Malignant canine pulmonary neoplasia (lung cancer), either primary or secondary, tends to be extremely aggressive. Primary lung cancer accounts for less then 1 percent of all canine cancers, according to Canine Cancer website. Usually, metastatic occurrence in the lymph nodes or other regions of the body has occurred at the time of diagnosis, making surgery unfeasible. Both primary lung cancer that has spread to other regions and metastatic lung cancer that arose in another location but has spread to the lungs must be treated using chemotherapy drugs in order to reach all areas of cancer involvement.
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Risk Considerations
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Lung cancer affects both male and female dogs equally. The average age of diagnosis tends to be around 11 years old. Secondhand smoke may play a part in dogs contracting primary lung cancer. Mesothelioma, a form of cancer that arises in the mesothelium membrane, which encases the pleural cavity surrounding the lungs, also affects dogs. Asbestos exposure can cause mesothelioma in canines just like in humans. High quantities of asbestos fibers have been found in canine lungs suffering from mesothelioma, according to the University of Georgia Department of Veterinary Medicine's website.
Symptoms
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The dog often begins to suffer lethargy, weight loss, lack of appetite and shortness of breath. Coughing can occur and often produces bloody phlegm. Dogs often limp or have difficulty getting up from a sitting or lying position due to metastatic occurrence in the bones.
Diagnosis
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Before treatment can begin the veterinarian must make a complete diagnosis of lung cancer and also evaluate the cell type and the regions of possible spread. Most veterinarians perform a physical on the dog, order blood work and take numerous X-rays. A biopsy of the tumor or tumors using a needle is often taken to determine the cell type of the cancer. Often the biopsy is performed using a thoracoscope, which allows the veterinarian to enter the lungs through the dog's nose using a scope to collect cell samples.
Treatment
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Surgery is rarely performed if the cancer has spread. Chemotherapy is utilized; it is not a cure but can slow down the progression of the cancer to buy the dog time. The two main drugs used in chemotherapy for primary and secondary lung cancer are vinblastine and carboplatin. The drugs are utilized together or singularly for treatment. On rare occasions the combination of metronomic or Deramaxx (a nonsteroidal anti-inflammatory drug) with cyclophosphamide (Cytoxan) are used. The combination of these chemotherapy drugs appears to inhibit blood vessel production, which slows the growth of new tumors.
Prognosis
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If the dog can undergo complete surgical resection of a primary tumor it may live up to a year or more following treatment. Often the combination of surgery with chemotherapy will gain the dog a long remission time span of up to 22 months. Chemotherapy by itself is rarely very effective.
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