Sequential Low-Dose Rate Half-Body Irradiation and Chemotherapy for the Treatment of Canine Multicentric Lymphoma

Background: Sequential half-body irradiation (HBI) combined with chemotherapy is feasible in treating canine lymphoma, but prolonged interradiation intervals may affect efficacy. A 2-week interradiation interval is possible in most dogs receiving low-dose rate irradiation (LDRI) protocols at 6 Gy dose levels.
Hypothesis: LDRI incorporated into a cyclophosphamide, doxorubicin, vincritine, and prednisone (CHOP)-based chemotherapy protocol is effective for the treatment of lymphoma in dogs.
Animals: Thirty-eight client-owned animals diagnosed with multicentric lymphoma.
Methods: Retrospective study evaluating the efficacy and prognostic factors for the treatment of canine lymphoma with sequential HBI and chemotherapy.
Results: The median 1st remission was 410 days (95% confidence interval [CI] 241–803 days). The 1-, 2-, and 3-year 1st remission rates were 54, 42, and 31%. The median overall survival was 684 days (95% CI 334–1,223 days). The 1-, 2-, and 3-year survival rates were 66, 47, and 44%.
Conclusions and Clinical Relevance: Results of this study suggest that treatment intensification by a 2-week interradiation treatment interval coupled with interradiation chemotherapy is an effective treatment for dogs with lymphoma.     

Single agent gemcitabine chemotherapy in dogs with spontaneously occurring lymphoma

BACKGROUND: Gemcitabine has been shown to be effective as a single agent in a variety of tumors including nonHodgkin's lymphoma. Its use in veterinary medicine has been limited and to date this drug has not been used as a first-line therapy in dogs with lymphoma. HYPOTHESIS: Gemcitabine as a single agent may be efficacious in dogs presented for the first time with lymphoma. ANIMALS: Twenty-four dogs with spontaneously occurring lymphoma. METHODS: All dogs were clinically staged and given gemcitabine at 400 mg/m(2) over a 30-minute intravenous infusion weekly for 3 weeks and then given 1 week off treatment before starting a second cycle. RESULTS: A single dose of gemcitabine lowered both neutrophil count (decrease in mean neutrophil count from 10,640 cells/ microL to 3,140 cells/microL) and platelet count (decrease in mean platelet count from 201,290 cells/microL to 139,190 cells/microL) 7 days after administration. Consequently gemcitabine dosage was reduced at the second treatment in 8 of 21 dogs or a dose delay of 1-7 days and a reduction of dosage was used in 7 of 21 dogs. Seven dogs completed the assigned 4-week cycle. Two of these dogs had progressive disease and 5 had stable disease. No objective responses were seen in dogs treated with a second cycle of gemcitabine. CONCLUSIONS AND CLINICAL IMPORTANCE: Gemcitabine administration as a single agent resulted in hematologic toxicity and did not reduce lymphoma burden. If gemcitabine is to be used in veterinary medicine, additional prospective pharmacologic studies should be done to determine the appropriate dosage, regimen, and schedule of use before it can be recommended for use in the treatment of dogs with lymphoma as a single agent.     

Autologous marrow transplantation as consolidation therapy for canine lymphoma: efficacy and toxicity of various regimens of total body irradiation

Dogs with malignant lymphoma were given chemotherapy consisting of nitrogen mustard, vincristine sulfate, prednisone, L-asparaginase, and 6-mercaptopurine (MOPA-6) for 14 days. Among 62 dogs that completed treatment with MOPA-6, 47 (76%) had complete remission, and 13 (21%) had partial remission and 2 had no response to chemotherapy. Twenty-two of the 62 dogs were not returned by their owners for additional therapy and died 15 to 391 (median 21) days after MOPA-6 from infections or recurrent disease. A median of 1 month after starting MOPA-6 therapy, 40 dogs (35 in complete remission, 5 in partial remission) were given total body irradiation (TBI), followed by infusion of fresh autologous marrow. Twenty dogs were given 13.5 Gray (Gy) of TBI at 4 centi-Gray (cGy)/min. Among 16 evaluable dogs, 7 had recurrence of lymphoma at a median of 169 days. Two dogs died with veno-occlusive disease of the liver, 3 with pneumonia, 3 with hemorrhage, and 1 was killed. Twenty dogs were given 11.8 to 14.7 Gy of TBI at 2 cGy/min. Among 14 evaluable dogs, 9 had recurrence of lymphoma at a median of 117 days. The remaining 5 dogs were killed at 110 to 680 days; lymphoma was not present at necropsy. The results indicated that doses of TBI of 11.8 to 14.7 Gy did not reduce the recurrence of lymphoma, compared with results obtained in a previous study with 8.4 Gy of TBI. Furthermore, increased doses of TBI increased acute and delayed toxicities. Alternatively, recurrent disease may have been due to lymphoma cells contained in the infused remission marrow.     

Neutropenia associated with vincristine and L-asparaginase induction chemotherapy for canine lymphoma

Vincristine (VCR) and L-asparaginase (L-ASP) are commonly used to treat canine lymphoma. As single agents, these drugs are not myelosuppressive. However, in combination, VCR and L-ASP cause severe neutropenia in some dogs. It has been recommended that L-ASP be administered 12-24 hours after VCR to minimize toxicity. The purpose of this retrospective study was to determine the prevalence of neutropenia after VCR/L-ASP induction therapy for canine lymphoma and to evaluate risk factors for myelosuppression, especially the interval between VCR and L-ASP administration. Medical records of 147 dogs were reviewed. L-ASP was given 0 (n = 50), 6 (n = 23), 18 (n = 20), or 24 (n = 54) hours after VCR. Forty percent of the dogs were neutropenic 7 days after VCR/L-ASP, and 18% had neutrophil counts of <1,000 cells/microL. The median neutrophil count was 3,712 cells/microL (range 0-30,968 cells/microL). No correlation was found between administration interval and day 7 neutrophil count (P = .84) or development of gastrointestinal signs, including vomiting (P = .80), diarrhea (P = .52), and decreased appetite (P = .30). No significant predictors of neutropenia were identified. Higher clinical stage and substage b were associated with decreased appetite after treatment (P = .04 and .01, respectively). Sixteen percent of the dogs were hospitalized. This study demonstrates that VCR/L-ASP induction for canine lymphoma may result in neutropenia but that separation of VCR and L-ASP administration may not be necessary to avoid toxicity.     

Evaluation of ifosfamide for treatment of various canine neoplasms

lfosfamide (3-[2-chloroethyl]-2[(2 chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide) is an alkylating agent with a broad spectrum of antitumor activity. The efficacy and toxicity of ifosfamide were evaluated in 72 dogs with spontaneously occurring tumors. Forty dogs (56%) had lymphoma, 31 (43%) had sarcomas, and 1 had a metastatic carcinoma. Five dogs received ifosfamide at dosages <350 mg/m2 IV. Neither toxicity nor response were observed, and the remaining dogs received ifosfamide at 350 mg/m2 (n = 18) and 375 mg/m2 body surface area IV (n = 49). Saline diuresis and the thiol compound mesna were used to prevent urothelial toxicity. Fifty-two dogs had measurable tumors and could be evaluated for response. Complete responses were seen in 1 dog with metastatic leiomyosarcoma of the urinary bladder and in 1 dog with metastatic cutaneous hemangiosarcoma. One dog with lymphoma had a partial response for 112 days. Six dogs with splenic hemangiosarcoma received ifosfamide postsplenectomy and their median survival time was 147 days. The acute dose limiting toxicity was neutropenia 7 days after administration of ifosfamide. The median and mean neutrophil counts 7 days after ifosfamide at 350 mg/m2 were 2,035 cells/microL and 4,773 cells/microL, respectively (n = 12). The median and mean neutrophil counts 7 days after ifosfamide at 375 mg/m2 were 2,500 cells/microL and 3,594 cells/microL, respectively (n = 37). No dog developed clinical or microscopic evidence of hemorrhagic cystitis. Ifosfamide appears safe to use in tumor-bearing dogs, and the evaluation of combination chemotherapy protocols that include ifosfamide should be considered.     

A toxicity study of low‐dose rate half‐body irradiation and chemotherapy in dogs with lymphoma

Thirteen dogs with previously untreated multicentric lymphoma were enrolled in a prospective study investigating the effects of low‐dose rate total body irradiation (TBI) and chemotherapy. Dogs received either 6 or 8 Gy TBI in half‐body fractions, 2 weeks apart. Toxicity consisted of mild to moderate haematological and gastrointestinal (GI) signs. One dog died from treatment complications. Anorexia was noted independent of dose. Haematological toxicity was more common and more severe after 8 Gy treatment. GI toxicity was more likely postcaudal half‐body irradiation with 8 Gy. Other than leukotrichia, late effects from radiation were not observed. Results indicated that haematological and nonhaematological toxicity was dose dependent. However, the protocol was well tolerated and treatment intensification using a 2‐week inter‐radiation interval was possible in all dogs treated with 6 Gy. Preliminary survival data for these dogs were very encouraging, providing a strong rationale to analyse the efficacy of low‐dose rate irradiation (LDRI) in canine lymphoma.     

Combination of CCNU and DTIC chemotherapy for treatment of resistant lymphoma in dogs

BACKGROUND: Pleotropic-glycoprotein (P-gp)-mediated resistance is the usual cause of relapse in dogs with lymphoma. 1-(2-chloroethyl)3-cyclohexyl-1-nitrosurea (CCNU) and 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) are alkylating agents that are not affected by P-gp and lack cross-resistance to each other. A combination protocol offers the advantage of improved summation dose and synergistic activity. HYPOTHESIS: A combination of CCNU and DTIC that is well tolerated can be used to treat dogs with lymphoma that developed resistance or failed to respond to previously administered chemotherapy. ANIMALS: Fifty-seven dogs with lymphoma that were resistant to treatment with standard chemotherapy (L-CHOP; L-asparaginase, cyclophosphamide, doxorubicin, vincristine, prednisone). METHODS: Prospective phase I and II trials were performed. CCNU was given PO immediately before a 5-h IV infusion of DTIC. Concurrent antiemetics and prophylactic antibiotics were used. Treatments were administered every 4 weeks. RESULTS: Based on the results of 8 dogs in the phase I study, CCNU at 40 mg/m(2) PO combined with DTIC at 600 mg/m(2) IV was used to treat 57 dogs with resistant lymphoma. Thirteen (23%) dogs had a complete response (CR) for a median of 83 days and 7 (12%) had a partial response for a median of 25 days. The median L-CHOP CR duration of the dogs that did not respond to CCNU-DTIC was significantly longer than that of the dogs that did achieve remission with CCNU-DTIC (225 days versus 92 days, P= .02). The principal toxic event was neutropenia; the median neutrophil count 7 days after treatment was 1,275 cells/microL. Increases in alanine transaminase activity, possibly associated with hepatotoxicity, were detected in 7 dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: A combination of CCNU and DTIC can be an effective option to rescue dogs with resistant lymphoma.     

Clinical and immunological response of lymphoma dogs following chemotherapy and irradiation

The effect of chemotherapy or chemotherapy followed by total body irradiation and autologous bone marrow transplantation on clinical status and lymphocyte function was evaluated in 79 dogs with spontaneous lymphoma. Advanced disease led to the early deaths of 28 dogs (35%), and 24 dogs (30%) administered chemotherapy had a mean survival time of 85 days (range 33–199 days). Survival for eight dogs receiving chemotherapy and BCG was comparable to that produced by chemotherapy only. Thirteen dogs administered chemotherapy followed by irradiation and autologous marrow grafts had survival times ranging from 59 to > 807 days (median 222 days) with median unmaintained clinical remission lasting 151 days. Most treated dogs experienced improvement in health, reduction in lymph node sizes and normalization of liver function. Lymphocyte reactivity to mitogens and streptolysin-O antigen by untreated and treated lymphoma dogs was depressed (P<0.05) compared to response of normal lymphocytes. Mixed leukocyte reactivity of irradiated lymphoma dogs was impaired in the first 150 days post-irradiation and returned to normal values after 150 days. Lymphocyte responses of irradiated normal dogs paralleled those seen in lymphoma dogs. Mixed leukocyte reactivity was not correlated with tumor rejection since eight of nine dogs evaluated following irradiation relapsed during a period of vigorous reactivity to allogeneic stimulating cells.     

Chemotherapy followed by half-body radiation therapy for canine lymphoma

A protocol of induction chemotherapy followed by half-body radiation therapy for treatment of lymphoma was used in 94 dogs. Seventy-three (78%) dogs achieved complete remission. Substage (P = .011) and phenotype (P = .015) were identified as predictors of complete remission rate. Of these, 52 dogs received half-body irradiation. Cranial and caudal halves received a total dose of 8.0 Gy, given in 2 fractions of 4.0 Gy on consecutive days with cobalt-60 photons and a 3-week interval between halves. Median 1st remission for these dogs was 311 days. Anemia was identified as the only predictor for length of 1st remission (P = .024). Toxicoses after half-body irradiation generally were mild and infrequent and included myelosuppression and gastrointestinal signs. Thirty-one dogs relapsed and 20 resumed treatment with induction followed by maintenance chemotherapy. Seventeen (85%) dogs achieved a 2nd complete remission. Median overall remission for all 52 dogs was 486 days. Results of this study suggest that half-body radiation therapy after induction chemotherapy is well tolerated and might increase remission duration compared with conventional protocols that use chemotherapy alone, but this increase might not be long enough to be clinically relevant or to justify application of the method described herein.     

Paraneoplastic hypereosinophilia in a dog with intestinal T-cell lymphoma

A 9-year-old, intact male Doberman Pinscher was examined because of anorexia and weakness. Results of a CBC showed severe, microcytic, hypochromic anemia with mild eosinophilia (2944 cells/microL, reference interval 100-1250/microL) and thrombocytosis. Hypoferremia, hypoferritinemia, and a positive fecal occult blood test supported a diagnosis of iron deficiency anemia secondary to chronic intestinal hemorrhage. Abdominal ultrasound evaluation showed a thickened small intestinal loop, of which representative specimens were obtained during exploratory laparotomy. Histologically, the intestinal wall was infiltrated by a neoplastic population of large, round, lymphoid cells with vesicular chromatin, 1 or more prominent nucleoli, and a high number of mitotic figures. The cells were closely admixed with mature eosinophils, but were negative for metachromatic granules with toluidine blue. Immunohistochemically, tumor cells were positive for CD3, and negative for CD21, Pan B, and CD79a. A diagnosis of intestinal T-cell lymphoma was made. Chemotherapy was begun, with 30 mg/m;2 of doxorubicin administered intravenously every 3 weeks. Eosinophil concentration was 880/microL 2 weeks after surgery (on day 15 after presentation) but increased markedly to 62,914/microL on day 30, 62,400/microL on day 37, and 39,444/microL on day 58 after presentation. An association between hypereosinophilia and T-cell lymphoma is well established in human patients, in whom production of IL-5 by neoplastic T cells has been demonstrated. Hypereosinophilia has been reported only rarely with intestinal lymphoma in cats and horses, and with T-cell lymphoma in dogs.     

CCNU for the treatment of dogs with histiocytic sarcoma

BACKGROUND: Histiocytic sarcoma is an aggressive neoplasm of dendritic cells that carries a grave prognosis. The efficacy of chemotherapy against this disease is unknown. The purpose of this study was to determine the efficacy of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in dogs with incompletely resected or metastatic histiocytic sarcoma, to describe the clinical characteristics of these dogs, and to identify factors affecting prognosis. HYPOTHESIS: Our hypothesis is that CCNU has activity against canine histiocytic sarcoma and can improve survival in dogs with advanced disease. ANIMALS: Included in analysis are dogs diagnosed with histiocytic sarcoma who had gross measurable or residual microscopic disease and who received CCNU. METHODS: A multi-institutional, retrospective, single-arm cohort study was conducted. Available biopsy samples were tested with an antibody against CD18 when possible to confirm the diagnosis of histiocytic sarcoma. RESULTS: Fifty-nine dogs were treated at 8 institutions. Twenty-three tumor specimens were confirmed to be CD18 positive. Treatment with CCNU at 60 to 90 mg/m2 resulted in an overall response rate of 46% in the 56 dogs with gross measurable disease. All 3 dogs with minimal residual disease experienced tumor relapse but lived 433 days or more after starting CCNU. The median survival of all 59 dogs was 106 days. Thrombocytopenia (< 100,000 platelets/microL) and hypoalbuminemia were found to be negatively associated with prognosis and were predictive of < 1 month survival. CONCLUSIONS AND CLINICAL IMPORTANCE: Results suggest that CCNU is active against canine histiocytic sarcoma and may be useful in the treatment of dogs without negative prognostic factors.     

Half-Body Radiotherapy

Eight healthy mongrel dogs were treated with half-body irradiation (HBI) in a pilot study to evaluate the technique and radiotolerance of different organs. Cranial and caudal half-body fields were established using the 13th thoracic vertebra as the dividing point. Under general anesthesia, either 7 or 8 Gray (Gy) were delivered to one half of the body using opposing radiation portals. The other half of the body was similarly treated 28 days later. The dogs were monitored for 12 months. Significant radiation effects included transient bone marrow suppression and radiation sickness. There were no serious or life-threatening problems, but the 8 Gy group consistently showed more severe clinical signs and histologic changes than the 7 Gy group. Total body irradiation in two fractions of 7 or 8 Gy given 1 month apart appears to be a safe treatment that can be developed for therapy in veterinary oncology.     

Asparaginase and MOPP Treatment of Dogs with Lymphoma

Background: Dogs with multicentric lymphoma are treated with various cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP)-based chemotherapy protocols with variable success.
Objectives: To describe the progression-free survival (PFS) time and overall survival time (OST) of dogs with T-cell lymphoma or hypercalcemic lymphoma treated with l -asparaginase and mechlorethamine, vincristine, prednisone, procarbazine (MOPP).
Animals: Fifty dogs with T-cell lymphoma, hypercalcemic lymphoma, or both treated at 3 referral veterinary hospitals.
Methods: Retrospective study. Case were selected based on histologic or cytologic diagnosis of lymphoma; presence of the T-cell phenotype, presence of hypercalcemia or both; and absence of previous chemotherapy. The T-cell phenotype was determined by flow cytometry, immunocytochemistry, immunohistochemistry, or polymerase chain reaction of antigen receptor rearrangement.
Results: The overall response rate was 98% (78% complete response, 20% partial response). The median PFS for the entire study population was 189 days with 25% PFS at 939 days. The median OST for the entire study population was 270 days with 25% surviving 939 days. Twenty percent of the dogs required hospitalization for treatment related complications.
Conclusions and clinical importance: l -Asp/MOPP chemotherapy might result in longer PFS and OST for dogs with multicentric T-cell lymphoma, dogs with hypercalcemic lymphoma or both, than achieved with CHOP.     

Comparison of COAP and UW-19 protocols for dogs with multicentric lymphoma

BACKGROUND: Various chemotherapy protocols for treating lymphoma in dogs have been published; however, comparison of protocols from different studies is difficult, especially when evaluating survival time and toxicoses. HYPOTHESIS: The choice of COAP (C, cyclophosphamide; O, vincristine; A, cytosine arabinoside; P, prednisone) and a modified University of Wisconsin 19-week (UW-19) induction protocol has no influence on overall survival times in dogs with lymphoma. ANIMALS: One hundred and one dogs with multicentric lymphoma. METHODS: Retrospective study (2001-2006). Dogs induced with either an 8-week COP-based protocol (C, cyclophosphamide; O, vincristine; and P, prednisone) with maintenance therapy (COAP group) or a 19-week CHOP (C, cyclophosphamide; H, doxorubicin; O, vincristine; and P, prednisone) based protocol (UW-19 group) were compared in terms of the duration of first remission, survival time, toxicoses, and cost. RESULTS: There were 71 dogs in the COAP group and 30 dogs in the UW-19 group. Various protocols were used after the first relapse. The median duration of the first remission for the COAP and UW-19 groups were 94 days (range, 6-356 days) and 174 days (28-438 days), respectively (P < .01). The median survival times for dogs in the COAP and UW-19 groups were 309 days (6-620 days) and 275 days (70-1102+ days), respectively (P = .09). Dogs in the COAP group had a hazard ratio of 1.9 (95% CI 1.1-3.4) for death relative to the UW-19 group (P = .03), after controlling for the confounders (World Health Organization clinical stage, age, sex, use of doxorubicin during reinduction). The severity of neutropenia and gastrointestinal toxicoses were significantly higher in the UW-19 group than in the COAP group (P = .01 and P < .01, respectively). CONCLUSION AND CLINICAL IMPORTANCE: Use of a long-term doxorubicin-containing sequential combination chemotherapy protocol is associated with a decreased risk of relapse and death relative to a non-doxorubicin-containing protocol.     

Monitoring of Minimal Residual Disease (MRD) after Multidrug Chemotherapy and Its Correlation to Outcome in Dogs with Lymphoma: A Proof‐of‐Concept Pilot Study

Background: Tumor cell burden in dogs with lymphoma cannot be assessed accurately by diagnostic evaluation during clinical complete remission (CR). Recent advances in polymerase chain reaction (PCR)‐based methods enabled us to quantify minimal residual disease (MRD) in canine lymphoma. Hypothesis/Objectives: To quantify MRD in dogs with lymphoma treated with multidrug chemotherapy and to correlate it with remission duration after chemotherapy. Animals: Seventeen dogs with lymphoma that achieved CR by multidrug chemotherapy. Methods: Rearranged immunoglobulin heavy chain or T‐cell receptor γ chain gene fragments from lymphoma cells were PCR amplified and sequenced to prepare clone‐specific primers and probes for real‐time PCR to quantify MRD. MRD in the peripheral blood was monitored during and at the end of a 25‐week multidrug chemotherapy protocol. Correlation between MRD at the end of chemotherapy and remission duration after chemotherapy was analyzed. Results: MRD gradually decreased after initiation of multidrug chemotherapy, reached a nadir as low as <0.019–1.0 cells/μL at weeks 4–17, and remained low or slightly increased until week 25. MRD at the end of chemotherapy was negatively correlated with remission duration from the end of chemotherapy to relapse. Conclusion and Clinical Importance: MRD could be an objective marker to indicate tumor cell burden in dogs with lymphoma even in clinical CR. MRD at the end of chemotherapy could be a prognostic factor to predict remission duration after chemotherapy.     

Characteristics of cisternal cerebrospinal fluid associated with intracranial meningiomas in dogs: 56 cases (1985-2004)

OBJECTIVE: To determine CSF characteristics associated with intracranial meningiomas in dogs. DESIGN: Retrospective case series. ANIMALS: 56 dogs with intracranial meningiomas. PROCEDURES: Medical records of dogs with a histopathologic diagnosis of intracranial meningioma, in which CSF analysis had been performed, were reviewed. Information concerning total nucleated cell counts (TNCCs) and differential nucleated cell counts, RBC counts, and total protein concentration in CSF; seizure history and glucocorticoid administration; and location of meningiomas was recorded. RESULTS: TNCCs < 5 cells/microL were detected in 41 of 56 (73%) dogs; 5 of 56 (9%) dogs had TNCCs > 50 cells/microL. Analysis of CSF revealed predominantly neutrophilic pleocytosis in < 20% of dogs. There was a significant association between meningioma location (caudal portion of the cranial fossa or middle and rostral portion of the cranial fossae) and increased TNCCs (> or = 5 cells/microL). CONCLUSIONS AND CLINICAL RELEVANCE: Results were significantly different from those routinely reported in the veterinary literature. Neutrophilic pleocytosis, especially with TNCCs > 50 cells/microL, was not typical in CSF samples from dogs with intracranial meningiomas. Neutrophilic pleocytosis may not be detected in CSF samples from dogs with meningiomas located within the middle or rostral portion of the cranial fossae.     

Serum C-reactive protein concentrations in dogs with multicentric lymphoma undergoing chemotherapy

OBJECTIVE: To determine whether serum C-reactive protein (CRP) concentration is high in dogs with multicentric lymphoma, whether CRP concentration changes in response to chemotherapy, and whether CRP concentration can be used as a marker for relapse in dogs with multicentric lymphoma. DESIGN: Cohort study. ANIMALS: 20 dogs with multicentric lymphoma and 8 healthy control dogs undergoing chemotherapy with cyclophosphamide, vincristine, and prednisone (CVP) or with vincristine, cyclophosphamide, methotrexate, and L-asparaginase (VCMA) and 20 other healthy dogs. PROCEDURES: Serum CRP concentration was measured weekly during the first month of chemotherapy and then at 3-week intervals until relapse in dogs with multicentric lymphoma, weekly for 16 weeks in healthy dogs undergoing chemotherapy, and once in the healthy dogs not undergoing chemotherapy. RESULTS: For both groups of dogs with lymphoma, mean serum CRP concentration during week 1 (prior to treatment) was significantly higher than mean concentrations following induction of chemotherapy and at the time of relapse. Mean serum CRP concentration in the healthy dogs undergoing chemotherapy was not significantly different at any time from mean concentration for the healthy dogs not undergoing chemotherapy. No significant differences were observed between dogs treated with CVP and dogs treated with VCMA. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that serum CRP concentration is high in dogs with multicentric lymphoma but that serum CRP concentration is not a useful marker for relapse and that chemotherapy itself does not affect serum CRP concentration.     

Treatment of severe immune-mediated thrombocytopenia with human IV immunoglobulin in 5 dogs

BACKGROUND: Glucocorticoids with or without other immunotherapy are the initial treatment of choice for dogs with severe immune-mediated thrombocytopenia (IMT). The majority of treated dogs will have improvements in platelet counts within 5 to 7 days of starting therapy, but complications from hemorrhage often occur before a response is seen. Human IV immunoglobulin (hIVIG) blocks Fc receptors on mononuclear phagocytic cells in dogs; it is used in people with idiopathic thrombocytopenic purpura. HYPOTHESIS: The purpose of this study was to describe adverse effects and benefit of hIVIG in addition to conventional immunosuppressive therapy in dogs with severe IMT. ANIMALS: Five client-owned dogs with severe primary IMT. METHODS: Case series. The hospital database was searched for dogs with primary IMT treated with hIVIG. RESULTS: No adverse effects were noted during or after hIVIG infusion in any treated dog. Over a 6-month follow-up, all dogs were clinically normal when using conventional immunosuppressive therapy. Human IVIG was administered 3 days after initiation of immunosuppressive therapy in 4 dogs, and, after 2 days, in 1 dog. In all dogs, the mean platelet counts pre- and 24 hours post-hIVIG infusion (0.28-0.76 g/kg) were 2,500/pL and 50,600/microL (62,750/microL for the 4 responders), respectively. One dog failed to respond as promptly to hIVIG (0.34 g/kg), and the platelet count increased to 66,000/microL after 9 days of immunosuppressive therapy. The mean duration of hospitalization post-hIVIG in all 5 dogs was 1.8 days (12 hours for responders), and the mean total length of hospitalization was 4.6 days (3.5 days for responders). Active hemorrhage resolved and no packed red blood cell transfusions were required after hIVIG infusion for responders. CONCLUSIONS AND CLINICAL IMPORTANCE: Human IVIG was well tolerated and appeared to be associated with rapid platelet count recovery and amelioration of clinical signs in most dogs with IMT.     

Evaluation of cytoreductive efficacy of vincristine, cyclophosphamide, and Doxorubicin in dogs with lymphoma by measuring the number of neoplastic lymphoid cells with real-time polymerase chain reaction

Background: The cytoreductive efficacy of the individual components of multidrug chemotherapy for canine lymphoma is difficult to evaluate after complete remission. Objectives: To compare the cytoreductive efficacy of vincristine (VCR), cyclophosphamide (CPA), and doxorubicin (DXR) in dogs that received a 6‐month modified version of the University of Wisconsin‐Madison chemotherapy protocol (UW‐25). Animals: Twenty‐nine dogs with high‐grade B‐cell multicentric lymphoma. Methods: Rearranged immunoglobulin heavy chain gene fragments from lymphoma cells were amplified by polymerase chain reaction (PCR) and sequenced to prepare clone‐specific primers and probes for real‐time PCR. The number of lymphoma cells in peripheral blood was measured from diagnosis to week 11 of UW‐25. Results: The number of lymphoma cells after the 1st administration of VCR, CPA, and DXR in weeks 1–4 was decreased in 29/29 (100%), 15/29 (51.7%), and 26/27 (96.3%) dogs, respectively. The cytoreductive efficacy of CPA was less than that of VCR and DXR. VCR, CPA, and DXR administered in weeks 6–9 were effective in 5/26 (19.2%), 5/20 (25.0%), and 14/19 (73.7%) dogs, respectively, indicating the sustained cytoreductive efficacy of DXR. CPA nonresponders were heavier and exhibited a shorter 1st remission than CPA responders. Conclusion and Clinical Importance: When using UW‐25 for treatment of canine lymphoma, CPA was found to have less cytoreductive efficacy than VCR and DXR. Real‐time PCR‐based quantification of tumor cells is an objective marker of the efficacy of chemotherapeutic agents.     

Increase in minimal residual disease in peripheral blood before clinical relapse in dogs with lymphoma that achieved complete remission after chemotherapy

Background: We developed previously a minimal residual disease (MRD) monitoring system in dogs with lymphoma by exploring a highly sensitive real‐time PCR system. Objectives: To identify the change in MRD before clinical relapse in dogs with lymphoma that achieved complete remission after chemotherapy. Animals: Twenty dogs with multicentric high‐grade B‐cell lymphoma. Methods: MRD levels in peripheral blood mononuclear cells (PBMCs) were measured by real‐time PCR amplifying the rearranged immunoglobulin heavy chain gene. MRD measurement and clinical assessment were performed every 2–4 weeks for 28–601 days after completion of chemotherapy. An increase in MRD was defined as an increase by more than 0.5, calculated by log₁₀[copy number of MRD per 10⁵ PBMCs], based on the uncertainty level observed in a canine lymphoma cell line. Results: During the follow‐up period, 15 dogs relapsed in 28–320 days (median, 120 days) after completion of chemotherapy. An increase in MRD was detected 2 weeks or more before relapse in 14 of the 15 dogs, but an increase in MRD before relapse could not be detected in the remaining 1 dog. The time from increased MRD to clinical relapse was 0–63 days (median, 42 days). In contrast, no increase in MRD was detected in 5 dogs that did not experience clinical relapse. Conclusion and Clinical Importance: An increase in MRD can be detected before clinical relapse in dogs with lymphoma. Application of early reinduction therapy based on an increase in MRD before clinical relapse may improve treatment outcome in canine lymphoma.