Cancer in dogs: types, treatments and prognosis

Cancer

Cancer in dogs can affect everything from the skin to the bones. The disease is caused by uncontrolled cell growth and can take one of two forms: benign (does not grow in an unlimited and aggressive way, does not invade surrounding tissues, and does not spread to other parts of the body) and malignant (meaning it enters healthy tissues, grows aggressively and spreads to other areas of the body). Since some cancers grow slowly while others develop more quickly, be sure to see your vet as soon as possible if you notice anything unusual.

Types of cancer

There are several different types of cancer in dogs. The following are some of the more common ones, including their symptoms and treatments:

• * Hemangiosarcoma (HSA): an aggressive and malignant cancer that arises from the blood vessels and mainly affects the spleen, heart or skin. Skin shape is associated with sun exposure, and white-haired breeds are at higher risk. The lesions look like dark red or black growths on the skin and should be removed immediately as 1/3 will spread internally. Hemagiosarcoma of the spleen and heart usually presents with acute collapse/weakness and pale gums due to bleeding from the tumor. German shepherds, golden retrievers, boxers, and English setters seem to be predisposed. Surgical removal of the spleen and biopsy are needed to diagnose HAS, as the mass may be benign (hemangioma or hematoma). Surgery to remove the cardiac mass or open the lining of the heart is only palliative, and often the mass cannot be resected. While early and aggressive treatment, including chemotherapy, can prolong your dog’s life, complete remission is rare.
• Cutaneous Histiocytomas: Small, round, benign tumors that can appear anywhere on the skin of the body, but are most common on the head, ears, and neck of dogs under 3 years of age. They usually regress within 2-3 months, however, if the tumors are bothering your dog, they can be surgically removed. This tumor has been reported to be the most common skin cancer and the most commonly seen form of cancer overall.^6.7
• Lymphoma (LSA): A common malignant cancer (about 10-20% of all cancers in dogs) that occurs in the lymph nodes, spleen, liver, and other organs, and primarily affects middle-aged and older dogs. greater. Certain breeds such as Rottweilers, Scottish Terriers and Golden Retrievers are at higher risk and there is also speculation that it may run in families. Lymph node tumors appear as swellings, but other symptoms vary depending on the part of the body involved: the gastrointestinal form of this cancer causes vomiting, diarrhea, and weight loss; the thoracic form causes shortness of breath and muffled heart sounds. and the shape of the skin causes itchy red bumps to appear on the skin and inside the mouth. Biopsies, x-rays, and ultrasounds are used to diagnose lymphoma. Once lymphoma is diagnosed, it should be staged to determine the best course of treatment and provide a prognosis. Treatment often consists of chemotherapy +/- surgery. Some veterinary hospitals now offer a bone marrow transplant, but the cost (around $20,000) will probably prohibit most of us from seeking it. A consultation with a veterinary oncologist can determine the best course of treatment, which can sometimes add a year or more to a dog’s life.
• Breast Cancer: The most common cancer in female dogs and effectively affects older female dogs between the ages of five and ten who have not been spayed. German Shepherds, Cocker Spaniels, Poodles, and Terriers are overrepresented. Half of these tumors are malignant and the other half have spread at the time of diagnosis. Tumors can affect one or more of the mammary glands throughout your pet’s belly. They may be a single small mass or multiple large ulcerated masses. Malignant tumors are usually fast growing and benign tumors are usually slow growing. A biopsy and microscopic investigation will determine whether the tumors are benign or malignant. Immediate surgical removal of any breast tumor is recommended. If caught early, surgical removal of tumors can completely eliminate more than 50 percent of malignant cases. Spaying is also recommended if it has not already been done, since 50% of malignant tumors and some benign tumors have receptors for female hormones. Spaying early (before the first heat) reduces the risk of developing breast cancer. Chemotherapy is also sometimes used to treat some breast cancers. The prognosis depends on the type of cancer, the size of the mass, the extent of spread, ulceration, how fast it is growing, and the results of the biopsy.
• Mast Cell Tumors (MCTs) – These are a common skin tumor (20% of all skin tumors in dogs) found anywhere on the skin, especially the trunk. Boxers, Boston Terriers, Bullmastiffs, and English Setters are predisposed. MCTs vary in appearance and can be smooth, irregular, or ulcerated. They can also get bigger or smaller in a short period of time, especially when affected due to compounds in MCTs (histamine and heparin) that cause redness and swelling. Most MCTs are locally invasive and often difficult to remove. These tumors are classified into grades I-III, based on their behavior (invasiveness, how well differentiated they are, how fast they divide, etc.), with higher grades classified into stages. MCT usually spreads to the lymph nodes, liver, spleen, and bone marrow, so staging requires blood tests, X-rays, ultrasound, lymph node aspirations, bone marrow aspirations. Surgical removal +/- radiotherapy is the main treatment and requires wide margins. Chemotherapy is sometimes used, but the response is unpredictable. The prognosis is good for grades I and II, and the prognosis for dogs with grade III is guarded. Dogs that develop MCTs are likely to develop more, therefore they should be watched closely.
• Osteosarcoma (OSA): The most common bone tumor in dogs. It is an aggressive, malignant, highly metastatic bone tumor that most often occurs in the bones around the shoulder, wrist, and knee, but can develop in any bone. It primarily affects older large or giant breed dogs, with Great Danes, Saint Bernards, Great Pyrenees, Newfoundlands, Bernese Mountain Dogs, and Irish Wolfhounds being most at risk. The tumors usually cause pain, lameness, and swelling in the affected limb. Sometimes they present as a fracture. A biopsy is done to identify the cancer, and because of the high rate of metastasis, chest X-rays are also indicated. Other tumors can mimic OSA, such as chondrosarcoma, squamous cell carcinoma, and synovial cell sarcoma. Fungal infections can have similar symptoms, so fungal titers should also be done if there is a possible exposure. Treatment options include amputation, radiation, chemotherapy, and pain medications, depending on whether you want to ease the pain or try to find a cure. The prognosis depends on many factors and survival times vary from 3 months to 2 years.

Cancer can be a devastating diagnosis. Even if your pet has been diagnosed with cancer, fight it with the positive power of nutrition. Nutrient-dense foods that will give your dog the best chance at being healthy, like Prescription Diet n/d, can create a powerful platform from which your dog can fight cancer.