Regression Patterns of Iris Melanoma after Palladium-103 (¹⁰³Pd) Plaque Brachytherapy

Purpose To evaluate the patterns of regression of iris melanoma after treatment with palladium-103 (¹⁰³Pd) plaque brachytherapy. Design Retrospective, nonrandomized, interventional case series. Participants Fifty patients with primary malignant melanoma of the iris. Methods Palladium-103 plaque brachytherapy. Main Outcome Measures Changes in tumor size, pigmentation, and vascularity; incidence of iris neovascularization; and radiation-related complications. Results The mean age in the case series was 61.2±14.9 years. The mean tumor thickness was 1.4±0.6 mm. According to the American Joint Committee on Cancer, eighth edition, staging criteria for iris melanoma, 21 tumors (42%) were T1a, 5 tumors (10%) were T1b, and 24 tumors (48%) were T2a. The tumor was melanotic in 37 cases (74%) and amelanotic in 13 cases (26%); of these, 13 tumors (26%) showed variable pigmentation. After brachytherapy, mean tumor thickness decreased to 0.9±0.2 mm. Pigmentation increased in 32 tumors (64%), decreased in 11 tumors (22%), and was unchanged in 6 tumors (12%). For intrinsic vascularity (n = 19), 12 tumors (63%) showed decrease and 7 tumors (37%) showed complete resolution. Appearance of ectropion uveae showed diminution in 15 tumors (43%); newly present corectopia was observed in 6 patients (12%). On high-frequency ultrasound imaging, of the 42 tumors (84%) with low to moderate internal reflectivity, 30 tumors (60%) showed an increase in internal reflectivity on regression. Iris stromal atrophy was noted in 26 patients (52%), progression or new-onset cataract was noted in 22 patients (44%), neovascular glaucoma was noted in 1 patient (2%), and there were no cases of corneal opacity. There was no clinical evidence (0%) of radiation-induced retinopathy, maculopathy, or optic neuropathy. Mean follow-up in this series was 5.2 years (range, 0.5–17 years). Conclusions The most common findings related to iris melanoma regression after ¹⁰³Pd plaque brachytherapy included decreased intrinsic tumor vascularity, increased tumor pigmentation, and decreased tumor thickness with synchronous increase in internal ultrasonographic reflectivity. No irreversible sight-limiting complications were noted.