Lung Cancer in Dogs: Symptoms and Treatment

Lung cancer in dogs is a relatively rare but serious condition that occurs when malignant (cancerous) tumors develop in or spread to the lungs. These tumors can affect your dog’s breathing and may lead to life-threatening complications.

Understanding the symptoms, causes, diagnosis, and treatment options for lung cancer in dogs can help pet parents know what to expect and how to support their dog through treatment and recovery.

What Is Lung Cancer in Dogs?

Lung cancer in dogs is a relatively rare condition in which malignant (cancerous) tumors develop in or spread to the lungs. Unlike benign (non-cancerous) tumors, malignant tumors can spread throughout the body, causing serious and potentially fatal health complications.

Lung cancer can affect your dog’s breathing by reducing lung function.

Only about 1% of cancers diagnosed in dogs are in the lungs. However, because of the high blood supply to the lungs, a lot of cancers from elsewhere in the body tend to spread there.

This means that tumors found in the lungs more commonly spread from other parts of the body instead of originating within the lungs (a primary lung tumor).

While dogs could get lung cancer at any age, this mostly affects older dogs. The typical age for diagnosis is 9 to 11 years of age.

What Are the Types of Lung Cancer in Dogs?

The most common type of primary lung cancer in dogs is bronchoalveolar carcinoma. About 97% of primary lung tumors in dogs are carcinomas.

Carcinomas are cancers that begin in the tissues that line internal organs or in the skin.

Other types of cancer that rarely originate in the lungs include histiocytic sarcoma and lymphoma (cancer of the lymphatic system).

How Is Lung Cancer in Dogs Graded?

As in humans, veterinarians “grade” lung cancer in dogs to help make treatment decisions. The grade is based on how fast the tumor is growing, certain characteristics of the cells, and whether there is necrosis (death) of the cells.

According to the Veterinary Society of Surgical Oncology, 46% of primary lung carcinomas are grade I (spreading more slowly), 43% are grade II (moderately spreading), and 10% are grade III (spreading more quickly). Low-grade tumors generally have a better prognosis than high-grade tumors.

What Are the Symptoms of Lung Cancer in Dogs?

Lung cancer in dogs can cause respiratory symptoms, reduced activity, weight loss, and changes in appetite.

Dogs with lung cancer often won’t have symptoms until the tumor has advanced. These tumors may be found during chest X-rays performed for another health reason.

Symptoms include:

• Coughing
• Elevated respiratory rate
• Coughing up blood
• Exercise intolerance
• Respiratory distress
• Weight loss and muscle wasting
• Lethargy
• Decreased appetite

Lung cancers can also cause a secondary condition called hypertrophic osteopathy, which typically affects the long bones of the limbs. The connective tissue on the bones grows rapidly, causing the limbs to become swollen and firm. The pet may limp or be reluctant to move. 

The underlying cause of hypertrophic osteopathy is not well understood, but it typically resolves if the mass is treated.

What Causes Lung Cancer in Dogs?

The exact cause of lung cancer in dogs is unknown, but genetics and environmental pollutants, such as secondhand smoke, may play a role. Research into these potential contributing factors is ongoing.

Breeds thought to have a higher likelihood of developing lung cancer include:

• Boxers
• Doberman Pinschers
• Australian Shepherds
• Irish Setters
• Bernese Mountain Dogs

How Veterinarians Diagnose Lung Cancer in Dogs

Veterinarians diagnose lung cancer in dogs using tests such as chest X-rays, fine needle aspiration (FNA), bronchoscopy, bronchoalveolar lavage, and CT scans.

Lung cancer can’t be diagnosed with a basic physical examination. Diagnostic tests may include:

Chest X-Rays 

The first test a veterinarian will run is chest X-rays. For some pets, this will require light sedation. 

If the veterinarian sees a solitary, well-defined nodule in the lungs, this is more likely to be a primary lung tumor than a metastatic nodule that has spread from elsewhere.

Fine Needle Aspirate

To know what type of cancer your dog has, a veterinarian may perform a test called a fine needle aspirate (FNA) to collect a sample of cells. This test includes placing a needle through the chest wall and into the lesion to remove (aspirate) cells. 

Your pet will need to be sedated for this procedure.

Bronchoscopy and Bronchoalveolar Lavage

In some cases, the vet may perform a test called a bronchoalveolar lavage. During this test, sterile fluid is placed into the airway and then retrieved and studied. Malignant cells may be seen in the fluid, allowing for definitive diagnosis. 

This procedure is often done in conjunction with another test called a bronchoscopy, where a camera is inserted down into the larger airways. Your pet would need to be anesthetized for this procedure.

Additional Imaging and Cancer Staging

A computed tomography (CT) scan of the chest may be performed to assess the number and size of pulmonary masses. A CT may also be recommended for surgical planning.

Imaging of the abdomen and aspiration of peripheral lymph nodes may be advised to check for cancer spread. With primary lung tumors, the results will often be normal. If the nodules in the lungs are suspected to be metastatic from elsewhere, these tests may help determine where the cancer originated.

When Your Dog May Need a Veterinary Specialist

Your family veterinarian can likely perform chest X-rays, abdominal X-rays, aspiration of peripheral lymph nodes, and possibly ultrasound of the abdomen.

Aspiration of tumors in the chest, bronchoscopy, bronchoalveolar lavage, and CT scans are often outside of the scope of private practice, so you may be referred to a specialist.

How Is Lung Cancer in Dogs Staged?

Lung cancer in dogs is staged based on the size of the primary tumor, whether it has spread to nearby lymph nodes, and whether it has spread to other parts of the body (metastasized). 

Staging helps veterinarians determine the appropriate treatment plan.

While lung cancer in humans is often staged using Roman numerals, this system is not routinely used in dogs. However, some veterinarians may use these stages to explain the spread of cancer to pet parents. These stages include:

• Stage I: The tumor is small and has not spread to lymph nodes.
• Stage II: The tumor has grown larger and may have spread to nearby lymph nodes.
• Stage III: The cancer has spread to the lymph nodes between the lung lobes.
• Stage IV: Cancer has spread from the lung to other parts of the body.

How Veterinarians Treat Lung Cancer in Dogs

Surgery is the treatment of choice for a single lung tumor in dogs, while chemotherapy may be recommended for high-grade tumors, large tumors, or cancer that has spread.

The treatment plan depends on the type and severity of the cancer.

Surgery for Lung Cancer in Dogs

During surgery, the surgeon removes part of or the entire lung lobe, depending on the size and location of the mass. The veterinarian will likely biopsy lymph nodes in the chest to determine if the cancer has spread.

Chemotherapy for Lung Cancer in Dogs

Some veterinary oncologists may recommend chemotherapy for high-grade tumors, large tumors, or tumors that show evidence of metastasis. In most cases of primary lung tumors in dogs, chemotherapy alone does not improve survival.

Treatment Considerations for Metastatic Lung Cancer

Dogs that have metastatic nodules from cancer elsewhere in the body have a poorer prognosis. This is because these nodules prove the cancer has advanced enough to spread to the lungs. A consultation with a veterinary oncologist is recommended.

Recovery and Prognosis of Lung Cancer in Dogs

The prognosis for lung cancer in dogs depends on whether the cancer has spread, the tumor's characteristics, and the treatment received. Some dogs without metastases may be cured with surgery, while dogs with aggressive tumors generally have a poorer prognosis.

Survival and Prognosis of Lung Cancer in Dogs

In dogs that have no metastases and undergo surgery, the procedure may result in a cure. Some dogs can live for over two years post-surgery. Expected survival time ranges from three months to over a year, with dogs who have no clinical signs at time of diagnosis, low-grade tumors, and smaller tumors typically living longer than others.

Many pet parents elect not to have their pet go through open-chest surgery when there is evidence that the tumor is aggressive. Even with surgical treatment, the prognosis is three months in these cases.

Veterinary Monitoring After Lung Cancer Treatment

If you choose to pursue treatment for your dog’s lung cancer, your veterinarian may recommend frequent chest X-rays for the first year after surgery to monitor for recurrence. If your pet is undergoing chemotherapy, frequent monitoring of their bloodwork is required to ensure they are tolerating chemotherapy.

How To Keep a Dog With Lung Cancer Comfortable at Home

Other steps you can take to keep your pet comfortable include:

• Ensuring they have easy access to food and water
• Providing a comfortable area to rest
• Ensuring they avoid strenuous exercise
• Not smoking indoors
• Using a room air purifier
• Ensuring you’re consistent with your pet’s medications
• Speaking with your veterinarian if you’re concerned that your pet may be in pain

Palliative Care for Dogs With Lung Cancer

In dogs who are declining, your veterinarian will recommend a palliative care plan to keep your pet comfortable. Treatments could include anti-nausea medications, pain medications, cough suppressants, and anti-anxiety medications.