A Prospective Trial of Radiation Therapy Efficacy and Toxicity for Localized Mucosa-associated Lymphoid Tissue (MALT) Lymphoma

ABSTRACT Background We report the long-term results of a prospective trial conducted to determine the efficacy and safety of radiation therapy (RT) alone in treating localized MALT lymphoma. Methods Patients with localized MALT lymphoma were eligible and treated with involved field RT to doses of 24-39.6 Gy. Relapse-free survival (RFS) was the primary endpoint. Kaplan-Meier analysis was used to estimate RFS, progression free survival (PFS) and overall survival (OS) defined from time of study entry. Preplanned subgroup analyses were performed based on site of involvement. Results From 2000-2012, 75 patients were accrued; 73 received protocol-specified RT. Median follow-up was 9.8 years. Thirty-four patients had gastric MALT, 17 orbital, 13 head and neck non-orbit, 4 skin, and 5 disease of other sites. Thirteen of 34 patients with gastric MALT were H. Pylori positive at the time of initial diagnosis and underwent between 1-3 courses of triple antibiotic therapy. All gastric MALT patients had documented persistent MALT without H. Pylori on endoscopy prior to enrollment on study. All patients achieved a complete response with a median time of 3 months. Eleven patients (15%) had disease relapse, 9 of which were at sites outside the RT field with median time to progression of 38.3 months. Median PFS was 17.5 years and median RFS and OS were not reached. 10-year relapse-free rate was 83% (95% CI 74-93%). 10-year PFS rate was 71% (95% CI 60-84%). 10-year OS rate was 86% (95% CI 77-96%). RFS, PFS, and OS did not differ by disease site (P=0.17, 0.43, 0.50). All relapses were successfully salvaged. One patient developed metastatic gastric adenocarcinoma and was found to also have recurrent MALT on biopsy. Otherwise, all relapsed patients were alive without evidence of disease at last follow up, and no patient died due to MALT lymphoma. Sixty-seven patients (92%) experienced acute toxicity during radiation, all of which were grade 1 and 2 with only 1 grade 3 toxicity. Twenty-two patients (30%) experienced late toxicity, with only one Grade 3 toxicity. Conclusions This prospective study confirms that RT for MALT lymphoma provides excellent long-term relapse free survival with acceptable rates of toxicity. Current efforts are focused on RT de-escalation in an effort to further avoid treatment-related morbidity.