Electrochemotherapy in treatment of canine oral non‐tonsillar squamous cell carcinoma. A case series report

Non‐tonsillar squamous cell carcinoma (ntSCC) is a common and locally aggressive oral tumour in dogs. The treatments of choice are currently surgery and radiotherapy. Electrochemotherapy (ECT) is a local ablative anti‐tumour technique using electric pulses to enhance the intracellular diffusion of cytotoxic drugs. The aim was to retrospectively evaluate the outcome of patients with oral ntSCC treated with ECT. Twelve dogs with ntSCC were retrospectively enrolled. ECT was combined with IV bleomycin (15 000 UI/m²) alone in 11 cases and post‐surgery in 1. Parameters considered were: tumour site and size, electroporation parameters, response rate (complete remission [CR], partial remission [PR]), median survival time (MST), recurrence rate (RR), median disease‐free interval (DFI) and treatment toxicity (6‐point scale). Median tumour size was 1.65 cm (range 0.3‐8.0 cm) and the response rate was 90.9% (10/11; 8 CR and 2 PR). Two dogs underwent a second ECT. MST for dogs dead with tumour (n = 2) was 110 days and for dogs dead without tumour (n = 3) was 831 days. Among five surviving dogs, one experienced tumour recurrence and four were in CR. Results from two dogs were analysed separately. Overall RR was 27.3%. DFI and MST for dogs with recurrence were 50 and 115 days, respectively. Treatment toxicity was very low. We noticed that all dogs with tumours smaller than 1‐2 cm achieved CR without recurrence suggesting a favourable prognosis when using ECT. ECT for canine ntSCC could be considered a valid treatment option especially for smaller tumours, but a larger caseload would be needed to confirm this statement.     

Owner assessment of therapeutic interventions for canine atopic dermatitis: a long-term retrospective analysis

Background – Canine atopic dermatitis is a frequent diagnosis in veterinary medicine; however, the long‐term prognosis for canine atopic dermatitis has not been evaluated in a systematic fashion. Hypothesis/Objectives – To compare the relative efficacy of commonly used therapies for canine atopic dermatitis in two groups of dogs over 5 and 10 year time periods. Animals – Dogs were identified from the medical record database of a privately owned veterinary dermatology practice in the USA. Methods – Clients completed a four‐part, 28‐question, Internet‐based survey. Surveys were included in the analysis if one entire section was completed. Each question was completed independently of the answers to other questions. Results – Several respondents failed to complete all questions. Some respondents answered similar questions with contradictory answers. Each question was analysed individually. A total of 136 owner surveys were completed, 39 from the 10 year and 97 from the 5 year study dogs. Eighty‐five of 135 respondents indicated that their pet was receiving some form of medical therapy for atopic dermatitis at the time of the survey. Thirty of 90 respondents (33.3%) indicated that their dog improved during a dietary trial. Five dogs met the study’s definition for clinical cure. All five of these dogs had been treated with allergen‐specific immunotherapy. Conclusions and clinical importance – This study revealed that clients believe antihistamines can be a useful part of multimodal therapy for canine atopic dermatitis. The results also demonstrated that a significant number of canines benefited from dietary modification. In addition, allergen‐specific immunotherapy was the only treatment to induce true clinical remission of atopic dermatitis.     

A feasibility study of low-dose total body irradiation for relapsed canine lymphoma

Seven client owned dogs with confirmed relapsed lymphoma were enrolled in a prospective feasibility study investigating the effects of low‐dose total body irradiation (LDTBI) delivered in a single 1 Gy fraction. LDTBI for relapsed lymphoma was safe and well tolerated. The only major side‐effect of LDTBI was asymptomatic thrombocytopenia in all dogs. The median platelet nadir was 17 000/μL (range 4000–89 000), which occurred a median of 10 days (range 8–30) post irradiation. Three dogs had short‐term partial responses, two stable disease and two progressive disease (PD). Six dogs were euthanatized for PD, and one dog died while in partial remission. No dogs had clinical complications. Survival analysis was not performed, because the study design did not allow for evaluation of survival time. Larger studies incorporating LDTBI in the induction/consolidation phase of treatment need to be performed to determine the therapeutic efficacy of LDTBI.     

Evaluation of a commercial staphylococcal bacterin for management of idiopathic recurrent superficial pyoderma in dogs

Twenty-one dogs with idiopathic superficial recurrent pyoderma were entered into a double-blind, placebo-controlled study to evaluate the efficacy of a commercial staphylococcal bacterin. The study spanned an 18-week period. All dogs were administered sodium oxacillin orally for the initial 6 weeks of the study. Dogs were given the bacterin or placebo SC, twice weekly at 3- or 4-day intervals, beginning at week 0 and continuing for 18 weeks. Dogs given antibiotics plus the bacterin (n = 13) had a significantly (P less than 0.05) better treatment response than those given antibiotic plus placebo.     

A survey of the diagnosis and treatment of canine exocrine pancreatic insufficiency

A questionnaire was sent to veterinary surgeons who had diagnosed exocrine pancreatic insufficiency (EPI) by assay of low serum concentration of trypsin-like immunoreactivity in 302 dogs. Two-thirds of cases were German shepherd dogs, in which EPI was found equally in males and females. The disease was also diagnosed in 33 other breeds, most commonly in crossbreeds, spaniels, small terriers and collies, and was more common in females. Detailed replies on 160 cases were returned; 79 dogs were alive and 41 dead, with the remainder lost to long term follow-up. The major reasons for death were euthanasia because of the cost, the prognosis, and failure to respond to treatment. An adequate response to treatment was obtained in 92 per cent of dogs. Uncoated preparations of pancreatic enzyme replacement were found to be more successful, and the use of dietary manipulation and antibiotics were frequently reported to be useful adjunctive therapies.     

Assessment of tumor enhancement by contrast‐enhanced CT in solid tumor‐bearing dogs treated with toceranib phosphate

In humans, contrast‐enhanced CT (CECT) has been used to indirectly assess the antiangiogenic effects demonstrated by a number of tyrosine kinase inhibitors. This retrospective, cross‐sectional study aimed to quantitatively evaluate changes in tumor contrast‐enhancement (CE) using CECT in solid tumor‐bearing dogs treated with toceranib phosphate (TOC). The changes in tumor size and CE were measured using the Hounsfield unit (HU) scale in CECT images before TOC treatment and between 30 and 90 days after initiating the treatment. Among the 36 dogs treated with TOC, eight (22.2%) showed a partial response, 22 (61.1%) showed stable disease, and six (16.7%) showed progressive disease. Thirty (83.3%) of 36 dogs showed a decrease in tumor CE (median: ?20%, range: ?1% to ?48%) after initiating the treatment. The results indicated that tumor CE and size changes were observed in tumor‐bearing dogs that were treated with TOC; however, tumor CE was not significantly correlated with tumor regression. We suggest that these results could serve as pilot data to evaluate the antiangiogenic effects associated with TOC.     

Response of plasma fatty acid profiles to changes in dietary n‐3 fatty acids and its correlation with erythrocyte fatty acid profiles in dogs

An elevated level of long‐chain n‐3 fatty acids (FA) in tissue membranes has a positive influence on the progression and treatment of many diseases. Therefore, dietary supplementation of n‐3 FA is recommended in some diseases. Even though n‐3 FA are absorbed readily from the diet, their incorporation into tissues may be compromised in diseased animals. In a clinical setting, it is desirable to monitor the success of dietary intervention. Plasma FA as well as erythrocyte membrane (EM) FA can be used to monitor dietary FA intake. This study compares FA from EM and plasma with regard to their reaction time and reliability for monitoring dietary changes of tissue FA profiles in dogs. Thirty dogs were divided into three groups and fed for 12 weeks. The control group (CONT) was fed a commercial standard diet low in n‐3 FA. One group received the standard diet and 85 mg/kg body weight of a docosahexaenoic acid (DHA) concentrate (ADD). The third group was fed a commercial dog food containing fish oil (FO), which is rich in eicosapentaenoic acid (EPA). EM and plasma FA profiles were analysed by GC separately. Data on EM FA were published recently. n‐3 FA in plasma reached the new level after 2 weeks (8 weeks in EM). Dietary differences between DHA and EPA are obvious after 1 week already. The concomitant decrease in plasma n‐6 FA differed between ADD and FO. In general, the correlation of n‐6 FA between plasma and EM was low. We therefore conclude that analysis of plasma FA is sufficient for monitoring a diet‐induced increase in tissue n‐3 FA in dogs. However, EM FA should be analysed if the effect of dietary intervention on tissue n‐6 FA is important.     

Frequency of urinary tract infection in dogs with inflammatory skin disorders treated with ciclosporin alone or in combination with glucocorticoid therapy: a retrospective study

Background – Few studies have investigated the frequency of urinary tract infection (UTI) in dogs receiving long‐term ciclosporin therapy. Hypothesis/Objectives – The goal of the study was to investigate the frequency of UTI in dogs receiving ciclosporin with or without glucocorticoids. A secondary goal was to determine whether bacteriuria, pyuria and urine specific gravity were good predictors of UTI, and if ciclosporin dose, concurrent ketoconazole therapy, sex or duration of therapy affected the frequency of UTI. Animals – Eighty‐seven dogs with various inflammatory skin disorders and 59 control dogs with inflammatory skin conditions that had not received glucocorticoids or ciclosporin for 6 months were enrolled. Methods – This study was retrospective. The first urine culture from dogs receiving ciclosporin was compared with control dogs using Fisher’s exact test. A logistic mixed model was used to test for association between a positive bacterial culture and duration of treatment, dose of ciclosporin, concurrent ketoconazole therapy and sex. The sensitivities and specificities for bacteriuria, pyuria and urine specific gravity were determined. Results – Twenty‐six of 87 (30%) ciclosporin‐treated dogs had at least one positive culture. Compared with 3% positive control samples, 15% were positive in treated dogs (P = 0.027). The sensitivity and specificity were, respectively, 64.1 and 98.1% for bacteriuria, 74.4 and 70.9% for pyuria, and 56.4 and 65.3% for urine specific gravity. All other analysed parameters were not significantly different. Conclusions and clinical importance – The results suggest that routine urine cultures and assessment of bacteriuria by cystocentesis should be part of the monitoring for dogs on long‐term ciclosporin with and without glucocorticoids.     

Treatment of canine mast cell tumours with prednisolone and radiotherapy

This retrospective study describes 35 dogs with non‐resectable, grade I–III mast cell tumours on the head or limb treated with prednisolone (40 mg m^?2 daily) for 10–14 days prior to radiotherapy (4 × 800 cGy fractions at 7‐day intervals) from a 4 MV linear accelerator. Prednisolone was continued at a reduced dose rate (20 mg m^?2) during radiotherapy and for 2 months or longer afterwards. Eighteen of 24 tumours (75%) decreased in size in response to prednisolone treatment. By 6–8 weeks following radiotherapy, 12 dogs had achieved a complete remission and 19 a partial response. Two tumours remained static and two progressed during the course of treatment. The overall response rate was 88.5%. With long‐term follow‐up, 11 dogs experienced local recurrence (n = 4), metastasis (n = 5) or both (n = 2). The median progression‐free interval was 1031 days (95% CI 277.44–1784.56, Kaplan–Meier), with 1‐ and 2‐year progression‐free rates of 60 and 52%, respectively. Tumour grade did not predict the prognosis for this group of dogs, but tumour location did affect the outcome. Dogs with tumours located on the limb survived longer than those with tumours on the head. The combination of prednisolone with radiotherapy appears to have a useful role in the management of measurable mast cell tumours sited on the head and distal extremities.     

Pharmacokinetics of intravenous and subcutaneous cefovecin in alpacas

The purpose of this study was to determine the pharmacokinetics of cefovecin after intravenous and subcutaneous dose of 8 mg/kg to alpacas. Bacterial infections requiring long‐term antibiotic therapy such as neonatal bacteremia, pneumonia, peritonitis, dental, and uterine infections are a significant cause of morbidity and mortality in this species. However, few antimicrobials have been evaluated and proven to have favorable pharmacokinetics for therapeutic use. Most antimicrobials that are currently used require daily injections for many days. Cefovecin is a long‐acting cephalosporin that is formulated for subcutaneous administration, and its long‐elimination half‐life allows for 14‐day dosing intervals in dogs and cats. The properties of cefovecin may be advantageous for medical treatment of camelids due to its broad spectrum, route of administration, and long duration of activity. Pharmacokinetic evaluation of antimicrobial drugs in camelids is essential for the proper treatment and prevention of bacterial disease, and to minimize development of antibiotic resistant bacterial strains due to inadequate antibiotic concentrations. Cefovecin mean half‐life, volume of distribution at steady‐state, and clearance after intravenous administration were 10.3 h, 86 mL/kg, and 7.07 mL·h/kg. The bioavailability was 143%, while half‐life, C_max, and T_max were 16.9 h, 108 μg/mL, and 2.8 h following subcutaneous administration. In the absence of additional microbial susceptibility data for alpaca pathogens, the current cefovecin dosage regimen prescribed for dogs (8 mg/kg SC every 14 days) may need to be optimized for the treatment of infections in this species.     

Equine paranasal sinus disease: a long-term study of 200 cases (1997-2009): treatments and long-term results of treatments

Reasons for performing study: There is limited objective information available on the treatment and the long‐term response to treatment of the different types of equine sinus disease. Objectives: To document the treatments and long‐term response to these treatments in 200 cases of equine sinus disease (1997–2009). Methods: The treatments of horses affected with subacute primary sinusitis (n = 52); chronic primary sinusitis (n = 37); dental sinusitis (n = 40); sinus cyst (n = 26); traumatic (n = 13); dental‐related oromaxillary fistula (n = 8); sinus neoplasia (n = 10); mycotic sinus disease (n = 7); and intrasinus progressive ethmoid haematoma (n = 7) and the long‐term response to these treatments were retrospectively reviewed. Results: Treatments evolved throughout the study and latterly were as conservative as possible, including sinoscopic lavage and standing sinusotomy, with a maxillary sinusotomy approach preferred for the mainly mature horses treated in this study. Removal of intrasinus inspissated pus, including transendoscopically (by sinusotomy and via existing sinonasal fistulae), was the main treatment for chronic primary sinusitis and sinonasal fistulation was seldom performed latterly. Attempted oral extraction of infected cheek teeth, even if unsuccessful, facilitated subsequent dental repulsion, resulting in few post operative problems. Sinus cyst removal carried an excellent prognosis. Except for cases of sinus neoplasia (only 22% cured), an excellent long‐term response to treatment (91% fully cured, 7% partially cured) was obtained for all other types of sinus disease following a median of one treatment. Conclusions: More conservative treatments, including removal of intrasinus inspissated pus by sinoscopy, pre‐existing sinonasal fistula or sinusotomy, are effective for chronic primary sinus disease. Standing sinusotomy, mainly using a small maxillary site, was suitable for most cases of sinus disease in mature horses.     

Treatment of intrahepatic congenital portosystemic shunts in dogs: a systematic review

The aim of this study was to establish the evidence base for the treatment of intrahepatic congenital portosystemic shunts in dogs through a systematic review of the pertinent literature. Studies were filtered for evidence to answer the question “Which of the treatment options for intrahepatic CPSS in dogs offers the best short‐ and long‐term outcome?” Studies were assigned a level of evidence based on a system published by the Oxford Centre for Evidence‐Based Medicine. Thirty‐two studies were included in the review. Twenty‐six provided level 4 evidence and six provided level 5 evidence. There were no level 1, 2 or 3 studies. One study compared surgical treatment with medical management and one study compared suture ligation with ameroid constrictor placement. The remaining studies were case series describing the outcome for one treatment method alone. Methods and timings of assessments of short‐ and long‐term outcomes were highly varied, making direct comparisons challenging. The evidence regarding the treatment of intrahepatic congenital portosystemic shunts in dogs is weak, with only two studies directly comparing treatments. There is a lack of evidence regarding short‐ and long‐term outcomes on which to base clinical decisions.     

Evaluation of the oral antimitotic agent (ABT-751) in dogs with lymphoma

Background

ABT‐751 is a novel orally available antimitotic agent that targets microtubule polymerization. This mechanism may suggest potential activity in canine lymphoma.

Objective

Determine a maximum tolerated dose for ABT‐751, and assess long‐term tolerability and activity in canine lymphoma.

Animals

Thirty dogs with newly diagnosed (n = 19) or relapsed (n = 11) non‐Hodgkin's lymphoma.

Methods

Dogs (n = 11) were enrolled in a rapid dose escalation study to define the maximum tolerated dose. Upon definition of a maximally tolerated dose, a cohort expansion of 19 dogs allowed verification of long‐term tolerability and assessment of activity. Study endpoints in the cohort expansion included chronic tolerability, response rate, response duration, and time to progression. Additional endpoints included serum pharmacokinetics, lymph node drug concentrations, and changes in circulating endothelial cells.

Results

The maximum tolerated dose of ABT‐751 was 350 mg/m² PO q24h. Dose‐limiting toxicities included vomiting and diarrhea, which resolved with a schedule adjustment to 350 mg/m² PO q48h. ABT‐751 was consistently detected in lymphoma tissue samples from dogs treated at or above the maximum tolerated dose. In the cohort expansion, objective responses were seen in 3/15 (20%) dogs with a response duration ranging from 21 to 111 days. Decreases in circulating endothelial cells were seen in 10 dogs at day 7 (2 responding dogs and 8 nonresponding dogs).

Conclusion

ABT‐751 was well tolerated at 350   mg/m² PO q24h for 7 days and then q48h thereafter. Activity of ABT‐751 suggested a rationale for additional studies of ABT‐751 as part of a combination chemotherapy protocol for lymphoma or other canine cancers.     

Treatment of extrahepatic congenital portosystemic shunts in dogs – what is the evidence base?

A variety of surgical treatments and medical therapies are recommended for dogs with extrahepatic congenital portosystemic shunts (CPSS). The objective of this review was to assess the evidence base for the management of extrahepatic CPSS in dogs. An online bibliographic search was performed in November 2010 to identify articles relating to the question “Which of the treatment options for extrahepatic CPSS in dogs offers the best short‐ and long‐term outcomes?” Articles were assigned a level of evidence based on a modified grading system. Thirty‐eight articles were included in the review. Thirty‐six articles were classified as grade 4 and two as grade 5. The timings and methods of assessment of short‐ and long‐term outcomes varied widely between studies. One prospective study (grade 4a) showed that surgically treated dogs survived significantly longer than medically treated dogs. Four retrospective studies (grade 4b) compared the outcome of two surgical techniques but there were no statistically significant differences between treatment groups in terms of complications or outcome. The review found that the evidence base for the treatment of extrahepatic CPSS is weak. There is a lack of evidence of short‐ and long‐term outcomes to recommend one treatment over another.     

Antibiotic-responsive histiocytic ulcerative colitis in 9 dogs

Canine histiocytic ulcerative colitis (HUC) is characterized by colonic inflammation with predominantly periodic acid-Schiff (PAS)-positive macrophages. The inflammation results in colonic thickening, ulcerations, and distortion of normal glandular architecture. Resultant clinical signs consist of chronic large bowel diarrhea, tenesmus, and marked weight loss, and the disease frequently results in euthanasia. Conventional therapy consists of some combination of prednisone, azathioprine, sulfasalazine, and metronidazole. Nine dogs (8 Boxers and 1 English Bulldog) with histologic confirmation of HUC were treated with antibiotic therapy (either with enrofloxacin alone or in combination with metronidazole and amoxicillin). Clinical signs, physical examination findings, laboratory abnormalities, and the histologic severity of the disease were evaluated. Four of the 9 dogs had been treated previously with conventional therapy and had failed to respond favorably; then, these dogs were placed on antibiotic therapy (enrofloxacin, n = 1; enrofloxacin, metronidazole, and amoxicillin, n = 3) and had resolution of clinical signs within 3-12 days. Five dogs were treated solely with antibiotic therapy (enrofloxacin, n = 1; enrofloxacin and metronidazole, n = 1; enrofloxacin, metronidazole, and amoxicillin, n = 3), and clinical signs resolved in 2-7 days. Repeated biopsy specimens were obtained from 5 dogs after treatment, and all showed marked histologic improvement. The increase in body weight after treatment was statistically significant (P = .01). Three dogs currently are not on any treatment and have had resolution of clinical signs for up to 14 months. These observations suggest that an infectious agent responsive to antibiotics plays an integral role in the clinical manifestation of canine HUC, and they support the use of antibiotics in its treatment.     

FC‐21 Efficacy of topical tacrolimus ointment for treatment of plantar fistulae in German shepherd dogs

The objective of this open pilot study was to evaluate the efficacy of topical tacrolimus ointment for treatment of plantar fistulae in German shepherd dogs. Seven dogs (four males, three females) were included. All subjects had a 6‐month to 2‐year history of plantar fistulae involving the plantar aspect of two to four metatarsi/metacarpi. No other skin lesions were present and the dogs appeared otherwise healthy. Before treatment with tacrolimus, all dogs received antibiotics for 4–8 weeks. Hair was clipped to visualise the lesions. The presence of erythematous papules, oedema and fistulae was recorded for each foot. All dogs served as their own controls. Dogs with four legs involved had one front and one hind leg treated. Dogs with two to three feet affected had only one foot treated. Tacrolimus 0.1% ointment (Protopic^®) was applied twice daily onto the site of lesions. Partial improvement of treated lesions was seen in all cases within 3 weeks. After 6 weeks, treated lesions were in complete remission in four dogs, while the other three subjects had palpable but invisible lesions. Signs had not improved on the untreated legs. Follow‐up varied between 4 months and 2 years. Lesion remission persisted in six dogs with the intermittent application of tacrolimus. Adverse effects of treatment were not seen. In conclusion, the application of topical tacrolimus seems to provide a safe and effective treatment option for plantar fistulae in German shepherd dogs. Funding: Self‐funded.     

Endotoxemia and Tumor Necrosis Factor Activity in Dogs With Naturally Occurring Parvoviral Enteritis

A prospective, nonrandomized study was performed to evaluate the role of endotoxin and tumor necrosis factor (TNF) in dogs with parvoviral enteritis. Seventeen dogs with naturally occurring parvoviral enteritis were enrolled in the study. Plasma samples were obtained for quantification of endotoxin and TNF on presentation and at 3 and 6 hours after therapy with either fluids prior to antibiotics, or fluids concurrently with antibiotics. All dogs received standard supportive therapy. Fourteen of 17 dogs had endotoxin in their plasma during the study period; 7 of 17 dogs had measurable TNF. No endotoxin or TNF was detectable in plasma from normal puppies. An increase in TNF activity was pre dictive of mortality ( P = .041). There was a trend for increasing endotoxin activity to predict mortality ( P = .0769). Animals that received antibiotics with fluids were significantly older than those that received fluids prior to antibiotics, and there was a trend for animals that received antibiotics with fluids to have a decrease in endotoxin activity after treatment ( P = .054). Endotoxin and activation of the cytokine cascade are integral to the pathophysiology of parvoviral enteritis. Measures to limit endotoxemia and the systemic inflammatory response may improve survival.     

Long-term results of subtotal colectomy for acquired hypertrophic megacolon in eight dogs

Objectives : To evaluate the long‐term results of subtotal colectomy for acquired hypertrophic megacolon in the dog. Methods : Eight dogs with acquired hypertrophic megacolon underwent subtotal colectomy with preservation of the ileocolic junction. Long‐term follow‐up was obtained by clinical records and telephone interviews with the owners. Results : Eight large‐breed dogs (age range: 6 to 12 years; mean age: 10·75 years) were enrolled. The use of bone meal, low levels of exercise, chronic constipation with dyschesia and tenesmus refractory to medical management were factors predisposing dogs to acquired hypertrophic megacolon. The diagnosis was confirmed in all animals by abdominal palpation, plain radiography and postoperative histopathological findings. There were no intraoperative complications. One dog died as a result of septic peritonitis. The clinical conditions (that is, resolution of obstipation and stool consistency) of the remaining seven dogs were improved at discharge; all animals returned to normal defecation in five to 10 weeks (mean: 7·3 weeks) and were alive 11 to 48 months (mean: 40·5 months) after surgery. Clinical Significance : Predominantly bony diet and/or low levels of physical activity may predispose dogs to acquired hypertrophic megacolon. Our results emphasise the long‐term effectiveness of subtotal colectomy with preservation of the ileocolic junction in this condition.     

Minimal residual disease in lymph nodes after achievement of complete remission predicts time to relapse in dogs with large B‐cell lymphoma

Most dogs with large B‐cell lymphoma (LBCL) that undergo chemotherapy and achieve clinical complete remission (CR) eventually relapse. However, time to relapse (TTR) is unpredictable. The aims of this prospective study were to assess the influence of post‐chemotherapy lymph node (LN) infiltration by large CD21+ cells using flow cytometry (FC) on TTR, and to establish a cut‐off value of prognostic significance. Dogs with newly‐diagnosed, completely staged LBCL in CR after treatment were enrolled. Minimal residual disease (MRD) analysis by FC was performed on LN aspirates. TTR was calculated between MRD and relapse. Thirty‐one dogs were enrolled: 4% had stage V disease, and diffuse large B‐cell lymphoma was the most common histotype (74%). Based on LN infiltration at MRD evaluation, three groups were created: (a) acellular samples, (b) ≤0.5% infiltration and (c) >0.5% infiltration. Overall median TTR was 154 days (range, 31‐1974): 22 (71%) dogs relapsed during the study period, whereas 9 (29%) dogs did not. The difference among the three groups was significant (P = 0.042 log‐rank test): median TTR was not reached for dogs with LN infiltration ≤0.5% (range, 195‐429 days), 164 days (range 63‐1974) for dogs with acellular LN samples, and 118 days (range, 31‐232) for dogs with LN infiltration >0.5%. These results demonstrate that MRD assessment by FC on LN aspirates in dogs with LBCL in clinical CR predicts TTR. LN infiltration by >0.5% large CD21+ cells after treatment is an unfavourable prognostic factor.     

Dexamethasone, melphalan, actinomycin D, cytosine arabinoside (DMAC) protocol for dogs with relapsed lymphoma

BACKGROUND: In general, treatment of relapsed lymphoma is associated with a lower probability of response and shorter duration of remission. The purpose of this study was to evaluate the efficacy of the combination chemotherapy protocol DMAC (dexamethasone, melphalan, actinomycin D, and cytosine arabinoside) for reinduction of remission in dogs with relapsed lymphoma. HYPOTHESIS: That DMAC would be an effective reinduction protocol for dogs with relapsed lymphoma. ANIMALS: Fifty-four dogs. RESULTS: Seventy-two percent of the dogs achieved remission (44% complete remission [CR] and 28% partial remission [PR]), 11% had stable disease (SD), and 17% had progressive disease (PD). The median remission duration was 61 days (range, 2-467+ days). The median remission durations for dogs with CR, PR, and SD were 112, 44, and 27 days, respectively. Factors that affected the response rate were previous treatment with doxorubicin and an inability to achieve remission with the previous protocol. Thrombocytopenia occurred in 56% of the dogs (grade 1 in 3 dogs, grade 2 in 6 dogs, grade 3 in 7 dogs, and grade 4 in 7 dogs) and neutropenia in 17% of the dogs (grade 2 in 1 dog, grade 3 in 2 dogs, and grade 4 in 4 dogs). Gastrointestinal toxicosis occurred in 22% of the dogs (grades 1 in 5 dogs, grade 2 in 3 dogs, and grade 3 in 1 dog). CONCLUSIONS AND CLINICAL IMPORTANCE: The DMAC protocol is an effective rescue protocol for dogs with relapsed multicentric lymphoma. Although thrombocytopenia is a common manifestation of toxicity, in general, the protocol is well tolerated.