What Is Lung Cancer in Dogs?
Lung cancer in dogs represents a relatively uncommon form of cancer characterized by the invasion of malignant tumors into the lungs. In contrast to benign growths, malignant tumors have the potential to metastasize throughout the body, leading to severe and potentially life-threatening complications.
The condition impacts a dog’s breathing by impairing lung function. As dogs inhale, oxygen travels from their mouth through the trachea and into a network of small tubes known as bronchi, which extend into the lungs. Within the lungs, the bronchi terminate in minuscule sacs called alveoli, where gas exchange occurs. During this process, red blood cells release carbon dioxide to be exhaled, while simultaneously absorbing fresh oxygen.
Though lung cancer is a serious ailment in dogs, it is fortunately relatively rare, comprising only about 1% of all canine cancer diagnoses. However, due to the lungs’ rich blood supply, tumors from other parts of the body often metastasize to the lungs. Consequently, tumors found in the lungs typically stem from other primary sites rather than originating within the lungs themselves.
While dogs of any age could potentially develop lung cancer, it predominantly affects older dogs, with the typical age of diagnosis falling between 9 and 11 years old.
Types
The majority, approximately 97%, of primary lung tumors in dogs are classified as carcinomas. Carcinomas are cancers that originate in the tissues lining internal organs or the skin. The most prevalent form of primary lung cancer in dogs is known as bronchoalveolar carcinoma.
Similar to the approach in human medicine, veterinarians evaluate lung cancer in dogs through grading to assist in treatment decisions. This grading system considers the rate of tumor growth, specific cell characteristics, and the presence of cell necrosis (cell death). According to the Veterinary Society of Surgical Oncology, approximately 46% of primary lung carcinomas are categorized as grade I (spreading slowly), 43% as grade II (moderately spreading), and 10% as grade III (spreading rapidly). Generally, low-grade tumors have a more favorable prognosis compared to high-grade tumors.
There are also other types of cancer, such as histiocytic sarcoma and lymphoma (a cancer of the lymphatic system), which rarely originate in the lungs.
Symptoms
Dogs afflicted with lung cancer often do not exhibit symptoms until the tumor has progressed significantly. These tumors may be incidentally discovered during chest X-rays conducted for other health reasons.
Symptoms of lung cancer in dogs encompass:
- Coughing
- Increased respiratory rate
- Coughing up blood
- Difficulty in exercising
- Respiratory distress
- Weight loss and muscle atrophy
- Lethargy
- Decreased appetite
Additionally, lung cancers can induce a secondary condition known as hypertrophic osteopathy, which primarily affects the long bones of the limbs. Rapid growth of connective tissue on the bones leads to swelling and firmness in the limbs. Affected pets may exhibit limping or reluctance to move. Although the precise cause of hypertrophic osteopathy is not well understood, it often resolves with treatment of the underlying mass.
Causes
The precise cause of lung cancer in dogs remains unknown, although genetics is believed to be a contributing factor. Ongoing research suggests that environmental pollutants, such as secondhand smoke, might also play a role in the development of lung cancer in dogs.
Certain breeds are thought to have a heightened susceptibility to lung cancer, including:
- Boxers
- Doberman Pinschers
- Australian Shepherds
- Irish Setters
- Bernese Mountain Dogs
Diagnosis
Diagnosing lung cancer in dogs cannot be accomplished through a simple physical examination. Instead, veterinarians employ additional tests, which may include:
Chest X-rays: Initially, veterinarians conduct chest X-rays, often requiring light sedation for some pets. If a solitary, well-defined nodule is observed in the lungs, it is more likely to be a primary lung tumor rather than a metastatic nodule originating elsewhere.
Fine needle aspirate (FNA): To identify the type of cancer present, veterinarians may perform a fine needle aspirate (FNA) to collect cell samples. This procedure involves inserting a needle through the chest wall into the lesion to extract (aspirate) cells. Sedation is typically necessary for this procedure.
Bronchoscopy and bronchoalveolar lavage: In certain instances, veterinarians may conduct a bronchoalveolar lavage, wherein sterile fluid is introduced into the airway and then retrieved for analysis. Malignant cells in the fluid can facilitate a definitive diagnosis. This procedure is often combined with bronchoscopy, during which a camera is inserted into the larger airways. Anesthesia is required for this procedure.
A computed tomography (CT) scan of the chest may be recommended to evaluate the number and size of pulmonary masses. Additionally, a CT scan might aid in surgical planning.
Imaging of the abdomen and aspiration of peripheral lymph nodes may be suggested to assess for cancer spread. Results from these tests are often normal with primary lung tumors. However, if the lung nodules are suspected to be metastatic, these tests can help determine the cancer’s origin.
While family veterinarians can usually conduct chest X-rays, abdominal X-rays, and aspiration of peripheral lymph nodes, procedures such as aspiration of chest tumors, bronchoscopy, bronchoalveolar lavage, and CT scans are typically beyond the scope of general practice. Thus, referrals to specialists are common for these procedures.
Stages of Lung Cancer in Dogs
Upon your dog’s diagnosis of lung cancer, your veterinarian will proceed to stage the cancer, which delineates the extent of its spread within the body. This staging serves as the basis for formulating a treatment regimen. Lung cancer staging in dogs hinges on factors such as the size of the primary tumor, the involvement of nearby lymph nodes, and the presence of metastasis beyond the original site.
While human lung cancer staging often employs Roman numerals, this system is not standard practice in dogs. Nonetheless, some veterinarians may utilize these stages to elucidate the cancer’s spread to pet owners. These stages typically include:
- Stage I: Characterized by a small tumor without lymph node involvement.
- Stage II: Signified by tumor growth and potential spread to nearby lymph nodes.
- Stage III: Indicates cancer dissemination to the lymph nodes between lung lobes.
- Stage IV: Denotes cancer spreading from the lung to other body parts.
Treatment
The course of treatment varies based on the type and severity of the cancer. Surgery stands as the preferred treatment for a solitary tumor. During the procedure, the surgeon eliminates either a portion or the entire lung lobe, contingent on the mass’s size and location. Biopsy of chest lymph nodes may be conducted to ascertain the extent of cancer spread.
For high-grade tumors, large tumors, or those exhibiting signs of metastasis, some veterinary oncologists might propose chemotherapy. However, in the majority of cases involving primary lung tumors in dogs, chemotherapy as a standalone treatment does not significantly enhance survival rates.
Dogs harboring metastatic nodules originating from cancer elsewhere in the body typically face a less favorable prognosis. This is indicative of advanced cancer that has metastasized to the lungs. A consultation with a veterinary oncologist is advisable in such cases.
Living and Management
For dogs without metastases that undergo surgery, there’s potential for a complete cure. Some dogs may enjoy a lifespan of over two years post-surgery. Expected survival times vary, ranging from three months to more than a year. Dogs diagnosed without clinical signs, possessing low-grade tumors, and smaller tumor sizes generally have longer survival periods.
Many pet owners opt against open-chest surgery when the tumor exhibits aggressive characteristics. Even with surgical intervention, prognosis for these cases typically spans three months.
If you opt for treatment for your dog’s lung cancer, your veterinarian may advise frequent chest X-rays during the initial year post-surgery to monitor for recurrence. For dogs undergoing chemotherapy, regular bloodwork monitoring is necessary to gauge chemotherapy tolerance.
To ensure your pet’s comfort, consider the following measures:
- Facilitate easy access to food and water.
- Provide a cozy resting area.
- Limit strenuous physical activity.
- Avoid smoking indoors and utilize a room air purifier.
- Remain consistent with your pet’s medication regimen.
- Discuss any concerns about potential pain with your veterinarian.
For dogs experiencing decline, your veterinarian may recommend a palliative care plan aimed at maintaining comfort. Treatment options may encompass anti-nausea medications, pain relief, cough suppressants, and anti-anxiety medications.
Lung Cancer in Dogs FAQs
What do the end stages of lung cancer look like in dogs?
In the advanced stages of lung cancer, dogs may exhibit decreased appetite, weight loss, muscle wasting, lethargy, coughing, wheezing, and difficulty breathing. Some dogs may experience the accumulation of fluid in and around the lungs, leading to severe breathing difficulties. If you observe signs of labored breathing, it’s crucial to seek immediate veterinary care.
How aggressive is lung cancer in dogs?
The aggressiveness of lung cancer in dogs varies based on the tumor type and grade. Surgical removal without metastases could lead to a potential cure for your pet. However, if the tumor has spread to other parts of the chest or body, it indicates a more aggressive form of cancer.