Watchful waiting is an Acceptable Treatment Option for Primary Ocular Adnexal Mucosa-associated Lymphoid Tissue Lymphoma: A Retrospective Study

<jats:title>Abstract</jats:title> <jats:p><jats:bold>Background:</jats:bold>Primary ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma (POAML) is the most common subtype of ocular adnexal lymphomas, and most patients with POAML show an indolent clinical course and achieve long-term survival. Although radiotherapy (RT) is the standard of care for localized POAML, it can occasionally lead to permanent side effects.<jats:sup> </jats:sup>Other treatment strategies, such as rituximab (R) monotherapy and immunochemotherapy,<jats:sup> </jats:sup>have been used for POAML treatment, but their long-term benefits and relative merits remain unclear. Considering that watchful waiting (WW) is a potential option for some indolent lymphomas, WW is expected to be a therapeutic option for POAML. However, the benefits of WW for POAML patients are also unclear. The aim of this study is to determine the optimal treatment strategy for POAML.<jats:bold>Methods:</jats:bold>We retrospectively analyzed 75 patients who were diagnosed POAML between 2008 and 2019 in the institutions of the Kyoto Clinical Hematology Study Group. <jats:bold>Results: </jats:bold>The median age was 68 years, and 41 patients were women. Common 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, and more patients without subjective symptoms by tumor mass were subjected to WW (29 patients, 38.7%), while more patients with tumor-derived subjective symptoms were treated by tumor-directed therapy (24 [32.0%] received focal RT, and 19 [25.3%] received R monotherapy). Complete response rates were 79.2% and 42.1% in the RT and R groups, respectively. At 60 months’ 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 of new treatment between WW and RT groups (median: both not reached [NR], <jats:italic>p </jats:italic>= 0.187) and between WW and R groups (median: NR vs. 69.0 months, <jats:italic>p </jats:italic>= 0.554). No specific predictive factor for the future need of treatment was identified in the WW group. <jats:bold>Conclusions:</jats:bold>WW may be an acceptable treatment option for POAML, especially in asymptomatic patients.</jats:p>