Bone Cancer in Dogs
Bone Cancer in Dogs
In dogs, bisphosphonates are used as adjuvant therapy for the management of osteosarcoma. They inhibit osteoclast cells (bone busters), which are responsible for bone breakdown. This inhibition gives the osteoblast cells (bone builders) a chance to work without interference, strengthening the existing bone and creating new bone. Increasing the strength of the existing bone helps to decrease the risk of fractures, and stronger bone is less painful.
The most commonly used bisphosphonates are oral alendronate, intravenous pamidronate and intravenous zoledronic acid (zoledronate).
When studied in the laboratory, bisphosphonates also have a direct toxic effect on bone cancer cells, contributing to their death. There is also evidence that they may inhibit cancer cell growth by inhibiting the growth of new blood vessels within the cancer. Whether or not these effects occur clinically remains to be seen. Ongoing research suggests that bisphosphonates may also have a role in the inhibition of metastatic bone cancer cells, by their direct toxic effect.
Bisphosphonates are often used in conjunction with radiation therapy but can be used as part of a palliative pain management regimen without radiation or surgery. Most forms are administered every few weeks intravenously, but there has been some success with the use of oral alendronate in various protocols.
The major side effects of bisphosphonates include gastrointestinal toxicity (nausea, vomiting, diarrhea or change in appetite) and kidney toxicity. Urine tests and blood electrolyte and kidney tests should be checked prior to starting therapy and periodically during treatment, particularly if other medications such as anti-inflammatories are being prescribed.
Intravenous bisphosphonates are administered at the vet office. When the oral alendronate is prescribed, it is usually administered in the morning as a single dose with a small amount of food, followed by a small meal 30 minutes later.