall response rate of 70% was achieved, with 24% and 46% of dogs having a partial and complete response, respectively, to treatment with the PPC protocol. Response to the PPC protocol (complete or partial) and age were the only factors identified as prognostic for time from initiation of the PPC chemotherapy until death. Overall, the protocol was very well tolerated with only one dog requiring protocol discontinuation due to grade 4 thrombocytopenia. Eight dogs recorded gastrointestinal toxicities, seven grade I and one grade II toxicity. These findings demonstrate that the administration of a continuous oral combination chemotherapy can provide comparable survival times in the rescue setting in dogs with multicentric lymphoma with minimal side effects.

A bitesize introduction to canine hematologic malignancies

Hematologic malignancies are frequently diagnosed in dogs and result in a spectrum of clinical signs associated with specific disease types. The most frequently encountered hematologic tumors in dogs include lymphoma, lymphoid and myeloid leukemias, and mast cell, plasma cell, and histiocytic neoplasias. Coupled with the heterogeneous presentations of the different categories and subtypes of canine hematologic malignancies, outcomes for these tumors are also variable. Considering this, appropriate treatment options range from active surveillance to curative intent approaches harnessing surgical, chemotherapeutic, and radiation-based modalities. The underlying pathology of many of these diseases bears remarkable resemblance to that of the corresponding diagnosis made in human patients. We introduce some of the pathogenic drivers of canine hematologic cancers alongside their clinical presentations. An overview of standard-of-care therapies for each of these diseases is also provided. As comparative oncology gains recognition as a valuable setting in which to investigate the pathogenesis of neoplasia and provide powerful, clinically relevant, immunocompetent models for the evaluation of novel therapies, the number of clinicians and scientists participating in cancer research involving dogs is expected to increase. This review aims at providing an introductory overview of canine hematologic malignancies.

Circulating Endocannabinoids in Canine Multicentric Lymphoma Patients

The endocannabinoid system is increasingly being implicated in the pathogenesis and progression of various human cancers. Specifically, increased levels of 2-arachidonoylglycerol (2-AG) and oleoythanolamide (OEA) have been demonstrated in human diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukemia (CLL) patients, respectively. The objectives of this paper were to compare 2-AG, OEA, N-arachidonoylethanolamine (AEA), and palmitoylethanolamide (PEA) levels between dogs with multicentric lymphoma and healthy control dogs. In addition, evaluate 2-AG, OEA, AEA, and PEA levels as biomarkers for progression free interval (PFI) and overall survival time (OST) in the dogs with lymphoma. The study consisted of 26 dogs with multicentric B cell lymphoma, 14 dogs with multicentric T cell lymphoma, and 12 healthy control dogs. Serum 2-AG, OEA, AEA, and PEA levels were measured using liquid chromatography combined with tandem mass spectrometry (LC—MS/MS) in dogs with lymphoma and in healthy dogs. OEA, AEA, and PEA levels were significantly elevated in dogs with lymphoma compared to healthy controls (p < 0.05). Total AG was significantly higher in healthy control dogs (p = 0.049). There was no significant difference between dogs with B cell and T cell lymphoma for any of the measured endocannabinoids. Elevated PEA was significantly associated with decreased PFI (p = 0.04) in dogs with lymphoma with a hazards ratio of 1.816 [95% Confidence Interval (CI): 1.020–3.232]. Overall, dogs with lymphoma have elevated levels of OEA, AEA, and PEA. PEA levels have the potential to be a prognostic biomarker.

Predicting Dynamic Clinical Outcomes of the Chemotherapy for Canine Lymphoma Patients Using a Machine Learning Model

First-line treatments of cancer do not always work, and even when they do, they cure the disease at unequal rates mostly owing to biological and clinical heterogeneity across patients. Accurate prediction of clinical outcome and survival following the treatment can support and expedite the process of comparing alternative treatments. We describe the methodology to dynamically determine remission probabilities for individual patients, as well as their prospects of progression-free survival (PFS). The proposed methodology utilizes the ex vivo drug sensitivity of cancer cells, their immunophenotyping results, and patient information, such as age and breed, in training machine learning (ML) models, as well as the Cox hazards model to predict the probability of clinical remission (CR) or relapse across time for a given patient. We applied the methodology using the three types of data obtained from 242 canine lymphoma patients treated by (L)-CHOP chemotherapy. The results demonstrate substantial enhancement in the predictive accuracy of the ML models by utilizing features from all the three types of data. They also highlight superior performance and utility in predicting survival compared to the conventional stratification method. We believe that the proposed methodology can contribute to improving and personalizing the care of cancer patients.

Prognostic indicators for naïve canine non-indolent T-cell lymphoma treated with combination lomustine, vincristine, procarbazine and prednisolone chemotherapy

Lomustine, vincristine, procarbazine and prednisolone (LOPP) chemotherapy has been suggested to be an effective treatment for dogs with naïve non-indolent T-cell lymphoma (TCL). Studies evaluating prognostic factors for dogs with TCL treated with LOPP chemotherapy are lacking. The aim of this retrospective study was to assess potential prognostic factors for canine naïve non-indolent TCL treated with the LOPP protocol. This was a retrospective cohort study of naïve non-indolent TCL treated with the LOPP chemotherapy protocol at a single specialty veterinary oncology clinic. Sixty-seven dogs met the inclusion criteria. The outcomes assessed included progression free survival (PFS), overall survival time (OST) and duration of complete response (DCR). The overall median PFS was 118 days (range 7-2302 days). The median OST was 202 days (range 8-2302 days). The overall median DCR was 316 days (range 38-2261 days). Number of treatments administered (p < .0001), multicentric disease (p = .044) and the presence of hypercalcaemia (p = .006) were prognostic indicators for PFS. Increasing number of treatments (p < .0001) and age (p = .0088) were prognostic indicators for OST. To our knowledge, this is the first study to describe hypercalcaemia as a positive prognostic indicator of PFS for TCL treated with LOPP chemotherapy. LOPP chemotherapy can be considered as a first-line treatment protocol against naïve hypercalcaemic non-indolent TCL.

Survival time for dogs with previously untreated, peripheral nodal, intermediate- or large-cell lymphoma treated with prednisone alone: the Canine Lymphoma Steroid Only trial

OBJECTIVE

To evaluate survival times for dogs with previously untreated, peripheral nodal, intermediate- or large-cell lymphoma treated with prednisone alone.

ANIMALS

109 client-owned dogs recruited from 15 institutions in the United States.

PROCEDURES

Dogs were treated with prednisone at a dosage of 40 mg/m², PO, once daily for 7 days and at a dosage of 20 mg/m², PO, once daily thereafter. Quality of life (QOL) was assessed by owners with a visual analog scale when treatment was started (day 0), 1 and 2 weeks after treatment was started, and every 4 weeks thereafter. The primary outcome of interest was survival time as determined by the Kaplan-Meier method. Factors potentially associated with survival time were examined.

RESULTS

Median overall survival time was 50 days (95% CI, 41 to 59 days). Factors associated with survival time included substage (a vs b) and immunophenotype (B cell vs T cell). Owner-assigned QOL scores on days 0 and 14 were significantly positively correlated with survival time. When QOL score was dichotomized, dogs with day 0 or day 14 QOL scores ≥ 50 had significantly longer survival times, compared with dogs with day 0 or day 14 QOL scores < 50. No variables were predictive of long-term (> 120 days) survival.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that survival times were short for dogs with previously untreated, peripheral nodal, intermediate- or large-cell lymphoma treated with prednisone alone. Owner-perceived QOL and clinician-assigned substage were both associated with survival time. Findings provide potentially important information for clinicians to discuss with owners of dogs with lymphoma at the time treatment decisions are made.

Maintenance treatment in relapsed canine lymphoma after a short L-CHOP protocol

OBJECTIVE

A number of different rescue protocols for relapsed canine multicentric large-cell lymphoma have been described. The aim of this pilot study was to evaluate the efficacy of a maintenance treatment in dogs that experienced a second complete remission after a short L-CHOP-rescue protocol.

MATERIAL AND METHODS

Included in the study were dogs experiencing the first lymphoma relapse during a treatment-free period which were treated with a short L-CHOP protocol, achieved a complete remission and were afterwards treated with a continuous maintenance phase (MP) protocol. The L-CHOP protocol consisted of weekly treatments, with at least 3 additional treatments following complete remission. Thereafter the MP protocol with 2-week treatment intervals was conducted. It consisted of alternating oral home administration of different alkylating agents and one intravenously administered cytotoxic agent of a different mechanism of action. The dogs were presented either every 4 or 6 weeks for intravenous treatment and at this time a complete blood count was performed. The durations of the first remission, disease-free interval and overall survival time were evaluated.

RESULTS

A total of 20 dogs were included in the study. A median of 7 weekly applications were given before the treatment was switched to the MP protocol. During MP, 14 dogs were treated intravenously every 6 weeks and 6 dogs every 4 weeks. Haematological adverse events were mainly mild. During the L-CHOP-protocol, one septic event occurred, and 2 dogs were hospitalized due to gastrointestinal adverse events. No patient required hospitalization during the MP. Fifteen dogs completed at least one cycle in the MP and a median of 8.5 chemotherapeutic treatments were administered. The median disease-free interval was 264 days and the median overall survival time was 737 days.

CONCLUSION AND CLINICAL RELEVANCE

The protocol was generally well tolerated. Since 5 patients showed disease progression during the first cycle of the MP, dogs should ideally be evaluated for minimal residual disease before being switched to the MP. The case number in the presented study was low and the treatment relatively heterogeneous. Therefore, more dogs have to be treated with the proposed protocol before general recommendations can be made.

Horizons in Veterinary Precision Oncology: Fundamentals of Cancer Genomics and Applications of Liquid Biopsy for the Detection, Characterization, and Management of Cancer in 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.

Epigenetic Mechanisms in Canine Cancer

A plethora of data has highlighted the role of epigenetics in the development of cancer. Initiation and progression of different cancer types are associated with a variety of changes of epigenetic mechanisms, including aberrant DNA methylation, histone modifications, and miRNA expression. At the same time, advances in the available epigenetic tools allow to investigate and reverse these epigenetic changes and form the basis for the development of anticancer drugs in human oncology. Although human and canine cancer shares several common features, only recently that studies emerged investigating the epigenetic landscape in canine cancer and applying epigenetic modulators to canine cancer. This review focuses on the existing studies involving epigenetic changes in different types of canine cancer and the use of small-molecule inhibitors in canine cancer cells.

Genetic and environmental risk for lymphoma in boxer dogs

BACKGROUND

Non-Hodgkin lymphoma in humans is associated with environmental chemical exposures, and risk is enhanced by genetic variants in glutathione S-transferases (GST) enzymes.

OBJECTIVE

We hypothesized that boxer dogs, a breed at risk for lymphoma, would have a higher prevalence of GST variants with predicted low activity, and greater accumulated DNA damage, compared to other breeds. We also hypothesized that lymphoma in boxers would be associated with specific environmental exposures and a higher prevalence of canine GST variants.

ANIMALS

Fifty-four healthy boxers and 56 age-matched nonboxer controls; 63 boxers with lymphoma and 89 unaffected boxers ≥10 years old.

METHODS

We resequenced variant loci in canine GSTT1, GSTT5, GSTM1, and GSTP1 and compared endogenous DNA damage in peripheral leukocytes of boxers and nonboxers using the comet assay. We also compared GST variants and questionnaire-based environmental exposures in boxers with and without lymphoma.

RESULTS

Endogenous DNA damage did not differ between boxers and nonboxers. Boxers with lymphoma were more likely to live within 10 miles of a nuclear power plant and within 2 miles of a chemical supplier or crematorium. Lymphoma risk was not modulated by known canine GST variants.

CONCLUSIONS AND CLINICAL IMPORTANCE

Proximity to nuclear power plants, chemical suppliers, and crematoria were significant risk factors for lymphoma in this population of boxers. These results support the hypothesis that aggregate exposures to environmental chemicals and industrial waste may contribute to lymphoma risk in dogs.

Prognostic value of pretreatment plasma D-dimer level in dogs with intermediate to high-grade non-Hodgkin lymphoma

Pretreatment D-dimer levels have been reported to predict survival in several types of malignancies in human patients. The objective of this study was to evaluate the prognostic value of pretreatment D-dimer level in dogs with intermediate to high-grade non-Hodgkin lymphoma (NHL). In a prospective, randomized, double-blind study of F14512 vs etoposide phosphate, we assessed the prognostic value of pretreatment plasma D-dimer level in 48 client-owned dogs diagnosed with intermediate to high-grade NHL. The correlation between pretreatment plasma D-dimer level and various clinical features, progression-free survival (PFS) and overall survival (OS) was analysed. The median value of pretreatment plasma D-dimer level was 0.4 μg/mL (range: 0.1-14.3 μg/mL). High pretreatment plasma D-dimer level (>0.5 μg/mL) was detected in 44% (21/48) of dogs. High D-dimer levels were not correlated with naive vs relapsed lymphoma, clinical stage, substage, immunophenotype or treatment group. D-dimer levels >0.5 μg/mL were significantly associated with inferior median PFS (54 vs 104 days, P = .011) and OS (93 vs 169 days, P = .003). In the multivariate analysis, high D-dimer levels remained an independent predictor for worse PFS (HR: 3.21, 95% CI: 1.57-6.56, P = .001) and OS (HR: 3.87, 95% CI: 1.88-7.98; P < .001). This study suggests that pretreatment plasma D-dimer level can serve as a predictor of prognosis in dogs with intermediate to high-grade NHL. Further studies are warranted to confirm these findings.

Clinicopathological characteristics and prognostic factors for canine multicentric non-indolent T-cell lymphoma: 107 cases

Canine lymphoma, as the most common haematopoietic malignancy, encompasses a group of heterogeneous diseases and even within the T-cell immunophenotype, differences in clinical presentation and responses to treatment exist. The aim of this retrospective study was to determine outcomes and prognostic factors of 107 dogs with multicentric non-indolent T-cell lymphoma (TCL) receiving lomustine-based (70%) and non-lomustine-based (30%) treatment. The majority were Labradors, Boxers, mixed-breed dogs and Dogue de Bordeaux. Eighty-six percent were substage b, 77% had mediastinal involvement, 15% had suspected bone marrow involvement and 12% had other extra-nodal sites of disease. The overall response rate to induction therapy was 80%; dogs receiving procarbazine in the induction protocol (P = .042), dogs with neutrophil concentration below 8.7 × 10e⁹ /L (P = .006) and mitotic rate below 10 per 5 high power field (P = .013), had greater response rates. Median progression-free survival (PFS) for the first remission was 105 days; lack of expression of CD3 on flow cytometry (P < .0001) and pretreatment with steroid (P = .012) were significantly associated with shorter PFS. Median overall survival time (OST) was 136 days; co-expression of CD79a (P = .002), lack of CD3 expression on flow cytometry, presence of anaemia (P = .007), and monocytopenia (P = .002) were predictive of shorter OST. Multicentric non-indolent TCL in dogs is an aggressive cancer with new possible prognostic factors.

The Genetic and Molecular Basis for Canine Models of Human Leukemia and Lymphoma

Emerging details of the gene expression and mutational features of canine lymphoma and leukemia demonstrate areas of similarities and differences between disease subsets in the humans and dogs. Many features of canine diffuse large B-cell lymphoma resemble the ABC form of human DLBCL, including constitutive activation of the NF-kB pathway, and almost universal presence of double expressing MYC/BCL2 lymphomas. Frequent TRAF3 mutations and absence of BCL6 expression are differences with the human disease that need further exploration. Canine peripheral T-cell lymphoma is more common in dogs than in people and behaves in a similarly aggressive manner. Common features of canine and human PTCL include activation of the PI3 kinase pathways, loss of PTEN, and the tumor suppressor CDKN2. There is insufficient data available yet to determine if canine PTCL exhibits the GATA3-TBX21 dichotomy seen in people. Common to all forms of canine lymphoproliferative disease are breed-specific predilections for subsets of disease. This is particularly striking in PTCL, with the Boxer breed being dramatically overrepresented. Breed-specific diseases provide an opportunity for uncovering genetic and environmental risk factors that can aid early diagnosis and prevention.

Drug dose and drug choice: Optimizing medical therapy for veterinary cancer

Although novel agents hold great promise for the treatment of animal neoplasia, there may be room for significant improvement in the use of currently available agents. These improvements include altered dosing schemes, novel combinations, and patient-specific dosing or selection of agents. Previous studies have identified surrogates for "individualized dose intensity,", for example, patient size, development of adverse effects, and pharmacokinetic parameters, as potential indicators of treatment efficacy in canine lymphoma, and strategies for patient-specific dose escalation are discussed. Strategies for treatment selection in individual patients include conventional histopathology, protein-based target assessment (eg, flow cytometry, immunohistochemistry, and mass spectrometry), and gene-based target assessment (gene expression profiling and targeted or global sequencing strategies). Currently available data in animal cancer evaluating these strategies are reviewed, as well as ongoing studies and suggestions for future directions.

A Retrospective Study of Multi-agent Chemotherapy including either Cyclophosphamide or Lomustine as Initial Therapy for Canine High-grade T-cell Lymphoma (2011-2017)

Multi-agent chemotherapy (vincristine, epirubicin and prednisolone) including either cyclophosphamide (CEOP) or lomustine (LEOP) was given as first-line chemotherapy to treatment-naïve canine lymphoma patients with measurable, high grade T-cell lymphoma (HGTCL). All patients responded to either CEOP or LEOP. Toxicity was typical of multi-agent chemotherapy protocols and 25% of dogs receiving lomustine exhibited mild-to-moderate ALT elevation and 29% grade 3 or 4 neutropenia. Median progression-free survival (100 versus 269 days) and overall survival (155 versus 327 days) were significantly higher in patients receiving LEOP compared to CEOP. Overall survival was improved for patients receiving LEOP compared to those receiving CEOP followed by lomustine-based rescue therapy. The results of this retrospective study support further evaluation of lomustine as part of first-line, multi-agent therapy for patients with HGTCL.

Epidemiology, clinical and cytological features of lymphoma in Boxer dogs

The aim of this study was to evaluate the epidemiology, clinical and laboratory characteristics of canine lymphomas as well as some aspects of treatment outcomes. The study was conducted on Boxer dogs with lymphoma diagnosed by cytology and immunocytochemistry (CD3 and CD79 alpha). During the study period, lymphoma was diagnosed in 63 Boxers; 86.8% were T-cell (based on the Kiel classification: small clear cell lymphoma, pleomorphic small cell lymphoma, pleomorphic mixed T-cell lymphoma, pleomorphic large T-cell lymphoma, lymphoblastic lymphoma/acute lymphoblastic leukaemia) and 13.2% were B-cell lymphomas (according to the Kiel classification: B-cell chronic lymphocytic leukaemia, centroblastic/centroblastic polymorphic lymphoma). Overall survival (OS) was significantly longer in dogs with low-grade than with high-grade lymphoma (median OS of 6.8 and 4.7 months, respectively; P = 0.024). OS was not influenced by WHO clinical stage, WHO clinical substage, presence of splenomegaly, early administration of glucocorticoids or the time from the first presentation to the beginning of chemotherapy. There are no significant differences in clinical and laboratory parameters between low-grade and high-grade lymphomas. Boxer dogs are predisposed to T-cell lymphoma, with a predominance of high-grade tumour, especially pleomorphic, mixed small and large T-cell subtype. It is possible that Boxer dogs may respond less favourably to chemotherapy than patients of other breeds.

Novel Treatments for Lymphoma

Lymphoma is a common disease in companion animals. Although conventional chemotherapy has the potential to induce remission and prolong life, relapse is common, and novel treatments are needed to improve outcome. This review discusses recent modifications/adjustments to conventional standard of care therapy for canine and feline lymphoma, as well as cutting-edge immunotherapy and small-molecule-based approaches that are in varying stages of regulatory approval.

Evaluation of serum thymidine kinase 1 activity as a biomarker for treatment effectiveness and prediction of relapse in dogs with non-Hodgkin lymphoma

BACKGROUND

Serum thymidine kinase 1 (sTK1) activity is closely correlated with DNA synthesis.

OBJECTIVES

Evaluate sTK1 activity as a biomarker for treatment response and early detection of relapse in dogs with lymphoma.

ANIMALS

Ninety-seven client-owned dogs with naive or relapsed lymphoma and 23 healthy dogs.

METHODS

Prospective study. Serum TK1 activity measured by refined ELISA-based method (DiviTum assay, Biovica International) before treatment, at clinical response, and every 4 weeks until relapse or last follow-up.

RESULTS

Serum TK1 activity was ≤20 Du/L in 96% (22/23) of healthy dogs. Pretreatment sTK1 activity was >20 Du/L in 88% (85/97) dogs with lymphoma. At clinical response, sTK1 activity was significantly lower in dogs with complete (CR, n = 36) versus partial (PR, n = 29) response (P < .0001). Sensitivity (Se) and specificity (Sp) of sTK1 activity for detecting nonfully responders were 76% and 100%, respectively, with cutoff of 119.5 Du/L (AUC, 0.90; 95%-CI, 0.81-0.98; P < .0001). In dogs with CR, a 5-fold increase in sTK1 activity at a 4-week interval predicted relapse at the subsequent 4-week assessment with a Se 50% and Sp 94% (AUC, 0.72; 95%-CI, 0.55-0.90; P = .02). An increase of sTK1 activity (>2.7-fold value measured at clinical response) predicted relapse at subsequent 4-week assessment with a Se 61% and Sp 88% (AUC, 0.79; 95%-CI, 0.64-0.95; P = .004).

CONCLUSIONS AND CLINICAL IMPORTANCE

Monitoring sTK1 activity could help to detect complete responders and early disease progression in dogs with lymphoma.

Comparison of combination l-asparaginase plus CHOP or modified MOPP treatment protocols in dogs with multi-centric T-cell or hypercalcaemic lymphoma

OBJECTIVES

To compare the progression-free survival of dogs with high-grade T-cell lymphoma treated with either a cyclophosphamide, doxorubicin, vincristine and prednisone-based or a modified mechlorethamine, vincristine, prednisone and procarbazine chemotherapy protocol.

MATERIALS AND METHODS

In this retrospective study, cases were selected based on histologic or cytologic diagnosis of lymphoma, T-cell phenotype, hypercalcaemia, or both, and no previous chemotherapy for lymphoma. Treatment was not randomly allocated.

RESULTS

Seventy-three dogs were included in this study: 50 in the cyclophosphamide, doxorubicin, vincristine and prednisone group and 23 in the mechlorethamine, vincristine, prednisone and procarbazine group. The median progression-free survival was 133 days for dogs in the cyclophosphamide, doxorubicin, vincristine and prednisone group and 97 days for dogs in the mechlorethamine, vincristine, prednisone and procarbazine group. When golden retrievers (n = 16) were evaluated -separately, progression-free survival was longer in the cyclophosphamide, doxorubicin, vincristine and prednisone versus mechlorethamine, vincristine, prednisone and procarbazine treatment group (median PFS 154 days versus 70.5 days, respectively).

CLINICAL SIGNIFICANCE

The progression-free survival time for dogs with multi-centric T-cell lymphoma treated with a modified mechlorethamine, vincristine, prednisone and procarbazine protocol was similar to that of dogs treated with cyclophosphamide, doxorubicin, vincristine and prednisone. Further studies, including those evaluating golden retrievers separately, are needed to confirm these findings.

Retrospective analysis of doxorubicin and prednisone as first-line therapy for canine B-cell lymphoma

BACKGROUND

A doxorubicin (DOX)-based chemotherapy protocol, CHOP, is the most effective treatment for canine high-grade B-cell lymphoma; however, the cost and time requirements associated with this protocol are not feasible for many pet owners. An alternative treatment option is the use of DOX, the most effective drug, in combination with prednisone. Prior studies with single-agent DOX included dogs with T-cell lymphoma, a known negative prognostic factor, which may have resulted in shorter reported survival times than if dogs with B-cell lymphoma were analyzed separately. The purpose of this study was to evaluate the outcome of dogs with high-grade B-cell lymphoma when treated with DOX and prednisone with or without L-asparaginase (L-ASP). Identification of prognostic factors was of secondary interest.

RESULTS

Thirty-three dogs were included in the study; 31 dogs were evaluable for response with an overall response rate of 84%. The median progression free survival (PFS) and overall survival (OS) were 147 days and 182 days, respectively. The one-year survival fraction was 23%. No variable other than protocol completion was found to be significant for either PFS or OS including historical prognostic factors such as substage, thrombocytopenia, and body weight.

CONCLUSIONS

Dogs with high-grade B-cell lymphoma treated with DOX and prednisone with or without L-ASP have similar response rates, PFS, and OS to prior studies that did not differentiate between lymphoma immunophenotype. This protocol is not a replacement for CHOP; however, it is an alternative if time and cost are factors, while providing therapeutic benefit greater than prednisone alone.

Response rate to a single dose of vinblastine administered to dogs with treatment-naive multicentric lymphoma

Vincristine is included in vincristine, cyclophosphamide, doxorubicin and prednisone (CHOP) chemotherapy protocols, which are the gold-standard treatment for high-grade canine lymphoma. Vincristine can result in relatively high rates of gastrointestinal toxicity, whereas vinblastine is generally well tolerated and thus may represent an under-utilized and minimally toxic alternative to vincristine. Our objective was to determine the response rate and toxicity associated with a single dose of vinblastine administered to dogs with treatment-naïve, intermediate to large-cell, multicentric lymphoma. Twenty client-owned dogs were enrolled with signed owner consent. A Simon's minimax, phase II, two-stage trial was performed to test the efficacy of vinblastine administered at 2 mg/m² IV followed by a pilot trial of vinblastine at 2.5 mg/m² . No dogs were administered concurrent steroids or other chemotherapy. One out of 14 dogs receiving vinblastine at 2 mg/m² demonstrated a partial response. Three out of five dogs demonstrated a partial response to vinblastine at 2.5 mg/m² . Gastrointestinal toxicity was infrequent and low grade for both groups. The majority of dogs (80%) in the 2.5 mg/m² dosing group developed neutropenia 1-week post administration. Vinblastine was well tolerated but minimally efficacious at a dose of 2 mg/m² IV in dogs with treatment-naive, multicentric lymphoma. Because of poor response rates, treatment at this dose is not recommended. A small subset of dogs administered 2.5 mg/m² had significantly improved response rates (P = 0.04), suggesting that higher doses may have improved efficacy, although further research is indicated to confirm these preliminary findings.

Phase I/II evaluation of RV1001, a novel PI3Kδ inhibitor, in spontaneous canine lymphoma

Background

RV1001 is a novel, potent, and selective PI3Kδ inhibitor. The purpose of this study was to evaluate the safety and efficacy of RV1001 in canine Non-Hodgkin lymphoma (NHL).

Methods and results

Inhibition of endogenous pAKT by RV1001 in primary canine NHL cells was determined by Western blotting. A phase I study of RV1001 was performed in 21 dogs with naïve and drug resistant T and B-cell NHL to assess safety, pharmacokinetic profile, and response to therapy. The objective response rate was 62% (complete response (CR) n = 3; partial response (PR) n = 10), and responses were observed in both naïve and chemotherapy-resistant B and T cell NHL. This study provided the recommended starting dose for a phase II, non-pivotal, exploratory, open label multi-centered clinical trial in 35 dogs with naïve and drug resistant T and B-cell NHL, to further define the efficacy and safety profile of RV1001. The objective response rate in the phase II study was 77% (CR n = 1; PR n = 26). Clinical toxicities were primarily hepatobiliary and gastrointestinal, and were responsive to dose modifications and/or temporary drug discontinuation. Hepatotoxicity was the primary dose limiting toxicity.

Conclusions

RV1001 exhibits good oral bioavailability, an acceptable safety profile, and biologic activity with associated inhibition of pAKT in dogs with B and T cell NHL. Data from these studies can be leveraged to help inform the design of future studies involving isoform-selective PI3K inhibitors in humans.

Prognostic significance of clinical presentation, induction and rescue treatment in 42 cases of canine centroblastic diffuse large B-cell multicentric lymphoma in the United Kingdom

Canine lymphoma is a heterogeneous group of diseases and many previous studies have evaluated the response of a mixed population of lymphoma cases to one specific treatment protocol. The aim of this retrospective study was to describe the outcome and prognostic factors in 42 cases of multicentric centroblastic diffuse large B-cell lymphoma treated with either a COP-type (35%) or CHOP-type (64%) induction chemotherapy. The objective response rate to induction therapy was 94%; entire dogs had a greater rate of complete vs partial remissions than neutered dogs (P = .017). Median progression-free survival for the first remission (PFS1) was 182 days; absence of anaemia at diagnosis (P = .002) and pretreatment neutrophil:lymphocyte ratio (NLR) below 9.44 (P = .015) were independently predictive of longer PFS1. Fifty-eight percent of dogs received rescue protocols with an objective response rate of 81%; 31% of dogs received further rescue protocols (up to a total of 5) and the median number of protocols administered were 2. Median overall survival (OS) was 322 days, the 1-year survival rate was 38% and the 2-year survival rate was 9%. Lymphocyte:monocyte ratio above 1.43 (P = .031), NLR below 11.44 (P = .009), the combination of induction and rescue therapy (P = .030) and the total number of doxorubicin doses used (P = .002) were independently predictive of longer OS. Use of a COP-type protocol induction compared with CHOP did not undermine OS providing doxorubicin was used as rescue therapy.

Oral melphalan for the treatment of relapsed canine lymphoma

Oral melphalan has been included in multi-agent rescue protocols for canine lymphoma but its activity as a single-agent for this purpose has not been established. Inexpensive cost, ease of administration and tolerability make oral melphalan an attractive candidate for single-agent rescue therapy of canine lymphoma. Retrospective evaluation of 19 cases of relapsed canine lymphoma treated with oral melphalan was performed. Melphalan was primarily administered (n = 16) via a high dose protocol (HDM) with a median dosage of 19.4 mg m^-2 . Fifteen dogs (78.9%) were treated concurrently with corticosteroids. Response evaluation was possible for all dogs with a calculated overall clinical benefit (partial response [PR] + stable disease [SD]) of 31.6% (PR 3/19; SD 3/19). Times to progression following melphalan (TTP-M) were 14, 24 and 34 days for responders and 20, 28 and 103 days for dogs experiencing SD. Twelve of 17 dogs evaluable for toxicity experienced an adverse event (AE) with only 3 dogs experiencing a grade III or higher AE. Haematologic toxicity was common (11/17) while gastrointestinal toxicity was rare (1/17). Although treatment resulted in limited clinical benefit and non-durable responses, oral melphalan was well-tolerated and may be a reasonable rescue option in cases where minimal effective agents remain.

Specific immunotypes of canine T cell lymphoma are associated with different outcomes

Canine lymphoma is a heterogeneous disease with many different subtypes. Lymphoma of T cell type in particular is variable in outcome, and includes subtypes with non-progressive, slowly- and rapidly-progressive disease course. Association of immunotype with disease course is incompletely defined. Here, results of flow cytometric immunotyping of 127 canine T cell lymphomas were analyzed in relation to survival and progression free interval. Samples originated from 101 multicentric, 8 mediastinal, 6 cutaneous, 5 hepatosplenic, 5 gastrointestinal and 2 other anatomic subtypes of T cell lymphoma. Compared to multicentric T cell lymphoma, gastrointestinal lymphoma had shorter survival and progression free interval, and hepatosplenic lymphoma had shorter survival. Among dogs with multicentric T cell lymphoma, immunotypes of CD4⁺/CD8^-/MHCII⁺, CD4^-/CD8⁺/MHCII⁺ and CD4^-/CD8⁺/MHCII^- were associated with longer survival times than the immunotype of CD4⁺/CD8^-/MHCII^-, and immunotypes of CD4⁺/CD8^-/MHCII⁺, CD4^-/CD8⁺/MHCII^-, and CD4^-/CD8^-/MHCII⁺ were associated with longer progression free intervals. Dogs with multicentric T cell lymphoma and concurrent leukemia had shorter survival but similar progression free interval compared to those without leukemia. Body weight, sex, hypercalcemia, cell size, expression of CD3 and use of combination or single agent chemotherapy did not significantly affect outcome of multicentric TCL.

Patient characteristics, prognostic factors and outcome of dogs with high-grade primary mediastinal lymphoma

The goals of this retrospective study were to determine the patient characteristics of dogs with high-grade primary mediastinal lymphoma and to determine outcome and associated prognostic factors. A total of 42 dogs were identified, in which 36 received treatment and had follow-up information available. The most common clinical signs included lethargy, anorexia and polyuria/polydipsia. Hypercalcemia and pleural effusion were common findings at diagnosis. The phenotype was almost exclusively T-cell, most often in association with lymphoblastic cytomorphology as defined by the World Health Organization (WHO) lymphoma classification scheme. The overall progression-free survival (PFS) and overall survival (OS) were 133 and 183 days, respectively. Treatment with a CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) protocol was associated with an improved PFS (144 days) and OS (194 days) when compared with dogs that received other medical therapies (P = .005 and P = .002, respectively); the absence of pleural effusion at diagnosis was associated with an increased OS but not PFS. These results suggest that while the prognosis for dogs with mediastinal lymphoma is poor, survival may be improved with treatment using a CHOP-based protocol.

LOPP chemotherapy as a first-line treatment for dogs with T-cell lymphoma

BACKGROUND

The aim of this study was to describe the use of a lomustine (CCNU), vincristine, procarbazine and prednisolone (LOPP) protocol used for treatment of chemotherapy naive T-cell lymphoma patients and to describe the response rate, toxicity and disease-free interval compared historically to CHOP chemotherapy.

MATERIALS AND METHODS

Retrospective case study of 31 dogs with naïve T-cell lymphoma treated with a lomustine (CCNU), vincristine, procarbazine and prednisolone (LOPP) protocol.

RESULTS

Thirty-one dogs with T cell lymphoma were treated. The overall response rate was 97%. Of the 30 dogs that had a response to LOPP chemotherapy, the median disease free interval was 176 days (range 0-1745 days). The median overall survival time for this study group was 323 days (range 51-1758 days). All deaths in this study were attributable to lymphoma.

CONCLUSION

LOPP chemotherapy for T cell lymphoma is well tolerated with a low toxicity profile and an excellent overall response rate. This protocol showed minimal toxicity and comparable disease free interval and survival times for canine high grade T cell lymphoma treated with CHOP.

Lymphoid Neoplasia: Correlations Between Morphology and Flow Cytometry

Cytology is commonly used to diagnose lymphoma and leukemia. Frequently, a diagnosis of lymphoproliferative disease can be obtained via cytology, and some of the common subtypes of canine lymphoma and leukemia can have characteristic cytologic features. Flow cytometry is a critical tool in the objective diagnosis and further characterization of lymphoma and leukemia. Features of the immunophenotype, such as expression of certain cell surface proteins or cell size, can provide important prognostic information. This review describes the cytologic features, flow cytometry immunophenotype, and immunophenotypic prognostic information for 6 major types of canine lymphoma and leukemia.