Radiation Therapy Administration and Survival in Stage I/II Extranodal Marginal Zone B-Cell Lymphoma of Mucosa-Associated Lymphoid Tissue

Abstract

To determine the factors associated with the use of radiation therapy and associated survival outcomes in early-stage marginal zone lymphoma of the mucosa-associated lymphoid tissue (MALT). We extracted data on adult patients with stage I/II MALT lymphoma diagnoses between 1998 and 2010 recorded in the Surveillance, Epidemiology, and End Results (SEER) database. We studied factors associated with radiation therapy administration in a logistic regression model and described the cumulative incidence of lymphoma-related death (LRD) according to receipt of the treatment. The association of radiation therapy with survival was explored in multivariate models with adjustment for immortal time bias. Of the 7774 identified patients, 36% received radiation therapy as part of the initial course of treatment. Older patients; black or Hispanic men; white, Hispanic, and black women; and socioeconomically disadvantaged and underinsured patients had a significantly lower chance of receiving radiation therapy. Radiation therapy administration was associated with a lower chance of LRD in most sites. In cutaneous, ocular, and salivary MALT lymphomas, the 5-year estimate of LRD after radiation therapy was 0%. The association of radiation therapy with overall survival in different lymphoma sites was heterogeneous, and statistically significant in cutaneous (hazard ratio 0.45, P=.009) and ocular (hazard ratio 0.47, P<.0001) locations after multivariate adjustment. Demographic factors are associated with the use of radiation therapy in MALT lymphoma. Clinicians should be sensitive to those disparities because the administration of radiation therapy may be associated with improved survival, particularly in cutaneous and ocular lymphomas.