If your dog is diagnosed with osteosarcoma, chemotherapy, along with other treatments, can increase his longevity. While the disease shortens his life expectancy, chemotherapy treatments often mean he'll have a good quality of life for his remaining time. Most dogs tolerate chemo well, without side effects such as the hair loss occurring in people. Other than a few lethargic days following a treatment, dogs lead their normal lives.
How Chemotherapy Works
Chemotherapy drugs target cancer cells. They do so by destroying exceptionally fast-growing cells, which are typically cancerous. Chemotherapy can destroy or slow cells metastasizing, or spreading, from the original tumor. However, with osteosarcoma it's almost a certainty that the malignant cells have spread by the time of diagnosis. Chemo buys your dog time before the cancer returns, sometimes significant amounts of it. Because canines receive lower chemo dosages than humans, most dogs don't experience severe side effects. Your vet can prescribe medication, such as antiemetics, to prevent or treat any side effects.
Since osteosarcoma usually occurs in the leg bones, the initial treatment consists of amputating the leg containing the tumor. Your dog's first chemo treatments usually begin about two weeks after his amputation, or limb-sparing surgery if that was an option. Generally, he'll receive four to six intravenous treatments spaced about three weeks apart. His exact schedule depends on the type of chemo drugs he receives and whether he experiences side effects, especially those that lower his white blood cell count.
Dogs undergoing chemo for osteosarcoma usually receive three primary drugs, often in combination. These are doxorubicin, carboplatin and cisplatin, all used in fighting human cancers. The latter two include "platin" in their names because they contain platinum. While effective, those medications in particular are quite expensive. Either of the platins might be combined with doxorubicin. If your dog has kidney issues, he can't receive cisplatin. If his heart function is weak, doxorubicin, also known as Adriamycin, is out.
Prognosis With Chemotherapy
If your dog doesn't receive chemotherapy, he's likely to die before the first anniversary of his surgery. If he does receive chemo, odds are 50 percent that he'll survive one year and 20 percent that he'll still be around two years later. While those odds are sobering, with just surgical treatment he's only likely to live a month or two. Inevitably, osteosarcoma spreads to the lungs. When your dog develops a constant cough, breathing difficulties and similar symptoms, it's time to contact your veterinarian and let him go peacefully. Comfort yourself knowing you did everything you could for your best friend.