Lung Cancer in Dogs and Cats
Lung cancer is one of the most commonly diagnosed cancers in humans. Given how serious and common lung cancer is in humans, it’s normal to wonder if this deadly disease also affects our pets. Cancer is not uncommon in dogs and cats. There have been many diagnosed cancer cases in both species, the extent, and severity of which depends on the type of cancer and its location. There are types of cancer that commonly occur in both dogs and cats, and those that rarely develop. We’ll discuss below if lung cancer is one of them.
What is lung cancer?
A primary lung tumor, or lung cancer, is a type of cancer that originates from the tissues and cells of the lungs. Most lung cancer develops from the epithelial tissues of the lungs, which grow and spread to nearby lung tissues, other regions of the lungs, and can metastasize to nearby organs and tissues such as the heart and the pericardium.
Lung cancer is different from secondary lung tumors which often result from metastasis of other types of cancer in the body. The lungs, being an organ of gas exchange in the body, are highly vascularized and are a common location of metastasis for different types of cancer. It’s common for the lungs to become affected when cancer located in a different part or organ system starts to spread.
Do dogs and cats develop lung cancer?
As with humans, secondary lung tumors are common in dogs and cats suffering from different types of cancer. Chest radiographs (x-rays) are one of the screening tests done in both dogs and cats diagnosed with cancer to check for the presence of metastasis.
However, a primary lung tumor or lung cancer rarely happens in both species. This type of cancer is commonly seen in older dogs and cats, usually around 10-15 years of age. There is no sex predilection for lung cancer but certain breeds like Bernese Mountain Dogs, Persian cats, Irish Setters, and Boxers are predisposed to developing carcinomas, the most common type of lung cancer.
The severity of illness caused by lung cancer in both dogs and cats depends on where it is located, the extent of lung tissues affected, the rate at which cancer spreads, and if cancer has metastasized to other organ systems.
Lung Cancer Symptoms in Dogs and Cats
Because of the location and the organ affected, symptoms of lung cancer in canine and feline patients are often respiratory-related. Dogs and cats with early-stage lung cancer are usually asymptomatic or present with very mild symptoms such as occasional coughing.
In cases with more advanced stages of lung cancer, breathing difficulties, excessive coughing, and exercise intolerance are often observed. Generalized signs of illness such as fever, vomiting, decrease in appetite, and lethargy are also seen in dogs and cats with more progressed lung cancer.
Locally invasive lung cancer can eventually spread into nearby organs like the esophagus, stomach, diaphragm, heart, and pericardium causing clinical signs such as gastrointestinal ulcers, breathing difficulties, and symptoms of heart disease. Lung cancer has a high risk of metastasis and often affects the bones, causing lameness and movement problems in affected dogs and cats.
Diagnosis of Lung Cancer in Pets
Nearly 25% of all lung cancer cases reported in both canine and feline patients are asymptomatic, which means no observable signs were seen before the discovery of lung cancer. In some cases, lung cancer diagnoses are incidental and only found during radiographic examination for a different health condition.
The most common diagnostic test used to detect the presence of lung cancer is radiographic imaging. This provides an accurate image of the presence of tumors in the lungs of the animal. Lung cancer, in radiographs, can appear as well-defined tumors found in the lung tissues, or extensive lesions on the lung parenchyma.
Unfortunately, radiographs are not useful in differentiating between primary and secondary lung tumors. Definitive diagnosis will come from histopathological examination. A biopsy sample may be obtained from the tumors in the lung for proper identification and differentiation. This can confirm if the tumors found in the radiograph are lung cancer or secondary lung tumors from metastasis.
Treatment Options for Pets with Lung Cancer
The recommended treatment for cases of lung cancer in both dogs and cats is surgical removal. Lung lobes with tumors can be removed surgically through a procedure called a lobectomy. This is often effective in solitary lung cancer or primary lung tumors that are relatively small in size. Lymph nodes associated with the affected lung lobe are also removed to reduce the risks of spread or metastasis.
For lung cancer cases that have affected the lungs extensively, radiation treatment and chemotherapy are often the treatments of choice to control the growth of cancer and prevent its spread to nearby tissues and organs. Sometimes, dogs and cats that have undergone lobectomy will also need to go through chemotherapy or radiation therapy to treat for remnant lung cancer cells and tissues.
What is the life expectancy for dogs and cats with lung cancer?
Unfortunately, the survival rate of dogs and cats with lung cancer is low. Animals that are not treated, or those with advanced stages of the disease and apparent metastasis often succumb to it in as fast as 2 months. Even with treatment, the expected survival time of canine or feline patients with lung cancer is up to 12 months only. Most patients die from lung cancer due to metastasis and involvement of other organ systems, leading to multi-organ failure.
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