Evaluation of symmetrically loaded COMS I-125 plaques using the plaque simulator software system and specific to juxtapapillary choroidal melanoma.

Purpose/Objective(s): The purpose of this study was to retrospectively evaluate the dosimetric coverage of I-125 plaque brachytherapy (IBT) specific to juxtapapillary choroidal melanoma (JCM) using the Plaque Simulator treatment planning system. Materials and Methods: Thirty patients with medium-sized JCM treated using COMS IBT and loaded non-uniformly but with circular symmetry, were identified from a prospective database. The distance from the tumor edge to the optic disk ranged from 0.75-2.5 mm, the median tumour thickness and longest diameter was 4.3 mm and 9.9 mm, respectively. The proximity of the tumor to the optic nerve did not allow the round plaque to be centered over the tumor, so the tumor edge closest to the optic nerve did not receive the dose specified as per the COMS study. Initially these cases were planned with an in-house treatment planning system, and each case was replanned with the Plaque Simulator treatment planning system (BEBIG, Germany) for accurate dosimetric evaluations. Results: With all corrections for dose calculation "ON" in the Plaque Simulator, mean dose to the tumor edge nearestthe optic nerve was significantly lowerthan COMS recommendations (61 Gy vs. 69Gy, p<0.02). However, the tumour control rate was 90%, eye preservation rate was 90%, and rate of developing systemic metastases was 7%. Complications included cataract in 53%, neovascular glaucoma in 10%, retinopathy in 53%, and papillopathy in 33% of patients which was comparable to previously reported COMS outcomes. Conclusion Despite relative underdosing secondary to the physical impediment of the optic nerve for JCM, our results imply that the tumor edge may not need as high a dose as compared to the tumor apex. Disclosure: No significant relationships. [ABSTRACT FROM AUTHOR]