Long-Term Clinical Efficacy of Radiotherapy for Patients with Stage I-II Gastric Extranodal Marginal Zone B-Cell Lymphoma of Mucosa-Associated Lymphoid Tissue: A Retrospective Multi-Institutional Study.

Purpose: To evaluate long-term treatment outcomes in patients with localized gastric mucosa-associated lymphoid tissue (MALT) lymphoma treated with radiation therapy (RT).

Materials and methods: A total of 229 patients who received RT in ten tertiary hospitals between 2010 and 2019 were included in this multi-center analysis. Response after RT was based on esophagogastroduodenoscopy after RT. Locoregional relapse-free survival (LRFS) and disease-free survival (DFS) were evaluated.

Results: After a median follow-up time of 93.2 months, 5-year LRFS, DFS, and OS rates were 92.8%, 90.4%, and 96.1%, respectively. LRFS, DFS, and OS rates at 10 years were 90.3%, 87.7%, and 92.8%, respectively. Of 229 patients, 228 (99.6%) patients achieved complete remission after RT. Five-year LRFS was significantly lower in patients with stage IIE than in those with stage IE (77.4% vs. 94.2%, p=0.047). Patients with age ≥ 60 had significantly lower LRFS than patients with age < 60 (89.3% vs. 95.1%, p=0.003). In the multivariate analysis, old age (≥ 60 years) was a prognostic factor for LRFS [hazard ratio (HR) of 3.72 and confidence interval (CI), 1.38-10.03; p=0.009). Grade 2 or higher gastritis was reported in 69 (30.1%) patients. Secondary malignancies including gastric adenocarcinoma, malignant lymphoma, lung cancer, breast cancer, and prostate cancer were observed in 11 (4.8%) patients after RT.

Conclusion: Patients treated with RT for localized gastric MALT lymphoma showed favorable 10-year outcomes. Radiation therapy is an effective treatment without an increased risk of secondary cancer. The toxicity for radiotherapy to the stomach is not high.