Pulmonary fibrosis after high cumulative dose nitrosourea chemotherapy in a cat

Animal models of drug-induced pulmonary fibrosis: an overview of molecular mechanisms and characteristics

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease characterized by progressive loss of pulmonary function. Drug-induced interstitial lung disease has been reported as a severe adverse effect of some drugs, such as bleomycin, amiodarone, and methotrexate. Based on good characteristics, drug-induced pulmonary fibrosis (PF) animal model has played a key role in our understanding of the molecular mechanisms of PF pathogenesis and recapitulates the specific pathology in patients and helps develop therapeutic strategies. Here, we summarize the mechanisms and characteristics of given fibrotic drug-induced animal models for PFs. Together with the key publications describing these models, this brief but detailed overview would be helpful for the pharmacological research with animal models of PFs. Potential mechanisms underlying drug induced lung toxicity.

Interstitial lung diseases in dogs and cats part I: The idiopathic interstitial pneumonias

Interstitial lung diseases (ILDs), also called diffuse parenchymal lung diseases, are a large heterogenous group of non-infectious, non-neoplastic disorders characterized by varied patterns of inflammation and fibrosis (Travis et al., 2002). In humans, accurate classification of interstitial lung diseases (ILDs) requires multidisciplinary collaboration between clinicians, radiologists and pathologists. The same is likely to be true for canine and feline ILDs; however, this collaborative approach is rarely taken, leading to a paucity of knowledge of ILDs in small animal species. A proposed classification scheme of canine and feline ILDs, modified from a human classification scheme, consists of three major groups: idiopathic interstitial pneumonias (IIPs), ILDs secondary to known causes, and miscellaneous ILDs (Travis et al., 2002). The focus of this review is on the IIPs in dogs and cats. A framework of what is known about the major IIPs in humans will be used to draw parallels when relevant to the canine and feline species. Differences will also be highlighted. When available from the veterinary literature, clinical presentation, diagnostic results, treatment and/or prognosis will be reported. The review underscores that to advance in our knowledge of veterinary IIPs and other ILDs, clinicopathologic features, advanced imaging and histopathology must be carefully integrated and larger groups of animals studied.

Interstitial lung diseases in dogs and cats part II: Known cause and other discrete forms

In addition to idiopathic interstitial pneumonias, interstitial lung diseases (ILDs) can occur secondary to known causes or be classified as discrete syndromes. Also known as diffuse parenchymal lung diseases, the ILDs represent a heterogenous group of non-infectious, non-neoplastic disorders characterized by varied patterns of inflammation and fibrosis. Characteristically associated with the true interstitium (i.e. the anatomic space lined by alveolar epithelial cells and capillary endothelial cells and the loose-binding connective tissue), it is important to understand ILDs are associated with pathology of the distal lung parenchyma and thus lesions can be bronchiolocentric or resemble alveolar filling disorders. Injury to the distal lung can occur via inhalation or hematogenous routes. This review will build on a proposed classification scheme adapted from human medicine to describe known cause and discrete forms of ILDs in dogs and cats.

Suspected drug-induced infiltrative lung disease culminating in acute respiratory failure in a dog treated with cytarabine and prednisone

OBJECTIVE

To describe a case of suspected drug-induced infiltrative lung disease (ILD) and acute respiratory failure associated with the administration of cytarabine and prednisone in a dog requiring mechanical ventilation.

CASE SUMMARY

A 4.5-year-old, female spayed Yorkshire Terrier presented to the ICU with acute onset of respiratory distress following a 24-hour cytarabine infusion. The patient was previously diagnosed with meningoencephalitis of unknown etiology (MUO), caudal occipital malformation, and syringohydromyelia, and was being treated with oral prednisone and levetiracetam, and cytarabine infusions. The patient developed tachypnea and dyspnea, and had diffuse crackles on auscultation of all lung fields, and hypoxemia 6 hours following completion of the fourth cytarabine infusion (300 mg/m² ). Thoracic radiographs revealed diffuse, bilateral infiltrates consistent with noncardiogenic pulmonary edema or acute respiratory distress syndrome. Respiratory distress and hypoxemia persisted despite oxygen supplementation and furosemide therapy and led to initiation of mechanical ventilation. Approximately 12 hours later, the dog became progressively hypoxemic with worsening pulmonary edema. The owners elected euthanasia. Postmortem examination revealed pulmonary edema and diffuse interstitial pneumonia. Histopathologic evaluation revealed pulmonary edema, severe acute neutrophilic and histiocytic pneumonia, and multifocal interstitial fibrosis. Bacterial culture yielded no growth.

NEW OR UNIQUE INFORMATION PROVIDED

Drug-induced ILD is rarely reported in the veterinary literature, and has not previously been reported in dogs receiving cytarabine. As with administration of any medication, adverse events may occur. While ILD is unlikely to be commonly recognized, it may be considered in veterinary patients receiving chemotherapy that acutely become dyspneic.

A case of atypical diffuse feline fibrotic lung disease

An 11-year-old cat presented for respiratory distress and weight loss. Thoracic radiographs were interpreted as a diffuse bronchointerstitial pattern with bronchiectasis and a mild ventral alveolar pattern on the lateral views. Computed tomography revealed a severe diffuse reticular pattern, relatively hyperattenuating in subpleural regions, with diffuse traction bronchiectasis and some degree of honeycombing. Despite the absence of basal predominance, this pattern was considered to be suggestive of usual interstitial pneumonia (UIP). Other differentials (other types of interstitial lung disease, infectious pneumonitis, neoplasia, or early edema or hemorrhage) were considered less likely based on history and other test results. The cat was discharged without any treatment, and euthanased 5 months later. Post-mortem histological analysis of the lung revealed end-stage lung, with extensive fibrosis that was more severe in subpleural regions, fibroblastic foci and honeycombing, suggestive of UIP. A probable diagnosis of idiopathic pulmonary fibrosis (IPF) was made. The diffuse distribution of the lesions was atypical compared with previous tomographic and histologic descriptions of IPF in cats. This case report suggests a heterogeneity of the pulmonary fibrotic disorders in cats that warrants further investigation for better characterization and classification.

Radiographic and histopathologic characteristics of pulmonary fibrosis in nine cats

Pulmonary fibrosis is a progressive fatal interstitial lung disease that is often idiopathic, occurs in multiple species, and may be caused by a number of inciting factors. The purpose of this retrospective, multicenter study was to describe the radiographic and histopathologic characteristics of idiopathic and induced pulmonary fibrosis in a group of cats. Cats with thoracic radiographs and histopathologically confirmed pulmonary fibrosis were recruited using the American College of Veterinary Radiology list serve. A board-certified veterinary radiologist and diagnostic imaging intern reviewed radiographs and recorded characteristics by consensus. Findings from additional imaging modalities were also recorded when available. All histopathology samples were re-reviewed by a veterinary pathology resident. A total of nine cats met inclusion criteria. All patients had a broad range of radiographic characteristics that included broncho-interstitial pattern, alveolar pattern, pulmonary masses, pulmonary bullae, pleural effusion, and cardiomegaly. Cats with available echocardiographic studies had characteristics that included right ventricular dilation and hypertrophy and pulmonary arterial hypertension interpreted to be secondary to primary lung disease. Cats with available CT studies had characteristics that included focally increased soft tissue attenuation, masses, and ventral consolidation that exhibited no improvement with dorsal versus ventral recumbency. Histopathology showed pulmonary fibrosis, type II pneumocyte hyperplasia, and smooth muscle hypertrophy in all patients. Epithelial metaplasia was present only in one patient. Findings from the current study indicated that cats with pulmonary fibrosis have highly variable radiographic characteristics and that these characteristics may mimic other diseases such as asthma, pneumonia, pulmonary edema, or neoplasia.

Cats and chemotherapy: treat as 'small dogs' at your peril

PRACTICAL RELEVANCE

To safely and effectively treat cats with cancer it is important to understand the drugs being used and some species-specific concerns in relation to chemotherapy.

CLINICAL CHALLENGES

While many of the same principles in treating cats with chemotherapy and targeted agents hold true as for other species, including dogs, cats display altered metabolism of drugs and species-specific toxicities that can present particular challenges for veterinarians.

AUDIENCE

This article is aimed at practitioners who treat feline cancer or who help manage cats undergoing cancer therapy.

EVIDENCE BASE

The article reviews the known literature regarding species differences between dogs and cats relating to the use of chemotherapy and targeted therapies. For many of the drugs mentioned there are limited studies and caution must be exercised when using drugs that have a low therapeutic index.

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.

Evaluation of lomustine as a rescue agent for cats with resistant lymphoma

This retrospective study evaluated the use of lomustine as a rescue agent for 39 cases of resistant feline lymphoma. Parameters assessed included lymphocyte cell size, number of previous chemotherapy drugs and number of previous chemotherapy protocols received, time from lymphoma diagnosis to initiation of lomustine therapy, body weight and anatomic location of lymphoma. Cell size, number of previous chemotherapy drugs, number of previous chemotherapy protocols and anatomic location were all significant prognostic factors for the progression-free interval. Twenty-one cats (54%) received more than one dose of lomustine. The overall median progression-free interval (MPFI) was 39 days (range 7-708 days). The MPFI for large versus small and intermediate cell lymphomas was 21 versus 169 days, respectively. The MPFI for gastrointestinal versus non-gastrointestinal lymphomas was 180 versus 25.5 days, respectively. Lomustine has an acceptable efficacy and safety for use as a rescue agent in feline lymphoma.

Pleuropulmonary Changes Induced by Drugs in Patients with Hematologic Diseases

Patients with hematologic diseases who are being treated with therapy drugs, or receive radiation therapy or blood transfusions may develop a host of potentially fatal infectious and noninfectious pulmonary complications [1]. The increased complexity of multimodality and high-dose treatment regimens with the intended benefit of augmented antineoplastic efficacy and prolonged disease-free survival, the use of a panel of novel drugs to treat malignant and nonmalignant hematologic conditions (e.g., azacytidine, bortezomib, cladribine, dasatinib, fludarabine, imatinib, lenalidomide, rituximab, and thalidomide), total body irradiation (TBI) and hematopietic stem cell transplantation (HSCT) have increased the incidence of severe sometimes life-threatening pulmonary complications.