Science Digest: Clinical presentation, treatment response and prognosis of paediatric and juvenile lymphoma in cats

5 November 2024

November is Pet Cancer Awareness Month, so we’re taking a look at a study published in the Journal of Small Animal Practice (JSAP) that characterised lymphoma in paediatric and juvenile cats.

Lymphoma is the most common malignant neoplasia in cats, with an estimated incidence of 32 per 100,000 cats in the UK¹, and a first peak seen at a young age (<24 months)². However, there’s a lack of research on the clinical presentation, disease characteristics, responses to treatment and prognosis in paediatric and juvenile feline leukaemia virus (FeLV)-negative cats. This information is particularly important for owners who need to decide on whether to proceed with treatments in a young cat³.

A study led by Francesco Rogato and published in JSAP reported the clinical presentation, tumour characteristics, treatment responses and probability of long-term survival in cats aged up to 18 months with lymphoma, by retrospectively reviewing electronic medical records of five UK veterinary referral hospitals³. In total, 33 client-owned cats aged up to 18 months and diagnosed with lymphoma between 2008 and 2022 were identified and included in the study.

The median age at diagnosis was 12 months (ranging from 3 to 18 months). The most common presenting clinical complaints were dyspnoea (63% of cases), lethargy (48%), peripheral lymphadenopathy (42%), inappetence (36%), weight loss (18%), vomiting (12%), polyuria-polydipsia (6%) and nasal discharge (3%). The most recorded haematological abnormalities were anaemia (26%) and lymphopenia (33%), and the most common biochemistry abnormalities were increased liver enzymes’ activity and increased renal parameters. Based on clinical presentation and staging results, the most common anatomical forms were mediastinal (42%), disseminated disease (30%) and renal (15%), with all cats having intermediate to large cell lymphoma. Three out of 29 cats tested were positive for FeLV but none for FIV.

Of the cats in the study, 26 were treated with multi-agent chemotherapy protocols. Objective response rate to first-line multi-agent chemotherapy protocols was high (96%), although complete response was achieved in only 46% of cats, which is lower than previously reported in cats with mediastinal, nodal and extranodal lymphomas, and partial response was seen in 50% of cats. The median survival time for cats treated with chemotherapy was 268 days, similar to that previously reported in an older population, which would imply a similar outcome between younger and older cats. Complete response to chemotherapy was linked to a longer progression-free survival (median 858 days), whereas this decreased to 150 days for cats with a partial response.

Chemotherapy was generally well tolerated, with no cats requiring hospitalisation due to chemotherapy-related toxicities. Eleven cats suffered from grade I chemotherapy-related toxicities, including neutropenia, diarrhoea and inappetence; four cats suffered from grade II toxicities, including neutropenia, thrombocytopenia and inappetence; and only two cats experienced severe toxicities (one grade III and one grade IV neutropenia). This along with the small number of cats (four) requiring dose reductions, supports the use of standard chemotherapy doses in paediatric and juvenile cats.

The overall 1-, 2- and 3-year survival probability for cats treated with chemotherapy was 25%, 25% and 14%. Seven cats were considered long-term survivors, surviving more than two years, with no signs of stunted growth, chronic health conditions or development of different neoplastic conditions recorded. Twenty-six cats died or were considered dead due to lymphoma and five died due to causes unlikely related to lymphoma.

Take home message

Paediatric and juvenile cats with lymphoma showed a high response rate to multi-agent chemotherapy protocols with rare significant toxicities, in this study. Some cats surviving long-term (over two years) may indicate a more favourable outcome in a subset of patients, although further studies are needed to identify specific genetic and prognostic biomarkers to better predict outcomes.

References

¹Economu L, Stell A, O’Neill DG et al. (2021) Incidence and risk factors for feline lymphoma in UK primary-care practice. Journal of Small Animal Practice. 62(2), 97-106.

²Gabor LJ, Malik R & Canfield PJ (1998) Clinical and anatomical features of lymphosarcoma in 118 cats. Australian Veterinary Journal. 76(11), 725-32.

³Rogato F, Tanis JB, Gil P et al. (2023) Clinical characterisation and long-term survival of paediatric and juvenile lymphoma in cats: 33 cases (2008-2022). Journal of Small Animal Practice. 64(12), 788-796.