Metronomic chemotherapy is a rather new way of using traditional chemotherapy drugs to slow cancer growth. “Metronomic” refers to a low dose of continuous treatment. Think metronome. It is different from the traditional way of using chemotherapy which involves giving patients a high dose, or what we call a “maximum tolerated dose” (MTD) of chemotherapy. With MTD therapy, there is a higher risk for side effects and usually treatments are spread out every 1 to 3 weeks, so that the body has time to heal from these big doses, in between treatments. With metronomic chemotherapy, such a low dose is used that the treatment can be safely be given every day. You might ask, how can you kill cancer with such a tiny dose of chemotherapy? It’s a good question. What ends up happening is that we inhibit a process called angiogenesis. Angiogenesis is the process of new blood vessel formation within tumors. Tumors use angiogenesis so that they have a blood supply to grow and get nutrients. The goal of metronomic chemotherapy is to stop angiogenesis so that we can starve tumors. Metronomic chemotherapy stops angiogenesis because the drugs are directly toxic to cells called endothelial cells, which are the building blocks of blood vessels walls. Metronomic chemotherapy can inhibit a variety of other factors that contribute to new blood vessel formation. It also can stimulate other natural factors in the body that inhibit angiogenesis.
Did you know that tumors have their own immune system? They do! And they use their immune system to fight off the body’s immune system. Metronomic chemotherapy can suppress the tumor’s immune system, helping the body to better fight the cancer.
There are several cancer types that we are using metronomic chemotherapy to treat in both cats and dogs. The primary tumors we are treating include soft tissue sarcoma, bladder tumors, thyroid tumors and liver tumors.
Although metronomic chemotherapy is not thought to work quickly, over time, it can slow tumor growth and maintain good quality of life for our dog and cat cancer patients. It tends to be fairly easy to administer and is relatively inexpensive. There does require some monitoring due to the long term risk for bone marrow toxicity. If you are interested in this type of therapy for your pet, we encourage you to schedule an appointment to talk to one of our oncologists.
post by Dr. Kim Freeman