Metronomic chemotherapy in dogs is a relatively recent type of chemotherapy that employs low doses of oral (pulse) chemotherapy administered on a regular basis. The chemotherapy is provided at lower doses than traditional chemotherapy since it is given every day or every other day, resulting in a lower toxicity profile. Because of the lower toxicity, there are usually fewer adverse effects.
Metronomic Chemotherapy in Dogs
The maximum tolerated dose, or MTD, of conventional chemotherapy, is high and the highest dose is what is provided to the dog with cancer in most cases. The purpose of traditional chemotherapy is to eliminate cancer cells that divide quickly. Normal cells, on the other hand, can also multiply quickly, so it can harm them as well.
The cells of the gastrointestinal tract and white blood cells are most typically affected. Veterinary oncologists often include a break interval in the chemotherapy program, usually a full week, to allow these cell types to recuperate. The normal MTD treatment schedule is weekly, while some treatment plans allow for three-week pauses.
The purpose of metronomic chemotherapy is not to kill cancer cells directly. Metronomic chemotherapy targets and suppresses the proliferation of tumor blood vessels. The tumor receives nutrition from tumor blood vessel cells, which are more active than normal blood vessel cells. Angiogenesis is the technical term for blood vessel growth, therefore you’ll hear metronomic chemotherapy referred to as “anti-angiogenic.”
Some low-dose chemotherapy medicines, such as cyclophosphamide, have been shown to affect tumor immunology by altering a subgroup of immune system cells called T-lymphocytes.
When Can Metronomic Chemotherapy in Dogs Be Utilized?
Understanding the processes and efficacy of this method is still in its early stages. In order to halt the course of metastatic disease in some patients with metastatic disease — such as the spread of the tumor to the lungs — some veterinarians utilize this strategy.
Another use is for dogs who have failed standard of care. That is, if their disease returned or advanced after taking the recommended drugs, or if there is no standard of therapy for a rare cancer.
Although metronomic chemotherapy is a relatively new concept, doctors have long employed a low-dose oral strategy for certain tumors. Low grade/small cell lymphomas (particularly in cats) treated with Leukeran, and multiple myeloma treated with melphalan in dogs are two examples.
The most prevalent medicine used in metronomic procedures in people and pets is cyclophosphamide (CYC). For its potential anti-cancer action on some tumors, CYC can be taken with a non-steroidal anti-inflammatory medicine (NSAID) such as piroxicam.
Palladia is a new oral mast cell tumor (MCT) medication that also has anti-angiogenic and anti-proliferative properties for other malignancies. GI side effects are the most common, and the most are mild to moderate in severity. Most Palladia side effects are controllable with early recognition, which is crucial. That implies, if necessary, adjusting or temporarily halting Palladia. Diarrhea, vomiting, lethargy, GI ulcers, and weight loss are all possible side effects.
Responses can take weeks because the therapy is targeting tumor blood vessels. To notice an effect, wait at least six to eight weeks. Remember that stabilizing the condition can still be considered a success in a tumor that has failed prior therapies.
If metronomic chemo is beneficial, six weeks is the average amount of time it’s provided.
Potential Side Effects
Metronomic procedures are generally well tolerated, with the majority of adverse effects being minor (mild decreased appetite, vomiting, diarrhea).
Although rare, CYC can induce sterile hemorrhaging cystitis, which is an inflammation of the bladder. Increased straining, peeing tiny amounts, and sometimes bloody urination are symptoms associated. CYC should be stopped in these situations.