Emerging Treatment Strategies for Primary Breast Extranodal Marginal Zone Lymphoma of Mucosa-associated Lymphoid Tissue

Introduction: We report our experience in treating patients with primary breast extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) to better elucidate the natural history and optimal treatment approach for these patients.

Patients and methods: Patients with localized primary breast MALT lymphoma treated between 1995 and 2016 were included. Disease-related endpoints including progression-free survival (PFS) were analyzed.

Results: Eleven patients met inclusion criteria; all patients were women with a median age of 62 years (range, 42-75 years). Most (73%) patients presented with stage I disease, and most (73%) patients were treated initially treated with radiation therapy (RT). Local control following RT was 100%; all patients with progression following RT experienced distant relapse. Additionally, none of the 3 patients treated with ultra-low-dose RT (4 Gy) experienced subsequent progression (local or distant). Six (55%) patients progressed after initial therapy, of whom 5 received initial RT; the 5-year PFS after initial therapy was 60%. Salvage systemic therapy was utilized in all patients with progression, with 5 of 6 patients receiving single-agent rituximab. Of the patients treated with salvage therapy, only 1 experienced second relapse, with a 5-year PFS of 100% after salvage systemic therapy. With a median follow-up of 8 years, there were no deaths in the cohort.

Conclusions: Patients with primary breast MALT lymphoma achieve excellent outcomes. Initial RT affords local control, and although subsequent distant progression is common, salvage rituximab yields high rates of PFS.