Meichner K, Kruse BD, Hirschberger J and Hartmann K. Changes in prevalence of progressive feline leukaemia virus infection in cats with lymphoma in Germany. Vet Rec. 2012; 171: 348.
Lymphoma is the most common feline cancer, comprising more than half of all hemolymphatic (blood and lymph system) tumors. Feline leukemia virus (FeLV) is a type of virus known to cause cancer (oncogenic retrovirus) and FeLV infection is a known risk factor for lymphoma development. In the past, FeLV infection accounted for the majority of cats that developed lymphoma. However, in the past 20 years, various reports suggest that a shift away from FeLV-associated tumor development has occurred once FeLV screening and vaccination became more commonplace.
FeLV infection outcome has also been recently reclassified into four categories (progressive, regressive, abortive, focal). Progressively infected cats have persistent antigenemia (viral antigen in the blood), high proviral load, and a median survival time of 2.4 years. The purpose of this large retrospective study, which included 390 client-owned cats, was to compare the incidence of cats with lymphoma and progressive FeLV infection in southern Germany between two time periods; namely, an early period between 1980 and 1994, and a later period between 1995 and 2009. Age distribution and other differences in FeLV antigen-positive and FeLV antigen-negative cats with lymphoma were also assessed.
Incidence of progressive FeLV infection in cats with lymphoma significantly decreased from 59% to 13% between the two time periods, consistent with other recent studies worldwide. During the earlier period, young to middle-aged cats (median 7 years) were likely to have lymphoma while during the later period mostly older cats (median 11 years) were diagnosed with lymphoma. Decreased prevalence of progressive FeLV infection likely contributed to this change in age distribution. Mediastinal lymphoma was uncommon (10% of cases), but half of these cats tested positive for FeLV antigen.
FeLV-antigen negative cats with lymphoma that responded to chemotherapy showed significantly longer remission duration (472 days) than FeLV antigen–positive cats (25 days); however, survival time was not significantly affected (25 days versus 27 days). This incongruity was likely due to the high percentage of non-responders (74%) to chemotherapy among FeLV antigen-negative cats in the present study. The retrospective nature of this study over a 30-year period and the lack of chemotherapy standardization could account for high percentage of non-responders. In conclusions, this is the first study over such a long period of time that evaluated cats with lymphoma and assessed their association with progressive FeLV infection. [GO]