You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Lung cancer is a serious, potentially fatal disease which affects both cats and dogs from time to time. Successful treatment depends upon the type of cancer involved and early detection.

Lung cancer is a debilitating, potentially life-threatening  disease which is seen in both cats and dogs.

The signs of lung cancer include :

• Increased breathing (respiratory) rate
• Coughing
• Difficulty breathing, gasping
• Weight loss

 There are two main types of the disease :

• Primary lung cancer - this is when the cancer arises in the lung tissue itself
• Secondary (or metastatic) lung cancer. This is when the original (primary) cancer is in another organ, but it spreads to the lung. Most often this spread occurs because cancer cells enter the bloodstream and are carried to the lungs where they become lodged. Cancers can also spread locally to other organs, or get carried to other major organs such as the liver or the brain.

Most malignant forms of cancer can spread to the lungs but some of the most common include :

• Thyroid carcinomas
• Urinary bladder carcinomas
• Bone tumours (osteosarcoma)
• Mammary (breast) tumours

Primary lung cancer is less common than secondary lung cancer. When it occurs primary lung cancer can involve just one lung lobe, and so surgical removal can be successful. On the other hand secondary lung cancer is most likely to involve more than one lung lobe, and sometimes all lung lobes are affected - which makes surgical removal difficult or impossible. When surgical removal of metastatic cancer is possible long term disease-free survival can be expected in about 25% of the cases.

If the cancer cannot be removed surgically there are other forms of treatment which can be used including chemotherapy. There are several factors that will influence how successful medical treatment can be including :

• How early in the course of the disease it is diagnosed
• What type of primary cancer was involved - some forms grow much more quickly than others

Even if a complete cure is not possible, the use of chemotherapy can give a period of improvement in the clinical signs, and slow the progression of the disease (called a period of remission). When signs start again it is called a relapse.

In humans there is a high correlation between cigarette smoking and lung cancer, and between exposure to asbestos and a particular form of lung cancer called mesothelioma. Studies looking at lung cancer in pet dogs showed only a weak relationship between lung cancer and exposure to smoking in the home (so called "passive smoking"). However, there was no increased risk associated with the number of smokers in the house, greater numbers of cigarettes being smoked, or increased time spent indoors. Mesotheliomas are reported occasionally in animals.

There is a lower risk of contracting lung cancer in long-nosed (dolicocephalic) breeds of dog, than in short-nosed (brachycephalic) or medium-sized nose (mesocephalic) breeds of dog..

Updated October 2013