Unpacking the HORROR Of Lung Cancer In Dogs

Canine Lung Cancer

Lung cancer in dogs is not common, but don’t hold your breath because cases are on the rise. The higher incidences of dog lung cancer may be due to increased pet longevity, improved diagnostics, and regular health screening in older dogs.   

A diagnosis of lung cancer often carries a poor prognosis due to the fact that most pets only show subtle symptoms. Most of the time, cancer progresses without detection, which limits treatment options. Read our article and find out A Guide on Common Cancers in Dogs.

What are the Symptoms and Signs of Lung Cancer in Dogs?

A quarter of patients with underlying lung cancer do not show any signs of disease until the end stages. 

When suspecting lung cancer in dogs, symptoms to look out for may be subtle. The clinical manifestations of the condition depend on the location, size, and type of cancer. The following reported symptoms occur in dogs with lung cancer:

• Weight loss and depressed appetite.
• Increased respiratory rate and effort. Dyspnoea (difficulty breathing) is often present in end-stage cancer.
• Lethargy and exercise intolerance.
• Vomition.
• Thoracic discomfort when lying in sternal recumbency or a bow-legged stance of the forelimbs.
• Poor coat condition.
• Coughing or wheezing.
• Fever.

The Occurrence of Misdiagnosed Lung Cancer in Dogs

When diagnosing lung cancer in dogs, x-rays are the most common and accessible imaging modality available to GP vets. Radiographs are sometimes difficult to interpret, and some lung patterns or effusions may obscure masses. A significant number of dogs do not exhibit overt clinical symptoms, increasing the risk of misdiagnosing cancer.

Vets often detect pulmonary pathology during survey chest radiographs, but sometimes x-rays are not enough to provide a specific diagnosis. 

To ensure an accurate diagnosis, recommendations of the following tests may occur: 

• Radiographs must be taken with at least three orthogonal views to localize the tumor or lung pattern.
• Blood work to assess specific parameters form a complete blood count and serum biochemistry.
• An abdominal ultrasound assesses if the cancer has metastasized to other soft tissue organs. 
• Biopsies or ultrasound-guided aspirates help to sample the mass and are sent to a  pathologist to be identified and staged.
• A CT scan is an excellent imaging modality to investigate if the mass has spread to more than one lung lobe, neighboring lymph nodes, or the mediastinum. Specialists can also determine surgical margins from a CT scan. 

The Various Stages of Canine Lung Cancer

Canine lung tumor classifications fall into two categories: primary lung tumors and metastatic lung tumors.

A primary lung tumor is rare in dogs. The tumor originates from the lung tissue and is often malignant. Metastasis regularly occurs in the lymph nodes, the lining of the chest cavity, the bones, and the brain. 

A metastatic lung tumor is a growth that has spread from cancer originating elsewhere. Once metastatic cancer seeds itself in the lungs, it carries a very guarded prognosis.

To determine the severity of lung cancer in dogs, stages of disease progression allow clinicians to offer owners a better idea of what to expect after their pet receives a lung mass diagnosis.

• Stage 1: The cancerous mass localizes in a specific area without showing signs of spreading to neighboring lymph nodes or other tissues.
• Stage 2: The cancerous mass has increased in size but has not spread.
• Stage 3: The cancer has increased in size and shows signs of spreading to neighboring lymph nodes and other tissues. 
• Stage 4: The cancer spreads to the other organs and is referred to as end-stage lung cancer in dogs.

What are the Causes?

Researchers and clinicians do not have a definitive reason for what causes lung cancer in dogs. The most common factor dogs developing lung cancer have in common is old age. Dogs older than ten years have a higher prevalence of lung cancer. 

Some breeds suffer from lung cancer more often than others, such as Boxers, Australian shepherds, Dobermans, and Burmese mountain dogs. Some studies show that exposure to carcinogens such as chronic cigarette smoke may increase dogs’ risk of developing lung cancer. 

Blastomycosis vs. Lung Cancer – The Differences

Blastomycosis vs. lung cancer in dogs is a critical differentiation when faced with chest radiographs that show pulmonary soft tissue opacities. 

Blastomycosis is a fungal infection that dogs pick up from the soil or decomposing leaves. It is a zoonosis. The fungus results in pyogranulomatous lesions often seen in the lungs and skin. Spores are aerosolized and inhaled after rain, dew, or fog.

The symptoms of blastomycosis are very similar to lung cancer and can include the following:

• Weight loss.
• Non-productive coughing.
• Depressed appetite.
• Difficulty breathing. 
• Ocular disease and skin lesions.
• Fever. 

The condition is diagnosed from biopsies or radiographs showing non-calcified nodules, lung consolidation, and enlarged bronchial and mediastinal lymph nodes. A diffuse nodular interstitial lung pattern is noticeable, with dense masses seen when the bronchial lymph nodes become enlarged. 

The preferred treatment is Itraconazole for a minimum of 2 months. Only seventy percent of dogs make a full recovery, and the other twenty percent tend to have recurrent episodes months or years after clinical symptoms subsided. 

The prognosis in dogs with mild lung disease is good, but in dogs with severe lung disease or neurological involvement, the prognosis is poor. 

Is Lung Cancer in Dogs Painful?

Lung cancer is painful because it results in discomfort and stress, especially if a dog has chronic coughing, vomiting, labored breathing, or thoracic distension. 

The decreased oxygen perfusion of the blood also leaves the dog feeling lethargic and depressed. The degree of pain a dog experiences depends on the type of cancer and the amount of inflammation in the thoracic cavity. 

A dog’s quality of life is negatively affected by pain when they develop lung cancer due to the secondary complications associated with neoplastic disease. 

What is the Life Expectancy of a Dog With Lung Cancer?

When a vet diagnoses lung cancer in dogs, life expectancy estimates depend on the stage of the disease. Even with a low-grade diagnosis, the prognosis is often very guarded to poor. 

Stage 1-2 refers to a well-differentiated or low-grade tumor. The average expected survival time is between twelve to sixteen months with surgery only.

Stages 3-4 are poorly differentiated or high-grade tumors. The average expected survival time is around three months with surgery and chemotherapy. 

If a pet does not undergo treatment and owners elect for palliative care, the patient’s life expectancy reduces to weeks, and their quality of life deteriorates rapidly. 

How is Canine Lung Cancer Treated?

Treatment options for lung cancer in dogs are limited and very costly. The course of action depends on the type and stage of cancer your pet suffers from.

Surgery for low-grade tumors is the top recommendation to remove the affected lung lobe. The surgery is a specialist procedure; most dogs tolerate it well if they have no other underlying conditions, such as heart or renal disease. 

Stereotactic radiation (SRS/SRT) is a novel therapy that offers a non-surgical approach to dogs with primary lung cancers. The radiation shrinks the tumor when directly applied to the affected area, and the treatment shows few side effects. The treatment is not curative but shows promise in improving life expectancy by a few additional months. 

Can it be Prevented?

Unfortunately, there is no definitive cause of lung cancer in dogs, so there is no proven prevention. Nutritional supplements that decrease oxidative damage can help deter cancer. Ideally, the best option is to ensure your dog avoids exposure to carcinogens such as secondhand smoke or pesticides.  

Metastatic Lung Cancer in Dogs

Clinicians diagnose metastatic lung cancer dogs more frequently than dogs suffering from primary lung tumors. The main areas of metastasis include adjacent lung lobes, lymph nodes, the lining of the thoracic cavity, the bones, and the brain.

Tumors spread through the body via the blood or the lymphatic system. Determining the degree of metastasis helps determine if surgery is a safe option or if the lung cancer has spread too far to undergo successful treatment or removal.

A Final Word

Lung cancer in dogs is a challenging diagnosis to make and treat. The limited treatment options and short survival time make lung cancer difficult to accept. A dog’s quality of life should always come into careful consideration when an owner considers treatment options. 

Dr. Kaylee Ferreira

Originally from the deep eastern suburbs of Johannesburg in South Africa, I grew up fairly feral, without shoes, on a farm surrounded by pets of all shapes and sizes. I have always kept close company with animals but never thought that they would be such a big part of my life by becoming a part of my career. I love being a veterinarian as it is such a diverse occupation, always changing and always challenging. I qualified as a vet in 2015 from Onderstepoort.

I have worked in rural communities between rabid goats, cows and dogs but chose to settle in the lovely bushveld area of the Lowveld where I then opted to start “living la vida locum”after a few years in private practice.  My husband – who truly loves me as he suffers from severe animal allergies (married the vet anyway), our dog Lily and our equally animal obsessed daughter love to spend our off time in an old Series 2 Land Rover.

I started my own locum company, Kubuntu Veterinary Services in June 2018 as it offered broader opportunities to gain more experience in different clinics with different practitioners, as well as learn more about different management styles and strategies. The name of the company is associated with a South African term “ubuntu” which means humanity, but sometimes it is translated as “I am because we are” which in a more philosophical sense means “the belief in a universal bond of sharing that connects all humanity”.