Cancer is a powerful word that elicits fear and apprehension. What makes cancer so dreadful is that the disease is most often caused by a mutation of the body's own cells. The body literally turns on itself.
Cancer cells break all the rules. They no longer maintain their normal function or behavior, multiplying rapidly at the expense of surrounding tissues. These mutated cells also can spread via the bloodstream or lymphatic system to distant tissues. A healthy body can police most abnormal cell activity, either by repairing or destroying the cells. But with cancer, mutated cells continue to proliferate unchecked.
Risk factors and detection
More than 100 different cancers affect dogs. And with a dog population that's living longer than ever, cases are on the rise.
Genetics play a role, and certain breeds are predisposed to specific cancers. For example, boxers, English bulldogs, and Boston terriers are at higher risk for mast cell tumors. Bone cancer is more common in the giant and large dog breeds; hemangiosarcomas (malignant tumors of the blood vessels) affect more German shepherds and golden retrievers; and cancer of the lymph nodes is more common in golden retrievers, boxers, and English bulldogs.
Unaltered dogs are at greater risk for cancer of the mammary glands, ovaries, uterus, prostate, and perianal glands than spayed or neutered dogs. Exposure to sun and sunburn increases the risk of certain skin cancers.
Signs vary depending on where the cancer appears, but common signs include:
- an unexplained lump or swelling anywhere on the body
- swollen lymph nodes
- weight loss
- lethargy
- loss of appetite
- anemia.
Call your veterinarian if you notice any of these signs. Examinations and laboratory tests help your veterinarian diagnose and treat cancer, but he or she needs your watchful eyes to detect changes in your dog's habits, demeanor, or body.
Your veterinarian will perform a complete physical examination and may use a syringe and needle to collect a few cells from the lump. Blood tests, X-rays, ultrasound, and surgical biopsy also help diagnose cancer and determine its stage. Some hospitals provide such advanced imaging techniques as CT (computed tomography) scans or MRIs (magnetic resonance imaging). These imaging techniques help locate tumors that are undefined or undetectable with radiography or ultrasonography.
Not all lumps are cancerous. Some are benign growths, but veterinarians can't tell just by looking at them. They must send a tissue sample for laboratory evaluation.
Prevention
A balanced diet and healthy lifestyle can help reduce your dog's chances for developing many cancers, but she also needs routine veterinary care and examinations. Petting and grooming your dog regularly helps you detect any unusual lumps. Spaying or neutering will reduce the risks of reproductive-related cancers.
Skin cancer is on the rise in dogs as well as in people. Minimize your dog's sun exposure—especially light-coated or thin-haired pets—by providing shade over outdoor kennels or keeping your dog indoors during the peak times for harmful ultraviolet rays, usually 10 a.m. to 4 p.m.
Treatment
Medical advances continue to generate more effective cancer treatments that manage the disease and provide comfort to dogs. Surgery, radiation therapy, and hyperthermia offer potential cures for some types of cancer. Chemotherapy and immunotherapy can relieve symptoms and may induce relatively long disease-free periods.
Your veterinarian will recommend treatments based on several factors: your dog's condition, the cancer type, and its stage. In early stages, for example, the cancer often is localized and responds well to aggressive therapy. Once cancer metastasizes, or spreads to other body parts, treatment becomes more difficult.
Your veterinarian should explain all treatment options and discuss the pros and cons of each therapy. You play an important role in your dog's treatment by monitoring her well-being at home and by discussing your concerns and expectations with your dog's doctor.
To increase effectiveness and decrease side effects, your veterinarian likely will combine several treatment options.
Surgical therapy can be used to remove or decrease the size of a tumor, or your veterinarian may operate to obtain a biopsy sample. Surgery can cure some cancers, but most require additional treatment methods.
Radiotherapy eradicates some tumors and shows little effect on others. A radiation specialist will use this therapy to treat radiation-responsive tumors that are difficult or impossible to remove surgically. The side effects of radiotherapy include skin inflammation, hair loss, and cataract formation.
Immunotherapy alters or stimulates the body's immune system using drugs, immunostimulants, and antibodies. Immunotherapy's effectiveness is unknown, and many researchers are examining whether certain drugs can direct the body to fight cancer.
Chemotherapy is the most common cancer treatment. Because chemotherapy can cause such serious side effects as severe vomiting and diarrhea or inhibiting the body's ability to produce blood cells, your veterinarian will regularly examine your dog and conduct blood tests during the course of therapy.
Other treatment options include:
- hyperthermia, which involves applying heat (a few degrees above normal body temperature) to the whole body or specific areas using ultrasound, radiofrequency, or electromagnetic radiation
- cryosurgery, which involves applying extreme cold to freeze and kill tumor cells
- phototherapy, which involves administering a drug that makes tumor cells light-sensitive and then exposing them to a laser beam.
Your veterinarian's first goal in cancer treatment is to induce remission, eliminating the signs of cancer. The second step: Maintain remission. If your dog suffers a relapse, the veterinarian will try to reinduce remission. There are no guarantees that your dog will reach remission. If your dog doesn't respond to treatment, the veterinarian will try to minimize your pet's pain.
During this time, your dog needs supportive, attentive, and tender-loving care. Cancer patients often need special nutritional support, blood transfusions, and intravenous fluids. And because cancer treatments often impair the immune system, your dog is at high risk of developing secondary infections. You'll need to isolate your dog from other animals and report any fever or other abnormalities to your veterinarian immediately.
Prognosis
The prognosis depends on the stage and cancer type. When caught early, your dog has a good chance to live a happy and relatively comfortable life for several years. Her chances continue to improve as researchers develop more effective treatments and as doctors better understand the cancer process.
If your dog's condition deteriorates, talk to the veterinarian about your options. Making your dog comfortable and relieving her pain are the best ways you can show her you love her.
