Ruthenium brachytherapy for uveal melanomas: Factors affecting the development of radiation complications

Purpose: To investigate how treatment complications are related to dosimetric parameters after ruthenium-106 brachytherapy for uveal melanoma, in a large, clinically homogeneous population. Methods and Materials: A retrospective review was performed to evaluate patients affected by small and medium size uveal melanoma, treated with ruthenium-106 brachytherapy from December 2006 to December 2014. We excluded tumors with posterior margin within 1 mm from the edge of the optic disc and foveola. Main outcome measures were occurrence and time to radiation-related maculopathy, cataract, and optic neuropathy. Secondary end points included local recurrence and distant metastases. Kaplan-Meier analysis with log-rank test and univariate Cox proportional hazards model at 3 years were performed to identify the covariates affecting the outcome of radiation complications. Results: Two hundred thirty-nine patients, with sufficient data to evaluate the end points, were enrolled. Three years after plaque treatment, radiation maculopathy was found in 61 (25.5%) patients, cataract developed in 10 patients (4.2%) receiving a dose of 27 Gy or higher to the lens, and optic neuropathy was observed in 13 patients (5.4%) with an optic nerve dose exceeding 50 Gy and tumor proximity to optic disc of less than 4 mm. Tumor recurrences and tumor-related metastasis were found respectively in 20 (8.36%) and 14 (5.85%) patients. Conclusions: Radiation maculopathy occurs within a median time of 31 months in 25% of cases after plaque treatment for uveal melanoma. The most significant risk factors are total dose and distance of tumor margin from the fovea. If the distance is greater than 11.22 mm, no signs of retinal damage are detected.