The ARC guide to lymphoma in dogs

Most dogs have a form of lymphoma called “multicentric lymphoma”. This means the lymphoma is primarily within the lymph nodes. Lymphoma can also occur in other parts of the body (for example the skin or gastrointestinal tract).

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Summary

Determining the specific type of lymphoma that a dog is suffering from is very important as different lymphoma types have different prognoses and treatments. The survival times for dogs with lymphoma can range from weeks to years and the treatment of different forms can also be very different. Treatment for the most common types of lymphoma (“multicentric high-grade lymphoma”) often initially involves weekly or fortnightly chemotherapy doses. However there are some less aggressive forms of lymphoma which can be treated with daily tablets at home, or sometimes with no treatment initially other than ongoing monitoring.

The most common type of lymphoma is multicentric high-grade lymphoma. This type of lymphoma is primarily within the lymph nodes however can also affect the liver, spleen, blood, or bone marrow. This type of lymphoma is treated with chemotherapy. Chemotherapy in dogs is generally tolerated very well, with most dogs having no severe side effects and living a normal life throughout treatment. In most cases the lymphoma initially responds well to treatment, with 80-95% of dogs going into remission. However most dogs will eventually relapse (the lymphoma comes back).

There are several factors that can give us an indication of an individual patient’s prognosis. These include:

  • whether they have B-cell or T-cell lymphoma
  • whether they are unwell prior to starting treatment (“sub-stage a or b”)
  • where the lymphoma is in the body (“stage”)
  • if they have been treated with steroids
Arc Puppy White Brown Face Lying With Owners Hand On Head

Chemotherapy

The most effective chemotherapy protocols are multi-agent protocols. These involve giving a rotating cycle of different chemotherapy drugs. With these protocols 80-95% of dogs will achieve remission (the lymphoma will shrink away to undetectably low levels). For B-cell lymphomas the average survival time is around 1 year, however around 20-25% of dogs will live for over 2 years. T-cell lymphomas tend to be more resistant to treatment, with average survival times traditionally reported to be around 6 months. Recently better survival times have been reported by using newer chemotherapy protocols, however these are still less than for B-cell lymphomas.

We use different chemotherapy protocols depending on whether the lymphoma is B-cell or T-cell. Our most common protocols for lymphoma involve giving 16 doses of chemotherapy with 1-2 week gaps between each dose. The entire protocol lasts 25 weeks for both B-cell and T-cell protocols (although some of the drugs are different).

There are also single-agent protocols, which involve giving just one drug periodically, typically once every 2-3 weeks. These protocols involve less frequent treatments and are still relatively effective however there is a lower chance of achieving remission and the remissions do not last as long compared to multiagent protocols. For B-cell lymphomas around 50-75% of dogs will achieve remission and the average survival is around 6-8 months.

Palliatively care

Lymphoma can also be treated palliatively with steroids alone. Generally this will result in a short term improvement, however most dogs will relapse within 1-2 months. Steroids induce chemotherapy resistance in lymphoma, so we do not recommend using steroids before starting chemotherapy.

Before starting treatment we recommend “staging” the disease. This involves assessing how widespread the lymphoma is, and whether there are any other underlying diseases present that might impact our treatment.

This is a full list of staging tests that can be performed. Not all tests must be performed, however the more information we have before treatment the more prognostic information we can provide you, and the less likely it is that we will encounter unexpected side effects/problems. If any of these tests have already been performed recently, we may not need to repeat them.

Essential tests

  • Lymph node samples (aspirates or biopsies) to give us a definitive diagnosis of lymphoma.
  • Routine haematology test to assess blood cell levels. This ensures the bone marrow is functioning and
  • gives a rough indication of bone marrow involvement.
  • Routine biochemistry tests to assess liver and kidney function before starting chemotherapy.
  • Routine urinalysis to assess kidney function and as a baseline before chemotherapy.

Additional tests

That are strongly recommended before starting chemotherapy are:

  • Lymph node samples (aspirates or biopsies) to give us a definitive diagnosis of lymphoma.
  • Routine haematology test to assess blood cell levels. This ensures the bone marrow is functioning and
  • gives a rough indication of bone marrow involvement.
  • Routine biochemistry tests to assess liver and kidney function before starting chemotherapy.
  • Routine urinalysis to assess kidney function and as a baseline before chemotherapy.

Additional tests to complete staging to give the best prognostic information and fully assess for concurrent diseases are:

  • Bone marrow aspirate (usually from the rib or sternum) to assess for bone marrow infiltration. The results of this are prognostic.
  • Aspirates of the liver and spleen to assess for lymphoma infiltration.

If your pet will be receiving doxorubicin (a chemotherapy for B-cell lymphoma) then we may also recommend an
echocardiogram to assess cardiac function, as this drug can impact the heart.

Additional tests

If the diagnosis of lymphoma is not definitive after lymph node aspirates we may recommend additional tests to ensure we have an accurate diagnosis. The most common scenarios when we recommend additional tests are:

  • When the samples (usually fine needle aspirates and immunocytochemistry) have been performed and are suggestive of lymphoma, but not definitive.
    In this case we will advise taking a biopsy or performing advanced tests to get a definitive diagnosis. We will generally not recommend starting chemotherapy until we have a definitive diagnosis of lymphoma.
  • When the fine needle aspirates and immunocytochemistry show cells that could represent a low-grade (less aggressive) lymphoma.
    In this case we will generally recommend surgically removing a lymph node for histology and immunohistochemistry. Low-grade lymphomas are less common than high-grade lymphomas. However, the distinction is important, as they are usually treated without chemotherapy or with less intensive chemotherapy. To avoid using unnecessary chemotherapy, it is important we perform additional tests if there is a chance the lymphoma is low-grade.