Hodgkin’s Disease and Non-Hodgkin’s Lymphoma
Lymphoma is a general term for cancers of the lymphatic system. The lymphatic system is part of the immune system. It consists of a network of vessels and nodes. The vessels carry a watery fluid called lymph, which contains infection-fighting white blood cells, to all parts of the body. Scattered throughout the network of vessels are lymph nodes, where white blood cells are made and stored. Clusters of lymph nodes are found in the underarms, groin, neck, chest and abdomen. The spleen, bone marrow, thymus and tonsils are also parts of the lymphatic system.
Lymphoma develops when white blood cells known as lymphocytes become abnormal and start dividing without control. Because lymphatic tissue is present in many parts of the body, lymphoma can start almost anywhere. It can occur in one lymph node, in a group of nodes, or in an organ. It can then spread to almost any area of the body.
Hodgkin’s disease is one type of lymphoma, named after Dr. Thomas Hodgkin who first identified the disease in 1832. All other lymphomas are collectively classified as non-Hodgkin’s lymphoma. Hodgkin’s disease and non-Hodgkin’s lymphoma are distinguished by how the cancer cells look under a microscope. Non-Hodgkin’s lymphoma is far more common.
What’s the difference between Hodgkin’s disease and non-Hodgkin’s lymphoma?
Although Hodgkin’s disease and non-Hodgkin’s lymphoma are both cancers of the lymphatic system, the malignant cells appear very differently under a microscope and may originate from different subtypes of lymphocytes. (Remember: Lymphocytes are a type of white blood cell.)
Hodgkin’s disease is characterized by a specific type of cell called a Reed-Sternberg cell, which is a large, cancerous lymphocyte with more than one nucleus. There are four types of Hodgkin’s disease, each distinguished by the number of Reed-Sternberg cells relative to the number of other types of white blood cells.
Non-Hodgkin’s lymphomas are more likely to invade the bone marrow, gastrointestinal tract and skin than Hodgkin’s disease. Some types spread very rapidly (over months), and some spread slowly (over years). There are 13 types of non-Hodgkin’s lymphoma. Among them are Burkitt’s lymphoma, which originates from a subtype of lymphocytes known as B lymphocytes, and mycosis fungoides, a lymphoma that originates from cells known as T lymphocytes.
What causes lymphoma?
The cause of lymphoma is unknown, but some experts suspect a virus, most notably the Epstein-Barr virus. HTLV-1 (human T-cell lymphotropic virus type I) has been associated with a very rare type of non-Hodgkin’s lymphoma. (HTLV-1 is a retrovirus similar to HIV [human immunodeficiency virus], which causes AIDS.)
What are the risk factors associated with lymphoma?
Researchers have identified a few factors that may increase a person’s likelihood of getting Hodgkin’s disease or non-Hodgkin’s lymphoma. People who have reduced immune function (for example, those with AIDS or those on immunosuppressive therapy, such as organ transplant patients) are at higher risk. So, too, are people with a history of infection with the Epstein-Barr virus.
For non-Hodgkin’s lymphoma, exposure to radiation and certain chemicals, such as benzene, has also been linked with an increased chance of getting the disease. In addition, genetic disorders that cause children to be born with deficient immune systems raise the risk of developing the cancer.
What are the symptoms of lymphoma?
In Hodgkin’s disease, the first noticeable symptom is usually an enlarged lymph node, most frequently in the neck but sometimes in the groin or underarm area. In non-Hodgkin’s lymphoma, the first symptom is usually several enlarged lymph nodes in either a single area, such as the neck or groin, or throughout the body.
Other symptoms associated with both types of lymphoma include: unexplained fever, weight loss, constant fatigue, night sweats and itchy skin. When lymph nodes inside the chest become swollen, they can place pressure on the windpipe. This can cause symptoms such as coughing and shortness of breath.
Keep in mind that there can be many reasons for these symptoms other than cancer.
How is lymphoma detected?
Lymphoma is most often found when a lump appears in lymph nodes in the neck, underarm or groin. If the nodes remain enlarged for more than a week, especially if other symptoms are present, the doctor may suspect lymphoma. Abnormal blood cell counts and the results of other blood tests and imaging tests may also suggest cancer, but in order to make a definitive diagnosis, a biopsy is necessary.
There are several types of biopsies, and the choice of procedure depends on which node(s) is enlarged and how much tissue is needed for a clear diagnosis. If the enlarged node is close to the surface of the neck, for example, the doctor may perform a needle biopsy, in which a needle and syringe are used to draw out a sample of fluid and small pieces of tissue from the tumor. For an enlarged lymph node deep inside the chest, however, it may be necessary to cut through the skin to remove the entire node or part of a large tumor. Regardless of how the sample is obtained, a pathologist will examine it under a microscope to check for cancer cells.
How is lymphoma staged?
Staging is the process of determining the extent to which a cancer has progressed. The information is used to develop an optimal treatment plan.
For lymphoma, staging is based on how far the cancer has spread (stages I, II, III, and IV) as well as the absence (A) or presence (B) of certain symptoms, such as unexplained fever, weight loss and night sweats. As an example, a cancer may be described as IIIA or IIIB. In general, the higher the number and letter, the more serious the lymphoma.
In addition to stages, non-Hodgkin’s lymphomas are broadly classified into two groups: aggressive (also called high grade or intermediate), which grow quickly and cause severe symptoms, or indolent (also called low grade), which grow slowly and cause fewer symptoms.
To stage lymphoma, the doctor may use some of the same tests used for the diagnosis, including imaging tests, such as a CT scan (computed tomography) or MRI (magnetic resonance imaging), and more extensive lymph node biopsies. In addition, a bone marrow biopsy may be performed. During this procedure, a large needle is used to remove a narrow cylinder of bone and marrow. (Alternatively, the doctor may perform a bone marrow aspiration, in which a smaller needle and syringe are used to draw out a small amount of bone marrow.) The tissue samples are taken from a large bone, usually the back of the hip bone. They are then examined under a microscope to check if cancer cells have invaded the bone marrow. A bone marrow biopsy may only be recommend for patients who have fevers or night sweats or are anemic (have low red blood cell counts), as these are signs that the lymphoma is in the bone marrow.
How is lymphoma treated?
Individual treatment plans for lymphoma depend on the type of lymphoma, how far the cancer has spread, whether it’s aggressive or indolent, and the age and overall health of the patient. Thanks to traditional chemotherapy and newer treatment methods, lymphomas have a relatively high cure rate.
Hodgkin’s disease: For Hodgkin’s disease, chemotherapy and radiation therapy are the main treatment methods.With either one or both of these therapies, about 90 percent of patients with early-stage Hodgkin’s disease are cured. Patients with advanced-stage disease are treated with various combinations of chemotherapy drugs. About two-thirds of these patients are cured.
For patients who stop responding to standard therapy, bone marrow stem-cell transplantation is an option. This complex therapy provides doctors with a way to use very high doses of chemotherapy for more effective treatment. It involves harvesting stem cells (primitive blood cells) from the patient’s bone marrow or the blood stream through a process called apheresis. After the stem cells have been removed and stored, the patient is given extremely high doses of chemotherapy that destroy the bone marrow. The stored stem cells are then returned the patient as a blood transfusion. If successful, it takes several weeks after the stem cells are reinfused for the cells to mature and start making new blood cells.
Non-Hodgkin’s lymphoma: The success of treatment for non-Hodgkin’s lymphoma depends on whether the disease is aggressive or indolent. Aggressive lymphomas have the fastest-growing cancer cells, which means the cells are most vulnerable to the cancer-killing effects of chemotherapy and radiation. While indolent lymphomas do usually respond to chemotherapy and radiation, they are less likely to be completely cured by these treatments, and recurrences are common.
Because aggressive lymphomas grow very rapidly, some types can be life-threatening within months if left untreated. However, if an aggressive lymphoma is diagnosed at Stage I, the chance for a cure is about 80 to 90 percent, and even some of the most advanced cases have a 30 percent chance of a cure.
Usually a combination of several chemotherapy drugs combined with radiation therapy is used for Stage I. Chemotherapy alone is used for all other stages. If the cancer recurs, different chemotherapy drugs are used. Bone marrow transplantation is another option.
Indolent lymphomas may take as long as seven to 10 years before causing any problems. As a result, treatment is not always started immediately. Instead, the doctor may take a “watchful waiting” approach, and chemotherapy and/or radiation therapy are started once symptoms appear.
In some cases, indolent lymphomas are treated from the outset with radiation or chemotherapy, whether or not symptoms are present. The lymphoma often goes into remission, but it may recur many years later as an indolent form or as one of the aggressive kinds. In either case, chemotherapy is used again to treat the cancer. (Occasionally, radiation therapy is also used again, but not to treat the same area of the body.)
In addition to chemotherapy and radiation for treating non-Hodgkin’s lymphoma, a biological therapy called rituximab (Rituxan) is now available. Rituxan, a drug approved by the Food and Drug Administration in 1997 for the treatment of certain indolent lymphomas, is a monoclonal antibody. Monoclonal antibodies, which are genetically engineered in a laboratory, are designed to attach to certain substances on the surface of cancer cells. (Rituxan attaches to a substance called CD20, which is found on some types of indolent non-Hodgkin’s lymphoma cells.) The patient’s body recognizes the monoclonal antibody as an invader, and the immune system kills the cells to which it is attached.
Presently, chemotherapy and radiation therapy are the first treatments given for non-Hodgkin’s lymphoma, and Rituxan is used if these fail or cancer comes back after a remission. However, in the future, Rituxan may become the first line of therapy, depending on the results of research currently under way.
Another biological therapy is interferon. Interferon is a protein naturally produced by white blood cells to help the immune system fight infections. Some research has suggested that interferon can help shrink the tumors of certain types of non-Hodgkin’s lymphoma. It is still not clear, however, which patients are appropriate candidates for interferon therapy and whether it should be given to these patients in addition to chemotherapy.
Although indolent lymphomas are less responsive to treatment than aggressive varieties, this does not mean that the prognosis for indolent cancers is necessarily poor. In fact, indolent lymphomas can progress so slowly that treatment, although it may not cure the disease, can often prolong life to the point where an older adult lives a normal lifespan and dies from another cause.
Is there a lymphoma vaccine under development?
Yes. But, unlike conventional vaccines, the lymphoma vaccine is not intended to prevent lymphoma in healthy people. Rather, it is given to patients in remission from an indolent lymphoma to strengthen the body’s natural defenses to prevent a relapse. The vaccine contains a tiny amount of protein taken from the patient’s own tumor. This allows the body to detect the tumor protein and produce defenses against it, priming the immune system to be ready to destroy any cells it encounters that contain the tumor protein. In a study of 20 patients who were vaccinated, 18 remained in complete remission four years after the therapy began. A larger trial is now under way; however, it could take eight years to produce results.
The lymphoma vaccine will be an exciting addition to the therapeutic arsenal for fighting lymphomas.