Tumor Grade and Mitotic Count Are Prognostic for Dogs with Cutaneous Mast Cell Tumors Treated with Surgery and Adjuvant or Neoadjuvant Vinblastine Chemotherapy

OBJECTIVE

Canine cutaneous mast cell tumors (cMCTs) have variable rates of recurrence and metastasis. We evaluated how various prognostic factors affect survival, recurrence, and metastasis in dogs with cMCT who underwent surgery and vinblastine chemotherapy.

ANIMALS

90 dogs with cMCT treated with surgery and vinblastine at a veterinary referral institution were included.

METHODS

Medical records were retrospectively reviewed. Prognostic factors were evaluated.

RESULTS

Most dogs (94%) had grade 2 or 3 cMCTs. Neoadjuvant vinblastine was used in 18 dogs, and none progressed locally before surgery. The use of neoadjuvant vinblastine was associated with a higher chance of local recurrence (p = 0.03) but not survival. Shorter survival times were found for tumors that were high-grade (p < 0.001), grade 3 (p < 0.001), or a MC of >5 (p < 0.001). Dogs with grade 2 tumors that were low-grade lived longer than those with high-grade tumors (p < 0.001). Histologic tumor-free margins and the ability to achieve local tumor control were not associated with outcome.

CLINICAL RELEVANCE

Both grading systems and MC were prognostic for survival in this population of dogs, supporting the need for the standard reporting of histopathologic findings. Neoadjuvant chemotherapy can be effective in downsizing cMCTs but does not influence survival. These findings are consistent with previous publications, showing the benefits of a more modern population of patients, surgical treatments, and histopathologic assessments.

High-Grade, Stage 2 Mast Cell Tumors: Outcome in Dogs With Local and Systemic Therapy

Canine mast cell tumors (MCTs) have highly variable clinical behavior, and predicting outcomes in individual dogs remains challenging. Many studies combine dogs with varying tumor grades, clinical stage, or treatments, confounding those results. The purpose of this retrospective study was to determine outcome and prognostic factors in a specific subset of dogs with high-grade, stage 2, cutaneous MCTs treated with adequate local control via surgery with or without radiation therapy and adjuvant cytotoxic chemotherapy. Seventeen dogs met the inclusion criteria, and the median survival time was 259 days. Development of local recurrence, tumor location, and presence of ulceration were all associated with shorter survival times. Tumor size, mitotic count, chemotherapy protocol, lymph node classification, and radiation therapy were not significantly associated with outcome. In this study, a specific population of dogs characterized by high-grade MCTs with local lymph node metastasis who received aggressive local and systemic therapy had a median survival of about 8.5 mo. Dogs with ulcerated tumors, recurrent tumors, or tumors located on the head had a worse outcome despite aggressive therapy. These results may serve as a basis of comparison for future research exploring alternative treatment combinations in this specific population of dogs.

Tyrosine kinase inhibitors as an alternative treatment in canine mast cell tumor

The current gold standard treatment for canine mast cell tumors (MCT) uses vinblastine sulfate (VBL) as chemotherapy, although tyrosine kinase inhibitors (TKI) have recently been shown to be worthy candidates for treatment. This systematic review aimed to analyze the overall survival (OS), progression-free survival (PFS), overall response rate (ORR), and complete (CR) or partial response (PR) in dogs with MCT treated with TKI compared to standard VBL treatment. The systematic review was registered in the Open Science Framework (OSF) database under the identifier 10.17605/OSF.IO/WYPN4 (https://osf.io/). An electronic search was performed in nine databases. References from eligible studies were also selected to find more registers. A total of 28 studies met the eligibility criteria, and one more was recovered from the references of eligible studies, totaling 29 selected studies. The overall response rate, complete response, and partial response were higher in dogs treated with tyrosine kinase inhibitors than in dogs treated with vinblastine. The overall survival and progression-free survival of vinblastine-treated dogs were higher compared to tyrosine kinase inhibitors-treated dogs. Dogs with mutated KIT treated with tyrosine kinase inhibitors have longer overall survival and progression-free survival compared to those treated with vinblastine. It is important to consider the limitation of the study which should temper the interpretation of the results, videlicet, the extracted data lacked sample standardization and included variables such as animal characteristics, mutation detection methods, tumor characteristics, and treatment types which may have influenced the outcome of the study.

Systematic review registration

https://osf.io/, identifier: 10.17605/OSF.IO/WYPN4.

Evaluation of Tumor Grade and Proliferation Indices before and after Short-Course Anti-Inflammatory Prednisone Therapy in Canine Cutaneous Mast Cell Tumors: A Pilot Study

Glucocorticoid administration is a common clinical practice that attempts to decrease the inflammation associated with and improve the resectability of canine mast cell tumors (MCTs). However, the impact of neoadjuvant glucocorticoids on the histological features and proliferation indices of canine MCTs is unknown. The objective of this study was to evaluate changes in tumor grade, mitotic count, Ki67, AgNOR, and AgNORxKi67 scores following short-course anti-inflammatory neoadjuvant prednisone in canine patients with MCTs. This was a prospective single-arm pilot study. Client-owned dogs with treatment-naïve cytologically confirmed MCTs were enrolled. Patients underwent an initial incisional biopsy followed by a 10–14-day course of anti-inflammatory prednisone and surgical resection. All histological samples were randomized, masked, and evaluated by a single pathologist. Unstained paired pre- and post-treatment samples were submitted to a commercial laboratory for Ki67 and AgNOR immunohistochemical analysis. There were 11 dogs enrolled with 11 tumors. There were no statistical differences between the pre- and post-treatment histological parameters of mitotic index, Ki67, AgNOR, or Ki67xAgNOR. There were no clinically significant alterations between pre-treatment and post-treatment in the assignment of tumor grades. A short course of anti-inflammatory prednisone does not appear to alter the histological parameters that affect grade determination or significantly alter the proliferation indices in canine MCTs.

Diagnosis, Prognosis and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors

Mast cell tumors (MCTs) are hematopoietic neoplasms composed of mast cells. It is highly common in dogs and is extremely important in the veterinary oncology field. It represents the third most common tumor subtype, and is the most common malignant skin tumor in dogs, corresponding to 11% of skin cancer cases. The objective of this critical review was to present the report of the 2nd Consensus meeting on the Diagnosis, Prognosis, and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors, which was organized by the Brazilian Association of Veterinary Oncology (ABROVET) in August 2021. The most recent information on cutaneous and subcutaneous mast cell tumors in dogs is presented and discussed.

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.

Canine cutaneous and subcutaneous mast cell tumours: a review

Cutaneous and subcutaneous mast cell tumours are common neoplasms in the dog. While the majority can be treated with adequate local therapy alone, a subset demonstrates a biologically aggressive behaviour associated with local recurrence or metastasis. This article reviews the diagnosis and tumour staging of canine mast cell tumours alongside treatment options and the evidence supporting their use. In addition, prognostic markers are evaluated to highlight how one can recognise mast cell tumours that may behave in a biologically aggressive manner as well as the challenges of tumours that are large, infiltrative or in locations not amenable to wide surgical excision.

Outcome of dogs with intermediate grade low mitotic index high Ki67 mast cell tumours treated with surgery and single agent lomustine

OBJECTIVES

The objective of this retrospective study was to evaluate the outcome of dogs when grade II mast cell tumour (MCT) with low mitotic index (MI) and high Ki67 were treated with adjuvant lomustine.

ANIMALS

Client owned dogs with spontaneously occurring disease treated with adjuvant chemotherapy for grade II mast cell tumour with low MI (≤5/10HPF) and high Ki67 (>1.8%) with no evidence of metastatic disease at presentation.

PROCEDURES

Lomustine was administered every 3 weeks with three or four planned cycles. Response to treatment was assessed by regular re-staging ultrasound with or without cytopathological examination of liver and spleen or through medical records from the referring veterinarian. Disease-free interval (DFI) and median survival time (MST) were calculated using Kaplan-Meier method.

RESULTS

Twenty-one dogs were included. All dogs underwent surgical excision and two dogs received adjuvant radiotherapy. None of the patients developed local recurrence. Three dogs (14.3%) developed metastatic disease. The DFI of these dogs was 141, 186 and 223 days. Median follow-up period of the whole study population was 1112 days (358-2619). MST for patients with metastatic disease was 417 days. MST of the whole group was not reached. One-year and 2-year survivals were 95.2% and 90.5%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

This study population had low rates of tumour recurrence and improved survival compared to previously published data of similar population of dogs with low MI/high Ki67 MCT without adjuvant chemotherapy.

Canine and Feline Cutaneous Mast Cell Tumor: A Comprehensive Review of Treatments and Outcomes

Mast cell tumor (MCT) or mastocytoma is one of the most frequent malignant cutaneous tumors in the dog, and the second most frequent in the cat. Several mast cell tumor therapeutic approaches have been proposed in the past years for dogs and cats, resulting in very distinct outcomes. The current comprehensive literature review presents a critical approach to the scientific information published about the MCTs treatments and the subsequent prognosis and survival times, in dogs and in cats diagnosed with MCTs. A systematic review of the literature following the Cochrane principles and methodology was performed. The authors resorted to MEDLINE, Scopus, Google Scholar and Web of Science databases to select the 133 publications with evidence-based treatments for MCTs in companion animals. Results of the review suggest that the recommended treatment, prognosis and survival times for dogs and cats with MCTs depends at all times on the clinical staging, histological grade and location of the tumor.

Epidemiology of Breed-Related Mast Cell Tumour Occurrence and Prognostic Significance of Clinical Features in a Defined Population of Dogs in West-Central Italy

Canine mast cell tumours (MCTs) present a wide variety of challenging clinical behaviours in terms of predicting the prognosis and choosing appropriate treatment. This study investigated the frequency, risk, and prognostic factors of MCTs in dogs admitted to a single veterinary teaching hospital (VTH). Breed, age, sex, and sexual status in ninety-eight dogs with MCTs (MCT-group) were compared with a control group of 13,077 dogs (VTH-group) obtained from the VTH clinical database from January 2010 to January 2016. Within the MCT-group, signalment, location, size, mass number, ulceration, histopathological grading, presence of lymph node, or distant metastases were compared with each other and with the outcome. Boxers (OR 7.2), American Pit Bull Terriers (OR 5.4), French Bulldogs (OR 4.4) and Labrador Retrievers (OR 2.6) were overrepresented. The MCT-group was significantly older than the VTH-group (p < 0.0001). In comparison with the VTH group, in the MCT-group neutered dogs (OR 2.1) and spayed females (OR 2.3) were predominant compared to intact dogs and intact females, respectively. Ulceration (OR 5.2) and lymph node metastasis (OR 7.1) occurred more frequently in larger MCTs. Both ulceration and MCTs > 3 cm were highly associated with lymph node metastasis (OR 24.8). Recurrence was associated with MCT-related death (OR 10.50, p = 0.0040), and the latter was associated with shorter survival times (p = 0.0115). Dogs with MCTs > 3 cm (p = 0.0040), lymph node metastasis (p = 0.0234), or elevated WHO stage (p = 0.0158) had shorter survival times. A significantly higher frequency of MCTs was found in specific breeds, and in older and neutered dogs. MCTs > 3 cm and lymph node or distant metastases were associated with shorter survival times.

Comparative oncology: The paradigmatic example of canine and human mast cell neoplasms

In humans, advanced mast cell (MC) neoplasms are rare malignancies with a poor prognosis. Only a few preclinical models are available, and current treatment options are limited. In dogs, MC neoplasms are the most frequent malignant skin tumours. Unlike low‐grade MC neoplasms, high‐grade MC disorders usually have a poor prognosis with short survival. In both species, neoplastic MCs display activating KIT mutations, which are considered to contribute to disease evolution. Therefore, tyrosine kinase inhibitors against KIT have been developed. Unfortunately, clinical responses are unpredictable and often transient, which remains a clinical challenge in both species. Therefore, current efforts focus on the development of new improved treatment strategies. The field of comparative oncology may assist in these efforts and accelerate human and canine research regarding diagnosis, prognostication, and novel therapies. In this article, we review the current status of comparative oncology approaches and perspectives in the field of MC neoplasms.

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.

Oncolytic Sendai Virus Therapy of Canine Mast Cell Tumors (A Pilot Study)

Background: Canine mastocytomas (mast cell tumors) represent a common malignancy among many dog breeds. A typical treatment strategy for canine mastocytomas includes surgery, chemo- and radio-therapy, although in many cases the therapy fails and the disease progression resumes. New treatment approaches are needed. Aims: The goal of this pilot study was to examine safety and efficacy of oncolytic Sendai virus therapy administered to canine patients with cutaneous or subcutaneous mastocytomas. Materials and Methods: Six canine patients, with variable grades and stages of the disease, received virus therapy, either as a monotherapy, or in combination with surgery. The therapy included two or more virus applications administered weekly or biweekly. Each application of Sendai virus (107-108.6 EID50) consisted of multiple individual 0.01-0.1 ml injections delivered intratumorally, intradermally around a tumor, and under a tumor bed. Results: The treatment was well tolerated, with minor transitory side effects. Of the six dogs, two did not receive surgery or any other treatment besides the virus injections. The other four animals underwent radical or debulking surgeries, and in three of them the subsequent administration of Sendai virus completely cleared locally recurrent or/and remaining tumor masses. Five dogs demonstrated a complete response to the treatment, the animals remained disease free during the time of observation (2-3 years). One dog responded only partially to the virotherapy; its after-surgical recurrent tumor and some, but not all, metastases were cleared. This dog had the most advanced stage of the disease with multiple enlarged lymph nodes and cutaneous metastases. Conclusion: The results of the pilot study suggest that Sendai virus injections could be safe and efficient for the treatment of dogs affected by mastocytomas.They also suggest the need of further studies for finding optimal schemes and schedules for this kind of therapy.

Combination vinblastine, prednisolone and toceranib phosphate for treatment of grade II and III mast cell tumours in dogs

This retrospective study evaluates the progression-free interval and survival outcomes of 40 canine (Canis familiaris) patients with Patnaik grade II and III mast cell tumours treated with combination vinblastine, prednisolone and toceranib phosphate from 2011 to 2015. Patients were subdivided into three groups; patients who received neoadjuvant therapy for poorly operable lesions, patients who received adjuvant therapy following surgical resection and patients being palliated for gross metastatic disease. Median survival time (MST) for the neoadjuvant group was not reached. Median survival time for the remaining groups was 893 days and 218 days, respectively. This combination demonstrated response in 90% (26/29) patients with measurable disease. The predominant side effects related to this chemotherapy combination were gastrointestinal in origin. Further prospective studies are required to further validate the efficacy of this treatment protocol.

Pulse-Administered Toceranib Phosphate Plus Lomustine for Treatment of Unresectable Mast Cell Tumors in Dogs

BACKGROUND

Nonresectable mast cell tumors (MCT) in dogs remain a therapeutic challenge, and investigation of novel combination therapies is warranted. Intermittent administration of tyrosine kinase inhibitors (TKI) combined with cytotoxic chemotherapy may effectively chemosensitize canine MCT while decreasing cost and adverse effects associated with either agent administered as monotherapy.

HYPOTHESIS/OBJECTIVES

The primary study objectives were to (1) identify the maximally tolerated dose (MTD), (2) determine the objective response rate (ORR) and (3) describe the adverse event profile of pulse-administered toceranib phosphate (TOC) combined with lomustine.

ANIMALS

Forty-seven client-owned dogs with measurable MCT.

METHODS

Toceranib phosphate was given PO on days 1, 3 and 5 of a 21-day cycle at a target dosage of 2.75 mg/kg. Lomustine was given PO on day 3 of each cycle at a starting dosage of 50 mg/m(2) . All dogs were concurrently treated with diphenhydramine, omeprazole, and prednisone.

RESULTS

The MTD of lomustine was established at 50 mg/m(2) when combined with pulse-administered TOC; the dose-limiting toxicity was neutropenia. Forty-one dogs treated at the MTD were evaluable for outcome assessment. The ORR was 46% (4 complete response, 15 partial response) and the overall median progression-free survival (PFS) was 53 days (1 to >752 days). On multivariate analysis, variables significantly associated with improved PFS included response to treatment, absence of metastasis, and no previous chemotherapy.

CONCLUSIONS AND CLINICAL IMPORTANCE

Combined treatment with pulse-administered TOC and lomustine generally is well tolerated and may be a reasonable treatment option for dogs with unresectable or metastatic MCT.

Canine mast cell tumors: diagnosis, treatment, and prognosis

Mast cell tumors (MCTs) are the most common malignant skin cancer in dogs, and significant variability exists in their biological behavior. Most MCTs are cured with appropriate local therapy, but a subset shows malignant behavior with the potential to spread to lymph nodes, liver, spleen, and other areas and to thus become a systemic cancer. Because of this variable behavior, it is difficult to predict how any individual tumor is going to behave. The variability thus creates uncertainty in deciding what a particular dog’s prognosis is, whether staging tests to assess for metastasis are needed, and even what treatments will be necessary for best outcome. In addition to controversies over the potential for development of systemic disease, or diffuse metastasis, controversies also exist over what treatment is needed to best attain local control of these tumors. This article will briefly discuss the diagnosis of MCTs in dogs and will summarize the literature in regards to the controversial topics surrounding the more aggressive form of this disease, with recommendations made based on published studies.

Tolerability of Lomustine in Combination with Cyclophosphamide in Dogs with Lymphoma

This retrospective study describes toxicity associated with a protocol of lomustine (CCNU) and cyclophosphamide (CTX) in dogs with lymphoma. CCNU was administered per os (PO) at a targeted dosage of 60 mg/m2 body surface area on day 0, CTX was administered PO at a targeted dosage of 250 mg/m2 divided over days 0 through 4, and all dogs received prophylactic antibiotics. Ninety treatments were given to the 57 dogs included in the study. Neutropenia was the principal toxic effect, and the overall frequency of grade 4 neutropenia after the first treatment of CCNU/CTX was 30% (95% confidence interval, 19–43%). The mean body weight of dogs with grade 4 neutropenia (19.7 kg ± 13.4 kg) was significantly less than the mean body weight of dogs that did not develop grade 4 neutropenia (31.7 kg ± 12.4 kg; P = .005). One dog (3%) developed hematologic changes suggestive of hepatotoxicity. No dogs had evidence of either renal toxicity or hemorrhagic cystitis. Adverse gastrointestinal effects were uncommon. On the basis of the findings reported herein, a dose of 60 mg/m2 of CCNU combined with 250 mg/m2 of CTX (divided over 5 days) q 4 wk is tolerable in tumor-bearing dogs.

The radiosensitizing effect of the aurora kinase inhibitors, ENMD-2076, on canine mast cell tumours in vitro

ENMD-2076 is an aurora kinase inhibitor that also has multi-target tyrosine kinase inhibitor properties. In this study, the mRNA and the protein expression of aurora-A and aurora-B were evaluated in three canine mast cell tumour cell lines. Dose-dependent cytotoxicity was seen in the cells treated, and it affected the cell cycle with cells in the G2/M phase being selectively killed. The cells were also evaluated for radiosensitivity with/without ENMD-2076, and radiosensitization was seen after 3 Gy and 6 Gy exposures with ENMD-2076 for 48 h. Protein expression of caspase-3 was gradually increased, and the expression intensity was highest at 24 h post irradiation in cells without ENMD-2076 treatment, which indicates that radiation exposure with ENMD-2076-induced cell death faster than radiation treatment alone. Our study results suggest the potential usefulness of treating canine mast cell tumours with aurora kinase inhibitors alone or in conjunction with radiation therapy.

Aggressive local therapy combined with systemic chemotherapy provides long-term control in grade II stage 2 canine mast cell tumour: 21 cases (1999-2012)

This retrospective case series evaluates the outcome of 21 dogs with grade II stage 2 mast cell tumour (MCT) treated with adequate local therapy and adjuvant systemic chemotherapy (prednisone, vinblastine and CCNU). The median survival for all dogs was 1359 days (range, 188-2340). Median disease-free interval was 2120 days (149-2325 days). Dogs treated with surgery and chemotherapy had shorter survival (median, 1103 days; 188-2010 days) than those that underwent surgery, radiation therapy and chemotherapy as part of their treatment (median, 2056 days; 300-2340 days). Two patients had local recurrence in the radiation field and four patients had de novo MCT. Distant metastasis was not observed in any dogs. The results of this study suggest that, in the presence of loco-regional lymph node metastasis in grade II MCT, the use of prednisone, vinblastine and CCNU after adequate local-regional therapy can provide a median survival in excess of 40 months.

Low apparent risk of CCNU (lomustine)-associated clinical hepatotoxicity in cats

The purpose of this study was to evaluate the prevalence of serum alanine transaminase (ALT) increases in cats treated with 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU, lomustine). The medical records of 95 cats treated with CCNU were reviewed, 29 of which met study criteria (at least one treatment with CCNU as a single agent, and at least one pretreatment and one post-treatment complete biochemical profile). Cats that received concurrent prednisone or dexamethasone were included, but those that received concurrent hepatoprotective or hepatotoxic medications were excluded. Cats included in the study were diagnosed with hepatic carcinoma, mammary carcinoma, lymphoma, mast cell tumor, plasma cell tumor and gastrointestinal leiomyoma. CCNU was given as a single agent at 31-60 mg/m(2), once every 4-8 weeks. Serum alanine transaminase (ALT) activity was measured after at least one dose of CCNU. Four cats (13.7%) had increased ALT activity above the reference interval before starting treatment. Two additional cats (6.8%) developed increased ALT activity above the reference interval 1 month after treatment with CCNU. One cat developed clinical signs potentially associated with hepatotoxicity, without a concurrent increase in ALT, 3 weeks following the final dose of CCNU. No association between dosing frequency, cumulative dose, initial starting dose or concurrent medications, and increases in ALT were found. Clinically significant hepatic injury is seemingly uncommon in cats treated with CCNU.

A randomized trial investigating the efficacy and safety of water soluble micellar paclitaxel (Paccal Vet) for treatment of nonresectable grade 2 or 3 mast cell tumors in dogs

BACKGROUND

Effective treatments for dogs with advanced stage mast cell tumors (MCT) remain a pressing need. A micellar formulation of paclitaxel (paclitaxel [micellar]) has shown promise in early-phase studies.

HYPOTHESIS/OBJECTIVES

The objective was to demonstrate greater activity for paclitaxel (micellar) compared with lomustine. The null hypothesis was μ(p) = μ(L) (ie, proportion of responders for the paclitaxel [micellar] and lomustine groups, respectively).

ANIMALS

Two hundred and fifty-two dogs with advanced stage nonresectable grade 2 or 3 MCT.

METHODS

Prospective multicenter randomized double-blind positive-controlled clinical trial. The primary endpoint was confirmed overall response rate (CORR) at 14 weeks. A secondary endpoint, biologic observed response rate (BORR), also was calculated. Safety was assessed by the characterization and grading of adverse events (AE).

RESULTS

Overall CORR (7% versus 1%; P = .048) and BORR (23% versus 10%; P = .012) were greater for paclitaxel (micellar) compared with lomustine. Paclitaxel (micellar)-treated dogs were 6.5 times more likely to have a confirmed response and 3.1 times more likely to experience a biologic observed response. The majority of AE with paclitaxel (micellar) were transient and clinically manageable. Twenty-seven dogs (33%) receiving lomustine were discontinued because of hepatopathy compared with 3 dogs (2%) receiving paclitaxel (micellar) (P < .0001; odds ratio 26.7).

CONCLUSIONS AND CLINICAL IMPORTANCE

Paclitaxel (micellar)'s activity and safety profile are superior to lomustine. The addition of an active and novel taxane to the veterinary armamentarium could fill a substantial need and, as its mechanism of action and AE profile do not overlap with currently available TKI, its availability could lead to effective combination protocols.

Phase II clinical evaluation of lomustine chemotherapy for feline vaccine-associated sarcoma

Treatment of feline vaccine-associated sarcoma (VAS) is challenging, in part due to the high likelihood of tumour recurrence despite aggressive local therapy. Lomustine is potentially an attractive agent to add to the current treatment armamentarium. In this de-escalating phase I/II prospective trial, 28 cats with measurable VAS were treated at target dosages of 38-60 mg m(-2) every 3 weeks until disease progression. The overall response rate was 25%, with a median progression-free survival and median duration of response of 60.5 and 82.5 days, respectively. Haematologic toxicity, specifically cumulative neutropenia, was significant, and dose reductions and treatment delays were common. Although these data support further investigation of lomustine for the treatment of VAS, safe, multidosing protocols must first be determined.