Mucosa-associated lymphoid tissue (MALT) lymphomas account for only 5% of NHLs, and yet they represent the most common low-grade lymphoma involving the stomach. Gastric MALT lymphomas tend to occur in association with Helicobacter pylori infection. More than 60% of patients respond to antibiotics, and many of those are cured (Wotherspoon et al: Lancet 338:1175-1176, 1993; Wotherspoon et al: Lancet 342:575-577, 1993; Zucca et al: Ann Oncol 8:723-737, 1997; Roggero et al: Ann Intern Med 122:767-769, 1995). Treatment for patients who do not respond to antibiotics has included standard therapies for indolent NHL, such as alkylating agents and purine analogs.
Those MALT lymphomas that develop at sites distant from the stomach are usually unresponsive to antibiotic treatment and require alternative strategies, including systemic chemotherapy. Since these tumors are CD20-positive, rituximab is a reasonable therapeutic option to explore.
Visconti et al (abstract #4418) retrospectively reviewed five patients with gastrointestinal MALT lymphomas who had not responded to antimicrobial therapy and were subsequently treated with rituximab. The primary tumors were in the stomach in three patients but in extragastric sites in the other two. Four patients attained a CR and the fifth patient, a PR; three of the five were still in remission at a median of 13 months.
Actual clinical trials should be conducted in this patient group to better characterize the nature of responses to rituximab. Until such data are available, antibiotic therapy should still be considered for appropriate patients.