Dr. Nicole Ehrhart, surgical oncologist at the Veterinary Medicine Teaching Hospital, is offering clients alternatives to amputation and intravenous chemotherapy for canine bone cancer patients. She is also using a new blood indicator for improved accuracy of prognosis following treatment of bone cancer.
Two "limb-sparing" techniques can replace the traditional treatment of amputation. The limb can be saved with a transplant of donor bone from a cadaver or, through a process called "bone transport," the patient can grow new bone to replace the bone that was surgically removed.
With the bone transport technique, a cross-sectional piece of the remaining normal bone is cut and moved a short distance from the area it was removed from. The body recognizes this as a fracture and begins to heal it. A device called an Ilizarov, named after the Russian scientist who developed it, holds the cut piece of normal bone in place and allows it to be moved a short distance each day. As the cut piece is moved further and further away from its original site, new bone grows behind it. This technique reduces the risk of infection (which occurs in about 35 percent of patients receiving donor bone) because there is a constant supply of blood to the growing bone.
Bone transport has been used successfully in people with bone loss from trauma, such as motorcycle accidents. Dr. Ehrhart is breaking new ground by combining the bone transport approach with chemotherapy. Her findings may prove beneficial for human patients, especially children, whose bones are still growing and among whom bone cancer is more prevalent than among adults.
If chemotherapy is shown to hinder new bone growth, Dr. Ehrhart plans to compare groups of dogs receiving and not receiving chemotherapy to isolate cytokines that regulate cells' ability to produce bone and cartilage. The next phase will be to give these cytokines to dogs receiving chemotherapy to try to stimulate bone growth.
The VMTH is one of only two institutions with USDA permission for clinical use of a biodegradable polymer sponge that is implanted in the body and provides slow-release chemotherapy as it dissolves over time. In preliminary trials this method has been shown to work as well as IV chemotherapy. The slow-release chemotherapy has the potential to control local recurrence of the tumor as well as metastatic disease. This method is also less toxic than IV chemotherapy and requires fewer doses.
Dr. Ehrhart is also studying a bone-specific alkaline phosphatase, which may be a good indicator of post-surgical survival time. Patients with higher than normal levels of this enzyme in their blood before they have surgery have a poorer prognosis than patients with lower levels. If the enzyme level does not return to normal after surgery, the patient has a lower chance of survival and a lower remission-free interval than normal, regardless of the stage, location, and amount of cancer present and of metastatic disease. This information will provide a more accurate prognosis than before. Patients with higher bone-specific alkaline phosphatase levels can be treated more aggressively with chemotherapy after surgery in order to achieve the same survival rates as patients with lower levels.