Early results of proton beam radiotherapy of posterior uveal melanomas
Noonan CP., Damato BE.
Purpose. To determine early results of proton beam radiotherapy of small posterior uveal melanomas in selected patients deemed unsuitable for plaque radiotherapy because of proximity to optic disc or fovea. Methods. 94 patients with a tumour thickness <=5.5 mm (i.e. treatable with ruthenium plaque radiotherapy), but with tumour extension to within 2 disc diameters of disc or fovea were selected from a total of 157 patients treated between 1991 and 1995. Results. Mean patient age was 56.3 yrs; tumour diameter was 9.9mm, thickness was 3.4mm. Median follow-up was 559 days. 25.5% of tumours involved fovea, 13.8% involved disc and 4.3% involved both structures. Kaplan Meier estimations showed actuarial rates for retention of eye, vision of 6/60 or better, and vision of 6/12 or better to be 83% at 995 days, 59% at 843 days, and 60% at 581 days respectively. Reasons for enucleation were tumour recurrence (2) and rubeotic glaucoma (2). The main causes of severe visual loss were tumour involvement of macula (47%), maculopathy (40%), optic neuropathy (11%), and rubeotic glaucoma (2%). If the posterior tumour margin extended to one disc diameter of the optic disc the actuarial rate of optic neuropathy at 900 days increased from 3% to 57% (Log Rank Test, p=0.001). By the close of the study, two patients developed local recurrence and two patients died of metastases. Conclusions. Proton beam radiotherapy of small posterior choroidal melanomas is useful for conserving the eye, but visual prognosis is poor because of macular damage by tumour or radiation, or because of optic neuropathy.