Chemotherapeutic agents are controlled toxins that kill rapidly dividing cells. Cancers are caused by uncontrolled cell division, and therefore are highly susceptible to these agents. However, there are other areas that are also affected, leading to side effects.
- B = bone marrow suppression
- A = alopecia (hair loss)
- G = gastrointestinal (vomiting and diarrhea)
Bone marrow suppression:
Bone marrow cells are dividing all the time, and are the primary source of all the cell lines in the blood. Suppression of these lines can lead to low red blood cells (causing fatigue), low platelets (causing bleeding), or low white blood cells (causing an increased risk of infection). For this reason, we run a complete blood count (CBC) prior to each treatment. For some drugs, we need to check again between treatments when the cells will be at their lowest levels (the nadir). If the levels are too low, then immediate treatment may be needed, or in some cases, the dose of the drug will be adjusted for the next treatment.
Chemotherapy-associated alopecia is primarily seen in dog breeds with continuously-growing hair coats, such as Old English sheepdogs, poodles and Maltese terriers. It occurs rarely in other breeds, however any shaved hair will be slow to re-grow. The primarily affected areas are: face, whiskers, shoulders, and back. Cats usually just lose their whiskers. There is nothing we can do to prevent this, but it rarely causes any significant problems for the patient.
It is unknown what percentage of patients experience nausea without vomiting. But based on human experience, it is likely to be high. We want to prevent this as much as possible by using anti-nausea medications. Patients are given an infection of an anti-nausea medication prior to the chemotherapy treatment, and owners are sent home with more medication to be used as needed. Owners are also supplied with medication to treat any diarrhea. Most patients do not have symptoms. If a patient proves sensitive to a certain drug, then either the dose will be adjusted or the drug will be discontinued.
Other side effects:
Each drug has specific other possible side effects. These may require additional testing or monitoring, and will be discussed with the family prior to treatment.
Call if your pet is:
- vomiting more than three times in an hour or six times in a day
- suddenly lethargic or has a fever
- not eating
- passing blood from any part of the body
- appearing to be painful of anxious