Proton beam therapy for iris melanomas

To describe the results in terms of local control, eye preservation and systemic evolution of iris melanomas treated by proton beam irradiation.

Retrospective review of the charts of patients with iris melanoma treated by proton beam therapy between April 1998 and September 2002. Ciliary body melanomas with iris involvement or tumours with extrascleral invasion were excluded. Treatment consisted of 60 Gy of proton beam irradiation delivered in four fractions to the tumour volume.

A total of 21 patients were treated, median follow-up of 33 months (8-72 months). 15 patients presented a lesion with documented growth. The median clinical diameter was 5 mm (2-8 mm), the median ultrasound diameter 4.8 mm (2-7.7 mm) The patients were 6% T1, 57.1% T2, and 14.3% T3 all N0M0. The iridocorneal angle was invaded by the tumour in 71.4% of patients. At the end of follow-up, all patients were alive with no proven metastatic disease except one patient with suspicious liver lesions. None of the patients showed tumour progression or ocular relapse. The tumour response at 2 years was a flat lesion for 6.3% of cases, partial regression in 75% and stable in 18.8%. None of the patients required secondary enucleation. The main complication was cataract (45% within 24 months of treatment). Raised intraocular pressure was observed in 15% of patients but no neovascular glaucoma.

Proton beam therapy shows potential utility for selected cases of localised iris melanomas allowing excellent local tumour control and eye preservation. Further follow-up on larger series is needed to confirm these results.