Involved-Site Radiation Therapy for H. Pylori-Independent Gastric MALT Lymphoma: 26 Years of Experience with 178 Patients

Abstract

Gastric mucosa associated lymphoid tissue lymphoma (GML) is often associated with Helicobacter pylori (H. pylori) infection. Eradication of H. pylori is effective for up to 80% of patients. For H. pylori-independent GML, treatment options include surgery, immunotherapy, chemotherapy and radiation therapy (RT). The purpose of this study is to investigate the efficacy and safety of involved site radiation therapy and routine endoscopic surveillance, hypothesizing that radiation is highly effective for H. pylori–independent GML and most patients are curable with RT alone. A single institution database at a tertiary referral cancer center was queried for patients with H. pylori-independent GML treated with radiation between 1991 and 2017. Prior to treatment, pathology was confirmed by hematopathology experts and patients underwent staging with either computed tomography scan, positron emission tomography, endoscopic ultrasound, or a combination of techniques. All patients received involved site radiation therapy to the stomach. The clinical treatment volume (CTV) included the stomach and first part of the duodenum. Perigastric lymph nodes and other parts of the duodenum were also included in CTV if involved with disease. Response was assessed by follow up endoscopies (EGDs) within 10-12 weeks following RT with multiple biopsies at frequent intervals, as well as appropriate radiographic imaging. Survival analysis was calculated using the Kaplan Meier estimator and toxicity was graded according to CTCAEv4 criteria. There were 178 patients identified (56% female). Median age was 63 years (range 25-91 years). Eighty-eight percent of patients presented with stage I disease; 6% were stage II and 6% were stage IV. Median RT dose was 3000 cGy over 20 fractions. Post treatment EGD with biopsy was obtained in 173 patients, of which 95% demonstrated a complete pathologic response. Intriguingly, 4 patients had abnormal posttreatment EGD biopsies that spontaneously resolved. One patient experienced grade 3 toxicity. Over a median follow up of 9 years, 8% experienced local failures and 10% developed distant sites of disease. Eighty-three percent of patients remained lymphoma free. Five and 10-year overall survival estimates from all causes were 97% and 84%, respectively. RT is a highly effective, safe treatment for GML with excellent overall survival and very rare acute or late treatment related toxicities. Spontaneous resolution of abnormal post treatment biopsies offers an intriguing window into histologic responses to radiation. Favorable outcomes from this large retrospective sample of patients provide credible and compelling support for the use of RT for H. pylori-independent GML as standard of care.