A single‐center experience of low‐dose radiotherapy for primary extranodal marginal zone lymphoma of bronchus‐associated lymphoid tissue (BALT)

Abstract

Introduction: Extranodal marginal zone lymphoma of bronchus-associated lymphoid tissue (BALT) is a rare cancer for which optimal treatment strategies are not well defined. Retrospective analyses show equivalent or superior outcomes with surgical resection compared to systemic therapy or active surveillance. Despite a well established role for radiotherapy in the management of other types of extranodal marginal zone lymphoma (MZL), its role in BALT lymphoma is underexplored. Methods: We screened 153 patients with a diagnosis of primary BALT lymphoma treated at a single institution from 1995 to 2022. Inclusion criteria comprised patients aged 18 years or older, histologically confirmed BALT lymphoma, and receipt of radiotherapy at initial presentation or disease progression/recurrence. We excluded patients with synchronous evidence of lymphoma involving non-thoracic extranodal sites and/or lymphadenopathy outside of the mediastinum and hilum, as these patients might represent MZL with secondary lung involvement as opposed to primary BALT lymphoma. All patients underwent baseline PET/CT staging. We extracted patient, tumor, imaging, and treatment characteristics from the electronic medical record. We defined active surveillance as at least 3 months of follow up prior to initiating active therapy combined with documentation of this plan in the medical record. We assessed treatment response using the RECIL 2017 criteria. Results: We report the largest to date single-center retrospective analysis of 13 patients (median age 67 years, range 33–84 years) with localized BALT lymphoma treated with radiotherapy. The median tumor size was 3.6 cm (range 0.8–8.2 cm) with a median SUV of 3.9 (range 1.3–11.4). Most patients (n = 8, 62%) received radiotherapy for BALT lymphoma after failing first-line treatment, including active surveillance (n = 3), surgical resection (n = 2), or systemic therapy (n = 3). Of 15 irradiated lesions, most (n = 10, 67%) received very low-dose radiotherapy (VLRDT) of 4 Gy (range 4–36 Gy). With a median follow-up of >50 months, only 3 patients experienced progression of disease, none within the irradiated field (1 following VLDRT and 2 following full-dose RT). Among all treated lesions, the overall response rate was 100% (n = 5, 33% partial response [PR] and n = 10, 67% complete response [CR]). Among 10 lesions treated with VLDRT, 6 (60%) achieved CR; among 5 lesions treated with full-dose RT, 4 (80%) achieved CR. There were no events of secondary lung cancers within or in proximity to the irradiated field. Conclusions: Radiotherapy, including VLDRT, is a feasible, well tolerated, non-invasive and effective treatment strategy for primary BALT lymphoma that can be considered in both the upfront and recurrent treatment settings. The research was funded by: National Cancer Institute (P30 CA008748) Keywords: Extranodal non-Hodgkin lymphoma, Indolent non-Hodgkin lymphoma No conflicts of interests pertinent to the abstract.