Prognostic Effect of Systemic Therapy and Radiation Therapy in Stage I Nodal Marginal Zone Lymphoma

Purpose: Nodal marginal zone lymphoma (NMZL) localized to a single lymphatic region (ie, stage I) is a relatively rare diagnosis. Current guidelines permit these patients to be either observed or treated with systemic therapy (ST), radiation therapy (RT), or both modalities. The prognostic effect of ST or RT compared with observation has not been established. The purpose of this study was to assess the prognostic effect of therapy in stage I NMZL. Methods and Materials: The National Cancer Database was queried (2004-2018) for all patients with stage I NMZL. Patients were stratified based on treatment received. Propensity score matching (PSM) was performed overall and for each disease site to create 1:1 matched cohorts of patients who received RT and those who did not. Kaplan-Meier analysis evaluated overall survival (OS). Univariable (UVA) and multivariable Cox proportional hazard analyses identified clinical and treatment factors prognostic for OS. Subset analysis excluded patients deceased within 1 month of diagnosis to account for immortal time bias. Results: A total of 3201 patients (median age 67) met inclusion criteria. A total of 1042 patients (33%) were head/neck/face, 208 (7%) intrathoracic, 613 (19%) intra-abdominal, 382 (12%) axilla/upper extremity, 292 (9%) inguinal/lower extremity, 86 (3%) pelvic, and 578 (18%) unspecified. A total of 1562 patients (49%) received no treatment, 721 (23%) received ST alone, 799 (25%) received RT alone, and 119 (4%) received both ST and RT. After PSM, ST was not prognostic on UVA while RT was prognostic on both UVA and multivariable analysis. After PSM, the 5-year OS was 84% for those who received RT and 79% for those who did not (P = .026). On subset analysis, these findings remained statistically significant for the head/neck/face cohort and the axilla/upper extremity cohort. After accounting for immortal time bias and performing PSM on this subset, the 5-year OS was 82% for those who received RT and 77% for those who did not (P = .047). Conclusions: In the overall cohort, RT improved OS compared with no RT, and ST was not a factor associated with OS. A radiation oncologist should be consulted for all patients with stage I NMZL for multidisciplinary decision making.