Despite a good prognosis for some types of cancer, due to the fatality and toxicity of the medication associated with it, pet owners are often confronted with a dilemma whether to go for a treatment or not. Most of the times, cancer in dogs occurs in old age making dogs more vulnerable to the side effects of conventional treatment. Surgery has a limited scope in as far as it can only excise parts of the tumor.
There is a dire need for exploring new areas of cancer treatment. Despite significant developments in this field, a lot more needs to be done to develop new strategies and drugs that target only cancerous cells and spare the normal cells.
The development of any new treatment needs to be done keeping in mind that any medication should cure the disease with a minimum of side effects. To achieve this goal the therapy has to target and destroy only the cancer cells while it allows the normal healthy cells to live.
Let us try to understand how radiation and chemotherapy work to kill malignant cells. These therapies make use of the fact that malignant tumors have cells that grow rapidly by division whereas the normal cells are mostly in a resting stage. Chemotherapy attempts to intervene at the DNA function of cells to divide and multiply thus leaving the normal cells alone.
There is an exception to this rule because even some normal cells like those in bone marrow and the GI lining naturally continue to divide and replace dead cells all the time. Moreover, sometimes normal cells start dividing and replacing after the treatment is given. This leaves a very small margin of error.
Another limitation of conventional drugs is the field of recurrence. There is a great amount of heterogeneity within the cells of a single tumor. As the tumor increases in size, some of the cells get lesser blood supply causing them to divide at a reduced pace compared to others in the same tumor. This results in making some cells resistant to drugs and they can survive even after the patient is cured of the disease. These cancerous cells remain dormant for a time and lead to recurrence of cancer at a later stage.
On the other hand, surgery has a different set of limitations. Pet cancer, including canine and feline cancer has the uncanny property of surfacing when it has already metastasized to neighboring, distant and even vital organs. This either rules out surgery or at best results in partial excision of a tumor. And therefore, chemotherapy and radiation become necessary. It is only in rare cases like liver cancer where pet owners can notice the condition early enough for treatment since the symptoms of liver cancer in dogs are quite apparent at an early stage.
Total excision is only possible in cases of a benign tumor, which is, in most cases, harmless. On the other hand, any increase in dosage of chemotherapeutic drugs or time of radiation exposure has an accompanied and corresponding risk of increase in toxicity. Pet owners need to take an educated decision based on the general health of the dog and risks involved. In fact owners have to strike a balance between compassion, quality of life after treatment and benefits likely to be derived from treatment.