MALT lymphoma

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is a B-cell non-Hodgkin lymphoma (NHL). MALT lymphoma is called extranodal because it starts in tissues or organs outside of the lymph nodes. It develops in lymphatic tissue in the mucous membranes or tissues that line body organs or cavities.

MALT lymphomas are also called maltomas. MALT lymphomas occur nearly equally in men and women, and usually in people in their 60s.

Most MALT lymphomas start in the stomach. More than 60% of people with MALT lymphoma of the stomach have a history of a bacterial infection caused by Helicobacter pylori (H. pylori). Other bacterial or viral infections are also linked to MALT lymphoma.

People with MALT lymphoma in areas other than the stomach often have a history of autoimmune disorders such as Hashimoto’s thyroiditis or Sjogren’s syndrome. These areas include:

• other parts of the gastrointestinal tract, such as the small intestine or colon (the longest part of the large intestine)
• the lungs
• tissue around the eye
• the skin
• the salivary glands
• the thyroid
• the bladder
• the breasts

MALT lymphoma is usually slow growing (indolent) but sometimes it can be fast growing (aggressive). It usually takes a long time for it to spread outside the area where it started, and it is often diagnosed when it is stage 1 or 2. Even if several extranodal sites develop, it doesn’t mean that it has spread throughout the body (called widespread disease).

In rare cases, MALT lymphoma can change into a faster-growing (more aggressive) type of NHL.

MALT lymphoma in the stomach is treated differently than MALT lymphoma in other parts of the body. Early stage MALT lymphoma is also treated differently than advanced MALT lymphoma.

The following are treatment options for early stage (stage 1 or 2) MALT lymphoma that is only in the stomach.

Antibiotics are often the first treatment if a biopsy confirms you have H. pylori infection. Antibiotics may be the only treatment needed if a follow-up biopsy shows that the infection has cleared and there is no evidence of lymphoma.

Radiation therapy may be used if antibiotics don’t work. External beam radiation therapy is directed at tumours in the stomach.

Chemotherapy is sometimes used if MALT lymphoma doesn’t respond to antibiotics. Single drugs, such as chlorambucil (Leukeran) or cyclophosphamide (Cytoxan, Procytox) may be used. Sometimes a combination of chemotherapy drugs like CHOP may be given. CHOP is cyclophosphamide, doxorubicin (Adriamycin), vincristine (Oncovin) and prednisone.

Targeted therapy uses drugs to target specific molecules (such as proteins) on the surface of cancer cells. These molecules help send signals that tell cells to grow or divide. By targeting these molecules, the drugs stop the growth and spread of cancer cells while limiting harm to normal cells. Rituximab (Rituxan) is a targeted therapy drug that may be given if antibiotics aren’t effective or if MALT lymphoma progresses after chemotherapy.

Surgery is sometimes used to remove part or all of the stomach (called a partial or total gastrectomy). This is done if the lymphoma remains after antibiotics or if it progresses. Surgery is not used as often as it was in the past to treat MALT lymphoma in the stomach because other therapies can usually treat it successfully.

Early stage MALT lymphoma that starts in an area other than the stomach may be given local treatments, such as surgery or radiation therapy.

Surgery to remove the area affected by lymphoma may be an option depending on where it is in the body and how big it is.

External beam radiation therapy may be given to the affected area.

More advanced MALT lymphomas (stage 3 or 4) in the stomach or other parts of the body may be offered the following treatments.

Watchful waiting (also called active surveillance) may be an option because MALT lymphoma develops slowly and may not need to be treated right away. The healthcare team will carefully monitor the person with MALT lymphoma and start treatment when symptoms appear or there are signs that the disease is progressing.

Radiation therapy may be used if the lymphoma is large, causing symptoms or growing. External beam radiation therapy is directed at the tumour and some tissue around it.

Chemotherapy may be used instead of radiation therapy if the lymphoma is large, it is growing, there is cancer throughout the body (it is widespread) or it comes back after it is treated. The following drugs or combinations of drugs may be given:

• fludarabine (Fludara)
• bendamustine (Treanda)
• chlorambucil (Leukeran)
• CHOP – cyclophosphamide (Cytoxan, Procytox), doxorubicin (Adriamycin), vincristine (Oncovin) and prednisone
• CVP – cyclophosphamide, vincristine and prednisone

Targeted therapy may be given if MALT lymphoma in the stomach doesn’t respond to antibiotics, if the lymphoma is not linked with H. pylori infection or if the lymphoma comes back (recurs) after treatment. The targeted therapy drug rituximab may be given alone or combined with chemotherapy.