Background
International multicenter prospective study (IELSG). Patients with extranodal marginal zone lymphoma (EMZL / MALT lymphoma) of the orbit/ocular adnexa. Examined outcomes of involved-field radiotherapy (IFRT) as primary treatment for localized orbital MALT lymphoma. Wirth et al reported on RT outcomes and patterns of failure in this series from the International Extranodal Lymphoma Study Group.
Interventions and follow up
Arm A: Involved-field radiotherapy (IFRT) 24–26 Gy to orbit (n=not specified for single arm)
Arm B: N/A (prospective single-arm registry)
Primary endpoint: Local control and patterns of failure
mFollow up: Not specified
Arm B: N/A (prospective single-arm registry)
Primary endpoint: Local control and patterns of failure
mFollow up: Not specified
Results
Local control rate: ~98% with IFRT 24–26 Gy
5-yr OS: ~96%
5-yr DFS: ~75–80%
Distant failure rate: ~20–25% (new sites of lymphoma; systemic recurrence)
5-yr OS: ~96%
5-yr DFS: ~75–80%
Distant failure rate: ~20–25% (new sites of lymphoma; systemic recurrence)
Adverse events
Main adverse events: Grade 1–2 conjunctivitis, dry eye, and cataract most common. Grade ≥3 ocular toxicity rare with 24–26 Gy. Lacrimal gland dose minimization important to prevent severe dry eye.
Conclusions
Involved-field RT to 24–26 Gy achieves excellent local control for localized orbital MALT lymphoma, with ~75–80% disease-free survival at 5 years. Distant failure (new MALT sites) is the dominant failure pattern, reflecting the indolent but systemic nature of EMZL.
Key Limitations
Key Limitations: Prospective registry rather than randomized trial. Systemic treatment was not standardized for patients with distant failure. Comparison with antibiotic therapy (e.g., Chlamydia-targeted treatment) for ocular MALT was not addressed. Long-term ocular toxicity with modern proton or photon techniques may differ.
Clinical Context
This IELSG report established IFRT 24–26 Gy as the standard of care for localized orbital MALT lymphoma, now reflected in ILROG and NCCN guidelines. Modern practice uses 24–25.2 Gy to the entire orbit with attention to lacrimal gland doses, and systemic evaluation at relapse.
References