Complications from Plaque versus Proton Beam Therapy for Choroidal Melanoma: A Qualitative Systematic Review

Plaque brachytherapy has been a mainstay of treatment for choroidal melanoma to achieve intraocular tumor control. The most common radioisotopes used for treating smaller sized tumors are Iodine-125 in North America and Ruthenium-106 in Europe. Proton beam radiotherapy is available at a few centers and may also be used to achieve local tumor control. Both plaque and proton beam therapy are known to be associated with a range of complications that may affect visual outcome and quality of life. These include radiation retinopathy, optic neuropathy, neovascular glaucoma and local treatment failure, requiring enucleation. While differences in the rates of these complications have not been well established in the literature for patients treated with plaque versus proton beam therapy for choroidal melanoma, certain geographic regions prefer one treatment modality over the other. The purpose of this qualitative systematic review was to compare and contrast reported complications that developed with plaque and proton beam therapy for the treatment of choroidal melanoma in studies published over a ten-year period. Reported rates suggest that patients with proton beam therapy had potentially higher rates of complications, including vision loss, enucleation, and neovascular glaucoma compared to those with plaque therapy. The rates of optic neuropathy, radiation retinopathy, and cataract formation were widely variable for the two treatment modalities and rates of metastasis and metastasis-free survival appeared similar with both treatments. The most common reported predictors of ocular complications following both types of therapy were tumor distance from the optic nerve, tumor thickness, and radiation dose, suggesting that inherent tumor characteristics play a role in visual prognosis.