Lung Cancer (Adenocarcinoma) in Dogs

Primary lung cancer in dogs is relatively rare in dogs (under 1% of all cancer in dogs), but pulmonary adenocarcinoma is the most common type of canine lung cancer. As a matter of fact, almost 80% of primary lung cancer is caused by adenocarcinoma. This is an extremely aggressive cancer that grows quickly and can spread fast, so it is essential to the survival of your dog to treat this disease early. Similar to other cancers in dogs, it is seen more often in dogs over seven years of age. All breeds are at risk for this lung cancer, but it affects dogs with short or medium noses (i.e. Beagle, Boxers, Terriers) more often than other breeds. Many times, primary pulmonary adenocarcinoma is found on an x-ray during a veterinary visit for another issue.

Pulmonary adenocarcinoma is cancer of the lungs, which can be primary (originates in the lungs) or secondary (originates somewhere else in the body), is a serious disease that can be fatal if not found and treated early. Pulmonary adenocarcinoma spreads rapidly to other parts of the body, such as lymph nodes, bones, heart, liver, spleen, and brain. If the disease is not found and treated before it has spread to the lymph nodes, the prognosis is not good. Unfortunately, approximately a quarter of all dogs with primary pulmonary adenocarcinoma do not show any symptoms besides tiredness and decreased appetite.

There are many symptoms that are general in nature, such as weakness and loss of appetite, so it is sometimes difficult to know when your dog is really ill enough for a trip to the veterinarian’s office. A good rule to go by is that if your dog has had a chronic cough without any phlegm for more than a few days, you should take him to see the veterinarian just to be on the safe side.

• Difficulty breathing
• Rapid breathing
• Extreme tiredness
• Weakness
• Loss of appetite
• Weight loss
• Vomiting
• A cough with bloody sputum
• Fever
• Muscle pain and weakness

Types

• Primary pulmonary adenocarcinoma is cancer that originates in the lung
• Secondary pulmonary adenocarcinoma is cancer that has metastasized from somewhere else in the body

The cause of primary pulmonary adenocarcinoma is unknown, but there are several risk factors:

• Secondhand smoke
• Toxic chemical exposure
• Middle to old age (over seven years old)
• Short or medium sized nose (i.e. beagles, boxers, terriers)
• Idiopathic (unknown origin)

Secondary pulmonary adenocarcinoma is caused by a cancer somewhere else in the body.

The veterinarian will do a comprehensive physical exam and ask for your dog’s complete medical history including any recent injury, illness, or abnormal behavior. Provide the best description you can of your dog’s symptoms and when they started. Be certain to include any changes in appetite or weight loss. The next step is to get your dog’s vital signs, which include respiration and heart rate, blood pressure, temperature, and weight. The veterinarian will pay special attention to your dog’s breath sounds.

The most important test in diagnosing pulmonary adenocarcinoma is images of the lungs with radiography or CT scan. The veterinarian will also want to get an MRI of the surrounding areas to see if the cancer has spread from somewhere else. Some blood tests will be done, such as complete blood count (CBC), blood gases, and chemistry profile, including glucose levels. Other tests your veterinarian will do are a urinalysis, bronchoscopy, and a fine needle aspiration of tumor or fluid from lymph nodes for histopathology. The veterinarian will most likely refer you to a veterinary oncologist for treatment.

The best choice of treatment for this primary pulmonary adenocarcinoma is a lobectomy, which is the removal of the tumor and adjacent lung lobes. The surrounding lymph nodes and tissue may be removed as well if the oncologist suspects it may have metastasized. If the oncologist does not think the lung can be saved, the removal of the lung is the only choice for survival. Chemotherapy and radiation treatments may also be done in some cases. Secondary pulmonary adenocarcinoma is almost never treated with surgery because if the cancer has spread from another part of the body to the lungs, there is nothing more to do than make your dog comfortable.

The chances for your dog’s survival will depend on whether it is primary or secondary pulmonary adenocarcinoma, and how far it has spread. It will also depend on the age and health of your dog. If your dog has primary pulmonary adenocarcinoma and the veterinarian is able to remove the whole tumor, your dog has about a 50% chance of living more than one year. This is the kind of cancer that will often recur even if all of the cancer is removed the first time. If your dog has secondary pulmonary adenocarcinoma, the veterinarian will probably suggest that you just make your dog as comfortable as possible. When cancer has spread from another part of the body to the lung, it is usually too late for treatment. It is recommended that your dog not spend his last few months undergoing painful treatments that will make him sick.