LYMPHOMA, GASTROINTESTINAL

About the Diagnosis


The defining characteristic of a cancer is that it is growth of cells in an unorganized or inappropriate way. Typically cancers are defined as benign or malignant. Benign tumors are slow-growing, do not invade surrounding tissues, and are mature cell types. They are growing inappropriately but are generally fairly organized about it. Malignant tumors are fast-growing, invade neighboring tissue, and "revert" back to a less mature cell type. These are chaotic and random growers and therefore more difficult to find and kill.

Lymphoma or lymphosarcoma is an immune cell cancer. The cells of the immune system are designed to be mobile and active throughout the body. In this way, they are able to respond to an infection in the tip of a toe or the center of the body. Lymphocytes are small white blood cells. There are several subclasses of lymphocytes. These subclasses are defined by the jobs they perform in the complex process of identifying a foreign subject, attacking and killing the subject, removing the remains, and preparing for future invasions by that same or a similar intruder.

Cancers of the immune system can grow into and distribute themselves throughout or in sections of another organ. This is typical of lymphoma of the intestinal tract. Sometimes all that can be found is a mild thickening, but when the tissue is looked at microscopically (from a biopsy or aspirate), then the abundant lymphocytes are identified.

The majority of normal lymphocytes grow and develop in bone marrow and lymph nodes and then travel to an area of the body where they are needed. They start off as medium-sized cells and grow smaller as they develop and become more specialized in their role in the immune system. Normal lymphocytes are found throughout the body; when they become cancerous, they become abundant in a focused area or areas. The more tissues that are affected, the more malignant the lymphoma is considered.

In an effort to help predict the course of disease, as well as guide treatment and therapy, people have developed some standards to further classify malignancy in immune cancers. Historically, the guidelines were the size and maturity of the cells in addition to the tissue or tissues that were affected. Small, more mature cells generally are slower-growing and are associated with longer survival times. Large, more immature cells tend to be faster-growing and are associated with shorter survival times. Unlike lymphoma of dogs and peripheral lymphoma of cats, gastrointestinal large cell lymphoma seems to become drug resistant faster.

In the recent past, great efforts have been made to help identify the cellular type of lymphocyte using special chemical stains with biopsy or aspirate tissue. This information, B-cell lymphoma, T-cell lymphoma, Natural Killer cell lymphoma, and so forth, may in the future aid veterinarians to better guide treatment and prognosis. This technology can also help identify clones of immune cells (cancerous) versus a normal immune response, therefore allowing us to diagnosis cancer at an early and more treatable stage.

Cats: Gastrointestinal lymphoma, small cell type, is a common cancer of older cats (average 9 to 11 years). The diagnosis is made based on biopsy samples of the stomach or intestine. Small cell lymphoma of the intestine of cats is a mild form of malignancy, and with treatment, cats typically live with minimal or no symptoms for years. By contrast, large cell lymphoma of the intestine of cats is more aggressive, and survival on the scale of weeks to months, even with extensive treatment, is the average.

Dogs: In dogs, gastrointestinal lymphoma tends to be an aggressive and difficult-to-control tumor, unless it is confined to a single area of the intestine (focal). Treatment involves surgery if a single area is identified, but this situation is uncommon. More typically, dogs with gastrointestinal lymphoma have diffuse lymphoma throughout the digestive/gastrointestinal system, and the required treatments are injections and pills of anticancer medications (chemotherapy).

Living with the Diagnosis

The goal of therapy is to improve and restore good quality of life. This will secondarily extend your pet's life by reducing or removing the cancer burden. There are different chemotherapy protocols or plans. These plans use different strength drugs, as well as different dosages of the same drugs. Plans should be chosen by your veterinarian with guidance from you as to your expectations. The more aggressive the treatment is, the more likely we are to reduce the cancer burden; unfortunately, this comes with an increased risk of chemotherapy-related problems and side effects. Reducing treatment to the levels of few or no side effects reduces the likelihood of treatment-related problems but also may not keep the cancer away for as long a period of time.

Initial response to chemotherapy can be an important marker for success and survival. Cats that respond well to initial therapy tend to have longer survival times. It should also be noted that researchers have documented that cats in general tolerate chemotherapy well. They do not lose their hair, they are often noted to be active, eat well, and generally appear healthier than before starting chemotherapy. Regardless of the plan chosen and the approach taken, a pet with gastrointestinal lymphoma usually receives long-term if not lifelong therapy. This means regular administration of oral medications at home. This often includes multiple pills, liquids, and so forth given per day.
Often pets with gastrointestinal lymphoma will have eventual recurrence of symptoms. Whether this is vomiting, diarrhea, or simply decreased appetite and weight loss, recurrence of symptoms is generally the same as the original symptoms. In addition, the medications that are being given can also cause some if not all of the same symptoms.

Frequent rechecks by your veterinarian therefore may be necessary. The rechecks may be able to differentiate drug side effects from recurrence of disease, or they may need to just change therapy and monitor results of the change. Either way, you should have a good working relationship with your veterinarian.

Treatment

Small cell gastrointestinal lymphoma of cats often responds well to oral chemotherapy combinations. Oral corticosteroids such as cortisone given daily or twice daily are typical, in addition to one of a couple of other oral medications given less frequently (twice weekly, once every 4 weeks, etc., depending on the drug chosen). Oral corticosteroids are given in the lowest amount that remains effective because long-term use at high doses can cause excessive weight gain, gastrointestinal irritation and ulceration, thin skin, and diabetes mellitus. Typical oral chemotherapeutics can suppress the immune system, can cause gastrointestinal irritation and ulceration, and can cause decreases in red and white blood cells. Your veterinarian should monitor treatment responses and should provide you with a plan for rechecks and follow-ups to try to minimize the risk of significant side effects.

DOs

• Understand the important steps in treating any dog or cat thought to have lymphoma:

o Confirmatory testing-is it lymphoma or not?

o Once lymphoma is confirmed, a decision on treatment is needed (Try it to see if it works, or not at all? If going ahead with treatment, will it be complete, including chemotherapy, in order to try for the greatest chance of beating the cancer back or minimal, in order to provide some short-term benefit?).

o If relapse occurs and the lymphoma comes out of remission, how long to continue with treatment?

o These questions are essential, and you should not hesitate to discuss them with your veterinarian both initially and throughout the period of treatment if you choose to pursue one.

• Realize that chemotherapy is different in humans versus pets and that dogs and cats rarely have any of the severe side effects that humans do.

• Realize that it is all right to start chemotherapy and see how it goes. If there is no improvement early on, the likelihood of successful long-term treatment is reduced significantly. Just because chemotherapy plans are designed for 6 months of treatment does NOT mean every animal has to go through all 6 months regardless of how they are feeling.

• Your pet's quality and quantity of life are dependent on you. You must give some of the medications, follow up as recommended by your veterinarian, and be watchful of side effects. Your participation in treatment can make all the difference.

• Decide in advance what standards would influence you to euthanize your pet. Stand by these standards, and try not to make emotional or fear-driven decisions in "the heat of the moment." Deciding these standards in advance can help enormously if a situation arises that requires you to make tough decisions.

DON'Ts

• Do not give up because of one bad day, but rather, be aware of overall trends. Have there been several bad days lately? Does this one bad day make you realize that your pet has not been himself/herself for quite some time? If so, then there is reason to question whether to continue, but if it is a single "off" day, things may be totally different a short while later.

When to Call Your Veterinarian

• Recurrence of symptoms (vomiting, diarrhea, decreased appetite, weakness, pallor, excessive drinking, excessive urination, fever, or weight loss) should be discussed with your veterinarian.

• Your veterinarian should provide you with specific symptoms and side effects based on the drugs prescribed. If not, you should feel comfortable calling and requesting them.

Signs to Watch For

• Enlargement of lymph nodes. Your veterinarian or the staff can help you learn how to check these periodically.

• Vomiting, diarrhea, decreased appetite, excessive drinking, excessive urination, weight loss. Some of these symptoms may be expected as a result of medications (e.g., prednisone, furosemide), so be sure to ask your veterinarian about whether to watch for these as expected medication-related effects or symptoms worthy of concern.

Routine Follow-Up

• Generally once per week for the first several visits, then more widely spread out depending on the particulars of your pet's situation and response to treatment.

• Usually, with chemotherapy, every visit begins with a blood test. This is an important precaution that looks for the early signs of intolerance to chemotherapy. The blood test may show that the white blood cell count is normal, and treatment can continue as planned. On the other hand, the blood test may show that the white blood cell count is low, which is one of the earliest clues that a previous dose of chemotherapy may have been more than could be handled. This tells the veterinarian that, even though symptoms may not be present and the dog or cat is happy and active and eating well, chemotherapy should probably be reduced in amount, delayed, or skipped altogether in order to let the body process all of the previous chemotherapy and be ready for the next treatment. In other words, the prechemotherapy blood test is important for every visit since it is a precautionary measure.