What is the role of external beam irradiation in the treatment of choroidal melanoma?

Updated: Feb 18, 2020
  • Author: Enrique Garcia-Valenzuela, MD, PhD; Chief Editor: Andrew A Dahl, MD, FACS  more...
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External beam irradiation using charged particles, either protons or helium ions, is a frequently used alternative method for the treatment of medium-sized choroidal melanomas (< 10 mm in height and < 15 mm in diameter), although it has been used for larger tumors. Its indications and success rates are similar to those of plaque brachytherapy. [16]

After conjunctival incision and localization of the melanoma with transillumination, radiopaque tantalum rings usually are sutured to the sclera to serve as reference markers for alignment of the radiation beam. A collimated beam delivers about 70 Gy, usually divided into 5 sessions.

Vital ocular structures are avoided through careful positioning of the head and eye. Irradiation causes damage of DNA in cancerous cells and tumor vessels, much as in plaque brachytherapy, with consequent tumor necrosis and regression. Treatment may be complicated by exudative retinal detachment, radiation cataract, dry eye syndrome, epithelial keratopathy, rubeosis, radiation retinopathy, and optic neuropathy.

Patients treated with external beam irradiation seem to have a survival rate comparable to that of patients treated with enucleation. Treatment is successful when it achieves arrest of tumor growth or regression in size. About 10-15% of eyes ultimately require enucleation, often because of neovascular glaucoma or local recurrence.

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