If your dog is diagnosed with osteosarcoma, or bone cancer, it's likely your veterinary oncologist will recommend chemotherapy as part of his treatment. Chemotherapy usually can't save a dog diagnosed with osteosarcoma, but it can prolong his life. Along with other treatments, including amputation and radiation, your dog might live a year or more with a good quality of life after diagnosis. In rare instances, the animal is cured.
Most dogs diagnosed with osteosarcoma in the leg will have the limb amputated prior to radiation and chemotherapy. Two weeks after amputation -- or limb-sparing surgery if that is an option -- chemotherapy begins. Even though your dog's primary tumor is gone, it's likely that cancer cells are circulating throughout his body. What eventually kills your dog is the metastasis -- or spread -- of these malignant cells to other organs. The goal of chemotherapy is to slow or halt that spread.
How Chemotherapy Works
Chemotherapy drugs work by attacking cells that grow and divide quickly -- such as cancer cells. Ideally, these medications eradicate cancer cells while not affecting normal cells. That's not always the case, as it can harm some cells that normally grow quickly. In humans, that's the reason many cancer patients lose their hair during chemo treatment. In dogs, fast-growing normal cells include those in the bone marrow and the lining of the gastrointestinal tract. Your veterinary oncologist carefully monitors your dog during treatment, so that any toxicity and side effects are addressed. Common side effects include nausea, appetite loss and a reduced white blood cell count, which can lower resistance to infection. Dogs generally have fewer side effects than their human counterparts, primarily because lower doses are used. Hair loss is uncommon.
Chemotherapy drugs used in canine osteosarcoma treatment are primarily carboplatin, cisplatin or doxorubicin. The latter is marketed under the trade name Adriamycin. Carboplatin and cisplatin are platinum medications, literally containing that element. These are the same drugs used to treat human cancer patients. Your dog will undergo four to six chemotherapy infusions, generally with alternating drugs. Each infusion is three weeks apart. Some dogs might receive only carboplatin, considered the drug of choice for canine chemotherapy treatment.
Dogs receiving only palliative care for osteosarcoma live an average of 2 months after diagnosis. Dogs treated only with amputation live an average of 4.5 months. Those receiving radiation therapy and chemotherapy -- but not amputation -- live between 4 and 10 months. Dogs receiving amputation with four chemotherapy treatments live approximately 10 months, while those receiving six treatments live considerably longer, an average of 17.5 months.