PURPOSE: Limited-stage gastric mucosa-associated lymphoid tissue (MALT) lymphoma can be treated with radiation alone. Due to the immediate proximity of the stomach to the heart, there is a theoretical risk of radiation-induced cardiac toxicity, the incidence of which has never been precisely studied. The aim of this study was to assess cardiac-specific mortality in patients treated for gastric MALT lymphoma with radiation. METHOD: This cohort study included all patients treated in the USA between 2000 and 2020 with radiation for gastric MALT lymphoma and whose clinical data were available in the Surveillance, Epidemiology and End Result database (17 registries). The primary endpoint was cardiac-specific survival. Assessed clinical variables were age, sex, race, stage of disease, type of treatment received and cause of death. RESULTS: A total of 1863 patients treated for MALT lymphoma with radiation were analysed. At 10years, cardiac-specific survival was 0.924 (95 % confidence interval [CI]: 0.906-0.942) and cancer-specific survival was 0.931 (95 %CI: 0.915-0.947), while non-cardiac/cancer-specific survival was 0.778 (95 %CI: 0.753-0.804). Cardiac-specific mortality was significantly higher in patients aged over 60years (hazard ratio [HR]: 9.07
P=0.002) and in cases of additional chemotherapy (HR: 1.83
P=0.017). CONCLUSION: Cardiac mortality in patients treated with radiation for gastric MALT lymphoma represents a minor contribution compared with other causes of death. As new radiotherapy protocols should further minimize the risk of cardiac toxicity, and given the curability of this type of lymphoma, improving overall survival should also focus on the multidisciplinary management of comorbidities.