Non-Hodgkin's Lymphoma: A Cancer of the Immune System

by Food and Drug Administration (FDA)

A relatively unknown yet deadly cancer has become more common in the last few decades and is now the sixth most common cancer in the United States, according to the National Cancer Institute. This cancer of the immune system, known as Non-Hodgkin's lymphoma (NHL), became more familiar to the general public as it struck such luminaries as Jackie Kennedy Onassis, Senator Paul Tsongas, and the Shah Mohammed Reza Pahlevi of Iran.

NHL has increased 75 percent over the last 20 years, making it the most rapidly rising cancer after lung cancer and melanoma, NCI says. The incidence of NHL increased from 8.5 per 100,000 people in 1973 to 15.1 per 100,000 in 1991, and mortality from the disease increased from 4.8 per 100,000 people in 1973 to 6.5 per 100,000 in 1991

Although recent studies have provided some intriguing clues, the cause of what some experts call the "NHL epidemic" is not known. Fortunately, advances in treatment seem to be keeping pace; the five-year survival rate for NHL rose from 31 percent to 51 percent over the past 30 years, according to NCI.

Cancers of the Immune System

NHL is a collection of more than a dozen different cancers of the lymphatic system, which generates the body's immune defenses. This system includes a network of channels akin to blood vessels through which lymphocytes — important white blood cells of the immune system — patrol the body for invading microbes. Along these lymphatic routes in the neck, armpits, abdomen, and groin are clusters of bean-shaped lymph nodes that house platoons of the infection-fighting lymphocytes. These cells also cluster in areas that serve as gateways to the body, including the mucous membranes lining the respiratory and digestive tracts, and the skin. Lymphocytes travel in the bloodstream, as well. The lymphatic system also includes such organs as the spleen, thymus and tonsils.

Because NHL can develop wherever in the body lymphocytes can be found, the cancer can crop up nearly anywhere. Symptoms can vary widely, depending on the cancer site. The most common symptom is a noticeable, usually painless swelling of a lymph node. NHL in the digestive tract can cause nausea, vomiting, or abdominal pain; in the chest, shortness of breath or cough may develop. If the brain is involved, patients may have headaches, vision changes, or seizures. If the bone marrow is affected, lymphoma cells may crowd out red blood cell precursors, causing anemia. Reddened patches on the skin can occur when lymphoma cells there prompt localized inflammation.

Because NHL can foster a hyperactive immune response, it often causes symptoms that develop when the body is fighting an infection, such as fevers, night sweats, tiredness, and weight loss. Another NHL symptom is widespread itching, apparently triggered by immune cells' release of histamines, the same compounds that cause itchiness in allergic reactions.

NHLs can affect people of all ages, although the incidence of NHL increases with age. About half of all cases are in people aged 60 and older.

The treatments for NHL include drugs and radiation therapy regulated by the Food and Drug Administration.

Diverse Group of Cancers

To diagnose NHL, doctors remove a small sample of the tissue thought to be cancerous. This procedure, known as a biopsy, is usually done with a local anesthetic. A pathologist examines the tissue under a microscope to look for cancer cells. The appearance of these cells and the proteins on their surfaces helps the pathologist determine the type of NHL the cancer is. The various types have distinctive appearances, carry different prognoses (predicted outcomes), and have different treatments. Whereas one type may be extremely deadly, another may be highly curable.

NHLs are classed as low-, intermediate- and high-grade. This classification scheme accurately predicts the survival of untreated patients, but is not as reliable in predicting outcome after treatment. Low-grade lymphomas are slow-growing tumors, and some patients can survive for more than a decade without treatment. Although chemotherapy often can shrink low-grade lymphomas, the cancer usually recurs within five years. Recurrent tumors can also be treated with chemotherapy or radiation, but over time, low-grade NHLs tend to become more aggressive and less responsive to therapy. Consequently, these types of lymphomas are not cured with currently available treatment.

In contrast, intermediate-grade and high-grade lymphomas are fast-growing tumors that, without treatment, generally are fatal within a year or two of diagnosis. Chemotherapy may cure many types of these lymphomas.

Doctors determine the stage of the cancer according to the number and location of tumors. This information, which also affects prognosis, is obtained from a physical exam, blood tests, and x-rays, CAT-scans, or ultrasound scans of various organs and tissues. Biopsies of the bone marrow and lymph nodes often are necessary. Regardless of NHL type, patients have a better prognosis with appropriate therapy if they have:

• the cancer in only one lymph node area or in only one area or organ outside the lymph nodes
• no tumors more than 10 centimeters in diameter
• no systemic symptoms, such as fevers or night sweats.

Younger patients also usually fare better than older ones.

A number of studies have pinpointed the genetic flaws that characterize different types or subtypes of NHL. Experts predict that this information will soon foster a new classification scheme that more accurately predicts outcome.

About the Author

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