Intraoperative echographic localization of iodine 125 episcleral radioactive plaques for posterior uveal melanoma

Purpose: Plaque radiotherapy has been reported to have a higher relapse rate than charged-particle radiotherapy for posteriorly located uveal melanomas, which also are more technically difficult to localize accurately. The authors used intraoperative echography in patients with posterior uveal melanoma to determine the rate of inaccurate localization of iodine 125 (¹²⁵I) episcleral plaques using standard localization techniques. Methods: The authors reviewed the records of 29 consecutive patients with medium- sized posterior uveal melanomas who underwent ¹²⁵I episcleral plaque radiotherapy with intraoperative echographic verification of plaque placement. Results: After careful plaque placement using standard localization techniques, 4 of 29 plaques (14%) did not cover at least one tumor margin. All four of these plaques were associated with posterior tumors with at least one margin posterior to the temporal arcades. Two (7%) additional juxtapapillary plaques were displaced away from the sclera by the optic nerve. In all six cases, it was possible to immediately reposition the plaque to achieve coverage of all tumor margins. Conclusions: Placement of ¹²⁵I episcleral radioactive plaques for posteriorly located uveal melanomas using standard localization techniques occasionally results in suboptimal plaque positioning. Intraoperative echography can identify plaques that are localized poorly and allows immediate adjustment to achieve optimal plaque positioning.