Salvage proton beam therapy for recurrent iris melanoma: outcome and side effects.

Purpose: This study aims to analyze the effect of salvage proton beam therapy for the treatment of recurrent iris melanoma.
Method: In this clinical case series, we retrospectively analyzed the data of eight patients who underwent proton beam therapy of the whole anterior segment as salvage therapy between 2000 and 2016 for recurrent iris melanoma after resection, ruthenium brachytherapy, or sector proton beam therapy. Two patients received salvage proton beam therapy for repeated tumor relapse. All patients were observed and prepared for proton beam therapy at the Charité and irradiated at the Helmholtz-Zentrum Berlin where they received 50 cobalt Gray equivalents (CGE) in four daily fractions. We investigated survival rates and ocular outcome.
Results: Median follow-up after salvage proton beam therapy was 39 months. No local recurrence was detected during follow-up. One patient died from hepatic metastases 5.5 years after salvage therapy. Secondary glaucoma occurred in seven out of eight patients during follow-up. Two patients had chronic corneal erosion and two other patients presented with corneal decompensation, necessitating Descemet membrane endothelial keratoplasty (DMEK), and perforating keratoplasty. Median visual acuity was 0.2 logMAR before salvage proton beam therapy and 0.7 logMAR at the end of follow-up.
Conclusion: Whole anterior segment salvage proton beam therapy has effectively controlled recurrent iris melanoma in our patients, but has been associated with a high incidence of radiation-induced corneal impairment and secondary glaucoma requiring extensive secondary treatment.