A reanalysis of the XXXX Study Medium Tumor Trial eye plaque dosimetry.

@entity5 @entity1 @entity320
PURPOSE: To recalculate the radiation doses delivered to structures of interest within the eye, i.e., the lens, @entity5 apex, 5-mm point, optic disk, and macula for @entity1 treated with eye plaque radiotherapy on the @entity320 Study (COMS) Medium Tumor Trial, using updated dosimetric data. METHODS AND MATERIALS: Using the Plaque Simulator planning system, doses were recalculated for a sampling of COMS @entity1 for each plaque size. Dosimetry parameters incorporated into the recalculation were line source approximation, a 90% Silastic transmission factor, and a 0% gold transmission factor. Generic solutions were generated from the dose recalculations for each plaque size and structures of interest combination. Doses for the remainder of the @entity1 population were recalculated using the generic solutions and compared with the originally reported COMS doses. RESULTS: Doses to all structures of interest were reduced 7%-21%, depending on the plaque size and structure combination. The reduction in dose for the macula, optic disc, lens, @entity5 apex, and 5-mm point was on average 10%, 18%, 8%, 11%, and 12%, respectively. The closer the macula and optic disk were to the plaque rim, the greater the dose reduction. Incorporation of the Silastic transmission factor accounted for a large part of the dose reduction. CONCLUSIONS: Incorporating anisotropy, line source approximation, and Silastic and gold shield attenuation into dose recalculations resulted in a significant and consistent reduction of doses to structures of interest within the eyes.
