Lung Cancer in Dogs: Symptoms, Treatment, and Prognosis (2024)

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Lung cancer in dogs may occur due to a tumor that starts in the lungs or one that spreads to the lungs from a different location. But either way, it can be a scary-sounding diagnosis. To help you know what to expect, integrative veterinarian Dr. Julie Buzby explains the causes, symptoms, diagnosis, treatment, and prognosis for lung cancer in dogs.

Lung Cancer in Dogs: Symptoms, Treatment, and Prognosis (1)

Compared to many other types of cancer, primary lung tumors (i.e. cancer that starts in the lungs) are rare in dogs, accounting for only 1% of cases of cancer in dogs. However, over the last 20 years or so, it seems that the number of lung cancer cases in dogs are rising.

Understandably, this is concerning for veterinarians and dog parents alike. While the exact reason for this change isn’t fully understood, it is good for dog parents to have the facts.

What is lung cancer in dogs?

Lung cancer in dogs occurs when abnormal cells replicate and form a tumor. This mass can destroy normal lung tissue and potentially spread to other locations. Sometimes the tumor originates in the lungs. This is called primary lung cancer. But in other cases, a tumor spreads to the lungs from elsewhere in the body. This is known as secondary lung cancer, and it is the far more common type of lung cancer in dogs.

Primary lung cancer in dogs

Unfortunately, about 80% of primary lung tumors in dogs are malignant (i.e. cancerous). Primary lung cancer starts out as a solitary mass affecting one lung lobe, but can invade other lobes. And it can spread to other parts of the body, including the lymph nodes, liver, kidneys, pancreas, chest cavity, bones, and brain.

The vast majority of all primary lung tumors in dogs are carcinomas, with the two most common types being adenocarcinomas (e.g. papillary or bronchogenic adenocarcinoma) or alveolar carcinomas (e.g. bronchioalveolar carcinoma). However, dogs can also have other primary lung tumors, including squamous cell carcinoma, osteosarcoma in dogs, mast cell tumor in dogs, histiocytic sarcoma, and anaplastic carcinoma.

Secondary lung cancer in dogs

On the other hand, cancer in a different area of the body can spread (i.e. metastasize) to the lungs, creating secondary lung tumors. Often, vets will refer to this as metastatic lung disease or metastatic lung cancer.

The lungs are one of the most common organs to be affected by metastasis. This is the case because your dog’s entire blood volume moves through the lungs. Thus, cancer cells that make it into the blood stream can easily go to the lungs, lodge there, and start creating lung tumors. Sometimes the dog may only have one tumor or a few tumors. But in other cases, there will be many tumors spread throughout the lung lobes.

Many common types of cancer spread to the lungs, including:

Lung masses that aren’t cancerous

Additionally, there are some lung problems that can look like lung cancer or have similar symptoms to lung cancer, but are actually due to a non-cancerous process. For example, sometimes focal masses in the lung can be due to infections like pneumonia in dogs or an abscess. Or a dog with fungal lung disease may have multiple spots in the lungs that look like metastatic lung cancer but aren’t.

How do dogs get lung cancer?

Cancer is more likely to happen in senior dogs, with an average age of 10 to 11 years. Like in humans, older dogs are at a higher risk due to the accumulation of cellular damage over time. Still, lung cancer can affect dogs of any age. All breeds can develop lung cancer, though Bernese Mountain Dogs, Boxers, Dobermans, and Irish Setters may have a slightly higher risk.

There is a known link between environmental tobacco smoke and lung cancer in people. But secondhand smoke has not been definitively proven to cause primary lung cancer in dogs. Even still, experts recommend avoiding exposing your pets to it. Research does suggest, though, that dogs exposed to air pollutants and to radon may have a higher risk of developing primary lung tumors.

What are the symptoms of lung cancer in dogs?

Should a dog develop lung cancer, the symptoms can be variable. Interestingly enough, one in four dogs with primary lung tumors will be asymptomatic at the time of diagnosis. (Those tumors may be found on imaging performed for other purposes.) However, dogs may also show some of the following signs of lung cancer:

Dog coughing and gagging—Over 95% of dogs who are symptomatic will be coughing
Lack of appetite
Being a lethargic dog
Weight loss
Coughing up blood
Difficulty breathing or abnormal sound to the breathing
Dog breathing fast
Difficulty exercising
Vomiting or regurgitation
Difficulty swallowing

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Additionally, if the dog has metastatic lung tumors, you may see clinical signs related to the original tumor. These symptoms could include bleeding into the abdomen, difficulty urinating, limping, or masses on the skin, mammary glands, or mouth.

How does the vet diagnose lung cancer in dogs?

If your vet suspects your dog may have lung cancer, he or she may start with performing a physical exam and gathering a history. Then he or she will discuss any recommended diagnostic tests.

X-rays

Chest X-rays are often the primary way your family veterinarian will find a lung tumor. But X-rays cannot determine what type of lung tumor it is. Also, a tumor must be at least 5 millimeters in size to show up on an X-ray. This is important to understand because 40% of dogs with metastatic lung cancer have tumors that are too small to be visible on an X-ray.

CT scan

A CT scan is the gold standard for detecting lung cancer. This is the case because it is the least likely to miss a tumor and can detect smaller nodules than X-ray. Additionally, it can help the vet determine if the tumor has invaded any surrounding tissue. However, you would need to go to a veterinary specialist near you for a CT as they are not typically available in a general practice setting.

Ultrasound

In some situations, the vet may recommend a lung or abdominal ultrasound. Lung tumors do show up on ultrasound. But an ultrasound can only evaluate the periphery of the lungs, so it can miss tumors that are deeper in the lungs.

Abdominal ultrasound is useful for looking for tumor spread or searching for the primary tumor.

Cytology or biopsy

In order to attempt to determine the type of lung tumor, the vet (or veterinary pathologist) will need to examine the tumor cells under a microscope. Sometimes, if the tumor is close to the chest wall, the vet can perform an ultrasound guided aspirate or biopsy (i.e. use a needle to get cells or tissue from the tumor). However, this method may provide a non-diagnostic sample.

Additional diagnostics

The vet may also recommend blood tests for dogs, urinalysis, a dog lymph node aspirate (i.e. looking at lymph node cells under the microscope) or other tests. These diagnostics allow the vet to look for tumor spread, rule out other problems, or make a treatment plan.

What are the stages of lung cancer in dogs?

Based in the diagnostic information the vet gathers, he or she may apply a staging system to a primary lung tumor. One potential staging system, based on the World Health Organization system is:

Stage I—Small primary lung tumor that has not spread elsewhere
Stage II—Tumor is larger and has spread to the lymph nodes nearby
Stage III—Cancer has spread to the lymph nodes in the mediastinum (i.e. area between the lungs)
Stage IV—Lung cancer has spread to the brain, kidneys, liver, or other organs

However, a new staging system for lung tumors in dogs has also been proposed. It is called the canine lung carcinoma stage classification (CLCSC). It’s based off the human lung cancer stage classification (HLCSC). CLCSC subdivides the tumors based on size since tumor size can be a prognostic indicator. The categories in that system are: less than or equal to three centimeters, between three and five centimeters, between five and seven centimeters, and greater than seven centimeters.

What is the treatment for dog lung cancer?

The treatment for lung cancer in dogs can vary depending on type and stage of the tumor, and whether it has metastasized.

Surgical lung lobectomy

If there is no evidence the tumor has metastasized, the treatment of choice is to have the affected lung lobe surgically removed (i.e. lung lobectomy). In most cases, this involves open-chest surgery (vs. a laparoscopic procedure).

However, if the surgeon discovers enlarged lymph nodes or a surgical lymph node biopsy indicates the tumor had actually spread, the dog may need follow-up chemotherapy or radiation.

Chemotherapy

If there are signs of metastasis, surgery isn’t a good option, or not all of the tumor was removed, chemotherapy can also be used to treat lung tumors. Your veterinary oncologist can help find the chemotherapy protocol that is right for your dog.

Radiation

Occasionally, the veterinary oncologist may recommend stereotactic body radiation therapy (SBRT) to try to precisely target the lung tumor. Or he or she may use hypofractionated radiation therapy to provide palliative care.

Supportive care

Regardless of the type of cancer present, your veterinarian may prescribe medications to help your dog feel better. They include:

Antibiotics—If there is evidence of a secondary bacterial infection in the lungs, antibiotics can be helpful.
Anti-inflammatory medications—These medications will help improve local inflammation around the cancer and decrease discomfort.
Cough suppressants—Certain pain medications can also help reduce cough, keeping dogs more comfortable.
Bronchodilators—These medications can help open the tiny lower airways in the lungs.

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Additionally, you can help support your dog by keeping a cool ambient temperature in the house and paying close attention to the temperature and humidity when taking your dog outside. Heat and high humidity can make it harder for your dog to breathe. You should also avoid exposing your dog to air fresheners, perfumes, smoke, or other irritants.

Palliative care

If treatment is no longer working or if you decide surgery, chemotherapy, or radiation aren’t right for your dog, you may switch your focus to palliative (i.e. comfort) care. What exactly this entails will depend in your dog’s situation.

If your dog has fluid building up around the lungs due to the tumor, therapeutic thoracocentesis (i.e. using a needle to remove the fluid from the chest) can help your dog breathe better. Or if your dog is painful due to tumor spread, your vet may recommend a combination of different pain medications to give your dog some relief.

If you have concerns about your dog’s comfort, please talk to your vet. He or she can work with you to find some solutions that might help your dog.

What is the prognosis and life expectancy for dogs with lung cancer?

The outlook for dogs with primary lung cancer can be variable. If the dog has a primary lung tumor that has not spread, he or she may survive for around 12 to 16 months, or sometimes even longer, after a lung lobectomy. But without treatment, or with more advanced lung cancer, average survival times may only be around two to three months.

Overall, the prognostic indicators for primary lung tumors include:

Lymph node spread—Prognosis is better if the tumor has not spread to the lymph nodes.
Tumor grade—Lower grade tumors have a better prognosis than higher grade tumors.
Tumor size—Smaller tumors carry a better prognosis.
Symptoms—Dogs who were asymptomatic at the time of diagnosis generally lived longer.
Tumor stage—Lower stage is more favorable.
Tumor type—The prognosis is better for papillary adenocarcinoma than other primary tumor types.

Since there is so much variation, your veterinarian or veterinary oncologist can give you a better idea of what to expect for your dog.

Additionally, your vet can help you understand the outlook if your dog has metastatic lung cancer. With all the different types of cancer that can spread to the lungs, it isn’t possible to give a specific idea of life expectancy here. However, in general, once a tumor has spread to the lungs, the overall prognosis tends to be poor.

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How do you know when to put down a dog with lung cancer?

Unfortunately, the day may come when you have to start considering if it is time to euthanize your dog with lung cancer. In end-stage lung cancer, your dog may have significant trouble breathing, be coughing frequently, not be able to eat well, be in pain, or have minimal energy. And his or her quality of life may decline as a result. In that situation, the kindest thing may be to set your beloved dog free from his or her struggles.

Lean on your support network and spend time with your dog

I know that hearing the word “cancer” can be scary. And lung cancer is no different. If your dog has been diagnosed with lung cancer, or lung cancer is on the table as a potential diagnosis, the best advice I can give you is to cling to your support system and to remember that you still have today with your dog.

Your veterinarian or veterinary oncologist can provide a wealth of medical information. But they can also give you emotional support and guidance for the journey. And your family and friends are there for you too. You don’t have to face this alone—and you shouldn’t.

Additionally, I urge you to pause your research for a moment, go sit with your dog, and enjoy just being with him or her. It is tempting to want to read and read about your dog’s condition, and I fully support that. But it is also important to stop for a moment and have some quality time with your dog. This can be a comfort to you, and to your dog too.

Was your dog diagnosed with a lung cancer?

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