Lungs are a vital organ in both humans as well as dogs, and one of the most important organs in the respiratory system that canines possess. Lungs are designed to move oxygen from the air into the blood stream, and then let carbon dioxide in the blood stream back out into the atmosphere. Because the lungs are such an important organ, a lung cancer diagnosis is very serious indeed.
Types of Dog Lung Cancer
In canines, there are typically two main types of lung cancer. The first is primary lung cancer, which is where a tumor originates in your dog’s lung or lungs. Currently this type of cancer accounts for less than 1% of all canine cancers, so it is considered relatively uncommon.
However, the number does seem to be increasing, though experts aren’t sure whether that’s because there is an increase in this type of canine cancer, or if it’s simply because of improved diagnostic capabilities and equipment. Primary lung cancer tumors are often malignant, and usually are visible as a mass on the lung when a chest x-ray is taken.
The second kind of lung cancer in dogs is called metastatic lung cancer, which means the cancer originated somewhere else in the body, but has spread to the lung. So, if a dog that first got cancer in their mouth for instance, or in their bones, they risk the chance of it metastasizing through the bloodstream to the lungs.
Unfortunately, canine lung cancer in both forms is aggressive and can spread very quickly. When it metastasizes, it may spread to the lymph nodes, as well as spread to thorax tissues. Sometimes it could spread to the central nervous system, depending on the type of carcinoma and how it’s classified.
When a cancer has metastasized to the lungs from elsewhere, there are usually multiple lung tumors that are found in or on the tissue, not just a single mass. However, it’s still important to have your dog thoroughly tested and treated by your vet to obtain a proper diagnosis, because sometimes dogs can present with several lung masses due to other health conditions such as fungal infections. In these cases, the masses are not cancerous.
Another thing to note is that with primary lung cancer tumors, they are often carcinomas and adenocarcinomas, although sometimes they can also be hemangiosarcomas.
Carcinomas form within the actual tissue of the lungs and may be entirely made up of lung tissue. Adenocarcinomas tend to spread to the dog’s central nervous system, while hemangiosarcomas tend to originate from elsewhere and spread to the lungs. Hemangiosarcomas may start first in the spleen or the liver or sometimes skin or soft tissue, and then spread. When it begins to spread, it can reach the lungs, heart, and kidneys, as well as muscle and bone.
What Causes Lung Cancer in Dogs?
Just like with people, the reasons dogs get cancer is never cut and dry. Scientists do know that cancer is ultimately considered cell damage caused by genetic mutations in the DNA, but they don’t know much about these mutations or their exact causes.
Scientists do know that sometimes certain chemicals could play a role in triggering or worsening certain cancers, and of course there are hereditary factors. Environment also plays a very large part in the development of lung cancers. Most notably, exposure to secondhand smoke.
In the same way, secondhand smoke increases the chances of lung cancer in humans, it’s also extremely unhealthy for your dog to breathe in. Unfortunately, there’s not much your dog can do about environmental factors such as secondhand smoke, because it falls on you as their pet owner to make sure that the air they are breathing is clean and toxin-free.
If you are a smoker and smoke around your dog, you are essentially forcing your dog to smoke too. Dogs that live in homes where they breathe in secondhand smoke on a regular basis run a pretty significant 60% risk in developing lung and/or nasal cancer.
Another interesting thing to note is that dogs with short or medium snouts seem to be more prone to developing lung cancers. It is thought that because their snouts are short, they are not as effective at filtering out carcinogens through their nasal passages and keeping them from reaching the lungs.
One cause of a very specific type of lung cancer called mesothelioma is triggered by asbestos. This mimics the very same type of cancer that humans can develop from asbestos.
Other causes of lung cancer in dogs relate to exposure to chemicals, as well as the age of your dog. Most dogs that get cancer of any type tend to be older. Again, though it’s difficult to definitively pinpoint the exact cause of lung cancer in dogs, these are the most common culprits.
Risk Factors of Lung Cancer in Dogs
While there are no definitive predilections to lung cancer when it comes to different breeds, it is thought that medium to large sized dogs seem to be the most susceptible, in particular Labradors and German Shepherds. Lung cancer is most often found in older dogs over the age of eight, with the average age of diagnosis for a dog being around eleven years old.
There doesn’t seem to be much of a difference between male and female dogs and the rate that they develop lung cancer at this time. However, it is thought that dogs living in urban areas may be at a slightly higher risk than their rural counterparts.
Signs and Symptoms of Lung Cancer in Dogs
What symptoms will manifest depends on the type of lung cancer your dog has developed and where exactly it may have spread to. When lung cancer is caught early, you may not notice any symptoms at all.
You may only notice a bit of weight loss or low energy levels. However, the earlier you catch it, the more likely you are to successfully treat it. If you wait until your dog is presenting with multiple symptoms, their chances of survival diminish greatly.
That said, here are some general signs and symptoms that indicate the possibility of lung cancer:
- Chronic cough
- No appetite
- Weight loss
- Exercise intolerance
- Coughing blood
- Bloody urine or stool
- Constant sneezing
- Difficulty breathing
- Rapid Breathing
- Shortness of breath
- Extreme lethargy and/or weakness
- Limping and lameness
- Muscle wasting
- Fever
- Collection of fluid in the abdominal cavity
Chronic coughing seems to be the most common abnormality that is seen in dogs with lung cancer. Often this cough is not productive, and does not produce any mucus or fluid, outside of some minor phlegm or blood.
Sometimes a tumor can be quite large and compress things like the trachea or a major airway, and this is what results in your dog having difficulty breathing. None of these symptoms are definitive on their own, as the signs of lung cancer can be similar to the signs seen in dogs suffering from other health conditions, like heart failure, pneumonia, or a heartworm infection. Therefore, it’s vital to see your vet to obtain an accurate diagnosis.
Diagnosing Lung Cancer in Dogs
Just as with any health condition, it’s important for you to keep a detailed record of your dog’s history and symptoms as well as when the symptoms started. This is helpful to your vet when making an accurate diagnosis.
Typically, your vet will start with a physical exam and may ask if your dog has experienced any sort of recent illnesses, changes in behavior or eating habits, or traumas. The physical exam itself may include assessing your dog’s vital signs, taking their weight, and an individual inspection of your dog’s mouth, nose, ears, and eyes. You vet may also perform a manual palpation of your dog’s body to check for lumps and abnormalities.
Your vet will most likely want to run tests, such as a CBC blood panel, a chemical panel, a blood gas test to see if your dog’s white blood cells are high or if your dog appears to have a high level of calcium. X-rays of the head, chest, and abdomen are often standard, as well as throat and nose cultures, and a urinalysis. Sometimes your vet may opt to run an ultrasound or an MRI or CAT scan if they can’t see clearly enough with the x-ray.
In some cases, your vet may wish to do an endoscopy to help them see inside your dog’s lungs. This is especially helpful before there’s any talk of surgery. Endoscopies are a low-risk procedure and often provide all the information necessary to give an accurate diagnosis. Sometimes a biopsy is required. Biopsies are usually the only way to figure out exactly what form of lung cancer your dog suffers from.
Your vet may wish to use a fine needle and syringe to aspirate the lung mass and remove microscopic cells to be evaluated. This also is a relatively low risk procedure, but in both procedures your dog may need to be sedated for his or her own comfort.
Regardless of treatment plans, almost all lung cancers require surgery first. This is to remove as much of the tumor or cancerous areas as possible, before starting the other treatments such as chemo and radiation. If diagnosed with lung cancer, your vet may choose to refer you to a veterinary oncologist for further treatment options.
Prognosis of Lung Cancer in Dogs
The prognosis of lung cancer in a dog really depends on the type of cancer your dog has developed and the extent of its spread throughout the rest of your dog’s body. Dogs that present with primary lung cancer with just a single, small mass in their lungs that has stayed contained are good.
50% of dogs with this type of cancer live at least one year beyond the removal of the mass. Depending on the grade of the tumor, dogs may live and survive upwards of 22 months or only survive an additional six months.
Interestingly, another factor that seems to play a role in survival rates is whether your dog shows symptoms or not. Dogs that show cancer symptoms seem to have a lesser survival rate than the dogs who present with no symptoms at all.
Unfortunately, it doesn’t matter the type of lung cancer or the treatment options you choose, lung cancer as a whole doesn’t have a great prognosis. There is a high mortality rate with this illness, largely because it is very aggressive and can often be medication resistant.
One factor to consider before starting treatment of your dog is the cost versus reward. The cost of treating lung cancer in dogs can be quite expensive depending on the severity of your dog’s cancer. In addition to the cost, there are no guarantees that your dog will survive for any extended period, and if he or she does, how much suffering will your dog be forced to endure because of it?
In some more advanced cases, it may be best to discuss with your vet ways to make your pet comfortable and allow the disease take its course, or consider euthanasia. If you do opt for treatment, there is no one method that works for all dogs. It is best to adopt a combination of treatments specifically tailored to the needs of your dog for optimal results.
At the end of the day treatment only increases your dog’s survival time, but how much time is hard to guess. However much additional time you are given with your dog, love them and provide them with care and affection. That way you can make their final weeks or months with you as enjoyable as possible.
Sources:
- “Lung Cancer (Adenocarcinoma) in Dogs – Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost.” WagWalking, 28 May 2016, Accessed 7 May 2017. www.wagwalking.com/condition/lung-cancer-adenocarcinoma.
- “Lung Cancer (Adenocarcinoma) in Dogs.” PetMD, Accessed 7 May 2017. www.petmd.com/dog/conditions/cancer/c_dg_adenocarcinoma_lung.
- “Lung Cancer.” Canine Cancer, Accessed 7 May 2017. www.caninecancer.com/lung-cancer/.
- “Stages of Lung Cancer in Dogs.” VetInfo, Accessed 7 May 2017. www.vetinfo.com/stages-of-lung-cancer-in-dogs.html.
- “Lung Cancer and Lung Surgery in Dogs.” Pet Health Network, Accessed 7 May 2017. www.pethealthnetwork.com/dog-health/dog-surgery-a-z/lung-cancer-and-lung-surgery-dogs.
