58Â° Congresso Nazionale SCIVAC: Oncologia veterinaria

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58° Congresso Nazionale SCIVAC • Milano, 7-9 Marzo 2008 • Oncologia veterinaria - Alle soglie del III Millennio Barbara E. Kitchell DVM, PhD, Dipl ACVIM, Michigan, USA Treatment for lymphoma Domenica, 9 Marzo 2008, ore 11.00 80
58° Congresso Nazionale SCIVAC • Milano, 7-9 Marzo 2008 • Oncologia veterinaria - Alle soglie del III Millennio Lymphoma treatment is characterized by early spectacular response, often followed by equally spectacular treatment failure. For the most part, lymphocytes have a limited life span. Each lymphocyte is committed to accomplish specific tasks, such as the production of antibodies, the recognition and destruction of viral infected or malignantly transformed cells, and the maintenance of memory so that antigens once recognized are less able to gain a foothold in the future. The immune effector cells of the body perform these tasks until the offending antigen is dealt with, then the simple economy of biology requires that what is no longer needed be down-regulated to conserve resources for other vital functions. In the case of lymphocytes, they accomplish this ecologic balancing act for the body by dying when they are no longer needed. Certain subsets of lymphocytes, such as stem cells and memory cells, have extremely long lifespans in the body, and may in fact be immortalized. However, the vast majority of the lymphocyte population is in a state of flux, constant cycling through birth and death. The most critical key to the successful eradication of cancer cells by modern medicine is the triggering of programmed cell death, or apoptosis. All normal cells have the ability to detect genotoxic insults and to undergo apoptosis as a biologically appropriate response to potential mutagens. Part of the reason for lymphocyte lability to therapeutic agents such as prednisone is that lymphocytes respond to these types of signals by rapid cell death. In the circumstance of treatment of lymphoma, we are simply exploiting the lymphocyte’s own highly refined cell death machinery to take out a susceptible population of cells. Unfortunately, cancers may arise clonally, but they are genetically unstable; after successive rounds of replication, more and more mutations accrue in cancer cells. This leads to the phenomenon of drug resistance, among other consequences. As yet, no consensus exists as to the most appropriate chemotherapy protocol for treatment of lymphomas in dogs and cats. The purpose of this discussion is to bring up the pros and cons of the currently available chemotherapy protocols in the context of known prognostic factors to better enable the practitioner to judge what might be the best approach for a given patient. EPIDEMIOLOGY Incidence rates for dogs with lymphoma have been reported at 24 cases/100,000 dogs at risk/year. The disease affects a wide range of animals, from the very young to the geriatric. The disease is generally seen in middle aged to older dogs, with no sex predisposition reported. Breeds at increased risk have been reported, including boxers, German shepherds, and golden retrievers. Familial distribution has been reported in bull mastiffs. In addition to breed predisposition, exposure to the herbicide 2,4D is associated with an increased risk in humans and dogs. While retroviral etiology is known in cats, birds, rodents, and humans, no retrovirus has been identified in the dog as yet. 81
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nr. 6312 Sedazione IL PASSATO È FI
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POSTER Gli estratti sono elencati i
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58Â° Congresso Nazionale SCIVAC: Oncologia veterinaria

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