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.     

Treating the locoregional lymph nodes with radiation and/or surgery significantly improves outcome in dogs with high‐grade mast cell tumours

High‐grade canine mast cell tumours (HG‐MCT) have a high rate of locoregional relapse. In this study, dogs with HG‐MCT treated with radiation therapy (RT) were retrospectively evaluated to determine the benefit associated with treating the locoregional lymph nodes (LNs). Forty‐two dogs were included. Variables assessed for association with overall survival (OS) and progression‐free survival (PFS) included WHO stage, tumour location and size, LN irradiation (prophylactic, therapeutic or none), LN treatment (yes or no), LN status at RT (metastatic or nonmetastatic) and RT intent (definitive vs palliative). Lower‐stage disease at irradiation was significantly associated with prolonged median PFS (425 vs 125 days for stage 0 vs 1‐4), and OS (615 vs 314 days for stage 0 vs 1‐4). Having any LN treatment and definitive RT were both significantly associated with prolonged OS. In order to evaluate the role of LN irradiation, dogs were divided into subgroups: (a) stage 0 at irradiation with no LN treatment (n = 14), (b) stage 0 at irradiation with prophylactic LN irradiation (n = 6), (c) stage 0 at irradiation but previously stage 2 (n = 5) and (d) stage >0 at irradiation (n = 17). Prophylactic LN irradiation significantly prolonged PFS (>2381 vs 197 days; group B vs A). Interestingly, dogs that were stage 2 and had LN treatment (C) had prolonged OS vs dogs with negative LNs and no LN treatment (A) (1908 vs 284 days; P = .012). This study confirms that prophylactic and therapeutic LN irradiation in dogs with HG‐MCT is beneficial and improves outcome.     

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.     

Evaluation of an actinomycin-D-containing combination chemotherapy protocol with extended maintenance therapy for canine lymphoma

In this retrospective study, a 6-drug (prednisone, L-asparaginase, vincristine, cyclophosphamide, doxorubicin, and actinomycin-D) chemotherapy protocol with extended maintenance for the treatment of lymphoma was evaluated for efficacy and toxicity in 39 dogs. The complete remission rate was 97%, with a median progression-free survival (PFS) of 331 d. The median overall survival (OS) was 461 d. Of the variables evaluated for prognostic significance, only immunophenotype and sex were found to be prognostic. Dogs with T-cell lymphoma had shorter PFS and OS than dogs with B-cell lymphoma. Castrated male dogs had a shorter PFS and OS than spayed female dogs. Although the majority of dogs experienced one or more episodes of chemotherapy associated toxicity, the majority of these episodes were mild and self-limiting. The results of this study warrant further investigation into the value of extended maintenance therapy and inclusion of actinomycin-D in combination chemotherapy protocols for canine lymphoma.     

Prognostic significance of hypermethylation of death‐associated protein kinase (DAPK) gene CpG island in dogs with high‐grade B‐cell lymphoma

Death‐associated protein kinase (DAPK) is a serine/threonine kinase and a tumour suppressor gene. Diffuse large B‐cell lymphomas with inactivated DAPK through hypermethylation of a CpG island is known to result in a biologically aggressive phenotype in humans. This retrospective study was carried out to analyse the prognostic significance of DAPK CpG island hypermethylation in canine lymphoma. We hypothesized that DAPK CpG island hypermethylation can be a negative prognostic indicator in dogs with nodal high‐grade B‐cell lymphoma. Forty‐seven dogs with high‐grade B‐cell lymphoma, according to the updated Kiel classification, were evaluated after being treated with a CHOP (vincristine, cyclophosphamide, doxorubicin and prednisolone)‐based chemotherapy protocol. The methylation status of the DAPK CpG island was examined by methylation‐specific PCR. Progression‐free survival (PFS) and overall survival (OS) were compared using the Kaplan‐Meier analysis and log‐rank test. The cox proportional hazard regression model was used to evaluate the effect of multiple variables. Hypermethylation of the DAPK CpG island was detected in 21 of the 47 dogs. The PFS and OS in dogs with the hypermethylation (median: 220 and 266 days, respectively) were significantly shorter than those of dogs without hypermethylation (median: 301 and 412 days, respectively) (PFS, P = .036; OS, P = .007). In the multivariate analysis, hypermethylation of the DAPK CpG island remained an independent prognostic factor in predicting shortened PFS (P = .047) and OS (P = .021) as well as clinical substage b. Overall, hypermethylation of the DAPK CpG island was a negative prognostic factor in canine high‐grade B‐cell lymphoma.     

Doxorubicin chemotherapy for presumptive cardiac hemangiosarcoma in dogs†

Sixty‐four dogs were treated with single‐agent doxorubicin (DOX) for presumptive cardiac hemangiosarcoma (cHSA). The objective response rate (CR + PR) was 41%, and the biologic response rate (CR + PR + SD), or clinical benefit, was 68%. The median progression‐free survival (PFS) for treated dogs was 66 days. The median survival time (MST) for this group was 116 days and was significantly improved compared to a MST of 12 days for untreated control dogs (P = 0.0001). Biologic response was significantly associated with improved PFS (P < 0.0001) and OS (P < 0.0001). Univariate analysis identified larger tumour size as a variable negatively associated with PFS. The high rate of clinical benefit and improved MST suggest that DOX has activity in canine cHSA.     

Outcomes of dogs with grade 3 mast cell tumors: 43 cases (1997-2007)

This study reports the outcomes of dogs with grade 3 mast cell tumors (MCTs). Clinical and histopathological data were available for 43 dogs. Median progression-free survival (PFS) and overall survival (OS) were 133 and 257 days, respectively. Tumor size, lymph node (LN) status, and mitotic index (MI) significantly influenced PFS in univariate analysis. Tumor size and LN status remained significant in the multivariate analysis. Lymph node status, local tumor control, LN treatment, and MI significantly influenced OS in univariate analysis but only LN status remained significant in multivariate analysis. These results confirm that locoregional control improves outcomes in patients with grade 3 MCTs.     

Are B‐symptoms more reliable prognostic indicators than substage in canine nodal diffuse large B‐cell lymphoma

In humans B‐symptoms refer to systemic symptoms of lymphoma such as fever, weight loss, and night sweats and influence the prognosis of patients. In canine lymphoma, substage B is used to describe any clinical sign observed. Aim of the retrospective study was to compare the prognostic value of substage B with B‐symptoms to predict treatment response and survival in canine nodal diffuse large B‐cell lymphoma. Affected dogs treated with CHOP chemotherapy between 2008 and 2019 were included. B‐symptoms were defined by weight loss greater than 10% of normal weight, fever and the occurrence of unexplained resting tachypnoea substituted human night sweats. Substage B was defined as any symptoms but lymphadenopathy. Fifty‐five cases were included. B‐symptoms were present in 20/55 (36%) and substage B in 40/55 (74%) patients. No significant associations between B‐symptoms or substage B and weight, sex, breed, WHO stage and lymphoma grade were found. Treatment response was negatively associated with both substage B (P = .02) and B‐symptoms (P = .001). B‐symptoms significantly decreased progression free survival (PFS) (95 vs 330 days, P = .001) and lymphoma specific survival (LSS) (160 vs 462 days, P = .001). Data showed that B‐symptoms might be a more reliable prognostic indicator than substage B in canine nodal diffuse large B‐cell lymphoma. Prospective studies assessing B‐symptoms in a larger cohort of patients and in other common lymphoma types are warranted. The abstract was presented at the fourth meeting of the European Canine Lymphoma Network Group in Lugano, 22 June 2019 and published in the proceeding of the meeting on the page 26.     

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.     

Serum acute phase proteins as clinical phase indicators and outcome predictors in naturally occurring canine monocytic ehrlichiosis

Background: Canine monocytic ehrlichiosis (CME), caused by Ehrlichia canis, is an important tick‐borne disease of global importance. Currently, limited information is available on the diagnostic and prognostic value of acute phase proteins (APPs) in dogs naturally infected with E. canis. Hypothesis: APPs may be useful indicators of the clinical phase of CME and predictive of the clinical outcome (death or survival). Animals: Fifty‐six dogs naturally infected with E. canis and 7 clinically healthy control dogs. Methods: C‐reactive protein (CRP), serum amyloid A (SAA), haptoglobin (Hp), and albumin concentrations determined on admission were retrospectively compared among 27 dogs with nonmyelosuppressive CME, 29 dogs with myelosuppressive CME and 7 healthy dogs. Diagnosis of CME was based on clinical and clinicopathological findings, seropositivity to E. canis, polymerase chain reaction amplification of E. canis‐specific 16S rDNA, microscopic observation of Ehrlichia sp. morulae in blood monocytes or some combination of these. Results: Mean concentrations of CRP, SAA, and Hp were significantly higher in the myelosuppressed dogs compared with the other groups, but no significant differences were found in the concentration of albumin. Survival analysis of the affected animals indicated that APP concentrations were not associated with clinical outcome; the latter was strongly associated with pancytopenia (odds ratio for death 22.7) and neutropenia (odds ratio for death 7.7). Conclusions and Clinical Importance: CRP, SAA, and Hp serum concentrations on admission are useful indicators of the clinical phase of CME, but are not useful predictors of clinical outcome.     

Clinical presentation,treatment and outcome in 31 dogs with presumed primary colorectal lymphoma (2001–2013)

The objective of this multicentre retrospective study was to describe clinical presentation, treatment and outcome and to determine prognostic factors for dogs with presumed primary colorectal lymphoma (PCRL). A total of 31 dogs were included. The predominant features of PCRL were high grade (n = 18) and immunophenotype B (n = 24). Most dogs were substage b (n = 25) with higher prevalence of haematochezia (n = 20). One dog had surgery only. Thirty dogs received chemotherapy; amongst them 13 had surgery or radiotherapy. Progression free survival (PFS) was 1318 days and disease‐related median survival time (MST) was 1845 days. Fourteen dogs were alive at the end of the study with a median follow‐up time of 684 days (3–4678 days). Younger dogs had longer PFS (P = 0.031) and disease‐related MST (P = 0.01). Presence of haematochezia corresponded with longer PFS (P = 0.02). Addition of local treatment to chemotherapy did not significantly improve the outcome (P = 0.584). Canine PCRL has considerably longer PFS and MST than other forms of non‐Hodgkin's lymphoma.     

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

Dogs with multicentric T-cell lymphoma are commonly treated with CHOP chemotherapy protocols that include cyclophosphamide, doxorubicin, vincristine and prednisone. The purpose of this study was to evaluate the use of CHOP chemotherapy for dogs with multicentric T-cell lymphoma. Identification of prognostic factors in this specific subset of dogs was of secondary interest. Twenty-three out of 24 dogs responded to CHOP chemotherapy and these dogs remained on the protocol for a median of 146 days. No variable was associated with progression free survival (PFS) including stage, substage, hypercalcemia or radiographic evidence of a cranial mediastinal mass. The median overall survival time (OST) for all dogs was 235 days. Dogs that were thrombocytopenic at presentation experienced a significantly longer OST (323 versus 212 days, P=0.01).     

Epirubicin as part of a multi‐agent chemotherapy protocol for canine lymphoma

The aim of the study was to report the outcome of treatment of 97 dogs with lymphoma that received a multi‐agent chemotherapy protocol containing epirubicin as the primary anthracycline. Seventy‐five dogs received a 25‐week protocol with no maintenance phase whilst 22 dogs received a maintenance phase. Complete response rate was 96% and time to first relapse (TTR) and overall survival (OS) time for all dogs were 216 and 342 days, respectively. Dogs with T‐cell lymphoma and those classified as WHO substage b had significantly poorer OS times and TTR. The protocol was well tolerated with toxicity similar to doxorubicin‐containing protocols. Epirubicin as part of a multi‐agent protocol is safe and effective in the treatment of canine multicentric lymphoma. There is a high initial response rate and an overall median survival time that is similar to other published doxorubicin‐containing protocols.     

Assessment of biomarkers influencing treatment success on small intestinal lymphoma in dogs

This study aimed to determine a reliable therapeutic biomarker for localized small intestinal lymphoma (SIL) in dogs based on clinical and histopathological features. We retrospectively investigated 84 dogs with localized SIL, including 36 dogs receiving surgery and 48 dogs receiving chemotherapy. The dogs receiving surgery were divided into two subgroups: 18 dogs (group 1) with overall survival (OS) <120 days (median OS) and 18 dogs (group 2) with OS ≥120 days. Correspondingly, the dogs receiving chemotherapy were divided into 24 dogs (group 3) with OS <98 days (median OS) and 24 dogs (group 4) with OS ≥98 days. Clinical, haematological, histopathological and immunohistochemical analyses were comparatively evaluated among the four subgroups. There was no significant difference in OS between the surgery and chemotherapy groups. In dogs receiving surgery, the rate of Ki67‐positive cells was significantly increased in group 1 compared to group 2 and showed no significant difference between groups 3 and 4. In dogs receiving chemotherapy, the rate of O6‐methylguanine‐DNA methyltransferase (MGMT) was significantly higher in group 3 than in group 4 and showed no significant difference between groups 1 and 2. Additionally, our data showed that OS in dogs with higher Ki67 expression might be significantly increased by chemotherapy than by surgery, that of those with higher MGMT expression might be significantly increased by surgery than by chemotherapy, and Ki67 and MGMT were independent of each other. Indices of Ki67 and MGMT are suggested therapeutic biomarkers to determine the optimal first‐line treatment for localized SIL in dogs.     

Associations among albuminuria, C-reactive protein concentrations, survival predictor index scores, and survival in 78 critically ill dogs

Background: Microalbuminuria and C‐reactive protein (CRP) are predictors of morbidity and survival in critically ill human patients. Hypothesis/Objectives: To evaluate results of microalbuminuria assays (untimed single‐sample urine albumin concentration [U‐ALB] and the urine albumin : creatinine ratio [UACR]), serum CRP, and survival predictor index (SPI2) scores as predictors of survival in critically ill dogs. Animals: Seventy‐eight dogs admitted to intensive care units at University of Tennessee (UT) and Colorado State University (CSU). Methods: Prospective observational study. Critically ill dogs were eligible for enrollment, unless euthanized because of financial constraints. Samples were collected within 3 hours of admission. Spearman's rank‐correlation coefficients were determined for U‐ALB, UACR, CRP, and SPI2. U‐ALB, UACR, CRP, and SPI2 were assessed for associations with 7‐ and 30‐day survival by Mann‐Whitney U‐tests and receiver operating characteristic (ROC) curves. P‐values < .0125 were considered significant. Results: UT (n = 49) and CSU (n = 29) patients did not differ significantly. Forty percent (31/78) of dogs died. SPI2 was inversely correlated with U‐ALB (r_s=?0.39, P < .001) and UACR (r_s=?0.41, P < .001). CRP was not correlated with SPI2 (P= .019), U‐ALB (P > .1), or UACR (P > .1). U‐ALB and UACR had very high correlation (r_s= 0.95, P < .001). SPI2, U‐ALB, and UACR differed significantly for survivors and nonsurvivors. SPI2, U‐ALB, and UACR had areas under the ROC curve (AUC) from 0.68 to 0.74 for survival prediction. Conclusions and Clinical Importance: Albuminuria and SPI2, but not CRP, are associated with survival in critically ill dogs. Suboptimal AUCs limit the value of microalbuminuria testing for clinical risk assessment. Additional studies are necessary to determine the usefulness of microalbuminuria testing in patient risk stratification for prospective research.     

Prognostic value of baseline absolute lymphocyte concentration and neutrophil/lymphocyte ratio in dogs with newly diagnosed multi‐centric lymphoma

Canine multi‐centric B‐cell lymphoma shares similarities with diffuse large B‐cell (Non‐Hodgkin's) lymphoma (NHL) in people. In people with NHL, lymphopenia at diagnosis and first relapse and neutrophil/lymphocyte ratio (N:L) > 3.5 are negative prognostic factors for survival. The objective of this study was to determine if lymphocyte concentration at diagnosis and first relapse and N:L were prognostic for survival in dogs with newly diagnosed multi‐centric lymphoma. Medical records of 77 dogs with multi‐centric lymphoma treated with a CHOP‐based chemotherapy protocol were retrospectively evaluated. Absolute lymphocyte concentration and N:L ratio at presentation of dogs pre‐treated with steroids was not significantly different from dogs who had not received steroids. On multivariate analysis, only immunophenotype remained significant for progression‐free survival (PFS), whereas no variables remained significant for ST. A prospective study of these haematologic variables is warranted to assess their true significance.     

Association between weight change during initial chemotherapy and clinical outcome in dogs with multicentric lymphoma

The majority of the known prognostic factors in dogs with lymphoma have been evaluated before treatment commences or at the time of diagnosis. Prognostic factors evaluated during the initial phase of treatment are less described but may provide important clinical information. In this retrospective study, 82 canine lymphoma patients were categorized according to the weight change between diagnosis and after 5 weeks of chemotherapy. Dogs that gained greater than 5% or lost greater than 5% of initial body weight were categorized as increased‐ or decreased‐weight groups, respectively. Those in which weight changed less than 5% were categorized as the maintained‐weight group. The median progression‐free survival (PFS) in the increased‐weight group, maintained‐weight group and decreased‐weight group was 226, 256 and 129 days, respectively. The decreased‐weight group had significantly shorter PFS than the increased and maintained groups (P = .023, P = .003, respectively). The median survival time (ST) in the increased‐weight group, maintained‐weight group and decreased‐weight group was 320, 339 and 222 days, respectively. There was no significant difference in ST among the three groups (P = .128). In Cox‐regression results, weight change group and initial body weight were significant risk factors associated to PFS (P = .007, P = .001, respectively) while only patient's initial body weight was a significant risk factor to ST (P = .013). In conclusion, evaluation of initial body weight and weight changes over time can provide valuable information regarding PFS and ST in dogs with multicentric lymphoma.     

Outcome and toxicity associated with a dose‐intensified,maintenance‐free CHOP‐based chemotherapy protocol in canine lymphoma: 130 cases

A dose‐intensified/dose‐dense chemotherapy protocol for canine lymphoma was designed and implemented at the Veterinary Hospital of the University of Pennsylvania. In this study, we describe the clinical characteristics, prognostic factors, efficacy and toxicity in 130 dogs treated with this protocol. The majority of the dogs had advanced stage disease (63.1% stage V) and sub‐stage b (58.5%). The median time to progression (TTP) and lymphoma‐specific survival were 219 and 323 days, respectively. These results are similar to previous less dose‐intense protocols. Sub‐stage was a significant negative prognostic factor for survival. The incidence of toxicity was high; 53.9 and 45% of the dogs needed dose reductions and treatment delays, respectively. Dogs that required dose reductions and treatment delays had significantly longer TTP and lymphoma‐specific survival times. These results suggest that dose density is important, but likely relative, and needs to be adjusted according to the individual patient's toxicity for optimal outcome.     

A comparison of 12‐ and 19‐week CHOP protocols using non‐randomized,contemporaneous controls

This study is a concurrent comparison of two versions of CHOP protocols, a 19‐week CHOP and a comparatively overall dose‐intense 12‐week CHOP. The 12‐week protocol was designed to be 58% more dose intense than the 19‐week protocol for both doxorubicin and cyclophosphamide; however, it was 21% less dose intense for vincristine (VCR). Forty‐seven dogs were included for evaluation, and the characteristics of each population were similar. For dogs receiving the 19‐week CHOP protocol, 89.5% experienced a complete response, with a median progression‐free survival (PFS) of 245 days and median overall survival (OS) of 347 days. For dogs receiving the 12‐week CHOP protocol, 89.3% experienced a complete response, with a median PFS of 141 days and median OS of 229 days. When evaluated by Log‐rank analysis, the difference of PFS (P = 0.047) and OS (P = 0.013) between the groups were statistically significant. In summary, these data suggest that despite overall increased dose‐intensity, dogs receiving treatment with a 12‐week CHOP protocol experience less durable remission than our standard 19‐week protocol in this population. Additional prospective investigation will be required to explore the implication that VCR dose intensity and/or shorter overall temporal drug exposure in this protocol may result in diminished efficacy.     

Prognostic significance of CD25 expression in dogs with a noninvasive diagnosis of B-cell lymphoma treated with CHOP chemotherapy

Prior studies have identified high CD25 expression in canine diffuse large B-cell lymphoma as a negative prognostic indicator. The objective of this retrospective study was to evaluate CD25 expression as a prognostic indicator in dogs with B-cell lymphoma (BCL) diagnosed with commonly used noninvasive diagnostics (cytology and flow cytometry [FC]) and treated with CHOP chemotherapy. Lymph node aspirates from 57 dogs with cytologic diagnosis of lymphoma composed of intermediate to large lymphocytes were analysed with FC. Percentage of neoplastic B-cells expressing CD25 and median fluorescence intensity (MFI) of CD25 were measured. Relationships of CD25 percent positivity and MFI to progression free survival (PFS) and survival time were evaluated. Median survival time (MST) of all dogs was 272 days (95% CI, 196–348 days) and median PFS was 196 days (95% CI, 172–220 days). Higher percentage of B-cells positive for CD25 was associated with decreased risk of death in multivariable analysis (p = .02). Dogs with higher CD25 positivity had longer MST and PFS than dogs with lower CD25 positivity (318 days versus 176 days and 212 days versus 148 days, respectively), but these differences were not significant. CD25 MFI was not significantly associated with outcome. Based on the results of this study, the association of CD25 expression and prognosis in dogs with BCL diagnosed using noninvasive methods should be interpreted with caution. Further evaluation, with studies that include histopathologic differentiation of lymphoma subtypes, is needed.