Diagnosis
Cancer that is in the lungs tends to spread to nearby lymph nodes. The lymphatic system is responsible for your dogs immune system response. X-rays are taken to see if the lymph nodes are enlarged from trapped cancer cells. Once these enlarged nodes are seen then a veterinarian will take a sample for testing (biopsy).
Causes
Canine lung cancer can be primary lung cancer or metastatic lung cancer.
Primary lung cancer is defined as lung tumors that originate in the lung. The tumors are almost always malignant and are usually carcinomas (often adenocarnimas), although can be hemangiosarcomas. The tumors are easily visible on a chest x-ray as one large solitary mass. Primary canine lung cancer is rare but is aggressive and can metastasize to the regional lymph nodes in the upper chest area. Adenocarcinomas tend to spread to the central nervous system.
Metastatic lung cancer originates in other parts of the body such as a leg bone, the mouth, or the thyroid gland, but has spread to the lung through the bloodstream. Metastatic lung tumors usually present themselves in multiples, not as a single mass.
Treatment
If the veterinarian suspects your dog has canine lung cancer, he may refer you to an oncologist who will be able to provide specialized treatment. Treatment of the disease depends on whether or not it has already begun to spread. If the disease is localized to one area, treatment will usually involve surgery. If it has already spread from other areas, canine lung cancer will have to be treated with radiation or chemotherapy.
In the case of primary lung cancer, surgery is the preferred treatment if the tumor is small, because complete excision may not be possible in all cases. Surgery is ruled out in cases of metastatic lung cancer. Chemotherapy, after surgery or as a primary treatment choice, has shown good results in controlling the progression of lung cancer. Lung cancer usually proves to be fatal, and after treatment, you will be required to provide extra home care to monitor the side effects of strong drugs and provide comfort for as long as the dog lives.
Prognosis
Dogs with small, low grade (well-differentiated) tumors without lymph node involvement, the average survival time is 16 months with surgery alone. Dogs with high grade (poorly differentiated) tumors with lymph node involvement have an average survival of 2 months. Because many patients will ultimately develop metastatic disease following surgery, chemotherapy is commonly recommended. However, it is unknown whether the use of chemotherapy following surgery significantly improves survival over surgery alone.
