Canine Lymphoma Patients Research Articles

An Antibody Specific for the Dog Leukocyte Antigen DR (DLA-DR) and Its Novel Methotrexate Conjugate Inhibit the Growth of Canine B Cell Lymphoma.

Canine B-cell lymphoma (CBL) is an incurable, spontaneous lymphoid malignancy constituting an accurate animal model for testing novel therapeutic strategies in human medicine. Resources of available species-specific therapeutic monoclonal antibodies (mAbs) targeting CBL are scarce. The aim of the present study was to evaluate the therapeutic potential of mAb B5, specific for the dog leukocyte antigen DR (DLA-DR) and its antibody-drug conjugate with methotrexate (B5-MTX). B5 induced caspase-dependent apoptosis of DLA-DR-expressing canine B cell lymphoma/CLBL1 and CLB70 leukemia lines, but not the GL-1 line not expressing DLA-DR. The cytotoxicity of B5-MTX to sensitive cells was further potentiated by a payload of MTX, but without any substantial off-target effects. The infusion of B5 and B5-MTX in a murine model of disseminated, advanced canine lymphoma, mediated >80% and >90% improvement in survival, respectively, and was well tolerated by the animals. Interestingly, the concentrations of soluble DLA-DR (sDLA-DR) antigens present in the blood serum of tumor-bearing mice were found proportional to the tumor burden. On this basis, sDLA-DR levels were evaluated as a potential biomarker using samples from canine lymphoma patients. In summary, the action of B5 and B5-MTX holds promise for further development as an alternative/complementary option for the diagnosis and treatment of canine lymphoma.

Changes in regulatory T cells in dogs with B-cell lymphoma and association with clinical tumour stage

Among several mechanisms that allow tumours to disarm the host immune system and thus to evade or suppress protective anti-tumour immunity, an important role for CD4<sup>+</sup>CD25<sup>+</sup>FoxP3<sup>+</sup> regulatory T cells (Tregs) has emerged. Numerous studies in humans have demonstrated increased Tregs in patients with carcinomas of the breast, lung, and pancreas, and this increased Treg has been correlated with poor prognosis. This study was performed (1) to investigate the percentage of Tregs in total lymphocytes of the peripheral blood in 12 canine patients with B cell lymphoma and (2) to investigate the change in the percentage of Tregs in canine lymphoma of different clinical tumour stages. On the flow cytometric analysis, the relative and absolute numbers of Tregs were significantly increased in 12 canine patients with B-cell lymphoma compared to five healthy beagles included in this study, and the greatest increases in the relative and absolute number of Tregs occurred in two dogs with more advanced World Health Organization clinical stages with bone marrow involvement compared to those in less advanced tumour stages without bone marrow involvement. This study provides basic information regarding the negative role of Treg recruitment in canine lymphoma patients and highlights the potential value of Treg levels as prognostic indicators in canine cancer patients.

Preclinical Evaluation of the Novel BTK Inhibitor Acalabrutinib in Canine Models of B-Cell Non-Hodgkin Lymphoma

Acalabrutinib (ACP-196) is a second-generation inhibitor of Bruton agammaglobulinemia tyrosine kinase (BTK) with increased target selectivity and potency compared to ibrutinib. In this study, we evaluated acalabrutinib in spontaneously occurring canine lymphoma, a model of B-cell malignancy similar to human diffuse large B-cell lymphoma (DLBCL). First, we demonstrated that acalabrutinib potently inhibited BTK activity and downstream effectors in CLBL1, a canine B-cell lymphoma cell line, and primary canine lymphoma cells. Acalabrutinib also inhibited proliferation in CLBL1 cells. Twenty dogs were enrolled in the clinical trial and treated with acalabrutinib at dosages of 2.5 to 20mg/kg every 12 or 24 hours. Acalabrutinib was generally well tolerated, with adverse events consisting primarily of grade 1 or 2 anorexia, weight loss, vomiting, diarrhea and lethargy. Overall response rate (ORR) was 25% (5/20) with a median progression free survival (PFS) of 22.5 days. Clinical benefit was observed in 30% (6/20) of dogs. These findings suggest that acalabrutinib is safe and exhibits activity in canine B-cell lymphoma patients and support the use of canine lymphoma as a relevant model for human non-Hodgkin lymphoma (NHL).

Detection of circulating tumor cells using GeneScan analysis for antigen receptor gene rearrangements in canine lymphoma patients.

The presence of circulating tumor cells (CTCs) serves as a prognostic marker and indicator of disease relapse, as well as a means of evaluating treatment efficacy in human and canine lymphoma patients. As an extension of our previous study for the construction of clinically useful GeneScan system, we utilized the GeneScan system for detecting CTCs in canine lymphoma patients. Samples from the primary lesion and peripheral blood mononuclear cells (PBMCs) were obtained from 32 dogs with lymphoma at initial diagnosis. All samples were subjected to polymerase chain reaction (PCR) for antigen receptor gene rearrangements (PARR) followed by GeneScan analysis. Common clonal rearrangements with identical amplified fragments were detected in both the primary lesion and PBMCs in 19 of the 32 dogs (59.4%). However, the detection rate of CTCs varied among the anatomical classification of lymphoma studied. GeneScan analysis following PARR would facilitate studies on determining the clinical significance of CTCs in canine lymphoma patients.

Abstract 3129: A platform to assess multiple therapy options simultaneously in a patient's own tumor

Abstract Proper selection of anti-cancer agents at the earliest stage of patient treatment following diagnosis of disease relapse is expected to substantially impact clinical response to treatment. Currently, genomic approaches to personalized cancer treatments have been yielded mixed results, while empirical tests to assess tumor responsiveness have been limited to ex vivo systems that disrupt the native tumor microenvironment and show limited predictive value. To address the need for multiplexed in vivo chemosensitivity testing, we have developed a technology that allows simultaneous assessment of multiple cancer therapeutics directly in a patient's tumor. This technology could provide a valuable decision-making tool to prioritize effective treatments in the oncology clinic. Data herein highlight how this technology enables controlled and reliable microinjection of multiple drugs simultaneously in preclinical tumor models, canine lymphoma, and human lymphoma patients. Consistent with the controlled drug delivery of this system, spatially localized, readily detectable, and mechanism-specific cellular changes were observed around sites of microinjection in response to classic chemotherapy drugs (vincristine and doxorubicin) as well as to a small molecule inhibitor of TOR kinase. Importantly, localized response (or lack thereof) to individual components of CHOP combination therapy correlated with response to long-term systemic drug administration across multiple cell line and patient-derived xenograft models of lymphoma. Underscoring the importance of assessing drug efficacy in the context of an intact in vivo system, tumor responses to vincristine were impacted by the local tumor microenvironment. Our results also emphasize the importance of selecting effective therapies early in the course of treatment, as drug resistance mechanisms induced cross-resistance to otherwise efficacious drugs. These studies set the stage for use of this platform in oncology drug development, where the ability to more rapidly assess drug efficacy using clinically relevant in vivo tumors may decrease the current reliance on in vitro cell-based models of cancer and possibly increase the likelihood of clinical success. This platform may thus be useful a clinical decision-making tool for selection of patient-specific anti-cancer therapies. Citation Format: Richard Klinghoffer, Alicia Moreno-Gonzalez, Michael Carleton, Jason Frazier, Marc Grenley, Ilona Tretyak, Nathan Hedin, Joyoti Dey, Joseph Casalini, Beryl Hatton, Sally Ditzler, James Olson, Daniel Pierce, Ellen Filvaroff, Nathan Caffo. A platform to assess multiple therapy options simultaneously in a patient's own tumor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3129. doi:10.1158/1538-7445.AM2014-3129

Detection of clonal antigen receptor gene rearrangement in dogs with lymphoma by real-time polymerase chain reaction and melting curve analysis

BackgroundMolecular techniques that detect canine lymphoma cells by their clonal antigen receptor gene rearrangement play an increasing role for diagnosis as well as for monitoring minimal residual disease during and after cytostatic therapy. However, the methods currently available are time-consuming and/or cost-intensive thus impeding the use in clinical routine. The aim of the present study was to develop and evaluate a real-time polymerase chain reaction (PCR) with subsequent melting curve analysis (MCA) for the detection of clonally rearranged antigen receptor genes in dogs with B and T cell lymphoma on non formalin-fixed and paraffin-embedded lymph node samples.ResultsIn lymph node aspirates from 30 dogs with multicentric B cell lymphoma, real-time PCR with MCA detected clonal rearrangement in 100% and conventional PCR with polyacrylamide gel electrophoresis (PAGE) in 93% of samples. Both methods correctly identified clonality in 80% of lymph node aspirates of 10 dogs with T cell lymphoma. None of the two PCR systems detected clonal rearrangement in samples from 9 dogs with lymph node hyperplasia. Using a dilutional series with regular lymphoid desoxyribonucleic acid (DNA), detection limits of lymphoma DNA were as low as 0.8% and 6.25% for B and T cell clonal rearrangement with real-time PCR and MCA and at 3.13% and 12.5% with the conventional system. Median absolute detection limits of lymphoma DNA were shown to be at 0.1 ng and 1 ng for the B and T cell immunophenotype with the real-time PCR system and at 10 ng each with conventional PCR and PAGE.ConclusionsReal-time PCR with MCA is a convenient and reliable method with a good analytical sensitivity. Thus, the method may assist the detection of clonal antigen receptor gene rearrangement in canine lymphoma patients in a clinical setting also in the presence of small amounts of neoplastic cells.

Expression of asparagine synthetase predicts in vitro response to l-asparaginase in canine lymphoid cell lines

l-asparaginase (L-asp), a bacterial enzyme that depletes extracellular asparagine, is used to treat acute lymphoblastic leukemia in humans and a variety of aggressive lymphoid malignancies in dogs. Resistance to this drug is an important cause of treatment failure in both species. Using canine lymphoid cell lines, we found that L-asp sensitivity is strongly negatively correlated with the level of methylation of the asparagine synthetase (ASNS) promoter. Selection for in vitro resistance was accompanied by increased ASNS promoter methylation and decreased ASNS mRNA expression. In addition, treatment with the hypomethylating agent 5-azacytidine increased resistance to L-asp. ASNS methylation and expression is not predictive of overall survival or progression-free survival in canine lymphoma patients treated with L-asp. Our data suggest that ASNS is an important factor in mediating the in vitro response of canine lymphoid cells to L-asp; however, resistance mechanisms may be more complex in dogs treated clinically with L-asp, potentially due to concurrent treatments.

Abstract C278: Topoisomerase 1 immunoassay provides proof of target engagement by the indenoisoquinoline class of topoisomerase 1 inhibitors in canine lymphomas.

Abstract Topoisomerase I (Top1) is the molecular target for a number of drugs used in cancer chemotherapy. Several third generation Top1 inhibitors are being evaluated, including the indenoisoquinolines (NSC 725776 and NSC743400) which are currently in clinical trials at the National Cancer Institute. We previously reported the development and validation of a quantitative ELISA to measure Top1 levels in cells and solid tissues [PloS ONE (2012) 7(12)]. We observed a large variation in baseline Top1 levels in xenografts and human patient biopsies using the published method. Baseline Top1 levels in needle biopsies for some patients were too low to allow for the reporting of a drug effect. We have modified our tissue processing procedures to improve assay sensitivity. We have also demonstrated the fitness of the assay in a clinical trial of the indenoisoquinolines for canine lymphoma as a stepping stone to human clinical trials. Baseline Top1 levels in canine lymphoma patients varied greatly, consistent with our previous findings in xenografts and a limited number of human tumor biopsies. These data suggest that it may not be possible to measure drug effect based on post-dose Top1 levels alone, but will require paired pre-dose and post-dose specimens from the same patient. Decreased Top1 levels following therapy (compared to pre-dose) were detected in tumors from a number of dogs, each treated with one of three indenoisoquinolines (NSC706744, NSC 725776 and NSC743400), demonstrating evidence of target engagement as predicted by in vitro and xenograft models. Measurement of baseline Top1 levels in this trial will be correlated with the degree of drug-related target reduction and evidence of drug efficacy in the dogs enrolled on this study. Funded by NCI Contract No. HHSN261200800001E. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C278. Citation Format: Thomas D. Pfister, Katerine V. Ferry-Galow, Tariq Mohabbat, Robert J. Kinders, Chand Khanna, Christina Mazcko, Ralph E. Parchment, Yves Pommier, Joseph E. Tomaszewski, James H. Doroshow. Topoisomerase 1 immunoassay provides proof of target engagement by the indenoisoquinoline class of topoisomerase 1 inhibitors in canine lymphomas. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C278.

Risk factors for development of sterile haemorrhagic cystitis in canine lymphoma patients receiving oral cyclophosphamide: a case–control study

Sterile haemorrhagic cystitis (SHC) is a known risk of cyclophosphamide treatment; however, most canine reports are case series. This case-control study examined risk factors for SHC in dogs with lymphoma receiving oral cyclophosphamide. Twenty-two dogs with SHC and 66 control dogs were identified. On univariate analysis, SHC risk factors included age (P = 0.041), induction protocol (P = 0.021) and cumulative cyclophosphamide dose (P = 0.002). On multivariate analysis, increasing cumulative cyclophosphamide dose was associated with increased risk of SHC and the 'short' induction protocol (protocol 1) was associated with decreased risk. Controlling for age and induction protocol, odds of SHC increased by 2.21 per 750 mg m(-2) increase in cyclophosphamide dose (P = 0.001). SHC from oral cyclophosphamide is a predominately delayed toxicity resulting from high cumulative doses.

Autologous Peripheral Blood Hematopoietic Cell Transplantation in Dogs with B‐cell Lymphoma

Peripheral blood CD34+ hematopoietic cell transplantation (PBHCT) is commonly used to treat human patients with relapsed non-Hodgkin diffuse, large B-cell lymphoma with cure rates approaching 50%. To determine the safety and feasibility of performing PBHCT to treat canine B-cell lymphoma (LSA) patients in a clinical academic setting. Twenty-four client-owned dogs diagnosed with B-cell LSA. After high-dose cyclophosphamide and rhG-colony-stimulating factor treatment, peripheral blood mononuclear cells were collected using cell separator machines. The harvested cells then were infused after a 10 Gy dose of total body irradiation (TBI). Post-irradiation adverse effects were managed symptomatically and dogs were discharged upon evidence of engraftment. More than 2 × 10(6) CD34+ cells/kg were harvested in 23/24 dogs. Preapheresis peripheral blood monocyte count was correlated with the number of CD34+ cells/kg harvested. Twenty-one of 24 (87.5%) dogs engrafted appropriately, whereas 2 dogs (8.3%) died in the hospital. One (5%) dog exhibited delayed engraftment and died 45 days after PBHCT. One dog developed presumed TBI-induced pulmonary fibrosis approximately 8 months after PBHCT. The median disease-free interval and overall survival (OS) of all dogs from the time of PBHCT was 271 and 463 days, respectively. Five of 15 (33%) dogs transplanted before they relapsed remain in clinical remission for their disease at a median OS of 524 days (range, 361-665 days). In most cases, PBHCT led to complete hematologic reconstitution. Therefore, PBHCT may be considered as a treatment option for dogs with B-cell lymphoma.

Comparison of polymerase chain reaction for antigen receptor gene rearrangement and flow cytometric analysis for the diagnosis of canine lymphoma

Lymphoma is the most common hematopoietic malignancy in dogs. Diagnosis of lymphoma is classically performed by morphological assessment and immunohistochemistry. But some cases in the early stage are difficult to distinguish and need more objective and accurate methods. So, Polymerase chain reaction (PCR) for antigen receptor rearrangements (PARR) and flow cytometric immunophenotype of lymphoma have been developed continuously. In this study, we performed these two methods to classify lymphoma type in 3 cases. According to PARR analysis, B cell origin lymphoma was diagnosed in two of three cases by testing PBMC and lymph node. All fine needle aspiration (FNA) samples of lymph nodes had high expression of CD21 on >88% of total cell population and PBMC samples also showed high expression of CD21 on >30% of total lymphocytes in those two cases, while the expression of CD3, CD4 and CD8 was absent. These results suggest that concurrent use of PARR and flow cytometric immunophenotype is more effective and valuable tool for the diagnosis and monitoring of canine lymphoma patients.

DIAGNOSTIC ACCURACY OF GRAY-SCALE ULTRASONOGRAPHY FOR THE DETECTION OF HEPATIC AND SPLENIC LYMPHOMA IN DOGS

Gray-scale ultrasonography is often used to screen for involvement of the liver and spleen in canine lymphoma patients but the utility of sonography for staging lymphoma has not been evaluated quantitatively. We performed abdominal sonography in 28 dogs with a confirmed diagnosis of lymphoma. Needle aspirates were obtained for cytology from three separate sites in the liver and three sites in the spleen and the sonographic appearance was noted at each site. Our hypothesis was that in dogs newly diagnosed with lymphoma, abnormal appearance of the liver or spleen on ultrasound examination is an indication that lymphoma is present in that organ. Cytologic evaluation was used as the gold standard. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of hepatic and splenic abnormalities seen on ultrasound for diagnosis of lymphoma were 72.7%, 80.6%, 77.4%, 76.3%, and 76.8% for the liver, respectively, and 100%, 23.3%, 64.6%, 100%, and 68.1% for the spleen, respectively. Based on these results, we recommend that aspirates be performed for detection of lymphoma in the spleen of dogs only when the spleen appears abnormal ultrasonographically and that cytology of the liver be performed, regardless of ultrasonographic appearance, to determine the presence or absence of lymphoma.

Doxorubicin and cyclophosphamide for the treatment of canine lymphoma: a randomized, placebo-controlled study*

Median survival times (STs) for doxorubicin-treated canine lymphoma range from 5.7 to 9 months. Because dogs treated with multi-agent protocols have longer STs, we sought to evaluate whether adding cyclophosphamide would improve outcome in canine lymphoma patients while maintaining an acceptable level of toxicity. Thirty-two dogs with stage III-V multicentric lymphoma were treated with doxorubicin every 3 weeks for five total cycles and prednisone at a tapering dose for the first 4 weeks. Dogs were randomized to receive either cyclophosphamide or placebo concurrently. Seventeen dogs received doxorubicin and placebo, while 15 dogs received doxorubicin and cyclophosphamide. Response, toxicity, progression-free interval (PFI) and ST were evaluated. The combination of doxorubicin and cyclophosphamide was well tolerated, causing no increase in adverse events over doxorubicin alone. Despite a numeric improvement in outcome in cyclophosphamide treated dogs, the addition of cyclophosphamide did not result in statistically improved response rate, PFI or ST.

Expression of the high mobility group A1 (HMGA1) and A2 (HMGA2) genes in canine lymphoma: analysis of 23 cases and comparison to control cases

Overexpression of high mobility group A (HMGA) genes was described as a prognostic marker in different human malignancies, but its role in canine haematopoietic malignancies was unknown so far. The objective of this study was to analyse HMGA1 and HMGA2 gene expression in lymph nodes of canine lymphoma patients. The expression of HMGA1 and HMGA2 was analysed in lymph node samples of 23 dogs with lymphoma and three control dogs using relative quantitative real-time RT-PCR. Relative quantity of HMGA1 was significantly higher in dogs with lymphoma compared with reference samples. HMGA2 expression did not differ between lymphoma and control dogs. With the exception of immunophenotype, comparison of disease parameters did not display any differences in HMGA1 and HMGA2 expression. The present findings indicate a role of HMGA genes in canine lymphoma. This study represents the basis for future veterinary and comparative studies dealing with their diagnostic, prognostic and therapeutic values.

Proteomic identification and profiling of canine lymphoma patients

This study employed proteomic and bioinformatic approaches to identify serum biomarkers in canine lymphoma patients. Chilled serum samples derived from non-lymphoma (n = 92) and lymphoma (n = 87) patients were shipped from first opinion veterinary practices, subjected to ion exchange chromatography and analysed by surface-enhanced laser desorption ionization mass spectrometry. Nineteen serum protein peaks were identified between the two groups as being significantly different (P < 0.05) based upon their normalized ion intensities. Two biomarkers were identified that were capable of differentiating lymphoma and non-lymphoma patients. Analysis of the test data provided a positive predictive value (PPV) of 82%. A clinical follow-up study was carried out on 96 canine patients suspected of having lymphoma. Evaluation of this data gave a specificity value of 91%, sensitivity of 75%, PPV of 80% and negative predictive value of 88%. In conclusion, the expression pattern of two serum biomarkers has enabled serum samples to be classified into either lymphoma or non-lymphoma categories.

Proteomic identification and profiling of canine lymphoma patients*

AbstractThis study employed proteomic and bioinformatic approaches to identify serum biomarkers in canine lymphoma patients. Chilled serum samples derived from non‐lymphoma (n = 92) and lymphoma (n = 87) patients were shipped from first opinion veterinary practices, subjected to ion exchange chromatography and analysed by surface‐enhanced laser desorption ionization mass spectrometry. Nineteen serum protein peaks were identified between the two groups as being significantly different (P &lt; 0.05) based upon their normalized ion intensities. Two biomarkers were identified that were capable of differentiating lymphoma and non‐lymphoma patients. Analysis of the test data provided a positive predictive value (PPV) of 82%. A clinical follow‐up study was carried out on 96 canine patients suspected of having lymphoma. Evaluation of this data gave a specificity value of 91%, sensitivity of 75%, PPV of 80% and negative predictive value of 88%. In conclusion, the expression pattern of two serum biomarkers has enabled serum samples to be classified into either lymphoma or non‐lymphoma categories.

Pax5 immunostaining in paraffin-embedded sections of canine non-Hodgkin lymphoma: A novel canine pan pre-B- and B-cell marker

The Pax5 gene encodes the B-cell specific activator protein (BSAP), a member of the highly conserved paired box (PAX)-domain family of transcription factors and a key regulator in the development and differentiation of B-cells. Pax5 serves as a valuable B-cell marker in the classification of human lymphoma patients as it is restricted to lymphomas of B-cell lineage. In dogs, detection of Pax5 protein in lymphoma tissue has not been reported. Therefore, we have investigated the expression and detection of BSAP using a monoclonal anti-Pax5 antibody (anti-BSAP, clone 24) in canine lymphoma tissue samples to evaluate its diagnostic relevance as a B-cell marker. A series of 25 lymph nodes from 23 canine non-Hodgkin lymphoma patients, a reactive canine lymph node, and a normal non-reactive canine lymph node, were evaluated. All B-cell non-Hodgkin lymphomas (15) were found to express Pax5 protein. In addition, there was a strong correlation between Pax5 and CD79a expression. Three CD3 positive and five CD3 and CD79a positive lymphomas were immunophenotypically negative for anti-Pax5, indicating a T-cell lineage. In conclusion, anti-Pax5 antibody may offer an excellent B-cell marker in canine lymphomas.

Quantitative assessment of minimal residual disease (MRD) in canine lymphoma by using real-time polymerase chain reaction

Lymphoma is the most common hematopoietic malignancy in dogs. Although a large proportion of dogs with lymphoma can achieve clinical remission by initial chemotherapy, most dogs die as a consequence of tumor relapse. We established a quantitative detection system for minimal residual disease (MRD) in canine lymphoma by using real-time polymerase chain reaction (PCR). A canine T-cell lymphoma-derived cell line, namely, UL-1, was used to examine the specificity and sensitivity of the MRD detecting system. Allele-specific oligonucleotide primers and probes were designed based on the sequence of T-cell receptor γ chain (TCRγ) gene fragment of UL-1 cells in conjunction with its downstream sequence, which were obtained from the dog genome database. The real-time PCR system for plasmid DNA containing the TCRγ gene derived from UL-1 cells and the genomic DNA of UL-1 cells revealed that the system was accurate for 10–100,000 copies per reaction and its sensitivity was 1 cell per 10,000 cells. In order to monitor the kinetics of tumor cell number in canine lymphoma, we quantified the level of MRD in the peripheral blood of 7 dogs with lymphoma under chemotherapy. Since the lymphoma cells from the 7 patients were shown to be B-cell origin from the finding of clonal rearrangement of immunoglobulin heavy chain (IgH) gene, allele-specific oligonucleotide primers and probes were prepared based on the sequence of rearranged IgH gene in each case. The number of peripheral blood tumor cells measured by the real-time PCR was comparable to that estimated by conventional hematological examination in 2 cases of stage V lymphoma. MRD in the peripheral blood was detectable in all 7 cases, even in the complete remission (CR) phase. In the 7 lymphoma dogs, changes in the MRD levels of peripheral blood generally paralleled with the changes in the volumes of lymph nodes. Molecular CR, in which the MRD level was below the detection limit, was not observed in any of these 7 patients under chemotherapy. The MRD level detected by the real-time PCR method described here would be useful for investigating the kinetics of tumor cell growth and its regression in canine lymphoma patients.

Impact of Chemotherapeutic Dose Intensity and Hematologic Toxicity on First Remission Duration in Dogs with Lymphoma Treated with a Chemoradiotherapy Protocol

Background: Dose intensity has proven to be critical in maximizing chemotherapeutic efficacy for numerous human cancers. To date, the impact of dose intensity and toxicity on first remission duration has not been thoroughly assessed in dogs with lymphoma. Hypothesis: Dogs that receive maximal dose intensity will have prolonged first remission duration. Animals: Sixty‐two dogs with lymphoma that were treated according to a standardized Chemoradiotherapy regimen and achieved durable complete remissions were identified from the medical records database of North Carolina State University. Methods: Dosage reductions and treatment delays resulting from chemotherapy‐related neutropenia were evaluated retrospectively, and each patient's actual summation dose intensity and frequency of myelotoxicity were calculated. Impact of dose intensity and frequency of neutropenia on first remission duration were evaluated by Cox proportional hazards regression. Results: Development of grade III or IV neutropenia during chemotherapy was found to be associated with prolonged first remission duration (P &lt; .01). Dose intensity did not have a significant impact on remission duration (P= .07). Conclusions and Clinical Importance: Results of this study suggest that dosage reductions and treatment delays instituted to avoid repeated neutropenic episodes do not reduce first remission duration. Prolonged remission duration in patients that developed grade III or IV neutropenic episodes indicates the need for further optimization of dosing strategies for canine lymphoma patients undergoing chemotherapy.

Impact of Chemotherapeutic Dose Intensity and Hematologic Toxicity on First Remission Duration in Dogs with Lymphoma Treated with a Chemoradiotherapy Protocol

Dose intensity has proven to be critical in maximizing chemotherapeutic efficacy for numerous human cancers. To date, the impact of dose intensity and toxicity on first remission duration has not been thoroughly assessed in dogs with lymphoma. Dogs that receive maximal dose intensity will have prolonged first remission duration. Sixty-two dogs with lymphoma that were treated according to a standardized chemoradiotherapy regimen and achieved durable complete remissions were identified from the medical records database of North Carolina State University. Dosage reductions and treatment delays resulting from chemotherapy-related neutropenia were evaluated retrospectively, and each patient's actual summation dose intensity and frequency of myelotoxicity were calculated. Impact of dose intensity and frequency of neutropenia on first remission duration were evaluated by Cox proportional hazards regression. Development of grade III or IV neutropenia during chemotherapy was found to be associated with prolonged first remission duration (P < .01). Dose intensity did not have a significant impact on remission duration (P = .07). Results of this study suggest that dosage reductions and treatment delays instituted to avoid repeated neutropenic episodes do not reduce first remission duration. Prolonged remission duration in patients that developed grade III or IV neutropenic episodes indicates the need for further optimization of dosing strategies for canine lymphoma patients undergoing chemotherapy.