Background
Analysis from UK MRC ALL trials. Children and adults with ALL and ocular/orbital involvement (leukemic infiltration of orbit, uvea, or optic nerve) treated with orbital RT. Evaluated outcomes of ocular RT in preserving vision and preventing CNS extension in ALL patients with ocular relapse or de novo ocular involvement.
Interventions and follow up
Arm A: Orbital/ocular RT 24–30 Gy (1.5–2.0 Gy/fx) to affected orbit(s) ± prophylactic RT to contralateral orbit; combined with systemic re-induction chemotherapy
Primary endpoint: Visual preservation rate, orbital relapse rate, CNS dissemination rate
mFollow up: 3.0 year
Primary endpoint: Visual preservation rate, orbital relapse rate, CNS dissemination rate
mFollow up: 3.0 year
Results
Visual preservation (RT + chemo): 80–90% (if treated before optic nerve compression)
Orbital control rate: >90% with RT doses ≥24 Gy
CNS dissemination post-orbital relapse: ~20% despite combined modality treatment
Orbital control rate: >90% with RT doses ≥24 Gy
CNS dissemination post-orbital relapse: ~20% despite combined modality treatment
Adverse events
Main adverse events: Dry eye syndrome (lacrimal gland dose), radiation keratitis, cataracts (lens dose — lens shielding technique important), retinopathy (rare at ≤30 Gy), orbital growth restriction (in young children). Systemic chemotherapy toxicities.
Conclusions
Orbital RT 24–30 Gy effectively controls ocular disease and preserves vision in the majority of ALL patients with ocular involvement when administered promptly before optic nerve or visual pathway injury. Combined with systemic intensification, outcomes for isolated ocular relapse are relatively favorable.
Key Limitations
Key Limitations: Retrospective, small numbers (ocular ALL relapse is rare). Variable RT techniques and doses across centers. Limited standardization of ophthalmologic follow-up. Late lens and lacrimal toxicity requires long-term follow-up beyond reported periods.
Clinical Context
Orbital RT remains the standard for ALL with ocular infiltration. Dose is typically 24 Gy for microscopic/uveal disease and up to 30 Gy for bulky orbital disease. Modern lens-sparing IMRT technique is critical to reduce cataract risk. Prompt ophthalmologic evaluation at relapse is essential to preserve vision.
References
References: Russo C et al, Leukemia 2008 (UK MRC ocular ALL)