Ultra-Low-Dose Radiation for Extranodal Marginal Zone Lymphoma of the Lung.

Purpose: Definitive intent radiation therapy (RT) for early-stage mucosa-associated lymphoid tissue (MALT) lymphoma typically includes a dose of 24 to 30 Gy. While modest, these doses may have associated toxicity. For patients with indolent B-cell lymphoma, there is increasing support for the use of ultra-low-dose RT (ULDRT) using 4 Gy in 2 fractions as part of a response-adapted approach, as high rates of complete response have been documented. This paradigm has been prospectively evaluated in the management of orbital and gastric indolent B-cell lymphomas; however, there is limited data guiding the use of ULDRT for lung MALT. Methods: We conducted a retrospective review of 20 patients at our institution with lung MALT treated with ULDRT as part of a response-adapted approach. Clinical variables including prior systemic therapy and symptoms were abstracted from the electronic health record. Responses were assessed using the revised Lugano criteria. Results: At a median follow up of 17 months following 4 Gy (IQR, 8-37 months), we observed 100% local control. Nineteen patients (95%) experienced a complete response. No patients with stage IE disease at RT (17/20; 85%) experienced distant progression. Nine patients (45%) were symptomatic prior to RT, with improvement or resolution of symptoms in 7 (7/9; 78%). One patient developed grade 2 pleuritic pain following RT, which resolved with a brief course of steroids. No other toxicities were noted. Conclusions: ULDRT, given in a response-adapted approach, is effective and well tolerated by patients with lung MALT.