recurrence of iris melanoma after proton beam therapy backgroundaims a retrospective service evaluation to report on recurrence of iris melanoma after proton beam therapy pbtmethods the cohort comprised 150 consecutive eyes with iris melanoma treated with proton beam radiotherapy treatment consisted of 531 gy of proton beam irradiation delivered in four fractions over four consecutive days main outcome measures were local tumour control and tumourrelated mortalityresults a total of 150 patients were treated the median followup time was 66 months range 12108 months the tumour ultrasound thickness ranged from 11 mm to 49 mm with a median of 24 mm the tumours in these patients had a median largest basal diameter of 67 mm range 2984 mm involving more than two clock hours of iris or angle in five patients the ciliary body was involved in three patients eight patients 53 presented with local recurrence diagnosed after a median followup of 24 months range 1284 months the recurrence was focal in two patients and diffuse in six six eyes were enucleated whereas one eye underwent iridocyclectomy and one received a second course of pbtconclusions pbt provides excellent local tumour control and ocular preservation with good retention of vision most recurrences occur because the extent of the tumour is clinically underestimated but some tumours are radioresistant recurrence can occur several years after treatment these findings indicate the need for wide safety margins and even radiotherapy of the entire anterior segment in patients with diffuse disease surveillance after treatment needs to be lifelong