Canine lymphoma

There are many different forms of lymphoma in the dog, just as there are in humans. Some types of lymphoma are associated with better outcomes than others but most types respond favourably to the administration of chemotherapy. There are some that do not and it is important to attempt to identify these cases as other treatments may be indicated.

Lymphoma is a cancer of the white blood cells (lymph cells) and can arise almost anywhere in the body. Although it is always frightening to learn that your pet has cancer, lymphoma is one of the most commonly treated forms of the disease.

Lymphoma in dogs can present in many different ways. The most common is for a dog to develop large swellings in areas where lymph nodes are found. The most prominent of these is under the back of the jawbone on either side. Typically these swellings will suddenly appear and can measure up to 2 cm or 1 inch or more. They often feel firm but are mobile under the skin if you manipulate them.

Your vet will first want to examine your dog. They may be able to feel enlarged lymph nodes on your dogs body. Chest X-rays or ultrasound may be needed to identify the presence of tumours in the chest or abdomen.

Diagnosis is made by taking a sample of the tumour tissue for examination. This can be done using a fine needle aspirate, core biopsy or surgical biopsy. A sample of the tissues affected can be examined under a microscope.

Some types of lymphoma are associated with high blood calcium concentrations (hypercalcaemia). It is important for the well-being of the patient that complications like this are identified and managed appropriately.

There are countless chemotherapy treatment plans (also known as protocols) that have been used for the management of canine lymphoma The principal candidates are described as multidrug chemotherapy protocols. They incorporate the three drugs Cyclophosphamide, Vincristine (Oncovin) and Prednisolone, usually called the COP protocol. Sometimes another drug, doxorubicin (also called Hydroxydaunorubicin or Adriamycin), is added and this is called a CHOP or COAP protocol. The COP protocols generally produce fewer unwanted side effects but may be less effective in inducing a complete remission.

The decision about which treatment plan to choose should be made in conjunction with your veterinary surgeon, whether they are your local vet or your oncology specialist. This is not a one-size-fits-all situation and your vet will advise you on what is best for your dog.

Chemotherapy induced side effects are usually minor if indeed they are noted at all. Nevertheless it is critical that the risk of these effects is addressed and discussed openly prior to the onset of therapy. In many cases the improvement in the patients condition substantially outweighs the minor impact of the treatment related side effects leading to an overall improvement in general health despite chemotherapy.

Sadly chemotherapy will not cure lymphoma. However the disease will go in to complete remission in up to 85 out of 100 dogs treated with a standard chemotherapy protocol. A remission means that the disease improves and clinical signs are reduced a complete remission means that it appears that the disease has completely resolved and your pet will show no signs of illness at all. The duration of this remission is variable; a few cases may survive for years but usually patients will survive somewhere between 2 and 6 months. On relapse of the disease, it is often appropriate to consider alternative therapy to attempt to regain control over the tumour.

Those animals that experience a complete remission of their disease have a better chance of longer term survival. Sometimes it is appropriate to repeat treatment with the same protocol they had before if this produced acomplete remission in the first place. In other cases it is more appropriate to employ a new rescue protocol. Chemotherapy rescue may be something that requires referral to a specialist oncology centre.

In dogs, the life expectancy with most types of lymphoma without treatment is limited to only a few months. If chemotherapy is given, life-expectancy increases to an average of 6½ to 12 months depending on the treatment plan. The average life expectancy on COP protocols is approximately 6½ months. The CHOP protocols achieve complete remission in a higher percentage of cases and the average life expectancy is improved as a consequence to approximately 1 year.

It is tremendously important to emphasise that patients undergoing chemotherapy (or any other cancer therapy for that matter) do so because their team of carers, the primary veterinary surgeon, the veterinary oncologist and the family at home, all feel that the treatment is improving quality of life at all times. Chemotherapy and cancer rightly carry a certain stigma. Your vet should take great pains to ensure that any potential side effects are discussed fully prior to embarking on a course of cancer therapy. This way you can make informed decisions about the treatment choices for your pet. The aim of cancer treatment in pets is to promote a good quality of life first and foremost and life expectancy second.