Cancer is a common disease in cats, just as in other domestic species and in human beings.
The experience obtained starting from the human medicine has result in the development of treatments in animals and many used medicines were developed for the human beings’ treatment, however some used in dogs and humans are not appropriate for cats.
Most of the tumors appears starting from the transformation neoplásica of a single stem cell. Initially the tumors grow quickly, but the growth speed decreases as the size increases.
The growth fraction constitutes the most important factor than it determines the answer of a tumor to the chemotherapy, because most of the medicines is active just against cells in growth and in division. The ideal period to treat a tumor with chemotherapy is in the beginning of her development course, when the load of tumor is low, the time of duplication is short and the growth fraction is high. The cells in rest inside of a tumor they are also essential, because they form a reservoir protected starting from which a tumor can retire. Therefore, those cells determine the definitive result of the treatment.
Initially, the tumors are composed of a group of cells reasonably homogeneous, but with successive cellular divisions, genetic mutations that check phenotype properties different in the cells daughters. Therefore, the cellular population of a tumor becomes heterogeneous regarding the characteristics biochemical, morphologic and of answer to the drug.
Some tumors are resistant to the chemotherapy; for instance, many carcinoma and the malignant melanoma. Big tumors and of slow growth they are also, because of the fraction of low growth. The tumor cells, in the same way can acquire resistance through mutation.
The theoretical objective of any cancer treatment is to reduce the population of tumor cells to zero. It can be used radical chemotherapy if the intention will cure the tumor. However, in veterinary medicine, it has a balance to be reached between effectiveness and toxicity of the treatment.
The chemotherapy should be reserved for malignant tumors that knowingly answer to the medicines. It is indicated against disseminated diseases or systemic, as lymphoma, myelona, leukemia. The chemotherapy rarely has value as only treatment of solid tumors, as carcinoma, sarcoma, melanoma, in that case the surgery or radiotherapy would be the first treatment choice.
Vet Therapy – Dr. Cynara Campanati