The typical canine lymphoma patient is a middle-aged dog brought to the veterinarian because one or more lumps have been found. The veterinarian rapidly determines that these lumps are actually lymph nodes and that many (if not all) of the peripheral lymph nodes (those near the skin surface) are enlarged and firm. Usually, the dog has not been showing any signs of illness; he simply has lumps.
The next step in determining a diagnosis is a blood panel and urinalysis to completely assess the patient's health, and one or more lymph nodes are aspirated or biopsied to confirm the diagnosis of lymphoma.
We know the average life expectancy for a patient with untreated lymphoma is about two months from the time of diagnosis. If this is your dog's situation, you probably need some time to absorb the cancer diagnosis. You have many general questions, and you know that a decision regarding chemotherapy must be made.
Most of the time, we do not know how dogs or people get cancer. There are many types of cancer and many possible causes of all those cancers (chemicals in our environment, especially cigarette smoke, sun exposure, assorted viruses and infections). There are important genetic factors as well.
Cancer starts with one or a small group of cells that have gone wrong. Such cells arise in our bodies all the time and we have an assortment of natural mechanisms to destroy these cells before they get out of hand. When these abnormal cells escape our natural mechanisms, cancer develops.
It is important to realize that cancer is not contagious and that, as a pet owner, you should not feel that you somehow caused this or brought it on your pet. Many people feel a need to find blame and latch onto the idea that a household cleaner or pesticide was the cause. This is a natural part of grieving, but it is important not to focus on cause unduly. Cause is not relevant to treatment; furthermore, there is no way to verify cause. At this time, there is no way to know what caused lymphoma development in a given patient. Dogs that are genetically predisposed include the Basset hound, boxer, Golden retriever, and St. Bernard. It is best to concentrate on treatment.
A cure practically speaking, is not in the cards. It is best to focus on a realistic outcome that provides the longest possible survival with a good quality of life. Different treatment protocols are associated with different disease-free intervals, meaning that the length of time your dog feels normal will vary depending on the protocol you choose. The disease-free interval also depends on patient factors (type of lymphoma, concurrent disease, prior treatment etc.). Obviously, the goal is to have as long a disease-free interval as possible.
If a biopsy has not been performed, it may be a good idea to do one to get the maximum information about the tumor (whether it is slow or fast growing, what type of lymphocytes are involved, etc.) as this information can help predict the response to chemotherapy.
Lymphoma is classified by stage: staging has less impact on therapy choices than one might think but it is true that patients in Stage V, the most advanced stage, have a poorer prognosis than those in the other stages.
Lymphoma is a rapidly growing malignancy that is able to arise and/or travel to anywhere where there is lymph tissue. Of course, there is lymph tissue in virtually every organ in the body. Eventually, the cancer will infiltrate an organ to such an extent that that organ fails (often this is the bone marrow or the liver). The patient loses appetite, vomits or gets diarrhea, weakens and dies. At some point the tumor becomes resistant to therapy and no further remissions can be obtained.
A common questions pet owners commonly have regarding chemotherapy for their dog is the median survival time for most dogs on chemotherapy. Approximately one year with 25 percent of dogs surviving two years. Lymphoma is a condition that not all veterinarians are comfortable treating. Discuss with your veterinarian whether referral to a specialist would be best for you and your pet.
A patient in remission is indistinguishable from a completely cancer-free patient. The lymph nodes will go down to normal size and if there were any signs of illness related to the cancer, these should resolve. The chance of achieving remission is pretty good with most protocols: 50-80 percent depending on the protocol selected. The real differences in protocols concern how long the remission is likely to last. There are patient factors in play that influence this. The most obvious sign will be that the lymph node enlargement has returned. This means that the cancer is now resistant to the drugs being used and new drugs must be chosen. (Seeking a second remission after the first remission has been lost is called a rescue.)
There are also many factors that influence how an individual will do relative to the average response. Important parameters to note when reviewing a protocol are: the disease-free interval (i.e., how long the patient is free from illness, survival time, typical duration of remission, expense and scheduling. There are several options, and remission will likely be possible at a low cost without seeing a specialist, but it will likely be a short one. This option is for patients for whom the other protocols are unavailable.
Dr. Lamb is the Veterinarian at the Manchester Animal Hospital.
