Primary gastric lymphoma is a general term for a type of cancer that originates within the stomach. Approximately 90 percent of cases of primary gastric lymphoma are either mucosa-associated lymphoid tissue (MALT) gastric lymphoma or diffuse large B-cell lymphoma (DLBCL) of the stomach. MALT gastric lymphoma is often associated with infection with the Helicobacter pylori bacterium. Within the medical literature, significant controversy exists regarding the exact definition, classification and staging of primary gastric lymphoma.
The term lymphoma refers to cancer that arises in the lymphatic system. Functioning as part of the immune system, the lymphatic system helps to protect the body against infection and disease. It consists of a network of tubes known as lymph vessels that drain a thin watery fluid known as lymph from different areas of the body into the bloodstream. Lymph collects in the tiny spaces between tissue cells and contains proteins, fats, and certain white blood cells known as lymphocytes. As lymph moves through the lymphatic system, it is filtered by a network of small structures known as lymph nodes that help to remove microorganisms (e.g., viruses, bacteria, etc.) and other foreign bodies from the bloodstream.
Most types of lymphoma result from errors in the production of a type of white blood cell (lymphocyte) or transformation of a single lymphocyte into a malignant cell. Abnormal, uncontrolled growth and proliferation of malignant lymphocytes may lead to enlargement of a specific lymph node region or regions; involvement of other lymphatic tissues, such as the spleen and bone marrow; and spread to other bodily tissues and organs, can lead to life-threatening complications. The specific symptoms (fever, night sweats, itchiness, etc.) and physical findings (weight loss, enlarged spleen, lumps over the neck or axilla, etc.) may vary from case to case, depending upon the extent and region(s) of involvement and other factors.
Most cases of primary gastric lymphoma are B-cell subtypes of non-Hodgkin lymphoma (NHL). NHL may be broadly classified into lymphomas that arise from abnormal B-lymphocytes (B-cell lymphoma) and those derived from abnormal T-lymphocytes (T-cell lymphoma). Most cases of lymphoma arise in the lymph nodes. When lymphoma arises outside the lymph nodes, it is referred to as extranodal lymphoma. Primary gastric lymphoma is the most common form of extranodal NHL.
NHL may also be categorized based upon certain characteristics of the cancer cells as seen under a microscope and how quickly they may tend to grow and spread. For example, NHL may be characterized as "low-grade" (or indolent), meaning it tends to grow slowly and result in few associated symptoms, or "intermediate-" or "high-grade" (aggressive) lymphomas, which typically grow rapidly, requiring prompt treatment. MALT gastric lymphoma is generally an indolent lymphoma; DLBCL of the stomach is generally an aggressive lymphoma. In some cases, individuals may have both forms of cancer at the same time.
The symptoms of primary gastric lymphoma are usually vague and nonspecific and common to many other conditions beside cancer. In many cases, there may be no noticeable physical findings upon diagnosis. Specific symptoms can vary dramatically from one person to another. Abdominal pain or cramping is probably the most common finding of primary gastric lymphoma and may be the initial symptom noted.
Additional symptoms that may occur in individuals with primary gastric lymphoma include a premature feeling of fullness or being sated (early satiety), abdominal tenderness, nausea, vomiting, unintended weight loss, a general feeling of poor health (malaise), and indigestion. Gastric bleeding may occur in some cases and can be the first noticeable symptom of primary gastric lymphoma. A mass large enough to be able to be felt (palpable) when applying pressure to the stomach may also be present in some advanced cases.
Less frequently, weakness, fatigue, night sweats, jaundice (yellowing of the skin and the whites of the eyes), fever, and dysphagia (difficulty swallowing) may occur. Additional less common findings associated with primary gastric lymphoma include abnormal enlargement of the liver (hepatomegaly) or spleen (splenomegaly), obstruction of the gastrointestinal tract, development of a hole or tear in the wall of the stomach (perforation), and the abnormal enlargement of the lymph nodes (lymphadenopathy).
The exact cause of primary gastric lymphoma is unknown. However, a strong association between infection with Helicobacter pylori (H. pylori) and the development of MALT gastric lymphoma has been established. H. pylori is a bacterium that is found in the stomach and the upper portion of the intestines and is best known as a cause of ulcers.
In approximately 90 percent of cases, MALT gastric lymphoma is strongly associated with chronic H. pylori infection. MALT gastric lymphoma originally arises from certain white blood cells (lymphocytes) found within the lymphoid tissue of the stomach’s inner lining (mucous membranes or mucosa). This lymphoid tissue is not normally found in the stomach, but develops as a result of chronic inflammation as occurs with chronic H. pylori infection.
Although H. pylori infection plays a role in the development of MALT gastric lymphoma, the infection is quite common in the general population. Yet, only a very small number of individuals with this bacterium develop MALT gastric lymphoma. This indicates that other factors, most likely including an abnormal response to the infection by the body’s immune system, also play a role in the development of MALT gastric lymphoma.
Some individuals with MALT gastric lymphoma have chromosomal abnormalities within the malignancy, specifically a translocation. A translocation means that a piece of one chromosome breaks off and attaches to another. These chromosomal abnormalities may be significant in terms of treatment or prognosis. For example, some affected individuals have a translocation involving chromosomes 11 and 18 (translocation t [11; 18]), which seems to be associated with poorer response to antibiotic therapy and the eradication of H. pylori infection.
DLBCL of the stomach may arise spontaneously in individuals without a previous history of cancer (de novo), or it may occur from the transformation of an indolent MALT gastric lymphoma into the more aggressive DLBCL form. Some researchers have suggested that DLBCL of the stomach may also be associated with H. pylori infection. Some individuals with DLBCL of the stomach have been infected with the bacterium, but some researchers believe that these cases are examples of long-standing MALT gastric lymphoma that has transformed into the more aggressive DLBCL of the stomach.
Primary gastric lymphoma is estimated to affect approximately 1 in 100,000 people in the general population in Western countries. Several reports have noted that the incidence is increasing. Most cases of primary gastric lymphoma occur in individuals 50 years or older, with a peak incidence in the 60s and 70s. However, cases have been reported in children, adolescents and young adults as well. Some reports suggest that men are affected more often than women. Primary gastric lymphoma has also been reported to occur more frequently in Caucasians than African-Americans.
Primary gastric lymphoma is the most common form of extranodal non-Hodgkin lymphoma (NHL), accounting for 30-40 percent of all extranodal sites. Primary gastric lymphoma accounts for 10-15 percent of all NHL cases. Although it is the most common extranodal site for NHL, primary gastric lymphoma is extremely rare, accounting for only 2-8 percent of all cases of primary gastric cancer.
Diffuse large B-cell lymphoma (DLBCL) and MALT lymphoma are the second and third most common subtypes of NHL (this is for all cases of these subtypes, not just those confined to the gastrointestinal tract).
Primary gastric lymphoma is diagnosed based upon a thorough clinical evaluation, detection of certain symptoms and physical findings, a detailed patient history and a variety of specialized tests. Such testing is necessary to confirm the specific type (and subtype) of NHL present, to assess the nature and extent of the disease and to determine the most appropriate treatments.
For individuals with suspected gastric lymphoma as suggested by patient history and physical examination, various diagnostic tests may be recommended. These may include blood tests, biopsies, bone marrow aspirates, and specialized imaging tests. For example, blood tests may include studies to evaluate the number and appearance of white blood cells, red blood cells, and platelets; tests to measure levels of the enzyme lactate dehydrogenase (LDH); and/or other studies. (High elevations of LDH may suggest that the lymphoma may have rapid progression, potentially requiring more intensive therapies.)
For individuals suspected of primary gastric lymphoma, a surgeon or gastroenterologist (a physician specializing in diseases of the digestive organs) will perform a procedure called an esophagogastroduodenoscopy (EGD), also called an upper GI (gastrointestinal) endoscopy. During an EGD, a light, flexible tube (endoscope) is inserted into the stomach or gastrointestinal tract to allow a physician to view the areas of abnormal tissue. An endoscope also allows a physician to perform a biopsy or biopsies (removal of a small sample of tissue or multiple samples for study under a microscope by a pathologist, a physician who specializes in diagnosing disease through the study of tissue, fluids and blood). The EGD and biopsy procedure may be conducted under local or whole body (general) anesthesia.
Microscopic analysis of affected tissue enables pathologists to determine additional histologic (microscopic) features that may be important in the malignancy’s classification, such as the size of malignant lymphocytes, appearance of the nucleus within a lymphoma cell, distribution or pattern of the abnormal cells, etc. In addition, specialized studies are conducted to help determine the malignancy’s specific cell type of origin. For example, gastric lymphoma cells–and the normal cells from which the malignancy develops–produce distinctive proteins (antigens) that may promote an antibody (immune) response (e.g., antigens such as CD20). They also may express certain antibodies on their outer surfaces (e.g., immunoglobulin M [IgM]). Thus, testing to identify such markers assists in determining the normal cells from which the malignancy derived, helping to distinguish primary gastric lymphoma from other types of lymphoma and aiding in diagnosis and disease management decisions.
Various specialized imaging procedures may also be recommended, such as standard x-ray imaging or computed tomography (CT) scanning. Specialized imaging procedures are generally used to help establish a diagnosis and to determine the extent of the disease. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of internal structures. For those with suspected or diagnosed NHL, CT scans may be taken of the neck, chest, abdominal, and/or pelvic regions to help detect enlargement of certain lymph nodes or spread of the malignancy to certain organs. Although abnormalities of the stomach mucosa are difficult to see on CT scans, such scans are useful in showing any extension or spread of the lymphoma to other parts of the body where they can be more easily seen on CT.
Over the past 15 years, PET scans (positron emission tomography) have replaced gallium scans as a way to detect lymphoma in parts of the body that may be easily missed on routine CT scans. Cancer cells, like lymphoma, metabolize sugar more rapidly than normal cells. PET scans are a nuclear medicine imaging technology where radioactive glucose is injected into the patient and cancer cells take up this glucose more rapidly and in much higher quantities than normal cells, causing the cancer cells to "light-up" on the scan. PET scans are useful in showing to what extent the lymphoma has spread. They can also be used to measure a patient’s response to treatment. PET scans are often performed in conjunction with a CT scan, and when this is done, a separate CT scan can often be omitted. Unfortunately, PET scans can light up in parts of the body where there is infection or inflammation in the absence of cancer, resulting in a false positive scan. Although PET scans are commonly used to stage and follow patients with nodal NHL, more research is needed to determine the role of PET scans in the staging and follow-up of patients with gastric lymphomas.
MRI (magnetic resonance imaging) can be considered when CT scans and/or PET scans do not provide the needed information. Nevertheless, MRI is not considered a standard imaging study used in the staging, workup, and follow-up of gastric lymphomas.
When an individual is diagnosed with primary gastric lymphoma, assessment is also required to determine the extent or "stage" of the disease. Staging is important to help determine how far the disease has spread, characterize the potential disease course, and determine appropriate treatment approaches. Some of the same diagnostic tests described above may be used in staging a primary gastric lymphoma (e.g., blood tests, CT scanning, bone marrow aspiration and biopsy). In addition, in some cases, additional biopsies may be obtained to assist in lymphoma staging.
Different staging systems have been proposed for primary gastric lymphoma. One of the more widely used staging systems used for primary gastric lymphoma was proposed by an international conference in Lugano, Switzerland, known as the Lugano Staging System for Gastrointestinal Lymphomas. The "E" subscript stands for extranodal. It includes the following stages:
Stage IE – Lymphoma is confined to the gastrointestinal tract.
IE1 = mucosa, submucosa
IE2 = muscularis propria, serosa
Stage II – Lymphoma extends into the abdomen from the primary site within the gastrointestinal tract.
II1 = local nodal involvement
II2 = distant nodal involvement
Stage IIE – Penetration of serosa to involve adjacent organs or tissues.
Stage IV – Disseminated extranodal involvement or concomitant supradiaphragmatic nodal involvement.
The diagnosis and therapeutic management of primary gastric lymphoma may require the coordinated efforts of a team of medical professionals, such as physicians who specialize in the diagnosis and treatment of cancer with chemotherapy and other drugs (medical oncologists), disorders of the gastrointestinal tract (gastroenterologists), disorders of the blood and blood-forming tissues (hematologists), or the diagnosis and treatment of cancer with radiation (radiation oncologists); oncology nurses; surgeons; dietitians; and/or other professionals.
Specific therapeutic procedures and interventions may vary, depending upon numerous factors, such as disease stage; tumor size; specific lymphoma subtype; the presence or absence of certain symptoms; individual's age and general health; and/or other elements. Decisions concerning the use of particular drug regimens and/or other treatments should be made by physicians and other members of the health care team in careful consultation with the patient based upon the specifics of his or her case; a thorough discussion of the potential benefits and risks, including possible side effects and long-term effects; patient preference; and other appropriate factors.
Because MALT gastric lymphoma is slow-growing (indolent) form of lymphoma and because some individuals remain free of symptoms or disease progression for many years, physicians may recommend a watch and wait strategy. Watch and wait refers to when physicians follow a patient with a slow-growing cancer without giving treatment until progression of the disease occurs. This allows some people to avoid undergoing such therapies for many years and even decades in some cases, thus delaying the need to experience the side effects associated with treatment.
A wide variety of treatment options exist for individuals with primary gastric lymphoma including antibiotic therapy, surgery, chemotherapy, and radiation therapy. These treatments may be used alone or in varied combinations. No particular treatment regimen or modality has been agreed upon to be best for individuals with primary gastric lymphoma.
For individuals with early stage MALT gastric lymphoma confined to the stomach, antibiotics alone may be prescribed. Many studies have shown that complete remission of MALT gastric lymphoma is possible in many cases. The eradication of H. pylori with antibiotics is considered by many physicians to be a reasonable initial therapy for individuals with early stage MALT gastric lymphoma. Thorough follow up studies (e.g., blood tests and endoscopic biopsies) are required to confirm the eradication of the bacteria and to assess the response of lymphoma therapy. Continued follow up is also necessary because relapse can occur if a person becomes re-infected with H. pylori.
On the other hand, anecdotal reports in the medical literature have described some cases of DLBCL of the stomach that have responded to antibiotic therapy including individuals who have gone into complete remission. Some researchers advocate that all individuals with DLBCL of the stomach and H. pylori infection should receive antibiotic therapy. Other researchers believe more research is necessary to determine whether antibiotic therapy is appropriate for treating this form of gastric lymphoma.
Some individuals with MALT gastric lymphoma may not respond to therapy with antibiotics. In these cases, radiation therapy to the stomach is often used. A dose of 30 Gy or 3000 cGy is typically given. In cases of advanced MALT lymphoma, and in cases of the more aggressive DLBCL of the stomach, chemotherapy is often used with or without radiation therapy. Higher doses of radiation (36 Gy or 3600 cGy) are used for cases of DLBCL of the stomach. Radiation therapy is a treatment method that uses radiation to destroy cancer cells using beams generated from a linear accelerator (a large advanced X-ray machine) aimed at the tumor. Chemotherapy is the use of several different drugs (given intravenously) alone or in combination to kill cancer cells.
Despite the success of surgery in the past, surgery's role in the treatment of primary gastric lymphoma is now only reserved for highly selected cases that do not respond to chemotherapy or radiation. The current standard of care for MALT gastric lymphoma is nonsurgical and includes antibiotics (if H. pylori positive) or locoregional radiation therapy to the stomach if there is persistent disease after antibiotics or if the patient does not have H. pylori infection. The current standard of care for gastric DLBCL is also nonsurgical and includes chemotherapy with or without subsequent locoregional radiation therapy depending on response to chemotherapy, or size of the initial tumor.
The most common chemotherapeutic regimen used to treat individuals with DLBCL of the stomach is R-CHOP. The "R" stands for rituximab (Rituxan®), a biological therapy (or immunotherapy), which has been highly successful in treating many types of lymphoma including DLBCL (although its role in treating of DLBCL of the stomach is less studied). Rituximab is a monoclonal antibody that is specifically directed against the CD20 antigen, which is a protein that may be found on the surface of certain lymphoma B-cells.
Monoclonal antibodies are produced by mature B-cells known as plasma cells; each plasma cell secretes a specific type of monoclonal antibody, which in turn acts against a specific antigen as part of an antibody-mediated immune response. New technology now enables laboratories to make large amounts of a specific monoclonal antibody that can be directed against a particular target, such as the CD20 antigen on lymphoma cells, often destroying the cell. Rituximab is often given with a standard chemotherapy regimen called "CHOP". CHOP stands for: cyclophosphamide, hydroxydaunorubicin (doxorubicin or Adriamycin®), Oncovin® (vincristine) and prednisone.
The response to such treatments may vary widely. Some individuals may have insufficient response to standard chemotherapeutic regimens or may experience relapses, or the disease may become resistant (refractory) to treatment, potentially leading to life-threatening complications. Therefore, researchers are exploring the potential effectiveness of differing combinations of various chemotherapeutic drugs, high-dose chemotherapy regimens followed by stem cell/bone marrow transplantation, and/or other investigational therapies that may be warranted for selected individuals, possibly at the time of diagnosis, following certain standard therapies, and/or for those with refractory disease or relapse. They are also investigating appropriate ways in which to combine various therapies and to reduce potential side effects.
Other therapies for individuals with primary gastric lymphoma include symptomatic and supportive measures as required. These include but are not limited to medications to counteract nausea and vomiting, intravenous fluids to treat dehydration, pain medications, antacids to lower the risk of ulcers, and bone marrow stimulating drugs to reverse the low white blood cell counts (leukopenia) and red blood cell counts (anemia) caused by chemotherapy.
After completing treatment for primary gastric lymphoma, it is recommended that the patient undergo an EGD with biopsy in 3 to 6 months. If the biopsies show no evidence of lymphoma or H. pylori infection, then patients should follow up with their oncologist every 3 to 6 months for 5 years, then once a year. There is no set recommendation for how often a patient should get an EGD after the first post treatment EGD, however, if a patient begins experiencing unexplained nausea, abdominal pain, or fullness after eating small meals, then an EGD should be done.
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Contact for Authors:
Charles R. Thomas, Jr., MD
Professor & Chair
Department of Radiation Medicine
OHSU Knight Cancer Institute
Join Y. Luh, MD, FACP
Clinical Assistant Professor
Department of Radiation Medicine
OHSU Knight Cancer Institute
Department of Radiation Oncology
St. Joseph Hospital
2700 Dolbeer Street
Eureka, California, USA 95501
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