Eye Plaque Brachytherapy

Abstract

Episcleral plaque brachytherapy for appropriately selected patients (medium-sized tumors with an apical height of 2.5–10 mm and maximum basal diameter of <16 mm) is a common treatment option for uveal (choroidal) melanoma. The goals of treatment are preservation of function (vision) with a good cosmetic outcome (retention of the eye) as well as control of disease and prevention of dissemination (local or metastatic). COMS guidelines recommend prescribing 85 Gy to 5 mm from the inner sclera for tumors <5 mm in apical height and to the tumor apex for tumors ≥5 mm in apical height, but a recent publication from our group has shown that dosing to the tumor apex even for tumors <5 mm in apical height results in similar tumor control probability but with improved toxicity profile (better preservation of vision). Precise localization of the tumor is the key to allow accurate placement of the radioactive plaque and thus to ensure complete coverage of all borders of the tumor. Failure to do so may result in tumor recurrence. A widely dilated pupil is paramount for adequate visualization of the posterior segment of the globe. After the conjunctiva is open at 360° and the rectus muscles are isolated with a 2-0 silk suture allowing rotation of the globe during the visualization process, a surgical pen is used to mark the borders of the tumor on the sclera utilizing transpupillary illumination. The plaque is left in place for approximately 5–7 days.

Local control for medium-sized tumors is ~90 % at 5 years after plaque treatment, thus making this technique a very effective approach in controlling this cancer.