Supporting the veterinary cancer patient on chemotherapy: neutropenia and gastrointestinal toxicity

New Therapies in Veterinary Oncology

The expanding number of specialized oncology therapeutics available in veterinary oncology can make staying updated on the most recent advances challenging. This article summarizes the mechanism of action, available supporting data, and clinical use of three key veterinary cancer/supportive care therapeutics: Laverdia-CA1, Canalevia-CA1, and Stelfonta. This information will help guide clinical use within your practice and can be incorporated into discussions with clients regarding the newest available options for their dogs with cancer.

Oral mirtazapine decreases the gastrointestinal adverse effects in cats on doxorubicin chemotherapy

Anorexia, depression, and vomiting are the common adverse effects of chemotherapy in humans and animals. Mirtazapine is primarily used as an appetite stimulant and antiemetic in dogs and cats. Therefore, we evaluated the efficacy of mirtazapine in reducing the gastrointestinal adverse effects in cats receiving doxorubicin chemotherapy. This single-masked, placebo-controlled crossover study enrolled 11 cats with malignant mammary gland tumors. The cats were randomly assigned to receive either mirtazapine (1.88 mg/cat) or placebo every 48 h for 2 weeks from the first initiation of doxorubicin chemotherapy. Each cat was then crossed over to the alternate group on the subsequent chemotherapy with a 1-week wash-out period. The owners were asked to record appetite score, activity score, episodes of vomiting and diarrhea for 2 weeks after each doxorubicin administration. Cats treated with mirtazapine showed significantly increased bodyweight compared with those on placebo (P = 0.010). The appetite and activity scores during mirtazapine treatment was significantly higher than those during placebo treatment (P = 0.005 and 0.018, respectively). Furthermore, the prevalence of episodes of vomiting during mirtazapine treatment was significantly lower than that during placebo treatment (P = 0.026). Our results demonstrate that mirtazapine can significantly increase bodyweight, appetite, and activity and reduce vomiting in cats after doxorubicin chemotherapy.

Pharmacokinetic study comparing doxorubicin concentrations after chemoembolization or intravenous administration in dogs with naturally occurring nonresectable hepatic carcinoma

Background

Chemoembolization is a viable treatment option for patients with nonresectable hepatic carcinoma (HC) and may allow delivery of chemotherapeutic drugs with decreased systemic toxicity.

Hypothesis/Objective

Compare the serum concentrations of doxorubicin after chemoembolization or IV administration in the same patient. We hypothesized that locoregional delivery may result in increased tumor chemotherapeutic drug concentrations, reflected by decreased measurable serum drug concentrations. Adverse hematological events were hypothesized to be decreased after locoregional delivery.

Animals

Seventeen client‐owned dogs with incompletely resectable HC.

Methods

Prospective, single‐arm clinical trial. Drug‐eluting bead transarterial chemoembolization was performed to varying levels of blood flow stasis (NO STASIS, STASIS). Intravenous doxorubicin (IVC) subsequently was administered in selected patients. Systemic exposure was quantified by area under the serum doxorubicin concentration time curve (AUC), maximum serum doxorubicin concentration (C_max), and time doxorubicin was last above the limit of quantitation (T_last). Nadir test results after treatments were used to evaluate adverse hematological events.

Results

Thirteen NO STASIS treatments, 15 STASIS treatments, and 9 IVC treatments were performed. Maximum serum doxorubicin concentration, AUC, and T_last were significantly lower when comparing NO STASIS or STASIS to IVC treatments. Of the patients with nadir results available, no adverse hematological events were observed after NO STASIS or STASIS treatments. Two patients developed adverse hematological events after IVC treatment.

Conclusions/Clinical Relevance

Drug‐eluting bead transarterial chemoembolization offers a viable treatment option for patients with incompletely resectable HC with the potential for increased local tumor doxorubicin concentrations, decreased systemic chemotherapeutic exposure, and fewer adverse hematological events.

Successful management and recovery of a dog with immune‐mediated thrombocytopenia following vincristine overdose

Objective

Case Summary

New or Unique Information Provided

Are severe adverse events commonly observed in dogs during cancer chemotherapy? A retrospective study on 155 dogs

Overall prevalence of severe adverse events (sAE) has been poorly studied in veterinary medicine and peer-reviewed studies mostly focused on a single protocol, making it difficult to have a general overview. The aim of this retrospective study was to assess the frequency and risk factors of sAE secondary to various protocols of chemotherapy in dogs. Medical records of 155 dogs receiving chemotherapy between January 2013 and December 2018 were reviewed. Adverse events (AE) were graded according to Veterinary Comparative Oncology Group-common terminology criteria for AE (VCOG-CTCAE) grading system. Statistical analyses were performed to determine whether demographic, cancer type and chemotherapy protocol were associated with development of sAE and their consequences. AE were reported at least once in 124 (80%) dogs and sAE were observed in 50 (32.3%) dogs. Among them, 23 (14.8%) had gastro-intestinal and 31 (20.0%) had myelotoxic events. sAE led to hospitalisation in 37 (23.9%) dogs, to chemotherapy arrest in 12 (7.7%) dogs and to euthanasia or death in 9 (5.8%) dogs. Haematopoietic tumours were statistically associated with a higher frequency of sAE (p = .004), gastrointestinal sAE (p = .009) and hospitalisation (p = .004). A body weight over 10 kg was associated with less haematological sAE (p < .001). The use of a multi-agent protocol was highlighted as a risk factor for sAE (p = .038) and haematological sAE (p < .001). sAE following chemotherapy and leading to hospitalisation, chemo arrest or death were relatively common. A special attention during chemotherapy follow-up should be given to small dogs and those receiving multi-agent protocol or treated for haematopoietic tumours.

LOPH: a novel chemotherapeutic protocol for feline high-grade multicentric or mediastinal lymphoma, developed in an area endemic for feline leukemia virus

OBJECTIVES

The aim of this study was to establish the safety and efficacy of a novel multidrug lomustine-based chemotherapeutic protocol for cats with high-grade multicentric or mediastinal lymphoma, in an area endemic for feline leukemia virus (FeLV).

METHODS

This prospective study included owned cats, diagnosed (cytologically) with multicentric or mediastinal lymphoma and treated with the LOPH (lomustine, vincristine [Oncovin; Antibióticos do Brasil], prednisolone and hydroxydaunorubicin [doxorubicin]) protocol. A complete blood count was performed before every chemotherapy session and any significant abnormalities recorded as possible related toxicities. Median survival time (MST) and disease-free interval were estimated by Kaplan-Meier curves.

RESULTS

Twenty-one cats were included in this study. Nineteen (90.5%) tested positive for FeLV and were therefore considered to have persistent viremia. Complete response was reported in 81% (n = 17/21), while three had partial remission and one had no response. Seven cats finished the induction protocol within 20-31 weeks (23.1 ± 4.5; median 20) and all seven received a maintenance protocol. The MST (lymphoma-related survival) for the 21 cats was 214 days. The MST was 214 days for cats with mediastinal lymphoma (n = 13), but it was not reached for multicentric lymphoma (n = 8; P = 0.9). The MST of cats with persistent FeLV antigenemia was 171 days. Grade I anorexia and vomiting occurred in 19% of the cats (n = 4/21). Hematologic toxicity was found in 100% of the cats at some point during their treatment, but it was mostly grade I or II. Neutropenia, thrombocytopenia and anemia occurred in 16/21, 21/21 and 15/21 cats, respectively.

CONCLUSIONS AND RELEVANCE

The LOPH protocol was well tolerated by cats with lymphoma and persistent FeLV viremia, and resulted in a better MST than similar studies with other protocols. Novel studies and controlled trials are necessary in order to evaluate the efficacy of different protocols according to the lymphoma subtype, anatomic form and FeLV status.

Biodynamic signatures from ex vivo bone marrow aspirates are associated with chemotherapy-induced neutropenia in cancer-bearing dogs

Background

Neutropenia is the most common dose‐limiting side effect of cytotoxic chemotherapy in cancer‐bearing dogs. Biodynamic imaging (BDI) is a functional imaging technology that measures dynamic light scattering from living, three‐dimensional tissues to characterize intracellular motion within those tissues. Previous studies have associated BDI biomarkers with tumour sensitivity to chemotherapy agents in dogs with naturally occurring cancer. We hypothesized that BDI, performed ex vivo on bone marrow aspirate samples, would identify dynamic biomarkers associated with the occurrence of specific degrees of neutropenia in tumour‐bearing dogs receiving doxorubicin chemotherapy.

Materials and Methods

Bone marrow aspirates were collected from 10 dogs with naturally occurring cancers prior to initiation of doxorubicin treatment. BDI was performed on bone marrow samples treated ex vivo with doxorubicin at 0.1, 1, 10 and 100 μM along with 0.1% DMSO as a control. Dogs then were treated with doxorubicin (30 mg/m², intravenously). Peripheral blood neutrophil counts were obtained on the day of treatment and again 7 days later. Receiver operating characteristic curves identified provisional breakpoints for BDI biomarkers that correlated with specific changes in neutrophil counts between the two time points.

Results

Provisional breakpoints for several BDI biomarkers were identified, specifying dogs with the largest proportionate change in neutrophils and with neutropenia that was grade 2 or higher following doxorubicin treatment.

Conclusions

Biodynamic imaging of bone marrow aspirates may identify those dogs at greater risk for neutropenia following doxorubicin chemotherapy. This approach may be useful for pre‐emptively modifying chemotherapy dosing in dogs to avoid unacceptable side effects.

Fasting reduces the incidence of vincristine-associated adverse events in dogs

Fasting has been shown to decrease chemotherapy‐associated adverse events (AEs), in part through insulin‐like growth factor (IGF‐1) reduction, and may induce a protective effect on normal cells during chemotherapy treatment in mice and people. The purpose of this study was to evaluate the effect of fasting on constitutional, bone marrow and gastrointestinal (GI) AEs, and serum glucose, IGF‐1 and insulin levels in dogs receiving vincristine. The study was a prospective, crossover clinical trial in tumour‐bearing dogs. Dogs were randomized to be fasted for 24 to 28 hours prior to and 6 hours following their first or second vincristine treatment, and fed normally for the alternate dose. A significant reduction in nausea, anorexia, lethargy and serum insulin was observed when dogs were fasted; however, no significant differences were found in other GI symptoms, neutrophil count, serum glucose or IGF‐1. Fasting prior to vincristine therapy is a safe and effective treatment modality that helped mitigate constitutional and GI AEs in tumour‐bearing dogs.

Chemotherapy-induced diarrhoea in dogs and its management with smectite: Results of a monocentric open-label randomized clinical trial

Chemotherapy-induced diarrhoea (CID) is a frequent chemotherapy adverse event in dogs. Yet, there is currently no consensus regarding its management. Smectite is a natural medical clay, widely used in the treatment of acute diarrhoea in humans. The objectives of this study were to assess the efficacy of smectite in the management of CID in dogs, and to collect epidemiological data on CID. For each episode of diarrhoea, dogs were randomized into two management groups: Smectite group, receiving smectite at 0.5 g/kg PO per day divided in two to three doses initiated at the start of CID; control group, without initial medication. In both groups, rescue metronidazole was prescribed if CID progressed or was not improved within 48 hours. Sixty dogs were recruited and received 426 chemotherapy administrations between June 2017 and March 2019. The incidence rate of CID was 110/426 (25.8%, 95% CI: 21.7%-30.2%), and significantly differed between the chemotherapeutic drugs administered (P < .001). Metronidazole was administered in 5/54 events (9.3%, 95% CI: 3.1%-20.3%) in the smectite group and in 40/56 events (71.4%, 95% CI: 57.5%-82.3%) in the control group (P < .001). The time to resolution of diarrhoea was shorter (P < .001) in the smectite group (median: 19.5 hours, interquartile range [IQR]: 13.5-32 hours) compared with the control group (median: 53 hours, IQR: 31.5-113.5 hours). The results of this study support the administration of smectite in the first-line management of CID in dogs.

Carboplatin-induced myelosuppression as related to body weight in dogs

Smaller dogs are known to have an increased risk of chemotherapy-induced myelosuppression for doxorubicin, mitoxantrone and melphalan. This retrospective study aimed to determine if dogs <15 kg and <10 kg experienced greater degrees of myelosuppression following treatment with carboplatin chemotherapy compared with dogs ≥15 kg. One hundred and one dogs treated with carboplatin for a variety of malignancies were retrospectively analysed. Eight dogs (61%) weighing <10 kg, three (38%) weighing 10 kg to <15 kg and 14 (17%) weighing ≥15 kg experienced a grade 3 or 4 neutropenia. Five dogs (38%) weighing <10 kg, two (25%) weighing 10 kg to <15 kg and 13 (16%) weighing ≥15 kg experienced a grade 3 or 4 thrombocytopenia. Dogs <10 kg were significantly more likely to develop a grade 3 or 4 neutropenia following carboplatin than dogs ≥10 kg (3.5 RR; 95% CI, 1.9-6.3; P < .001). Dogs <15 kg were also significantly more likely to develop a grade 3 or 4 neutropenia than dogs ≥15 kg (3 RR; 95% CI, 1.6-5.6; P = .004). Dogs <10 kg were significantly more likely to develop a grade 3 or 4 thrombocytopenia than those dogs ≥10 kg (2.5 RR; 95% CI, 1.1-5.6; P = .006). Hospitalization was significantly more likely for dogs <10 kg vs ≥10 kg (P = .014) as well as for dogs <15 kg vs ≥15 kg (P = .039). This study demonstrates an increased risk of carboplatin-induced myelosuppression in dogs <15 kg, and particularly those <10 kg. This information should be considered by clinicians when making decisions regarding the initial carboplatin dose for smaller canine patients, especially those <15 kg.

Evaluation of a 0.75 × 109 /L absolute neutrophil count cut-off for antimicrobial prophylaxis in canine cancer chemotherapy patients

Absolute neutrophil count (ANC) cut-offs for antimicrobial prophylaxis in veterinary cancer chemotherapy patients are empirical and vary between institutions. Evidence based cut-offs are vital for antimicrobial stewardship, particularly as global antimicrobial resistance rises. The primary objectives of this study were to evaluate the tolerability of a <0.75 × 10⁹ /l ANC cut-off for antimicrobial prophylaxis in dogs after receiving chemotherapy and its impact on antimicrobial prescription. Predicted nadir ANCs (pnANCs) were stratified into six groups (<0.75 × 10⁹ /l [receiving antimicrobial prophylaxis], 0.75-0.99 × 10⁹ /l, 1-1.49 × 10⁹ /l, 1.5-1.99 × 10⁹ /l, 2.0-3.59 × 10⁹ /l and 3.6-12 × 10⁹ /l [reference interval]). The incidences of post-nadir febrile neutropenia (FN) and non-haematological toxicity (NHT) were compared between groups. Five hundred and eighty-six pnANCs were recorded for 181 dogs. There were four episodes of post-nadir FN and 90 episodes of post-nadir NHT. There was no significant difference in incidence of post-nadir FN (P = .063) or post-nadir NHT (P = .084) between pnANC groups. Antimicrobial prophylaxis was prescribed following 8.8% of the chemotherapy administrations; had cut-off values of <1.0 × 10⁹ /l or <1.5 × 10⁹ /l been used it would have been prescribed in 15.3% and 25.8% of cases respectively. An ANC cut-off of <0.75 × 10⁹ /l for antimicrobial prophylaxis appears to be well tolerated and minimizes the prescription of antimicrobials.

Review of oncological emergencies in small animal patients

Oncological emergencies can occur at any time during the course of a malignancy and need to be recognized promptly to maximize successful outcomes. Emergencies are characterized as chemotherapy-induced, paraneoplastic syndromes, or directly related to the neoplasm. Prompt identification with treatment of these emergencies can prolong survival and improve quality of life, even in the setting of terminal illness. This review aims to educate the reader on the pathophysiology, clinical presentation and treatment of some of these emergencies, and to review the current veterinary literature to help educate veterinarians in primary and tertiary facilities to know how to diagnose and treat these serious conditions.

Gene module analysis of juvenile myelomonocytic leukemia and screening of anticancer drugs

Juvenile myelomonocytic leukemia (JMML) is a rare but severe primary hemopoietic system tumor of childhood, most frequent in children 4 years and younger. There are currently no specific anticancer therapies targeting JMML, and the underlying gene expression changes have not been revealed. To define molecular targets and possible biomarkers for early diagnosis, optimal treatment, and prognosis, we conducted microarray data analysis using the Gene Expression Omnibus, and constructed protein‑protein interaction networks of all differentially expressed genes. Modular bioinformatics analysis revealed four core functional modules for JMML. We analyzed the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway functions associated with these modules. Using the CMap database, nine potential anticancer drugs were identified that modulate expression levels of many JMML‑associated genes. In addition, we identified possible miRNAs and transcription factors regulating these differentially expressed genes. This study defines a new research strategy for developing JMML‑targeted chemotherapies.

Antibiotic prophylaxis in veterinary cancer chemotherapy: A review and recommendations

Bacterial infection following cancer chemotherapy-induced neutropenia is a serious cause of morbidity and mortality in human and veterinary patients. Antimicrobial prophylaxis is controversial in the human oncology field, as any decreased incidence in bacterial infections is countered by patient adverse effects and increased antimicrobial resistance. Comprehensive guidelines exist to aid human oncologists in prescribing antimicrobial prophylaxis but similar recommendations are not available in veterinary literature. As the veterinarian's role in antimicrobial stewardship is increasingly emphasized, it is vital that veterinary oncologists implement appropriate antimicrobial use. By considering the available human and veterinary literature we present an overview of current clinical practices and are able to suggest recommendations for prophylactic antimicrobial use in veterinary cancer chemotherapy patients.

Impact of Pretreatment Neutrophil Count on Chemotherapy Administration and Toxicity in Dogs with Lymphoma Treated with CHOP Chemotherapy

BACKGROUND

Prechemotherapy absolute neutrophil count (ANC) cutoffs are arbitrary and vary across institutions and clinicians. Similarly, subjective guidelines are utilized for the administration of prophylactic antibiotics in neutropenic dogs.

OBJECTIVES

To evaluate the impact of various ANC cutoffs on chemotherapy administration in dogs with lymphoma treated with CHOP chemotherapy and to determine whether an association between prechemotherapy ANC and subsequent toxicity exists. The secondary objective was to evaluate a currently used ANC cutoff to indicate prescription of prophylactic antibiotics.

ANIMALS

Dogs diagnosed with lymphoma treated with CHOP chemotherapy (n = 64).

METHODS

Six hundred and fifteen ANCs were stratified into 6 classes. The 3 ANC cutoffs 1.5 × 103 /μL, 2.0 × 103 /μL, and 2.5 × 103 /μL were assessed. The presence of an association between prechemotherapy ANC class and toxicity was determined. Afebrile neutropenic dogs with ANC <1.5 × 103 /μL but above the criteria for prophylactic antibiotics were evaluated.

RESULTS

Chemotherapy was not administered in 7% of visits with an ANC cutoff of 1.5 × 103 /μL; chemotherapy would not have been administered in 10% and 16% of visits with an ANC cutoff of 2.0 × 103 /μL or 2.5 × 103 /μL, respectively. There was no association among the 3 lower prechemotherapy ANC classes and toxicity. All dogs with ANC 0.75-1.5 × 103 /μL recovered spontaneously without medical intervention.

CONCLUSION AND CLINICAL IMPORTANCE

The number of dose delays was minimized with a prechemotherapy ANC cutoff of 1.5 × 103 /μL, and the prechemotherapy ANC class 1.5-1.99 × 103 /μL was not associated with an increased toxicity. Further investigation of an ANC cutoff near 0.75 × 103 /μL in which to prescribe prophylactic antibiotics is indicated.

Prospective study evaluating the incidence of bacteraemia and bacteruria in afebrile and febrile neutropaenic dogs undergoing chemotherapy

The purpose of this prospective study was to determine the incidence and character of bacteraemia and bacteruria in afebrile and febrile neutropaenic dogs undergoing cytotoxic chemotherapy. Fifty‐five neutropaenic dogs presenting to the University of Wisconsin Veterinary Medical Teaching Hospital were enrolled for a total of 57 neutropaenic episodes. The overall incidence of bacteraemia was 12.3% (n = 7/57). Three afebrile dogs and four febrile dogs were bacteraemic; this difference was not significant (P = 0.6968). The overall incidence of bacteruria was 7.5% (n = 4/53). Two afebrile dogs and two febrile dogs were bacteruric; this difference was not significant (P = 1.0). Of the positive blood cultures, the majority of organisms cultured (n = 6/7) were gram‐positive organisms with one gram‐negative organism. Three of the positive blood cultures showed in vitro resistance to more than one antimicrobial agent. Clinical parameters (age, body weight, heart rate, rectal temperature, neutrophil count, haematocrit and platelet count) were not predictive of bacteraemia. The results of this study were not sufficient to justify the use of blood cultures as a first‐line diagnostic test for neutropaenic patients. Blood cultures may have utility in individual case management for a minority of patients in guiding antibiotic choice in the case of resistant bacterial infections. Blood cultures may serve as a tool for antimicrobial de‐escalation, although further study is needed.

Cytotoxic effects of loperamide hydrochloride on canine cancer cells

Loperamide is a peripheral opiate agonist that can cause apoptosis and G2/M arrest in human cancer cell lines and may sensitize cells to chemotherapy. The objectives of this study were to investigate the effects of loperamide on viability, apoptosis and cell cycle kinetics in canine cancer cells and to establish whether the drug sensitizes cells to doxorubicin. Cell viability was assessed using Alamar Blue. Cell death and cell cycle were studied using flow cytometry with 7-Aminoactinomycin-D (7-AAD) and propidium iodide (PI), respectively. Loperamide decreased cell viability in a dose-dependent fashion and was most effective against canine osteosarcoma cells. In all cell lines, it induced a dose and time dependent apoptosis and resulted in accumulation in G0/G1. When co-incubated with doxorubicin, loperamide induced a synergistic cell kill in canine carcinoma cells. Investigation is warranted into the role of loperamide in the treatment of canine cancer.

Oncolytic virotherapy of canine and feline cancer

Cancer is the leading cause of disease-related death in companion animals such as dogs and cats. Despite recent progress in the diagnosis and treatment of advanced canine and feline cancer, overall patient treatment outcome has not been substantially improved. Virotherapy using oncolytic viruses is one promising new strategy for cancer therapy. Oncolytic viruses (OVs) preferentially infect and lyse cancer cells, without causing excessive damage to surrounding healthy tissue, and initiate tumor-specific immunity. The current review describes the use of different oncolytic viruses for cancer therapy and their application to canine and feline cancer.

Assessment of low-dose cisplatin as a model of nausea and emesis in beagle dogs, potential for repeated administration

Cisplatin is a highly emetogenic cancer chemotherapy agent, which is often used to induce nausea and emesis in animal models. The cytotoxic properties of cisplatin also cause adverse events that negatively impact on animal welfare preventing repeated administration of cisplatin. In this study, we assessed whether a low (subclinical) dose of cisplatin could be utilized as a model of nausea and emesis in the dog while decreasing the severity of adverse events to allow repeated administration. The emetic, nausea-like behavior and potential biomarker response to both the clinical dose (70 mg/m²) and low dose (15 mg/m²) of cisplatin was assessed. Plasma creatinine concentrations and granulocyte counts were used to assess adverse effects on the kidneys and bone marrow, respectively. Nausea-like behavior and emesis was induced by both doses of cisplatin, but the latency to onset was greater in the low-dose group. No significant change in plasma creatinine was detected for either dose groups. Granulocytes were significantly reduced compared with baseline (P = 0.000) following the clinical, but not the low-dose cisplatin group. Tolerability of repeated administration was assessed with 4 administrations of an 18 mg/m² dose cisplatin. Plasma creatinine did not change significantly. Cumulative effects on the granulocytes occurred, they were significantly decreased (P = 0.03) from baseline at 3 weeks following cisplatin for the 4th administration only. Our results suggest that subclinical doses (15 and 18 mg/m²) of cisplatin induce nausea-like behavior and emesis but have reduced adverse effects compared with the clinical dose allowing for repeated administration in crossover studies.

Determination of MDR1 gene expression for prediction of chemotherapy tolerance and treatment outcome in dogs with lymphoma

The multidrug resistance gene 1(MDR1) expression levels were analysed in 27 dogs with different types of malignant lymphomas receiving a standard chemotherapy protocol. Blood samples were used for MDR1 real-time PCR expression analysis. Treatment tolerance and outcome were evaluated on a regular basis by clinical examination and client questioning. Dogs developing severe adverse effects under treatment showed significantly lower basal MDR1 gene expression levels when compared with those who tolerated the drugs well. In the longitudinal MDR1 gene expression analysis during treatment, four dogs showed a greater than two-fold MDR1 up-regulation, compared to baseline expression. All four of these dogs, but none of the others, showed disease progression. In conclusion, basal and follow-up MDR1 gene expression levels could be of predictive value for the occurrence of severe adverse drug reactions and/or the development of MDR during chemotherapy for lymphoma in dogs.

Clinical efficacy and safety of a water-soluble micellar paclitaxel (Paccal Vet) in canine mastocytomas

OBJECTIVE

To determine the clinical efficacy and safety of a cremophor-free formulation of paclitaxel (Paccal Vet, Oasmia Pharmaceuticals) in dogs with mast cell tumours.

METHODS

Paccal Vet was administered at a median dose of 145 (range, 135 to 150) mg/m(2) intravenously once every 21 days for three cycles to 29 dogs with macroscopic grade 2 or 3 mast cell tumour. Efficacy was assessed by tumour response (Response Evaluation Criteria in Solid Tumours version 1.0) and performance status score. Progression-free survival, quality of life and safety/adverse events were also evaluated. Clinical safety was assessed by clinicopathological analyses and recording of adverse events.

RESULTS

Complete or partial response was observed in 59% of dogs. Performance status score remained constant or improved for 20 dogs and decreased by one grade for 9 dogs. Median time to progression was 247 (range, 42 to 268) days. Expected, transient frequently subclinical adverse events (primarily grade 3/4 neutropenia and grade 1/2 leukopenia) were observed in the majority of dogs. Nine dogs were euthanased and one dog died due to disease progression.

CLINICAL SIGNIFICANCE

Paccal Vet appears to be a clinically safe and effective treatment for canine mast cell tumours. Further controlled confirmatory investigation is warranted.

A dose-finding study with a novel water-soluble formulation of paclitaxel for the treatment of malignant high-grade solid tumours in dogs

A new formulation of water-soluble paclitaxel (Paccal® Vet) has been developed for canine cancer patients, without the need for pre-medication (traditionally required in non-water-soluble paclitaxel formulations). The objective of the study was to determine a clinically safe and efficacious dose of Paccal Vet and to estimate progression-free and overall survival and to evaluate single-dose pharmacokinetics in tumour-bearing dogs. A positive risk:benefit ratio was established for Paccal Vet administered at 150 mg m(-2) intravenous (IV) for three or more treatment cycles. Preliminary efficacy was demonstrated by best objective response rate (86%), median time to response (14 days) and median progression-free survival (131 days). Paccal Vet was associated with expected adverse events (AE) (e.g. myelosuppression), however the majority were transient, clinically silent and manageable. This is the first clinical report of a water-soluble formulation of paclitaxel suggesting successful administration and being safely used without pre-medication in dogs.