...he always scrambled from the car and pranced through your door with a smile on his face. In his view every visit to you was a party with friends.
Traditionally, chemotherapy has been delivered at maximally tolerated doses intended to maximize the killing of tumor cells. One of the drawbacks to this type of dosing is that some normal cells also rapidly divide and can therefore be affected. As a result, time off therapy is required to allow recovery. Unfortunately, this may also provide time for the cancer to rebound as well.
Currently, a different approach to chemotherapy is being studied. This is referred to as “metronomic” or continuous, “low dose” chemotherapy. As tumors enlarge, they require a greater blood supply and new blood vessels develop. The process by which new blood vessels are formed is called angiogenesis. Tumors will send signals to nearby blood vessels which induces new blood vessels to form and grow toward the tumor. Once this connection is established, the tumor receives oxygen and nutrients from the blood, enabling further growth and spread of the tumor.
Unlike standard chemotherapy whereby the primary target is the tumor cell, the direct target of the low dose chemotherapy is the growing blood vessel. These blood vessels are sensitive to extremely low dosages of chemotherapy and when given chronically, they can be pruned away from the tumor, resulting in decreased tumor growth and tumor death.
A metronomic protocol generally involves daily low dose chemotherapy and a non-steroidal medication. Cyclophosphamide and non-steroidal anti-inflammatory medications (such as Piroxicam, Meloxicam, and Deramaxx) have shown anti-tumor properties through this mechanism. The goal of this treatment regime is a bit different than traditional chemotherapy. Our hope is to stop the disease from growing and spreading, not necessarily to eliminate it completely. By using lower drug dosages, the side effects tend to be limited. These medications are given orally so they may be administered at home. Several veterinary studies have noted responses for bulky cancer (prior to surgery or no surgery) and in cases with roots left behind after surgery (microscopic disease setting).
Patients are evaluated with bloodwork, urinalysis and exams while on this therapy. Metronomic therapy can be combined with standard chemotherapy or radiation therapy and provides another therapeutic option for patients with cancer.