Regression Rate of Posterior Uveal Melanomas Following Iodine-125 Plaque Radiotherapy

AIM: To characterize the regression rate of posterior uveal melanoma following radioactive iodine-125 (I-125) plaque. MATERIALS AND METHODS: We retrospectively analyzed 95 patients with posterior uveal melanoma who were treated with only radioactive I-125 plaque and had more than 3 years follow-up. All patients were treated with plaque radiotherapy using tumor dose of 85 Gy at the tumor apex, following COMS protocol. Regression rate was assessed with standardized A-scan ultrasonography. Associations with tumor regression were evaluated by means of mixed linear regression modeling. RESULTS: Mean decrease in the tumor thickness (% original thickness) at 12, 24, and 36 months after radiotherapy for melanomas <3 mm in thickness was 29%, 38%, and 45%, for melanoma 3-8 mm in thickness was 32%, 44%, and 59%, and for melanoma more than 8 mm in thickness was 52%, 62%, and 68%, respectively. With a doubling of follow-up time (0.5-1 year, or 1-2 years of follow-up from treatment), tumors <3 mm in thickness at treatment showed a 0.5 mm decrease in tumor thickness, whereas melanomas 3-8 mm showed a 1 mm decrease, and melanomas >8 mm showed a 1.7 mm decrease. Uveal melanomas that developed systemic metastasis showed an additional 0.4 mm decrease with a doubling of follow-up time from treatment, compared with those that did not develop metastasis (P = 0.050). CONCLUSIONS: Posterior uveal melanomas with higher initial thickness show steeper and more reduction in tumor thickness following radioactive I-125 plaque. After the initial phases, the regression curve became similar for tumors with different thicknesses.