It is now more common for a person to be diagnosed with cancer than to get married, have a first child or get a college degree. Today, the human cancer diagnoses are divided almost equally among men (51 percent) and women (49 percent). Also, 37 percent say that cancer is the disease they fear the most — more than dementia and stroke or heart disease.
For many people, as equally alarming and scary is a cancer diagnosis in their pets — and cancer is very common in animals. Some statistics show cancer is three to four times more common in dogs than in humans, with a breakdown of the cancer types about the same as we see in people.
In my hospice and end-of-life care practice, it is almost 70 percent of the cases I see; and I see these every week. The other common life-ending diseases I see are equally divided among heart disease, end stage kidney disease, stroke and such severe arthritis it causes rear leg paresis and paralysis.
So what are the top cancers seen in our pets, the main symptoms; and what can be done?
Here is the list from most common to least:
1. Lymphoma or Lymphosarcoma
Lymphoma is about 20 percent of all canine cancers, and dogs are two to five times more likely than people to develop lymphoma. This tumor can affect any breed of dog at any age, but especially the Golden Retriever. The most common sign is enlargement of the lymph nodes — particularly under the jaw, in front of the shoulders and behind the knees. The dog may not have any other signs or may be showing subtle signs, such as a decreased appetite or weakness. Other signs such as pain and breathing difficulty all depend on where the internal lymph nodes become enlarged. Treatment may involve steroids and chemotherapy. But even with good chemotherapy, dogs may not live longer than a year after the diagnosis, with some dying within three to four weeks.
Hemangiosarcoma is a tumor that develops from cells that line blood vessels. This tumor most commonly affects middle-aged or older dogs of any breed. It develops slowly and is not painful to the dog. Signs usually do not show until late in the disease, when the dog suffers from internal bleeding due to the tumor rupturing. The organ most frequently affected is the spleen, but it can also affect the heart, liver and skin. Even with aggressive treatments, most dogs do not survive long once diagnosed. Survival times with surgery alone are reported to be two to three months — five to seven months when combined with chemotherapy.
Osteosarcoma is the most common type of primary bone tumor in the dog. It most frequently affects the long bones of the dog, but can be found in any bone, including the skull or ribs. This tumor is usually associated with the giant dog breeds, with Great Danes being 200 times more likely than toy breeds to be affected. Most dogs are between 7 to 10 years of age at the time of diagnosis. It is aggressive and can spread rapidly, generally to the lungs. Treatment usually involves amputation and chemotherapy. Survival is usually about six to 12 months. This cancer took my female Great Dane in 2016.
4. Mast cell tumor
Mast cells are immune cells found throughout the body that play an important role in allergic reactions, and tumors of these cells can develop. Boxers and bulldogs are more frequently diagnosed. Treatment involves surgery; and, because there is an unusual pattern of growth, your veterinarian will need to remove a large area around the tumor.
Melanoma, or malignant melanoma, is a tumor made of pigmented or dark skin cells that can be found anywhere on the dog’s body. Any dog can be affected, but dogs with dark skin or hair coats are more frequently diagnosed. Tumors located in the mouth and distally on a limb, such as on the foot or toes or that have spread to lymph nodes, are usually associated with a worse outcome or prognosis. Treatment is usually surgery, radiation therapy and chemotherapy. But in the past few years, a vaccine has been developed that has shown much promise for control of the tumor after surgical removal.
6. Squamous Cell Carcinoma
Squamous cell carcinomas can develop on the skin and inside the mouths of dogs. The location of squamous cell carcinomas is strongly associated with the dog’s survival time. Growths on the skin are often found early by the pet owner, and these respond well to surgery alone. Oral squamous cell carcinomas are considered aggressive, and less than 10 percent of dogs with tumors in the mouth will survive more than one year after diagnosis.
7. Mammary Carcinoma (Breast Cancer)
Tumors of the mammary glands are the most common tumor seen in female dogs that have not been spayed. Forty to 50 percent of these tumors are malignant and have spread to other locations at the time of diagnosis. Treatment usually involves surgical removal of the entire chain of mammary glands on the affected side, along with the lymph nodes. Chemotherapy is often also recommended.
8. Apocrine Gland Carcinoma (Anal Sac)
Apocrine gland carcinomas are also known as carcinomas of the anal sac in the dog. Approximately 50 percent of these tumors are diagnosed by your veterinarian during a routine rectal exam, and show no apparent clinical signs. This cancer is locally invasive, meaning they grow and invade tissues around the anal gland. This can make complete surgical removal difficult. Therefore, radiation is often done and can help reduce the size of the tumor.
Dogs that have surgery alone for apocrine gland carcinoma usually survive one year, while additional treatments can increase this to 18 months.
9. Transitional Cell Carcinoma
Transitional Cell Carcinoma is the most common tumor of the urinary tract in the dog. This tumor is invasive and is highly likely to metastasize to another area. Chemotherapy or even anti-inflammatory drugs and radiation could be helpful. Tumors of the bladder are often associated with blood in the urine and painful urination.
10. Soft Tissue Sarcoma
These tumors are made of connective tissue and located either within the skin or just below the skin. You often find these when just petting or grooming your dogs. An example of a tumor in this group is a fibrosarcoma, and they can grow large and metastasize.
It is most important that you watch your pet closely and do an at-home physical exam every month to see if any growths or bumps form. If so, please see your veterinarian for a professional evaluation. Just as in human medicine, much can be done for these cancers, but they should be caught early for treatment to have a chance.
Dr. Jim Humphries is a veterinarian and provides hospice and end-of-life care for pets in the Colorado Springs area. He also serves as a visiting professor at the College of Veterinary Medicine at Texas A&M University. He lives in Falcon with his wife, horses and Great Danes. www.HomeWithDignity.com