Inclusion Criteria:

• The patients must have histologically confirmed primary low-grade B-cell lymphoma of MALT of the stomach which including the following types : diffuse small lymphocytic, diffuse small cleaved, and some diffuse mixed small and large cell types by Working Formulation (Harris NL et al. 1994)(20).

• The diagnosis of primary gastric lymphoma must fulfill the criteria of Dawson :

  1. No enlargement of peripheral or mediastinal lymph node;
  2. Peripheral blood smear revealing no leukemic or lymphomatous abnormalities;
  3. Predominant of alimentary tract lesions with any adenopathy corresponding to accepted lymphatic drainage route; and
  4. No involvement of liver or spleen except by extension of contiguous disease .
• The monoclonality of B-cell must be confirmed by either immunohisto- chemistry (light-chain restriction) or molecular technique (IgH rearrangement).
• The patient must have no prior chemotherapy or radiotherapy for his/her gastric MALToma.
• Patients must have evaluable disease by endoscopy and the nodal status by computed tomography. Endoscopic ultrasonography (EUS)* is optional and for reference only.
• H. pylori infection will be evaluated by the following tests: histology, rapid urease test (CLO-test), and serology C13-urea breath test (UBT) and bacterial culture* are optional and for reference only.
• The following will be considered to have H. pylori infection : at least two of the following 3 tests show positive results, rapid urease test (CLO-test), histology and serology.
• For C13-urea breath test, rapid urease test and histology to examine H. pylori, the examination must be performed at least 4 weeks apart from the latest antibiotics or non-steroid anti-inflammatory drug ingestion.
• Patients must have either stage IE or IIE-1 disease, according to an adaptation of the Ann Abor staging system modified by Musshoff for primary extranodal lymphoma.
• Stage IE : lymphoma confined to the gastric wall without lymph node involvement.
• Stage IIE : localized involvement of one or more GI site(s) on one side of the diaphragm with lymph node infiltration, any depth of lymphoma infiltration into the gut wall.
• Stage IIE-1 : infiltration of adjacent lymph node.
• Patient must have signed the informed consent.

Exclusion Criteria:

• Patients who have extensive gastrointestinal tract involvement are not eligible.
• Patients who have had previous history of extranodal lymphoma are not eligible.
• Patients who have disease beyond stage IIE-2: infiltration of regional lymph node, e.g. paraaortic, renal hilar, retroperitoneal, mesenteric, or lymph node of gastrosplenic ligment and of hepatoduodenal ligment are not eligible.
• Patients who had a history of allergic reaction to Amoxicillin and Erythromycin /Clarithromycin are not eligible.
• Patients whose cardiopulmonary status not allow him/her to have repeat endoscopy are not eligible.
• Patients who had prior surgery, chemo- or radiotherapy for their primary gastric lymphoma are not eligible.
• Patients who had previous anti-H. pylori therapy are not eligible.