3454 - Treatment and Survival in Early-Stage MALT Lymphoma: A Retrospective Study of Outcomes at a Single Institution

X. Wang¹, L. R. Gao¹, Y. Wu¹, X. Feng², X. Liu¹, S. Qi¹, and Y. X. Li¹; ¹Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, ²Department of Pathology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Purpose/Objective(s): Early-stage mucosa-associated lymphoid tissue lymphoma exhibited a favorable prognosis following various forms of treatment. The optimal treatment and patterns of failure remain to be defined. The purpose of this study is to compare the outcome of primary radiotherapy with other treatment modalities in patients with early-stage MALT lymphoma. Materials/

Methods: A total of 375 patients diagnosed with early-stage MALT lymphoma between 1998 and 2021 were retrospectively analyzed. Primary therapy was classified as radiotherapy (RT, n = 178), and other therapies (non-RT, n=197). Overall survival (OS), progression-free survival (PFS), and local regional control (LRC) were analyzed. Standardized mortality ratios (SMR) were conducted to compare survival differences between treatment modalities by controlling for background mortality. SMR of >1.0 indicated worse-than-expected survival. SMR values near 1 with nonsignificant P values indicated similar to the matched generalized population. Competing risk analysis was conducted to evaluate the cumulative incidence of mortality and disease failure. mortality. Patient reported EORTC QLQ-C30 questionnaire was used to assess the quality of life (QOL).
Results: With a median follow-up of 63 months, the 5-year OS, lymphoma-related mortality, and competing non-lymphoma mortality were 94.8%, 0.8%, and 4.4%, respectively. The SMR was 1.59 (P = 0.002). However, RT was associated with better SMR of 1.12 (95% CI: 0.65-1.80; P = 0.72) compared with non-RT (2.18, 95% CI: 1.43-3.17; P = 0.001). Moreover, RT significantly improved PFS (86.5% vs. 63.3%, P < 0.001), with a lower 5-year cumulative incidence of locoregional failure (6.0% vs. 26.3%, P < 0.001) compared with non-RT therapy. In-field relapse rate at 5 years was 2.1% for the RT group. Patients had no severe long-term toxicities and exhibited a high QOL across treatments.
Conclusion: Patients with localized MALT lymphoma had favorable survival outcomes with a persistent risk of recurrence. RT improved the SMR and PFS in early-stage MALT with high quality of life. These findings suggest RT is a preferred initial treatment for patients with early-stage MALT lymphoma.