Chances are your life has been affected by cancer, whether the diagnosis was yours, a friend’s, a family member’s, or a pet’s. As our canine companions live longer and longer we are seeing more of them eventually being affected by cancer. According to the AVMA approximately 1 in 4 dogs will develop cancer at some point in their lives. Cancer can strike any breed of dog and at any age; however, like in humans cancer is more common in older individuals. Below is a discussion of the 5 most common cancers in dogs, many of which ultimately lead to the difficult decision to euthanize.
- Lymphoma
Lymphoma is a type of cancer that affects the lymphatic system. It is one of the most common types of cancer in dogs (and in cats). There are several types of lymphoma which are categorized by the systems affected. The four most common types of lymphoma in canines are: multicentric, alimentary, mediastinal and extranodal lymphoma. Multicentric lymphoma is by far the most common of the four. Clinical signs (symptoms) vary widely depending on which system is affected; for multicentric lymphoma owners usually notice enlarged lymph nodes leading to a veterinary visit and diagnosis. The cause of lymphoma is unknown, but it is believed to be related to genetics and environmental factors.
Treatment for lymphoma typically involves chemotherapy. The exact treatment protocol and prognosis will depend on many factors including type of lymphoma, stage of disease, and overall health of the pet.
- Hemangiosarcoma
Hemangiosarcoma is a type of cancer that affects the blood vessels. It is believed to originate in the bone marrow and rapidly spreads to other organs, often causing tumors in the heart or spleen. It is most commonly found in large breed dogs, such as Golden Retrievers, German Shepherds, and Labradors. There are no “classic” symptoms associated with hemangiosarcoma and its presence is often unknown until an internal tumor ruptures leading to sudden blood loss and collapse.
Treatment of hemangiosarcoma begins with surgery to remove the tumor. If the tumor ruptures, emergency surgery is needed to remove it and stop the bleeding. Additional treatments may include chemotherapy. However, survival times for dogs suffering are fairly bleak with 90% of patients passing before a year with both surgery and chemotherapy; patients who are treated with surgery alone have an average survival time of 1-3 months.
- Osteosarcoma
Osteosarcoma is a type of bone cancer that is most commonly found in large or giant breed dogs and usually affects the long bones of the limbs. Osteosarcoma is very painful; as such clinical signs may include limping and decreased activity as well as swelling around the affected bone.
Treatment for osteosarcoma typically involves amputation of the affected limb followed by chemotherapy. While this may seem extreme, dogs adjust considerably well with these treatments as the quality of their life usually improves dramatically. Sadly, the quantity of life is not greatly improved. By the time of diagnosis, most dogs with osteosarcoma will already have micrometastases and greater than 90% will succumb to metastatic disease within 2 years.
- Mast Cell Tumors
Mast cell tumors are the most common type of skin cancer found in dogs. They can occur anywhere in the body but are most often found on the skin of the trunk or limbs. Mast cell tumors may be raised, red, itchy, or change in size (getting bigger or smaller) and may seem innocuous. Because mast cell tumors can vary in appearance it is important to have a veterinarian examine and investigate any lumps or bumps you may notice on your dog.
Treatment and prognosis for mast cell tumors depends greatly on the location and depth of the tumor as well as whether it has spread and the grading of the tumor (how aggressive it is). Typically treatment involves surgery to remove the tumor followed by chemotherapy and/or radiation therapy. Some mast cell tumors are relatively benign and localized with surgery being all that is necessary; while others may spread aggressively despite extensive treatment. Surgical removal or biopsy of the tumor is important to gain the information needed to get a proper prognosis.
- Mammary Gland Tumors
Mammary gland cancer occurs when a tumor develops in one of the dog’s 10 mammary glands, which run down their body in two rows. Mammary tumors are most commonly found in older females that have not been spayed. Pet parents normally notice lumps and bumps or sometimes discharge from one of the glands of the dog’s mammary chains. There are different types of mammary tumors with approximately 50% being malignant.
Treatment for mammary gland tumors varies depending on the type of tumor. Often treatment involves surgery to remove the affected gland(s) with margins again depending on tumor type. Radiation and anti-inflammatory medications are usually the treatment of choice for inflammatory mammary carcinoma. Chemotherapy is reserved for advanced cases. As with the other cancer types discussed, prognosis varies depending on several factors including when the tumor was found.
According to the Animal Cancer Foundation approximately 6 million dogs in the United States are diagnosed with cancer annually. While much may be out of our control with a cancer diagnosis, we can help our pets through early detection and through treatment. Performing a quick exam of your dog while you pet or groom them can play a major role in early detection. As you make this part of your routine you will get a sense of what is normal and what is out of the ordinary for your dog. It is also important to note that chemotherapy in animals is often quite different from chemotherapy in human medicine. Dogs tend to tolerate treatments very well with few if any side effects. It is worth discussing with your veterinarian or veterinary oncologist to get more information, even if you ultimately choose not to pursue chemotherapy.
Unfortunately regardless of cause, all dogs will eventually approach the end of their journey. When this happens, it’s important to remember that euthanasia can help to prevent further suffering. Euthanasia can be performed by your veterinarian, veterinary oncologist or by a veterinarian who specializes in at-home euthanasia.
