Feline mediastinal lymphoma: a retrospective study of signalment, retroviral status, response to chemotherapy and prognostic indicators

Abstract

Historically, feline mediastinal lymphoma has been associated with young age, positive feline leukaemia virus (FeLV) status, Siamese breed and short survival times. Recent studies following widespread FeLV vaccination in the UK are lacking. The aim of this retrospective multi-institutional study was to re-evaluate the signalment, retroviral status, response to chemotherapy, survival and prognostic indicators in feline mediastinal lymphoma cases in the post-vaccination era. Records of cats with clinical signs associated with a mediastinal mass and cytologically/histologically confirmed lymphoma were reviewed from five UK referral centres (1998-2010). Treatment response, survival and prognostic indicators were assessed in treated cats with follow-up data. Fifty-five cases were reviewed. The median age was 3 years (range, 0.5-12 years); 12 cats (21.8%) were Siamese; and the male to female ratio was 3.2:1.0. Five cats were FeLV-positive and two were feline immunodeficiency-positive. Chemotherapy response and survival was evaluated in 38 cats. Overall response was 94.7%; complete (CR) and partial response (PR) rates did not differ significantly between protocols: COP (cyclophosphamide, vincristine, prednisone) (n = 26, CR 61.5%, PR 34.0%); Madison-Wisconsin (MW) (n = 12, CR 66.7%, PR 25.0%). Overall median survival was 373 days (range, 20-2015 days) (COP 484 days [range, 20-980 days]; MW 211 days [range, 24-2015 days] [P = 0.892]). Cats achieving CR survived longer (980 days vs 42 days for PR; P = 0.032). Age, breed, sex, location (mediastinal vs mediastinal plus other sites), retroviral status and glucocorticoid pretreatment did not affect response or survival. Feline mediastinal lymphoma cases frequently responded to chemotherapy with durable survival times, particularly in cats achieving CR. The prevalence of FeLV-antigenaemic cats was low; males and young Siamese cats appeared to be over-represented.

Figure 1

Age distribution of 55 cats with mediastinal lymphoma. Red bars represent Siamese; blue bars represent all other breeds together

Figure 2

Kaplan–Meier survival curve showing the overall survival of 38 cats with mediastinal lymphoma treated with a COP (cyclophosphamide, vincristine, prednisone) or a Madison–Wisconsin protocol. Median survival time was 373 days (range, 20–2015 days)

Figure 3

Kaplan–Meier curve showing survival of 38 cats with mediastinal lymphoma stratified according to treatment protocol received. The blue line indicates cats that received a COP (cyclophosphamide, vincristine, prednisone) protocol; the green line indicates cats that received Madison–Wisconsin protocol. There was no signficant difference in survival time between treatment protocols received (P = 0.216)

Figure 4

Kaplan–Meier curve showing survival curves stratified according to type of response.Those patients achieving a complete response (CR) had a significantly longer survival time than those achieving a partial response (PR) (P = 0.032)