S112 EXABS-223-IBCL Treatment Options for Marginal Zone Lymphoma Emanuele Zucca, MD1,2,3,* 1Clinic of Medical Oncology, Oncology Institute of Southern Switzerland, EOC, 6500 Bellinzona Switzerland 2Institute of Oncology Research, 6500 Bellinzona Switzerland 3Università della Svizzera Italiana, Faculty of Biomedical Sciences, 6900 Lugano, Switzerland *Corresponding author: emanuele.zucca@eoc.ch Keywords MALT lymphoma, extranodal lymphoma, splenic lymphomas Introduction The three main types of marginal zone lymphoma (MZL) recognized in current lymphoma classifications are extranodal MZL of mucosa-associated lymphoid tissue (MALT), splenic MZL, and nodal MZL. Recent reviews and guidelines have provided valuable insights into their management.1–4 Here we will summarize the available therapeutic options. Extranodal MZL Lymphomas Extranodal MZL lymphomas typically have an indolent course and may not require immediate treatment upon diagnosis. For asymptomatic patients with advanced stage disease, active surveillance is recommended.5 When treatment is necessary, the use of minimally toxic therapies is advised due to the excellent prognosis, even for advanced disease. Solid evidence supports the eradication of H. pylori as the initial treatment for gastric MALT lymphomas with H. pylori infection, regardless of the stage. The choice of the eradication regimen should consider regional patterns of antibiotic resistance. In localized, H. pylori-positive gastric MALT lymphomas, eradication of H. pylori leads to lymphoma regression and long-term clinical disease control in approximately 75% of patients. Some patients may have persistent monoclonal B cells or transient molecular or histological relapses without clinical or endoscopic evidence of disease, and they can be safely managed with a watchful waiting strategy.4 The optimal treatment for patients who fail antibiotic therapy or those with highly symptomatic extensive disease is more uncertain. The efficacy of antibiotic therapy for non-gastric extranodal MZLs is generally unproven,6,7 but long-term use of clarithromycin has shown promising results.8–11 Involved-site radiotherapy (24 Gy) is highly effective for localized H. pylori-negative gastric MZLs or cases without lymphoma regression after antibiotic therapy, as well as localized, nongastric extranodal MZLs, achieving long-term local control in approximately 90% of patients.12 Potential long-term complications include xerostomia after parotid irradiation, hypothyroidism after thyroid irradiation, and cataracts and dry eyes after orbital irradiation.12 Dose de-escalation to 4 Gy reduces toxicities, but its use beyond palliative indications is controversial. The addition of adjuvant chemotherapy to radiotherapy does not improve cure rates.4 Rituximab-based approaches are recommended for the treatment of symptomatic, advanced stage MZLs. In the absence of clear survival advantages, combination immunochemotherapy may be preferred over rituximab alone for severely symptomatic or bulky disease, or for patients valuing a longer treatment-free period. Bendamustine and chlorambucil are commonly used chemotherapy agents.13 A large, randomized study has shown that the combination of chlorambucil and rituximab is more effective than either chlorambucil or rituximab monotherapy.14 The choice of chemotherapy agents should consider patient age, fitness, and organ functions, as older/frail adults receiving bendamustinerituximab have shown higher rates of fatal toxicities. More intensive doxorubicin-containing combination regimens such as R-CHOP are active but more toxic and should be limited to patients with histological transformation or bulky masses. The need for rituximab maintenance in MZLs is controversial, as there is no evidence of survival benefit. Progression or relapse of the disease should be confirmed through histology, and cases showing signs such as asymmetric growth and uptake in PET scans, systemic symptoms, and elevated LDH may suggest transformation into an aggressive lymphoma. While there are no specific phase 3 trials for relapsed MZL, small phase 2 trials and a few FDA-approved treatments are available. Management in these cases is highly individualized and depends on factors such as disease stage, previous treatments, patient age, and overall health. Second- and subsequent lines of treatment may include rituximab single agent, particularly after durable first remission, and chemotherapy or lenalidomide plus rituximab.15–18 Several targeted agents, including monoclonal antibodies and small molecules, have been evaluated in phase-2 studies. BTK and PI3K inhibitors have also shown interesting activity.19–21 Patients with
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