Watchful waiting is an acceptable treatment option for asymptomatic primary ocular adnexal mucosa-associated lymphoid tissue lymphoma: A retrospective study.

Background: Primary ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma (POAML) is the most common subtype of indolent ocular adnexal lymphomas. Although radiotherapy (RT) is the standard of care for localized POAML, it can occasionally lead to permanent side effects. Other treatment strategies, such as rituximab (R) monotherapy and immunochemotherapy, have been used for POAML treatment, but their long-term benefits and relative merits remain unclear. While watchful waiting (WW) is a potential option for some indolent lymphomas, the benefits of WW for POAML patients are also unclear.

Methods: We here retrospectively analyzed 75 patients who were diagnosed with POAML between 2008 and 2019 in the institutions of the Kyoto Clinical Hematology Study Group.

Results: Commonly involved sites were conjunctiva (42.7%), orbit (36.0%), and lacrimal gland (12.0%), and most patients (92.0%) presented with Ann Arbor stage IE disease. The treatment strategy was selected at the physicians' discretion. More patients without subjective symptoms by tumor mass were subjected to WW (29 patients), while more patients with tumor-derived subjective symptoms were treated by tumor-directed therapy (24 received focal RT, and 19 received R monotherapy). Complete response rates were 79.2% and 42.1% in the RT and R groups, respectively. At 60 months of follow-up, the estimated proportions of POAML patients not requiring new treatment were 69.4%, 85.2%, and 53.8% in the WW, RT, and R groups, respectively. There were no significant differences in the time to start a new treatment between WW and RT groups (median: both not reached [NR], p = 0.187) and between WW and R groups (median: NR vs. 69.0 months, p = 0.554). No specific predictive factor for the future need of treatment was identified in the WW group.

Conclusion: Our results demonstrate WW may be an acceptable treatment option for POAML, especially for asymptomatic patients.