Inclusion Criteria:

• The patients must have histologically confirmed primary gastric MALT lymphoma with or without clustering large cells (extranodal marginal zone lymphoma, and diffuse large cell lymphoma with features of MALT by REAL/WHO classification, Harris NL et al. 1994).

  • 1.1 The diagnosis of primary gastric lymphoma must fulfill the criteria of Dawson [38].

    • (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.
  • 1.2 The diagnosis of MALT lymphoma will be made by histopathologists from individual hospitals, in accordance with criteria defined by Isaacson et al.

and Chang et al, and will be reviewed by the members of the TCOG Pathology Committee. This pathology review mechanism had been functioned well in the previous T1296 study (see J Natl Cancer Inst. 2005;97:1345-53)

• 1.3 The patient must have no prior chemotherapy or radiotherapy for his/her gastric lg- or hg-MALToma.

  • Patients must have evaluable disease by endoscopy and/or the nodal status by computed tomography. Endoscopic ultrasonography (EUS) is mandatory to evaluate the depth of tumor infiltration and for status of perigastric lymph node enlargement.

  • Patients must have documented H. pylori infection before treatment, which will be evaluated by the following tests: histology, rapid urease test (CLO-test), C-13 urease breath test and serology.

    • 3.1 The following will be considered to have H. pylori infection: if any of above 4 tests show positive result.

  • 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.

    • 4.1 Stage IE : lymphoma confined to the gastric wall without lymph node involvement.
    • 4.2 Stage IIE : localized involvement of one or more GI site(s) on one side of the diaphragm with lymph node involvement, any depth of lymphoma infiltration into the gut wall. 4.21 Stage IIE-1: involvement of perigastric lymph node. 4.22 Stage IIE-2: abdominal, but beyond perigastric, lymph nodal involvement.
  • Patient must have signed the informed consent and agree to provide achieved pathologic material for immunohistochemical study and for RT-PCR t(11;18)(q21;q21) determination.

Exclusion Criteria:

• Patients with extensive gastrointestinal tract involvement are not eligible.
• Patients with previous history of extranodal lymphoma are not eligible.
• Patients with stage IIE-2 or beyond disease: infiltration of regional lymph node, e.g. paraaortic, renal hilar, retroperitoneal, mesenteric, or lymph node of gastrosplenic ligament and of hepatoduodenal ligament; or involvement of lymph node above and below diaphragm (Stage III) or other visceral organ involvement (stage IV) are not eligible.
• Patients with cardiopulmonary status that do not allow repeat endoscopy are not eligible.
• Patients with prior antibiotics, chemo- or radiotherapy for their gastric lymphoma are not eligible.
• Patients who had previous anti-H. pylori therapy and without pretreatment pathology achieve material for histological review and immunohistochemical study are not eligible.