Lung Cancer in Dogs: Symptoms, Types, and Available Treatments

Lung Cancer in Dogs: Symptoms, Types, and Available Treatments

Lung Cancer in Dogs: Symptoms, Types, and Available Treatments

Despite cancer being the leading cause of death in older dogs, lung cancer itself is rare. However, lung tumors in dogs can be dangerous if not detected early on.

If you have noticed a change in your pet’s behavior and suspect it may be cancer, this article can help you understand the signs, diagnostic testing, and treatment options available if lung cancer is confirmed.

Key Takeaways

  • The cause of lung cancer is unknown, but older dogs and those exposed to pollution are at an increased risk of developing lung tumors.
  • Lung tumors either originate in the lungs (primary) or spread to the lungs from other body parts (metastatic).
  • Symptoms of lung cancer in dogs include difficulty breathing, weight loss, and lethargy.
  • Surgery and radiation therapy are the most effective treatments for lung cancer in dogs.
  • The life expectancy and prognosis of a dog with lung cancer depend on tumor size, location, and metastasis.

What Causes Lung Cancer in Dogs?

The exact cause of lung cancer in dogs has not yet been found. However, in most cases, it is a combination of several risk factors. 

Cancer develops when your dog’s body fails to regulate cell growth and reproduction. Instead of dying, the cancer cells multiply out of control and form masses called tumors.

Lung cancer is relatively rare in dogs and could be due to possible increased exposure to cancer-causing agents, as well as:

    • Regular inhalation of secondhand cigarette smoke: Although the link between exposure to cigarette smoke and lung tumors has not yet been conclusively proven, further studies are needed [1]
    • Polluted air: Breathing in dirty, polluted air has been shown to increase the risk of lung cancer in dogs [2]
    • Age: The older the dog, the greater its risk of developing lung cancer
    • Cancer in another body part: May spread to the lungs through the lymph nodes. If this occurs, the prognosis is typically very poor.
What Causes Lung Cancer in Dogs
Older dogs, especially females, showed to have an increased risk of developing cancer

Is Lung Cancer in Dogs Genetic?

There is evidence that links lung tumors in dogs to hereditary or genetic factors [3]. A dog’s genetics does not, however, exclude or guarantee it will develop cancer.

Are Some Breeds More Susceptible to Lung Cancer?

Due to the possible genetic causes of lung tumors, some breeds of dogs are more at risk for developing lung cancer than others.

The breeds include [4]

  • Bernese Mountain dogs
  • Doberman Pinschers
  • Australian Shepherds
  • Irish Setters

Can the Cancer Spread To Other Parts of the Dog?

The spread of cancer is called metastasis. Fluid in the chest cavity can facilitate the movement of cancer cells from one part of the body to another through the lymph nodes [5]. This process is called pleural effusion. 

Imaging tests like an abdominal ultrasound or chest x-ray can help your primary care veterinarian determine whether or not your dog’s lung cancer is spreading.

Types of Lung Cancer in Dogs

Various types of lung cancers can develop in dogs. They are divided into two main categories: primary and metastatic lung tumors. 

Primary Lung Tumors

Most primary lung tumors are carcinomas. Primary lung cancer begins in the lungs and could present as a single primary lung tumor or multiple tumors.

The most common types of primary lung tumors include [6]:

  • Adenocarcinoma: A fairly aggressive type of cancer that offers a relatively poor prognosis even if detected early on.
  • Alveolar carcinoma: This usually occurs in the lining of the alveoli

Primary lung tumors are rare in dogs, developing in about 2-4 dogs out of 10,000 [7].

Primary Lung Tumors
Lymph node negative dogs has a better survival rate than lymph node positive, who rarely survives past 1,000 days

Metastatic Lung Tumors

Unlike primary lung cancer, metastatic lung tumors do not start in the lungs. Instead, they spread from their origin to the lungs through the bloodstream or lymph nodes.

Most metastatic lung tumors start in the bones, lymph nodes, or spleen and have a much poorer prognosis than primary lung tumors [8].

Signs and Symptoms of Lung Cancer in Dogs

Both primary lung cancer and metastatic cancer exhibit similar clinical signs, although many dogs may not show any related symptoms.

Due to the cancer’s location, the majority of clinical signs are linked to the respiratory system and may include [9]:

  • Rapid breathing
  • Difficulty breathing
  • Exercise intolerance
  • Coughing
  • Weight loss
  • Lethargy
  • Poor appetite

Most dogs diagnosed with metastatic lung cancer may also exhibit signs of cancer in other parts of their bodies. The warning signs of cancer in dogs that may have metastasized include hypertrophic osteopathy, which involves the abnormal growth of soft tissue along a dog’s bones. Hypertrophic osteopathy can cause lameness, lethargy, and leg swelling [10].

If you are concerned your pet may have a metastatic lung tumor that originated elsewhere, take a look at our articles on skin cancer in dogs, spleen cancer in dogs, or stomach cancer in dogs.

Diagnosis of Lung Cancer in Dogs

Early and accurate diagnosis of lung cancer and determining the exact location of the tumor is essential to choosing the right treatment option for your dog.

Your primary care veterinarian can conduct diagnostic testing to do just that and may recommend further testing to examine the spread and size of the tumor.

Chest X-Ray

A vet will do chest x-rays of your dog to determine the location, size, and possible metastasis of the tumor. Although a CT scan is more sensitive to detecting masses, chest x-rays are about 81% accurate for diagnosing lung tumors, although this accuracy declines as dog size increases [11].

A chest x-ray is a non-invasive imaging test that can be done without general anesthesia. Results are usually ready in less than an hour and can be read by your vet as soon as it is available.

CT Scan

Computed tomography imaging or a CT scan can identify metastasis and locate primary tumors in dogs [12]. A CT scan provides a detailed image of your dog’s lungs and is one of the most widely used diagnostic tools. 

CT scans can be beneficial to a vet before surgery and are usually conducted under general anesthetic to minimize blurring. The whole process takes about 45 minutes, and the results are ready immediately.

Biopsy

Biopsies are one of the only ways to determine the exact type of tumor a dog has and help determine its prognosis [13]. One of the most common types is a keyhole biopsy done by your primary care veterinarian. 

The procedure involves making several minor cuts in the chest and inserting a camera through one while cutting a small tumor sample through the others. 

The vet will stitch up the cuts, and recovery usually takes between 1-4 days.

FNA and Cytology

Your vet can perform advanced diagnostics like a fine-needle aspiration (FNA) to determine whether or not a lung tumor is malignant through cytology which involves the careful examination of the sample tumor cells. An FNA is a non-invasive biopsy and usually consists of inserting a needle, guided by an ultrasound scan, into the tumor itself [14]

A small sample of the tumor is extracted, and the vet can use it to identify the type of tumor present. An ultrasound-guided aspirate is typically done under anesthesia. It does not take much more than half an hour to complete, although results may only be ready several days later. 

Your dog may be drowsy from the anesthesia and should be allowed to rest until completely recovered.

Treatment Options

An accurate diagnosis of lung cancer is necessary to recommend treatment options for your dog’s tumor. This includes knowing whether it is malignant, benign, metastatic, or primary. 

If a tumor has been confirmed, but your vet has not yet determined what type of cancer it is, further testing should be done before deciding on the treatment route you should take.

Surgery

Surgery is still the most widely recommended treatment for any tumor type. The location, how much lung tissue is involved, and whether it has spread to your dog’s lymph nodes are all essential considerations before deciding to move ahead with surgical removal of the tumor.

Metastasis of a lung tumor can affect nearly all the tissues inside the chest cavity. If more than one tumor is present, your vet may forgo surgery in favor of chemotherapy or radiation therapy.

Single primary tumors in a single lung lobe can be removed along with any lymph nodes connected to the lung tissue in a process called a lung lobectomy. This is either done by making a large incision in the chest and separating the chest bones or by making several smaller cuts and removing the tumor through the space between two ribs.

Dogs who had surgery and went into remission had a median survival time of 330 days [15].

Radiation Therapy

If a single primary lung tumor has metastasized or grown too large, your vet may suggest radiation therapy as surgery would be too dangerous. Radiation therapy is a widespread treatment for dogs with adenocarcinomas. 

Radiation therapy prevents cancer cells from dividing and multiplying. As a result, many dogs undergo the treatment for several months before being recommended for surgery due to a reduction in the tumor size [16].  

However, some dog owners are hesitant to agree to radiation therapy as the treatment could cause painful skin reactions and dermatitis [17].

Chemotherapy

A vet will recommend chemotherapy if other treatment options are not feasible. For example, if the cancer has spread to the dog’s lymph nodes or blood vessels, chemo may be a last resort to halt the tumor’s spread or as an added treatment after surgery, although there is no evidence that this is effective [18].

Chemotherapy
Dogs with primary lung tumor who were LN- showed a better survival rate, even without proper treatment than those who were LN+

Stereotactic Radiation Therapy (SRT)

SRT is a new form of radiation therapy where a very high dose of radiation is delivered directly to the tumor, preventing the dose from damaging surrounding tissues [19].

Stereotactic radiation therapy could be particularly beneficial in the early stages of lung cancer. However, not many veterinary clinics provide this treatment option.

Prognosis: What To Expect

Whether dogs recover from lung cancer depends on several factors, including [20]

  • Tumor size: The smaller the tumor, the better the prognosis
  • Location of the tumor: A well-differentiated tumor that isn’t lodged deeply in the lung or tissues has a better prognosis
  • Clinical signs of lung cancer: Dogs diagnosed with lung cancer that aren’t showing clinical signs of the disease have a better prognosis
  • Metastasis: Most dogs with metastasized tumors have a poor prognosis

Life Expectancy

The average survival time of dogs with lung cancers depends on the same factors as their prognosis. Furthermore, dogs with metastatic lung cancer have a far shorter life expectancy than dogs with primary lung tumors. 

Other factors that could reduce your dog’s life expectancy with lung cancer include:

  • Lymph node involvement: Dogs who have no cancer spread to the lymph nodes have a much longer average survival time than those with lymph node involvement
  • The presence of multiple tumors
  • Development of squamous cell carcinoma: A squamous cell carcinoma in the lung is rare but highly metastatic and can spread rapidly through your dog’s body [21]

It is difficult to estimate the possible life expectancy of a dog with lung cancer, but it can range from a few days to several years and depends on various factors.

How to Care for a Dog With Lung Cancer

Besides offering your dog love, care, and understanding while it is going through a very painful, taxing illness, several vet-prescribed oral medications can help treat the symptoms of lung cancer, including:

  • Opioids: Drugs like codeine, morphine, and hydrocodone can help reduce the pain your dog may be experiencing [22]
  • Non-steroidal anti-inflammatory drugs (NSAIDs): Medications like carprofen and prednisone can be used to treat pain and inflammation

Cannabidiol, extracted from cannabis plants, is an anti-inflammatory and analgesic that can help manage your dog’s pain more naturally [23].

Are Dogs in Pain With Lung Cancer?

Lung cancer in dogs can be excruciating, especially in the case of metastatic or malignant tumors. If you notice your dog whining, not moving around much, or refusing to eat, you may need to take them to the vet for a painkiller prescription.

What Do You Feed a Dog With Lung Cancer?

Diets low in carbohydrates and moderately high in protein, fiber, and fat benefit dogs with cancer [24].

A high protein, low carbohydrate and fat diet have also shown promise at increasing a dog’s average survival time [25].

When Is the Right Time to Euthanize a Dog With Lung Cancer?

In unfortunate cases, even though you’ve tried several treatment options, your dog may not enter remission, and its symptoms and condition will worsen. 

Deciding to euthanize your dog is incredibly difficult but must be considered, especially if you notice a drastic deterioration in their symptoms, like regular vomiting, significant weight loss, lethargy, and disinterest in their environment.

FAQ

Here are the answers to some of the most commonly asked questions about lung cancer in dogs.

How Long Can a Dog Live With Lung Cancer Without Treatment?

After developing lung cancer, dogs with primary metastatic tumors can live for an average of 60 days without treatment [26]

This amount increases and decreases according to the severity and prognosis of the cancer.

What Are the Signs of Lung Cancer in Dogs?

The clinical signs of lung cancer in dogs include: 

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  • Rapid or difficult breathing
  • Exercise intolerance
  • Weight loss

Diagnostic testing can help determine whether your dog has a tumor and, if so, what treatment should be considered.

Can Lung Cancer in Dogs Be Cured?

Primary lung tumors that have not metastasized are the most likely to be successfully treated by surgery and adjuvant radiation or chemotherapy. As of yet, there is no definite cure for cancer of any kind.

What Happens to a Dog With Lung Cancer?

Dogs can develop cancer due to various factors, including possibly increased exposure to cancer-causing agents. Once a dog develops cancer, it may or may not exhibit the clinical signs of the condition. 

If lung cancer is confirmed through simple or advanced diagnostics, a recommended treatment plan can help slow down the spread of the tumor or facilitate its removal through surgery. 

Dogs diagnosed and treated early on in the development of metastatic or primary lung tumors have the best chance of survival. They can live for several years after their initial diagnosis.

Conclusion

Despite the rarity of lung cancer in dogs, understanding the symptoms and causes of the condition can help you detect it early on. The earlier lung cancer is diagnosed and treated in a dog, the longer its life expectancy after treatment. 

Cancer is a scary diagnosis for any pet owner, but with the right treatment and quick action, your dog may be spared from the pain and discomfort the progression of the disease can cause.

References: 

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