Feline leukemia virus becoming uncommon with lymphoma

By Sarah Guy, medwireNews Reporter

Rates of feline leukemia virus (FeLV) in domestic cats with lymphoma have decreased in recent years, suggesting alternative etiologies for this cancer subtype, show German study results.

The findings also reveal that if lymphoma occurs in cats with FeLV, they are likely to be younger animals, and generally have a worse prognosis, notes the research team.

Tina Meichner and colleagues from the Ludwig Maximilian University in Munich compared the incidence of progressive FeLV infection and age distribution in 390 client-owned cats treated at their institution between 1980 and 2009. Data were divided into two time periods - 1980 and 1994 - during which time 178 cats were diagnosed with lymphoma; and 1995 to 2009, during which time 212 cats were diagnosed with the disease.

A total of 59% of cats were FeLV antigen-positive during the first time period, which reduced significantly during the second time period, to 13%, report Meichner et al. Cats were also significantly older at diagnosis of lymphoma during the second period, at 11 versus 7 years in the first period.

B contrast, FeLV-positive cats were significantly younger than their FeLV-negative counterparts overall, at 3.7 years versus 11.3 years.

A total of seven FeLV-positive cats were treated for lymphoma, with six (86%) achieving a partial response (decrease in tumor size between 50 and 100%) for a median 25 days, while 17 of 65 (26%) FeLV-negative cats treated for their lymphoma went into remission, with 22% achieving a complete response (resolution of all clinically detectable disease) and 4% achieving a partial response.

Median survival of cats with positive FeLV antigens was worse overall than those that were FeLV negative, at just 2 days for untreated FeLV-positive cats versus 5 days for untreated FeLV-negative ones, and 25 days for treated FeLV-positive cats versus 27 days for treated FeLV-negative ones.

However, the authors report that median survival rates did not differ significantly in either time period between cats that were FeLV positive or negative, or cats who were treated or untreated. Gender and breed also made no significant difference, they remark in Veterinary Record.

"The percentage of complete response was low, and this most likely explains why no significant difference concerning overall survival time could be found," conclude the researchers.

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