Metronomic Chemotherapy in Veterinary Patients with Cancer

Metronomic chemotherapy: bridging theory to clinical application in canine and feline oncology

Veterinary oncology has experienced significant evolution over the last few decades, with chemotherapy being currently applied to several neoplasms with therapeutic success. Traditionally, chemotherapy protocols are based on classic cytostatic drugs under the concept of maximum tolerated dose (MTD), which has been associated with a greater risk of toxicity and resistance. Thus, new therapeutic alternatives have emerged, such as metronomic chemotherapy (MC), introducing a new paradigm in cancer treatment. MC consists of administering low doses of chemotherapy drugs continuously over a long period of time, modulating the tumour microenvironment (TME) due to the combination of cytotoxic, antiangiogenic and immunomodulatory effects. This multi-targeted therapy has been described as a treatment option in several canine and feline cancers since 2007, with positive results already published in the literature, particularly in mammary carcinomas and soft tissue sarcomas in dogs. The aim of this review article is to describe the current knowledge about the use of MC in small animal oncology, with emphasis on its mechanisms of action, the most commonly used drugs and clinical outcome.

A pilot study of chemotherapy combinations in rats: Focus on mammary cancer treatment in female dogs

The use of combined chemotherapy is an essential alternative in treating breast cancer. However, knowledge of the pharmacokinetics of drugs is necessary to obtain maximum efficiency of the protocol and reduce adverse reactions. This study suggests for the first time the effect of the association of carboplatin with ivermectin and carboplatin with cyclophosphamide. This investigation was performed with 36 healthy Wistar rats, divided into four groups: group control, carboplatin (C), carboplatin preceded by ivermectin (C + IV), and carboplatin associated with cyclophosphamide (C + CI). Plasma concentrations quantification was performed using the High-Performance Liquid Chromatographic (HPLC) equipment with an Ultraviolet (UV) detector at eight different time points. Then, the animal was euthanized and necropsied. The bioanalytical method was validated for the two matrices (dogs and rats' plasma), with full validation in female dogs and partial validation in rats, as recommended by the EMA. In both matrices, the method was linear and reproducible. Here, we show the results in female rats' plasma. When comparing the experimental rats' groups (C; C + IV, and C + CI), there is a tendency to increase the bioavailability of carboplatin when used in association, a slight increase for C + IV and more evident to the C + CI group with an AUC rise higher than 2-fold (AUC0-∞ = 2983.61 for C; 4459.06 for C + CI; 7064.68 for C + CI min·mg·mL-1). The blood count, biochemistry profile, and histopathology of the organs revealed only alterations inherent to the metabolic effects of the drugs used. The carboplatin association with ivermectin appeared safe for this pilot group. We believe the carboplatin dose can be maintained without risk to the patient. However, in the carboplatin association with cyclophosphamide, a slight reduction in carboplatin's amount is suggested, seeking to avoid increased effects due to cyclophosphamide. Thus, studies with a more significant number per group must confirm the relevance of this pilot study.

Pharmacokinetics of Carboplatin in Combination with Low-Dose Cyclophosphamide in Female Dogs with Mammary Carcinoma

This prospective study aimed to evaluate the effect of metronomic cyclophosphamide on carboplatin’s tolerability, efficacy, and pharmacokinetics in dogs with mammary carcinoma. Sixteen female dogs with mammary carcinoma were divided into groups: 300 mg/m2 intravenous (i.v.) carboplatin therapy (G1 = 8) or 300 mg/m2 i.v. carboplatin which was associated with 12.5 mg/m2 oral cyclophosphamide in a metronomic regimen (G2 = 8). The investigated animals underwent a clinical evaluation, a mastectomy, a carboplatin chemotherapy, and serial blood sampling for the pharmacokinetic analysis. The adverse events and survival rates were monitored. A non-compartmental analysis was applied to calculate the pharmacokinetic parameters of carboplatin in the 2nd and 4th chemotherapy cycles. Carboplatin PK showed high interindividual variability with a 10-fold variation in the area under the plasma concentration−time curve (AUC) in G1. The systemic plasma exposure to carboplatin was equivalent in both of the treatments considering the AUC and maximum plasma concentration (Cmax) values. Although the red blood cells (p < 0.0001), platelets (p = 0.0005), total leukocytes (p = 0.0002), and segmented neutrophils (p = 0.0007) were reduced in G2, the survival rate increased (p = 0.0044) when it was compared to G1. In conclusion, adding low daily doses of cyclophosphamide to a carboplatin therapy showed promising outcomes in female dogs with mammary tumors.

Application of Biocompatible Drug Delivery Nanosystems for the Treatment of Naturally Occurring Cancer in Dogs

Background: Cancer is a common disease in dogs, with a growing incidence related to the age of the animal. Nanotechnology is being employed in the veterinary field in the same manner as in human therapy. Aim: This review focuses on the application of biocompatible nanocarriers for the treatment of canine cancer, paying attention to the experimental studies performed on dogs with spontaneously occurring cancer. Methods: The most important experimental investigations based on the use of lipid and non-lipid nanosystems proposed for the treatment of canine cancer, such as liposomes and polymeric nanoparticles containing doxorubicin, paclitaxel and cisplatin, are described and their in vivo fate and antitumor features discussed. Conclusions: Dogs affected by spontaneous cancers are useful models for evaluating the efficacy of drug delivery systems containing antitumor compounds.

Tolerability and outcome of palliative treatment for metastatic pulmonary carcinoma in cats

OBJECTIVES

Pulmonary carcinoma is uncommon in cats and reporting of outcomes following medical treatment is limited, especially in presence of metastases. The aim of this study was to describe the outcome of cats affected by metastatic primary pulmonary carcinoma and to evaluate the tolerability of palliative treatment in this patient population.

MATERIALS AND METHODS

Medical records were searched for cats with a cytological or histopathological diagnosis of primary pulmonary carcinoma and evidence of metastatic disease. Cats were treated with antineoplastic agents, corticosteroids, non-steroidal anti-inflammatory drugs (NSAIDs) or received no systemic treatment. Cases in which thoracic CT was not performed, and those lacking definitive diagnosis by cytology or histopathology or receiving curative-intent surgery were excluded.

RESULTS

Thirty-four cats were identified: 18 were treated with antineoplastic agents and 16 received corticosteroids, NSAIDs or no treatment. Presenting clinical signs included coughing (53%), tachypnoea (26%), gastrointestinal signs (35%) and lethargy (18%). CT scan identified metastases to the lung parenchyma in all cases and additional metastatic lesions in 10 of 34 (59%) cases; pleural effusion was detected in 11 cases (32%). The overall median survival time for all cats was 64 days [range 1-1352 days; 95% confidence interval (CI) 48-164]. Presence of respiratory signs at presentation was the only factor influencing survival in the multivariable analysis.

CLINICAL SIGNIFICANCE

Medical treatment was well tolerated and appeared to palliate clinical signs in cats with metastatic pulmonary carcinoma, albeit with a modest duration and short overall survival. The role and benefit of chemotherapy/antineoplastic agents versus conventional palliative drugs in this setting remains unclear.

Challenges of stem cell therapies in companion animal practice

Regenerative medicine using stem cells from various sources are emerging treatment modality in several refractory diseases in veterinary medicine. It is well-known that stem cells can differentiate into specific cell types, self-renew, and regenerate. In addition, the unique immunomodulatory effects of stem cells have made stem cell transplantation a promising option for treating a wide range of disease and injuries. Recently, the medical demands for companion animals have been rapidly increasing, and certain disease conditions require alternative treatment options. In this review, we focused on stem cell application research in companion animals including experimental models, case reports and clinical trials in dogs and cats. The clinical studies and therapeutic protocols were categorized, evaluated and summarized according to the organ systems involved. The results indicate that evidence for the effectiveness of cell-based treatment in specific diseases or organ systems is not yet conclusive. Nonetheless, stem cell therapy may be a realistic treatment option in the near future, therefore, considerable efforts are needed to find optimized cell sources, cell numbers and delivery methods in order to standardize treatment methods and evaluation processes.

Early caregiver burden in owners of pets with suspected cancer: Owner psychosocial outcomes, communication behavior, and treatment factors

BACKGROUND

Owners of companion animals with serious illnesses are likely to experience "caregiver burden." This topic has not been fully evaluated in veterinary oncology.

OBJECTIVES

To examine owners of a dog or cat with suspected cancer for relationships between early caregiver burden and (a) psychosocial factors: depression, stress, and quality of life; (b) owner communication behavior; and (c) specific pet treatment plan factors.

ANIMALS

None.

METHODS

This cross-sectional, observational study recruited 164 owners of a cat or dog presenting for evaluation by a veterinary oncology service at a single referral institution. Measures of caregiver burden, psychosocial function, treatment plan elements, and demographics were collected online via owner self-report. Medical records were reviewed to identify factors including diagnosis, medications, treatment schedules, and owner communications.

RESULTS

Caregiver burden correlated with higher stress (r_s = 0.40, P < .001), greater symptoms of depression (r_s = 0.50, P < .001), and lower quality of life (r_s = 0.39, P < .001). Pet treatment plan factors related to caregiver burden included changes in care routines, perception that compliance with new routines was challenging, and difficulty adhering to medication routines. There was low correlation between caregiver burden and owner-driven communications (r_s = 0.15, P = .07).

CONCLUSIONS AND CLINICAL IMPORTANCE

Findings suggest caregiver burden is similar in owners of pets with cancer and owners of pets with other diseases. Caregiver burden is present in the earliest stages of disease. Major correlates of burden including life-disruptive treatments and schedules provide key areas for potential intervention by veterinary teams.

Toxicity of a methotrexate metronomic schedule in Wistar rats

Metronomic chemotherapy is a relevant strategy that uses low doses of antineoplastic drugs for sustained periods to control tumor growth, an alternative frequently utilized in veterinary patients. This work aimed to evaluate the toxic effects of a metronomic oral dose of methotrexate (MTX) for 45 days in tumor-free Wistar rats when compared with control animals. Clinical alterations, body weight, food, and water intake were monitored daily, and bone marrow suppression, hematological, biochemical, and histopathological analyses were performed at three points (days 30, 45, and 60). MTX-treated animals did not demonstrate severe systemic involvement. At 30 days, compared with control animals, MTX-treated animals showed significant leukocytosis (11.9 ± 2.3 vs. 7.8 ± 0.2 10⁶/μL; P < .05) and augmentation of immature myeloid populations from bone marrow (9.0 ± 0.8 vs. 6.5 ± 1.5%; P < .05), and at 60 days, treated animals showed significant neutrophilia (35.0 ± 11.0 vs. 23.00 ± 3.0%; P < .05), depletion of bone marrow lymphocytes (8.2 ± 0.7 vs. 11.5 ± 1.9%; P < .05), and immature myeloid populations (7.2 ± 0.7 vs. 8.3 ± 0.6%; P < .05). At a histopathological level, splenic hypoplasia and respiratory inflammatory lesions were significant when compared with control animals, presenting mild to moderate myelotoxicity, immune suppression, and associated clinical compromise that persisted beyond treatment withdrawal. This suggested that MTX metronomic toxicity should not be neglected owing to the observed residual side-effects and special care should be taken regarding myelosuppression.

Branch pulmonary artery stent placement in a dog with heart base neoplasia

A 7-year-old French bulldog was presented for evaluation of cardiac neoplasia. Two-dimensional transthoracic echocardiography revealed a mass on the base of the heart, compressing the right pulmonary artery. Computed tomography exam confirmed that a surgical approach to remove the mass would not be viable. Stent placement in the right pulmonary artery was performed to relieve external compression caused by the neoplasia. When surgery is not feasible, pulmonary artery stenting could be one aspect of a multidisciplinary approach to palliative management of heart base neoplasia.

Metastatic Cardiac Hemangiosarcoma in a 6 Year Old Wheaten Terrier Mix

A 6 year old Wheaten Terrier mix with a history of collapse and lethargy was referred for evaluation of pericardial effusion. The echocardiogram identified pericardial effusion and a right auricular mass. No sign of metastasis was noted at this time in thoracic radiographs and abdominal ultrasounds. The patient underwent the right auriculectomy via right lateral thoracotomy. Several metastatic masses were located in the visceral aspect of the pericardium at the time of surgery and were all excised. The right auricular mass and pericardial masses were diagnosed as hemangiosarcoma with a sign of metastasis. The patient recovered from surgery uneventfully and was discharged the sixth day after surgery. The patient received doxorubicin followed by cyclophosphamide, piroxicam and Coriolus versicolor extract postoperatively. Pulmonary metastases were noted 229 days and the dog was euthanized 318 days after surgery. No clinical signs were noted until 309 days postoperatively.

Polyester Nanoparticle Encapsulation Mitigates Paclitaxel-Induced Peripheral Neuropathy

Chemotherapy utilizing cytotoxic drugs, such as paclitaxel (PTX), is still a commonly used therapeutic approach to treat both localized and metastasized cancers. Unlike traditional regimens in which PTX is administered at the maximum tolerated dose, alternative regimens like metronomic dosing are beneficial by administering PTX more frequently and in much lower doses exploiting antiangiogenic and immunomodulatory effects. However, PTX-induced peripheral neuropathy and lack of patient compliant dosage forms of PTX are major roadblocks for the successful implementation of metronomic regimens. Because of the success of polyester nanoparticle drug delivery, we explored the potential of nanoparticle-encapsulated paclitaxel (nPTX) in alleviating peripheral neuropathy using a rat model. Rats were injected intraperitoneally with 2 mg/kg body weight of PTX or nPTX on four alternate days, and neuropathic pain and neuronal damage were characterized using behavioral assessments, histology, and immunohistochemistry. The reduction in tactile and nociceptive pressure thresholds was significantly less in nPTX-treated rats than in PTX-treated rats over a 16-day study period. Histological analysis showed that the degree of dorsal root ganglion (DRG) degeneration and reduction in motor neurons in the spinal cord was significantly lower in the nPTX group than the PTX group. Further, immunofluorescence data reveals that nPTX-treated rats had an increased density of a neuronal marker, β-tubulin-III, reduced TUNEL positive cells, and increased high molecular weight neurofilament in the spinal cord, DRG, and sciatic nerves compared with PTX-treated rats. Therefore, this work has important implications in improving risk-benefit profile of PTX, paving the way for metronomic regimens.

Hemangiosarcoma in a Dog: Unusual Presentation and Increased Survival Using a Complementary/Holistic Approach Combined with Metronomic Chemotherapy

This case report documents the clinical and pathologic findings in a 12-year-old terrier mix with intraocular and splenic hemangiosarcoma. Pathologic findings in both the spleen and globe were consistent with hemangiosarcoma with a low mitotic count. Initial treatment consisted of enucleation and then splenectomy followed by one cycle of conventional doxorubicin chemotherapy. Due to poor tolerance, a subsequent treatment regimen consisted of metronomic chemotherapy with chlorambucil combined with an alternative/complementary regimen of I'm-Yunity (polysaccharopeptide) and Yunnan Baiyao. Follow-up thoracic radiographs and abdominal ultrasounds over a period of 24 months showed no evidence of pulmonary, hepatic, or right atrial metastases, during which time the patient had an excellent quality of life. However, shortly after achieving two-year survival, the patient developed new onset seizures unresponsive to anticonvulsant therapy. Therefore, a decision was made to euthanize the dog given that the most likely etiology of the seizures was a brain tumor. Overall, this is an exceptional treatment response given the poor survival statistics of hemangiosarcoma even with conventional chemotherapy. However, additional clinical pharmacology and clinical trial data are needed to further support the use of a complementary/holistic approach in combination with metronomic chemotherapy.

The use of low-dose metronomic chemotherapy in dogs-insight into a modern cancer field

The era of chemotherapy, which started in the middle of the last century, has been ruled by the routine use of dose-intense protocols, based on the "maximum-tolerated dose" concept. By promoting a balance between patient's quality of life and the goal of rapidly killing as many tumour cells as possible, these protocols still play a prominent role in veterinary oncology. However, with the opening of a new millennium, metronomic chemotherapy (MC) started to be considered a possible alternative to traditional dose-intense chemotherapy. Characterized by a long-term daily administration of lower doses of cytotoxic drugs, this new modality stands out for its unique combination of effects, namely on neovascularization, immune response and tumour dormancy. This article reviews the rationale for treatment with MC, its mechanism of action and the main studies conducted in veterinary medicine, and discusses the key challenges yet to be solved.

Immunological, anti-angiogenic and clinical effects of intratumoral interleukin 12 electrogene therapy combined with metronomic cyclophosphamide in dogs with spontaneous cancer: A pilot study

The immunological, anti-angiogenic and clinical effects of metronomic cyclophosphamide and 3 consecutive intratumoral interleukin (IL)-12 gene therapy (electrogene therapy (EGT)) treatments were evaluated in 6 dogs with spontaneous cancer. In all dogs, a decrease in peripheral leukocytes 2 days after IL-12 EGT coincided with erythema and swelling of the tumor. In the tumor, a transient increase in IL-12 levels was measured, whereas a continuous increase in interferon γ (IFNγ) and thrombospondin 1 (TSP-1) were determined in contrast to a continuous decrease in vascular endothelial growth factor (VEGF). In the serum, a transient increase in IL-12 and IL-10 levels were noted in contrast to a transient decrease in VEGF and TSP-1. The treatment resulted in a significant anti-angiogenic effect. Although all primary tumors continued to progress in time, this progression was slower than before treatment according to the contrast-enhanced ultrasound data. Besides the encouraging immunostimulatory and anti-angiogenic effects observed in all dogs we also noticed in 4 out of 6 dogs clinically relevant improvements in quality of life and weight. These results hold great promise for combinatorial strategies of IL-12 EGT and metronomic chemotherapy with conventional antitumor (immuno)therapies.

2016 AAHA Oncology Guidelines for Dogs and Cats*

All companion animal practices will be presented with oncology cases on a regular basis, making diagnosis and treatment of cancer an essential part of comprehensive primary care. Because each oncology case is medically unique, these guidelines recommend a patient-specific approach consisting of the following components: diagnosis, staging, therapeutic intervention, provisions for patient and personnel safety in handling chemotherapy agents, referral to an oncology specialty practice when appropriate, and a strong emphasis on client support. Determination of tumor type by histologic examination of a biopsy sample should be the basis for all subsequent steps in oncology case management. Diagnostic staging determines the extent of local disease and presence or absence of regional or distant metastasis. The choice of therapeutic modalities is based on tumor type, histologic grade, and stage, and may include surgery, radiation therapy, chemotherapy, immunotherapy, and adjunctive therapies, such as nutritional support and pain management. These guidelines discuss the strict safety precautions that should be observed in handling chemotherapy agents, which are now commonly used in veterinary oncology. Because cancer is often a disease of older pets, the time of life when the pet–owner relationship is usually strongest, a satisfying outcome for all parties involved is highly dependent on good communication between the entire healthcare team and the client, particularly when death or euthanasia of the patient is being considered. These guidelines include comprehensive tables of common canine and feline cancers as a resource for case management and a sample case history.

A retrospective analysis of chemotherapy switch suggests improved outcome in surgically removed, biologically aggressive canine haemangiosarcoma

Haemangiosarcoma (HSA) has an aggressive biological behaviour and carries a poor prognosis, with less than 10% of treated dogs surviving longer than 1 year. In this retrospective study a varied metronomic chemotherapy (MC) regimen preceded by adjuvant doxorubicin-based maximum-tolerated dose chemotherapy (MTDC) was compared with MTDC, in terms of efficacy [time to metastasis, (TTM) and survival time (ST)] and safety in dogs with biologically aggressive HSA. Dogs were eligible if they had no metastasis after MTDC and received either no further chemotherapy or MC maintenance. Twelve dogs received MTDC, and 10 received MC thereafter. Median TTM and ST were significantly longer for dogs receiving MTDC-MC (not reached versus 150 days, P = 0.028; and not reached versus 168 days, P = 0.030, respectively). Treatment was well tolerated. MTDC followed by MC is safe and suggests improved TTM and ST in dogs with surgically removed, biologically aggressive HSA that are treated in the microscopic setting.