Lymphoma is a malignant cancer of the immune system that can develop in any organ or body system. In cats, lymphoma most often develops in organs within the abdomen. Because lymphoma is a systemic disease, treatment has historically involved chemotherapy drugs that can have significant and serious adverse effects. Unfortunately, cats treated with chemotherapy have a relatively poor response to treatment. Combining chemotherapy with other forms of therapy may improve the outcome in cats with lymphoma. Preliminary data suggests that the combination of chemotherapy and radiation therapy is well tolerated in cats with lymphoma at other body sites. It may be possible to administer radiation therapy targeted to the abdomen in cats with lymphoma as well. This approach would enable the administration of higher and potentially more effective amounts of radiation therapy while preventing exposure to tissues outside the abdomen.