Lymphoma is a common hematopoietic tumour in both dogs and cats, although clinical presentation and response to treatment are different in these species. Prognostic factors are also different but generally include tumour location, histopathological grade (e.g. intermediate-high grade vs low grade) and immunophenotype.

Due to the high proliferation rate, a median survival of 4-6 weeks has been reported in untreated patients with intermediate-high grade lymphoma, while survival of only 1-2 months is achieved with palliative prednisolone treatment. Doxorubicin-based protocols (e.g. 19-week CHOP– vincristine, cyclophosphamide, doxorubicin, prednisolone) represent the standard of treatment in dogs because the highest rate of remission and longest survivals can be achieved (80-90% response, 12 months median survival, 25% survive more than 2 years).

COP protocols (vincristine, cyclophosphamide, prednisolone) or single agent doxorubicin protocols are less effective options (60-70%, 6-7 months median survival) and should be considered second line therapies. Difference in efficacy between first and second line protocols should be discussed with the owners before the option of a doxorubicin based protocol is abandoned. A 25-week CHOP protocol or COP protocols are generally used for the treatment of feline lymphoma; single agent doxorubicin is not effective in this species. Entirely oral protocols based on lomustine and prednisolone are frequently used in a rescue setting.. When remission is lost (either after an interval with no chemotherapy or after treatment at 2 or 3 week intervals), a large number of patients may experience a second remission.

Lymphoma tips

  • All marked lymphadenopathies should be investigated by cytology asap
  • Lymphoma is a quickly progressing disease so diagnosis should be prompt to avoid clinical deterioration prior to treatment
  • Chemotherapy significantly prolongs survival by maintaining excellent quality of life in most pets with lymphoma
  • Pets with recurrent or resistant lymphoma may still achieve a second or third complete remission if rescue chemotherapy protocols are started promptly
  • These may be complex cases to treat so seeking advice from clinical oncologist is strongly recommended

Treatment with chlorambucil and prednisolone is indicated for feline patients with small cell gastrointestinal lymphoma (69% response, median survival 17 months). Stage I lymphoma or nasal lymphoma can be treated with radiotherapy reaching median survivals up to 18 months; radiotherapy can also be used for palliative treatment of resistant lymphoma. Surgery plays a minor role in treatment of patients with lymphoma, although patients with stage I lymphoma could be treated with surgery and careful monitoring. Thorough staging (included bone marrow examination) before treatment is warranted in this case. Canine epiteliotrophic lymphoma generally carries a guarded prognosis, but fair survivals of up to 2 years have been reported with lomustine and prednisolone treatment so early treatment is of paramount important.