This study was conducted to evaluate the long-term outcomes in patients with stage IE and IIE mucosa-associated lymphoid tissue (MALT) lymphomas treated with involved field radiotherapy (RT).

Between 1989 and 2004, 192 patients with stage I and II MALT lymphomas were treated. The report focuses on 167 patients who received RT. The median age of patients was 58 years with a female predominance (2:1). Presenting sites were as follows: orbital adnexa in 71 patients, salivary glands in 28 patients, stomach in 25 patients, thyroid in 21 patients, and other sites in 22 patients. The median dose to nonorbital sites was 30 grays (Gy) (range, 17.5-35 Gy) and was 25 Gy for the orbit (range, 25-35 Gy). The median follow-up was 7.4 years (range, 0.67-16.20 years).

Complete response and complete response, unconfirmed (CR/CRu) was noted in 166 (99%) patients. The 10-year recurrence-free rate (RFR) was 76%, the disease-free survival (DFS) rate was 68%, the overall survival (OS) rate was 87%, and the cause-specific survival rate was 98%. According to presenting site, the 10-year RFR was 95% for thyroid, 92% for stomach, 68% for salivary glands, and 67% for orbit. Patients with thyroid and gastric MALTs had better outcome compared with patients with MALTs diagnosed at other sites (P=.004). Among those patients who achieved CR, 19% developed disease recurrence (n=31), chiefly in distant sites or untreated contralateral-paired organs. At the time of disease recurrence, 7 patients (23%) had transformed to diffuse large B-cell lymphoma, 2 of whom died of lymphoma. The 5-year OS rate after treatment failure was 83%.

Patients with localized MALT lymphomas are reported to have excellent clinical outcome after moderate-dose RT, and some are likely cured. In the current study, thyroid and gastric MALTs were found to have significantly less risk of distant recurrence. Despite disease recurrence, the overall survival remains excellent in these patients.