What is the role of plaque brachytherapy in the treatment of choroidal melanoma?

Updated: Dec 12, 2018
  • Author: Enrique Garcia-Valenzuela, MD, PhD; Chief Editor: Andrew A Dahl, MD, FACS  more...
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Answer

Answer

Plaque brachytherapy (see the image below) is a widely accepted alternative to enucleation for medium-sized posterior uveal melanomas (< 10 mm in height and < 15 mm in diameter).

Intraoperative photograph showing placement of a r Intraoperative photograph showing placement of a radioactive plaque for posterior choroidal melanoma.

Plaques containing various radioactive isotopes (eg, iridium, cobalt, and ruthenium) have been used. The most common material used in modern plaques is iodine-125, because of its lower energy emission (lack of alpha and beta rays), its good tissue penetration, and its commercial availability.

Radiation from this source causes tumor destruction through damage of DNA in cancerous cells and tumor vessels, with consequent tumor necrosis and regression. However, it is not devoid of complications. Detorakis et al found that after iodine-125 brachytherapy for choroidal melanoma, iris and anterior chamber angle neovascularization developed in 23% of eyes. [14]

A computerized calculation is used to determine the dose and the duration of plaque application for a radiation delivery of approximately 400 Gy to the base and 80-100 Gy to the apex of the tumor, at 50-125 cGy/h.

The basal size of the melanoma is estimated preoperatively and confirmed during surgery. Appropriately sized plaques are sutured temporarily to the sclera and limbus underlying the melanoma. A margin of 2 mm over the largest tumor basal dimension is adequate. Intraoperative techniques, such as transillumination or ultrasonography, are used to ensure proper plaque placement under the tumor.

Postoperative imaging confirmation of correct plaque localization is required. Radioactive plaques are left in place for 3-7 days. The goal of successful treatment is to achieve arrest of tumor growth or regression in size.

Local recurrence, usually requiring enucleation, occurs at a rate of about 12-16%. Plaque brachytherapy can cause complications, including cataract, rubeosis, scleral necrosis, keratopathy, radiation retinopathy, and optic neuropathy, but at a reduced rate compared with external beam irradiation.

A multicenter randomized trial from the COMS Group that addressed conservative management revealed that patient survival after treatment of medium-sized melanoma is similar when plaque radiotherapy is compared with enucleation. [15]


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