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

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.

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.