Purpose: Mucosa-associated lymphoid tissue (MALT) lymphoma is a distinct disease with specific clinical and pathologic features that may affect diverse organs. We analyzed our recent experience with Stage I/II MALT lymphoma presenting in the stomach and other organs to assess the outcome following involved field radiation therapy (RT).
Patients and methods: Seventy patients with Stage IE (62) and IIE (8) disease were treated between 1989 and 1998. Patients with transformed MALT were excluded. The median age was 62 years (range, 24--83 years), M:F ratio 1:2.2. Presenting sites included stomach, 15; orbital adnexa, 19; salivary glands, 15; thyroid, 8; lung, 5; upper airways, 3 (nasopharynx, 2; larynx, 1); urinary bladder, 3; breast, 1; and rectum, 1. Staging included site-specific imaging, CT abdomen in 66 patients (94%) and bone marrow biopsy in 54 (77%). Sixty-two patients received radiation therapy: 52 received RT alone, 7 received chemotherapy and RT, and 3 received antibiotics followed by RT. Median RT dose was 30 Gy (range, 17.5--35 Gy). Most frequently used RT prescriptions were 25 Gy (26 patients-18 orbit, 6 stomach, and 2 salivary glands), 30 Gy (23 patients), and 35 Gy (8 patients). Five patients had complete surgical excision of lymphoma and no other treatment (stomach 1, salivary 2, lung 2), whereas 2 patients with gastric lymphoma received antibiotics only. One patient refused treatment and was excluded from the analysis of treatment outcome, leaving 69 patients with a median follow-up of 4.2 years (range, 0.3-11.4 years).
Results: A complete response was achieved in 66/69 patients, and 3 patients had partial response (2 lung, 1 orbit). The 5-year disease-free survival (DFS) was 76%, and the overall survival was 96%. No relapses were observed in patients with stomach and thyroid lymphoma. The 5-year DFS for these patients was 93%, in contrast to 69% for patients presenting in other sites (p = 0.006). Among the 5 patients treated with surgery only, 2 relapsed locally (lung, and minor salivary gland). Among 62 patients who received RT, 8 relapsed (2 salivary, 3 orbit, 1 nasopharynx, 1 larynx, 1 breast). Three patients relapsed in the nonirradiated contralateral paired organ, 4 in distant sites, and 1 in both local and distant sites. The overall local control rate with radiation was 97% (60/62 patients).
Conclusion: Localized MALT lymphomas have excellent prognosis following moderate-dose RT. Gastric and thyroid MALT lymphomas have better early outcome, as compared to the other sites where distant failure is more common. Relapses were observed in nonirradiated paired organs or distant sites. Further follow-up is required to assess the impact of failure on survival.