Outcomes After Reduced-Dose Intensity Modulated Radiation Therapy for Gastric Mucosa-Associated Lymphoid Tissue (MALT) Lymphoma

In patients with gastric extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) lymphoma, the standard radiation therapy (RT) dose is ≥30 Gy. We report the outcome of patients treated with reduced dose 24 Gy compared with those treated with ≥30 Gy. We reviewed results from 32 patients who received a diagnosis of gastric MALT lymphoma between 2007 and 2017 who were treated with involved site RT using intensity modulated radiation therapy (IMRT). Response to therapy was based on post-RT endoscopic biopsy. Freedom from local treatment failure (FFLTF), freedom from treatment failure (FFTF), and overall survival (OS) outcomes were determined. The median age of patients at diagnosis was 58 years. Therapy for MALT was given prior to RT in 14 patients with residual biopsy proven disease documented in all cases (anti-microbial, n=11; rituximab, n=2; rituximab, cyclophosphamide, doxorubicin, vincristine, n=1). One patient received RT (36 Gy) and concurrent rituximab. The median RT dose was 30 Gy; it was 30 to 36 Gy in 66% of patients (n = 21) and 24 Gy in 34% of patients (n = 11). Post-RT biopsy documented a complete response in all patients. Failures occurred in the stomach and duodenum, respectively, at 3.6 and 4.5 years, after 30 Gy. At a median follow-up of 55.2 months (73.8 for ≥30 Gy compared with 28.7 for 24 Gy; P