Objectives

Cancer is the leading cause of death in dogs. Canine lymphoma is particularly devastating because it is frequently diagnosed and almost always fatal. Chromosomal aberrations from tumor biopsy samples have been studied, and certain repetitive anomalies were shown to correlate with prognosis. A relationship between cytogenetic changes in peripheral blood lymphocytes in human lymphoma and leukemia patients was recently established. Not only was predictive information obtained, but response to therapy could also be monitored. Evaluating peripheral lymphocytes instead of tumor is advantageous because: 1) More patients can be evaluated since it the rate of successful "spreads" is higher 2) No biopsy is required, so there is less expense and patient discomfort, and 3) peripheral lymphocytes are available even after the tumor has gone into remission creating a previously unexploited window for evaluation. If meaningful cytogenetic changes from lymphocytes are identified, this can become a powerful clinical tool in the treatment of canine lymphoma. Developing methods for early screening and/or predicting response to therapy would have a major clinical impact in this important disease.

Supporting data

Previous work using flow cytometry has demonstrated that canine lymphoma patients are marginally hypoploid. We anticipate that the patients will have slightly abnormal chromosome numbers at the time of diagnosis. Their abnormal chromosome counts will worsen during the course of treatment and then return to near normal counts after treatment ceases. Once the disease recurs, chromosome counts will return to or exceed their most abnormal count. We have identified numerical aberrations in 5 lymphoma patients, with 2 of the patients having multiple time points. Peripheral changes in chromosomes could provide a unique window for determining what is happening to the patient. Chromosome counts can identify numerical changes, such as chromosome deletions or duplications.

Conclusions

We have determined that chromosomal aberrations can be identified in the peripheral blood of canine lymphoma patients. Additionally, the frequency of aberrations changes during the course of treatment.