Vaginal swab cytology as a diagnostic tool for neoplasia of the lower urinary tract in 5 dogs.

Urothelial carcinoma (UC), or transitional cell carcinoma, is the most common canine urothelial malignancy in dogs. Females are predisposed and provide a challenge for diagnostic tumor sampling. The objectives of this study were to investigate the use and tolerability of vaginal swab cytology for UC diagnosis. Five dogs were identified with non-diagnostic urine sediment cytology and UC diagnosed on vaginal cytology with confirmation by another means. All patients tolerated the vaginal swab with minimal restraint. This study confirms the potential of vaginal swab cytology as a simple, inexpensive, and well-tolerated means for lower urinary tract UC diagnosis in female dogs. Key clinical message: Vaginal swab cytology is a non-invasive, low-cost method of obtaining a sample for cytological assessment for UC.

La cytologie vaginal par écouvillonnage comme outil de diagnostic de la néoplasie des voies urinaires inférieures chez cinq chiennes. Le carcinome urothélial (CU), ou carcinome à cellules transitionnelles, est la tumeur maligne urothéliale canine la plus courante. Les femelles sont prédisposées et constituent un défi pour l'échantillonnage diagnostique des tumeurs. Les objectifs de cette étude étaient d'étudier l'utilisation et la tolérabilité de la cytologie vaginale par écouvillonnage pour le diagnostic du CU. Cinq chiennes ont été identifiées avec une cytologie des sédiments urinaires non diagnostique et un CU diagnostiqué sur la cytologie vaginale avec confirmation par un autre moyen. Toutes les patientes ont toléré le prélèvement vaginal avec un minimum de contention. Cette étude confirme le potentiel de la cytologie vaginale par écouvillonnage en tant que moyen simple, peu coûteux et bien toléré pour le diagnostic du CU des voies urinaires inférieures chez les chiennes.Message clinique clé :La cytologie vaginale par écouvillonnage est une méthode non-invasive et peu coûteuse pour obtenir un échantillon pour évaluation cytologique du CU.(Traduit par les auteurs).

Maintenance therapy with toceranib following doxorubicin-based chemotherapy for canine splenic hemangiosarcoma.

BACKGROUND: Spenic hemangiosarcoma (HSA) in dogs treated with surgery alone is associated with short survival times, and the addition of doxorubicin (DOX) chemotherapy only modestly improves outcome. The purpose of this study was to evaluate the impact of toceranib administration on progression free survival in dogs with stage I or II HSA following splenectomy and single agent DOX chemotherapy. We hypothesized that dogs with splenic HSA treated with adjuvant DOX followed by toceranib would have prolonged disease-free interval (DFI) and overall survival time (OS) when compared to historical dogs treated with DOX-based chemotherapy alone. RESULTS: Dogs with stage I or II splenic HSA were administered 5 cycles of single-agent DOX every 2 weeks beginning within 14 days of splenectomy. Dogs were restaged 2 weeks after completing DOX, and those without evidence of metastatic disease began toceranib therapy at 3.25 mg/kg every other day. Forty-three dogs were enrolled in this clinical trial. Seven dogs had evidence of metastatic disease either before or at re-staging, and an additional 3 dogs were found to have metastatic disease within 1 week of toceranib administration. Therefore 31 dogs went on to receive toceranib following completion of doxorubicin treatment. Twenty-five dogs that received toceranib developed metastatic disease. The median disease free interval for all dogs enrolled in this study (n = 43) was 138 days, and the median disease free interval for those dogs that went on to receive toceranib (n = 31) was 161 days. The median survival time for all dogs enrolled in this study was 169 days, and the median survival time for those dogs that went on to receive toceranib was 172 days. CONCLUSIONS: The use of toceranib following DOX chemotherapy does not improve either disease free interval or overall survival in dogs with stage I or II HSA.

Pharmacokinetics and derivation of an anticancer dosing regimen for PAC-1, a preferential small molecule activator of procaspase-3, in healthy dogs.

PAC-1 is a preferential small molecule activator of procaspase-3 and has potential to become a novel and effective anticancer agent. The rational development of PAC-1 for translational oncologic applications would be advanced by coupling relevant in vitro cytotoxicity studies with pharmacokinetic investigations conducted in large mammalian models possessing similar metabolism and physiology as people. In the present study, we investigated whether concentrations and exposure durations of PAC-1 that induce cytotoxicity in lymphoma cell lines in vitro can be achievable in healthy dogs through a constant rate infusion (CRI) intravenous delivery strategy. Time- and dose-dependent procaspase-3 activation by PAC-1 with subsequent cytotoxicity was determined in a panel of B-cell lymphoma cells in vitro. The pharmacokinetics of PAC-1 administered orally or intravenously was studied in 6 healthy dogs using a crossover design. The feasibility of maintaining steady state plasma concentration of PAC-1 for 24 or 48 h that paralleled in vitro cytotoxic concentrations was investigated in 4 healthy dogs. In vitro, PAC-1 induced apoptosis in lymphoma cell lines in a time- and dose-dependent manner. The oral bioavailability of PAC-1 was relatively low and highly variable (17.8 ± 9.5%). The achievement and maintenance of predicted PAC-1 cytotoxic concentrations in normal dogs was safely attained via intravenous CRI lasting for 24 or 48 h in duration. Using the dog as a large mammalian model, PAC-1 can be safely administered as an intravenous CRI while achieving predicted in vitro cytotoxic concentrations.

Evaluation of factors associated with second remission in dogs with lymphoma undergoing retreatment with a cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy protocol: 95 cases (2000-2007).

OBJECTIVE: To evaluate factors associated with second remission in dogs with lymphoma retreated with a cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) protocol after relapse following initial treatment with a first-line 6-month CHOP protocol. DESIGN: Retrospective case series. ANIMALS: 95 dogs with lymphoma. PROCEDURES: Medical records were reviewed. Remission duration was estimated by use of the Kaplan-Meier method. Factors potentially associated with prognosis were examined. RESULTS: Median remission duration after the first-line CHOP protocol was 289 days (range, 150 to 1,457 days). Overall, 78% (95% confidence interval [CI], 69% to 86%) of dogs achieved a complete remission following retreatment, with a median second remission duration of 159 days (95% CI, 126 to 212 days). Duration of time off chemotherapy was associated with likelihood of response to retreatment; median time off chemotherapy was 140 days for dogs that achieved a complete remission after retreatment and 84 days for dogs that failed to respond to retreatment. Second remission duration was associated with remission duration after initial chemotherapy; median second remission duration for dogs with initial remission duration ≥ 289 days was 214 days (95% CI, 168 to 491 days), compared with 98 days (95% CI, 70 to 144 days) for dogs with initial remission duration < 289 days. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that retreatment with the CHOP protocol can be effective in dogs with lymphoma that successfully complete an initial 6-month CHOP protocol.

Biological behavior of oral and perioral mast cell tumors in dogs: 44 cases (1996-2006).

OBJECTIVE: To describe clinical outcome of dogs with mast cell tumors (MCTs) arising from the oral mucosa, oral mucocutaneous junction, or perioral region of the muzzle and evaluate the potential role of the chemokine receptor type 7 (CCR7) in the biological behavior of these tumors. DESIGN: Retrospective case series. ANIMALS: 44 dogs with MCTs of the oral mucosa (n=14), oral mucocutaneous junction (19), or perioral region of the muzzle (11). PROCEDURES: Medical records were reviewed for information on signalment, regional metastasis, treatments, cause of death, and survival time. Twenty of the 44 cases had stored histologic samples available for immunohistochemical staining for CCR7 RESULTS: For all dogs, median survival time was 52 months. Twenty-six (59%) dogs had regional lymph node metastasis on admission. Median survival time for dogs with lymph node metastasis was 14 months, whereas median survival time was not reached for dogs without lymph node metastasis. Intensity of staining for CCR7 was not significantly associated with the presence of regional lymph node metastasis or survival time. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that in dogs with MCTs arising from the oral mucosa, oral mucocutaneous junction, or perioral region of the muzzle, the presence of regional lymph node metastasis at the time of diagnosis was a negative prognostic factor. However, prolonged survival times could be achieved with treatment. In addition, CCR7 expression in the primary tumor was not significantly associated with the presence of regional lymph node metastasis or survival time.

Biological behaviour and ezrin expression in canine rhabdomyosarcomas: 25 cases (1990-2012).

There are few published reports of canine rhabdomyosarcomas. In human paediatrics, rhabdomyosarcomas account for 5%-10% of all tumours and >50% of soft tissue sarcomas. They have an aggressive biologic behaviour; most patients develop diffuse metastatic disease. Ezrin, a cytoskeleton linker protein, has been correlated with metastasis in a number of tumours, including rhabdomyosarcomas. The goal of this study was to describe dogs with non-urinary rhabdomyosarcomas including clinical findings, ezrin expression and outcome. Twenty-five dogs with rhabdomyosarcomas were identified from two institutions' databases. Signalment, primary tumour location, cytologic and histologic findings, metastatic sites, treatments, survival time and necropsy results were recorded. Immunohistochemical staining for ezrin expression was performed on archived samples; cellular localization of ezrin was characterized. The mean and median age of all patients was 4.3 and 2 years, respectively. Subcutaneous and retrobulbar/orbital were the most common primary tumour locations. Sixteen dogs had metastatic disease at diagnosis. Three dogs presented with diffuse disease where a primary tumour could not be identified. A round cell tumour was the initial diagnosis in 32% of cases, and 76% of cases required immunohistochemistry to establish the diagnosis. The median survival was 10 days. Twenty-one cases had archived samples available for ezrin staining; all but one was positive and exhibited both membranous and cytoplasmic localization. Rhabdomyosarcomas occur in young dogs, may have a round cell appearance, and exhibit aggressive biologic behaviour. Given ezrin's defined role in metastasis, its observed expression in the tumours in this study suggest its possible role in canine rhabdomyosarcoma's aggressive biologic behaviour.

Long-term survival in six cats with mediastinal cysts.

CASE SERIES SUMMARY: Mediastinal cysts were diagnosed as incidental findings in six cats evaluated for non-thoracic disease, including staging for historical bladder leiomyosarcoma, flea dermatitis and hairballs, and hyperthyroidism. Radiographically, the cysts appeared as soft tissue opacities cranial to the heart. Ultrasound revealed the masses to be thin-walled, single lumen, anechoic, fluid-filled structures. One cat also had thoracic and abdominal CT performed for cancer staging; the CT revealed a well-defined, fluid-attenuating mass without peripheral contrast enhancement in the cranial mediastinum. Fine-needle aspiration confirmed acellular fluid consistent with a cyst in five cases; in one case the cyst ruptured during aspiration and no fluid was obtained. Post-aspiration, all masses were no longer visible with ultrasound or radiographs. No treatment was recommended for the cysts. Long-term follow-up (2-9 years post-diagnosis) was available in all six cats. The cysts recurred in five cats but were never associated with clinical signs. RELEVANCE AND NOVEL INFORMATION: Mediastinal cysts are an important benign differential for cranial mediastinal masses in cats. Treatment for the cysts does not appear to be indicated. This series also includes the first CT description of this clinical entity.

Demographic characteristics, site and phylogenetic distribution of dogs with appendicular osteosarcoma: 744 dogs (2000-2015).

OBJECTIVE: To report demographic characteristics of a contemporary population of dogs with appendicular osteosarcoma and assess the relationship between demographic characteristics, site distribution, and phylogenetic breed clusters. DESIGN: Retrospective case series. METHODS: A search of the Veterinary Medical Database was performed for dogs with appendicular osteosarcoma as a new diagnosis. Entries were reviewed for the sex, neuter status, age at diagnosis, breed, affected limb, and tumor location. The reported breed for purebred dogs was used to categorize each dog into one of five phylogenetic groups based on microsatellite analysis. RESULTS: 744 client-owned dogs were included in the study. Study dogs were represented by a male-to-female ratio of 0.95:1.0, the majority of which (80.9%) were neutered. Most dogs were diagnosed between 7-10 years of age. The majority (77.8%) of dogs were large or giant-breed dogs. Purebred dogs comprised 80.4% of the population. The most common purebred breed affected by OS was the Rottweiler (17.1%). The most common phylogenetic group represented was Mastiff-Terrier (M-T, 26.3%). OS was more commonly located in the forelimb (64.2%) versus the hindlimb (35.8%), and the humerus was the most common site (20.9%). The distribution of age groups and tumor locations were significantly different between phylogenetic clusters. The distribution of age groups and neuter status were significantly different between size groups. CONCLUSIONS AND SIGNIFICANCE: The demographic data of canine appendicular OS are similar to previous reports. The data on phylogenetic associations can guide future studies aimed at evaluating the genomic mutations that contribute to OS development and its biological behavior.

Evaluation of information presented within mast cell tumour histopathology reports in the United States: 2012-2015.

For canine mast cell tumour (MCT), histopathology reports are one of the main factors considered in the decision-making process regarding need and type of adjunctive therapy. However, considerable variation exists in types of information reported, especially relating to surgical margins. The purpose of this study was to describe and evaluate how information is presented within canine MCT histopathology reports across the United States. The reports were collected from medical and surgical oncologists from 4 geographic regions of the USA: Midwest, Northeast, South and West. All reports were obtained between January 1st 2012 and May 1st 2015. Inclusion criteria required that the final diagnosis was MCT, a microscopic description was present, and it was not a scar revision. Three hundred and sixty-eight reports were collected from 26 contributors. While the majority of the reports contained a clinical history (85.9%), information for certain prognostic indicators such as location and mass size was lacking. Grading with both Patnaik and Kiupel systems were described in 76.5% of reports with a single system being used in 7.1% and 15.2% of reports, respectively. Subcutaneous MCT were assigned a grading scheme in 67.2% of reports with 33.3% stating appropriate limitations. Surgical margins were reported in 92% of the reports with 77.2% describing deep and lateral margins separately. Tissue composing the deep margin was only described in 10.9% of the reports. The present results indicate reporting of MCT has variability across pathologists with inconsistencies present in the reporting of clinical history, margin evaluation and subcutaneous MCT grading.

Platelet concentrations and platelet-associated IgG in greyhounds.

BACKGROUND: Greyhounds have lower platelet concentrations (PC) than dogs of other breeds have. No underlying cause has been investigated. HYPOTHESIS: We hypothesized that Greyhounds have lower mean PC because of breed variation, not immune-mediated causes. Our secondary hypothesis was that PC is dependent on the method of analysis. ANIMALS: Sixty privately owned Greyhounds in Kansas. METHODS: Blood samples were collected into evacuated glass tubes containing ethylenediamine tetraacetic acid (EDTA). Blood smears were evaluated for platelet clumps. All 60 samples had PC determined by manual, impedance, and buffy coat analyzer methods. Results of the 60 samples were compared with results of samples with (n = 25) and without (n = 35) clumps, and with control dogs. Platelets were assayed for the presence of surface-associated antigen (PSAIgG) by direct immunofluorescence. RESULTS: The mean PC was below that of the control dogs for the impedance method (P < .001). No significant difference in PC was detected between analysis methods or between samples with or without platelet clumps. Three of 60 (5%) of the Greyhounds had PC between 50,000 and 100,000/microL with impedance analysis; no samples had < 100,000/microL via buffy coat analysis. PSAIgG was not identified in any samples. CONCLUSIONS AND CLINICAL IMPORTANCE: The mean Greyhound PC for the impedance method was below the reference interval for control dogs but was not significantly different from PC determined by other methods. An immune-mediated cause for the lower PC was unlikely because no samples had PSAIgG. The decreased PC is most consistent with breed variation. As only 0-5% of samples, depending on analysis method, had PC < 100,000/microL, a Greyhound with a PC < 100,000/microL is not necessarily consistent with breed variation, thus diagnostic testing is indicated.

Evaluation of buffy coat smears for circulating mast cells in healthy cats and ill cats without mast cell tumor-related disease.

OBJECTIVE: To examine buffy coat smears for circulating mast cells in clinically normal cats and cats with illnesses unrelated to mast cell tumors and identify whether conditions other than mast cell tumors are associated with mastocytemia in cats. DESIGN: Prospective study. ANIMALS: 40 clinically normal cats and 40 cats with diseases unrelated to mast cell tumors (all cats were client owned). PROCEDURES: A blood sample for a CBC, serum biochemical analyses, and buffy coat evaluation was obtained from each cat. Ill cats underwent other testing on the basis of their disease process. RESULTS: No mast cells were detected in any sample. Eosinophilia was evident in 11 (27.5%) and 12 (30%) clinically normal and ill cats, respectively. Basophilia was identified in 4 (10%) and 8 (20%) clinically normal and ill cats, respectively. Eight of the 40 (20%) ill cats had neutrophilia. CONCLUSIONS AND CLINICAL RELEVANCE: Circulating mast cells were not identified in clinically normal cats or ill cats without mast cell tumor-related disease. Ill cats did have conditions that caused eosinophilia, basophilia, or neutrophilia. The absence of mast cells in buffy coats obtained from clinically normal and ill cats lends support to the current practice of buffy coat evaluation for tumor staging and follow-up examinations in cats with mast cell tumors. Further studies of buffy coat analysis in cats with different forms of mast cell tumors are indicated to specifically elucidate the test's prognostic value for those patients.

Communicating with oncology clients.

Empathic, honest, and consistent communications that establish realistic goals and focus on quality of life (during and after therapy) for pets with cancer provide the basis of an excellent client-veterinarian relationship. From this foundation, a client can team up with his or her veterinarian to make the best possible decisions for the pet and for himself or herself regarding care for the companion animal.

Characterization of long-term elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate beads in vitro by two distinct sample collection methods.

OBJECTIVE To characterize long-term elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate (CI-CSH) beads in vitro by comparing 2 distinct sample collection methods designed to mimic 2 in vivo environments. SAMPLES 162 CI-CSH beads containing 4.6 mg of carboplatin (2.4 mg of platinum/bead). PROCEDURES For method 1, which mimicked an in vivo environment with rapid and complete fluid exchange, each of 3 plastic 10-mL conical tubes contained 3 CI-CSH beads and 5 mL of PBS solution. Eluent samples were obtained by evacuation of all fluid at 1, 2, 3, 6, 9, and 12 hours and 1, 2, 3, 6, 9, 12, 15, 18, 22, 26, and 30 days. Five milliliters of fresh PBS solution was then added to each tube. For method 2, which mimicked an in vivo environment with no fluid exchange, each of 51 tubes (ie, 3 tubes/17 sample collection times) contained 3 CI-CSH beads and 5 mL of PBS solution. Eluent samples were obtained from the assigned tubes for each time point. All samples were analyzed for platinum content by inductively coupled plasma-mass spectrometry. RESULTS Platinum was released from CI-CSH beads for 22 to 30 days. Significant differences were found in platinum concentration and percentage of platinum eluted from CI-CSH beads over time for each method. Platinum concentrations and elution percentages in method 2 samples were significantly higher than those of method 1 samples, except for the first hour measurements. CONCLUSIONS AND CLINICAL RELEVANCE Sample collection methods 1 and 2 may provide estimates of the minimum and maximum platinum release, respectively, from CI-CSH beads in vivo.

Evaluation of the effects of anatomic location, histologic processing, and sample size on shrinkage of skin samples obtained from canine cadavers.

OBJECTIVE To evaluate effects of anatomic location, histologic processing, and sample size on shrinkage of excised canine skin samples. SAMPLE Skin samples from 15 canine cadavers. PROCEDURES Elliptical samples of the skin, underlying subcutaneous fat, and muscle fascia were collected from the head, hind limb, and lumbar region of each cadaver. Two samples (10 mm and 30 mm) were collected at each anatomic location of each cadaver (one from the left side and the other from the right side). Measurements of length, width, depth, and surface area were collected prior to excision (P1) and after fixation in neutral-buffered 10% formalin for 24 to 48 hours (P2). Length and width were also measured after histologic processing (P3). RESULTS Length and width decreased significantly at all anatomic locations and for both sample sizes at each processing stage. Hind limb samples had the greatest decrease in length, compared with results for samples obtained from other locations, across all processing stages for both sample sizes. The 30-mm samples had a greater percentage change in length and width between P1 and P2 than did the 10-mm samples. Histologic processing (P2 to P3) had a greater effect on the percentage shrinkage of 10-mm samples. For all locations and both sample sizes, percentage change between P1 and P3 ranged from 24.0% to 37.7% for length and 18.0% to 22.8% for width. CONCLUSIONS AND CLINICAL RELEVANCE Histologic processing, anatomic location, and sample size affected the degree of shrinkage of a canine skin sample from excision to histologic assessment.

Elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate beads in vitro.

OBJECTIVE To characterize the elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate (CSH) beads in vitro. SAMPLE 60 carboplatin-impregnated CSH beads and 9 CSH beads without added carboplatin (controls). PROCEDURES Carboplatin-impregnated CSH beads (each containing 4.6 mg of carboplatin [2.4 mg of platinum]) were placed into separate 10-mL plastic tubes containing 5 mL of PBSS in groups of 1, 3, 6, or 10; 3 control beads were placed into a single tube of PBSS at the same volume. Experiments were conducted in triplicate at 37°C and a pH of 7.4 with constant agitation. Eluent samples were collected at 1, 2, 3, 6, 12, 24, and 72 hours. Samples were analyzed for platinum content by inductively coupled plasma-mass spectrometry. RESULTS The mean concentration of platinum released per carboplatin-impregnated bead over 72 hours was 445.3 mg/L. Cumulative concentrations of platinum eluted increased as the number of beads per tube increased. There was a significant difference in platinum concentrations over time, with values increasing over the first 12 hours and then declining for all tubes. There was also a significant difference in percentage of total incorporated platinum released into tubes with different numbers of beads: the percentage of eluted platinum was higher in tubes containing 1 or 3 beads than in those containing 6 or 10 beads. CONCLUSIONS AND CLINICAL RELEVANCE Carboplatin-impregnated CSH beads eluted platinum over 72 hours. Further studies are needed to determine whether implantation of carboplatin-impregnated CSH beads results in detectable levels of platinum systemically and whether the platinum concentrations eluted locally are toxic to tumor cells.

Toxicity and efficacy of cisplatin and doxorubicin combination chemotherapy for the treatment of canine osteosarcoma.

Thirty-five dogs with appendicular osteosarcoma underwent amputation and chemotherapy with cisplatin and doxorubicin every 21 days for up to four cycles. Sixteen dogs completed all four cycles. Two dogs had therapy discontinued because of metastases. The remaining 17 dogs experienced toxicities necessitating protocol alteration or discontinuation. The median survival time of 300 days was not improved over previously reported single-agent protocols, but the 10 dogs that survived to a year lived a median of 510 days.

STEALTH liposome-encapsulated cisplatin (SPI-77) versus carboplatin as adjuvant therapy for spontaneously arising osteosarcoma (OSA) in the dog: a randomized multicenter clinical trial.

PURPOSE: This trial was designed to compare the efficacy of adjuvant STEALH liposome-encapsulated cisplatin (SPI-77) to "standard-of-care" carboplatin therapy in dogs with osteosarcoma (OSA) in the context of a randomized study design. METHODS: The study included 40 pet dogs with spontaneously arising OSA which were randomized to receive SPI-77 (350 mg/m(2) i.v. every 3 weeks for four treatments) or carboplatin (300 mg/m(2) i.v. every 3 weeks for four treatments) along with amputation of the affected limb. Median disease-free (DFS) and overall survival (OS) were compared using standard life-table analysis. RESULTS: The median follow-up was 693 days (range 321-730 days). Of 38 dogs eligible for follow-up, 25 were dead of their disease, 9 were alive and disease-free (8 receiving SPI-77, 1 receiving carboplatin; P=0.02), 2 were free of disease when they were lost to follow-up at 321 and 395 days, and 2 had died of an unrelated disease. The median DFS times for dogs treated with SPI-77 and carboplatin were 156 and 123 days, respectively ( P=0.19). The median OS times for dogs treated with SPI-77 and carboplatin were 333 and 207 days, respectively ( P=0.18). CONCLUSIONS: While STEALTH liposome encapsulation of cisplatin allowed the safe administration of five times the maximally tolerated dose of free cisplatin to dogs without concurrent hydration protocols, this did not translate into significantly prolonged DFS or OS. However, a larger proportion of dogs receiving SPI-77 enjoyed long-term DFS when compared with dogs receiving carboplatin.

Evaluation of a 6-month chemotherapy protocol with no maintenance therapy for dogs with lymphoma.

The purpose of this study was to compare a maintenance-free chemotherapy protocol based on CHOP (H from hydroxydaunorubicin = doxorubicin, O from Oncovin = vincristine) to a similar protocol with a maintenance phase for the treatment of canine lymphoma. Fifty-three dogs with multicentric lymphoma were treated with a 6-month modified version of the University of Wisconsin (UW)-Madison chemotherapy protocol (UW-25). Disease-free interval (DFI) and survival were compared to a historical control group of 55 dogs treated with a similar protocol with a prolonged maintenance phase. Remission rate for the study dogs was 94.2% (complete remission = 92.3%, partial remission = 1.9%). DFI and survival between the 2 groups did not differ significantly, with median DFI and survival of the study dogs equal to 282 and 397 days compared to 220 and 303 days for the control dogs (P = .2835 and .3365, respectively). Univariate analysis identified substage b (P = .0087), German Shepherd breed (P = .0199), and body weight > 18 kg (P = .0016) as significant for worse survival. Longer survival was associated with thrombocytopenia (P = .0436). Multivariate analysis revealed that substage (P = .0388) and weight (P = .0125) retained significance for DFI, whereas substage (P = .0093), thrombocytopenia (P = .0150), and weight (P = 0 .0050) retained significance for survival. Overall, the protocol was well tolerated by the dogs, with 41.5% (22/53) requiring a treatment delay or dose modification, but only 9.4% (5/53) needing hospitalization. The 6-month chemotherapy protocol based on CHOP with no maintenance phase provides similar DFI and survival times when compared to a similar protocol with a prolonged maintenance phase.