Comparative outcomes and toxicities for ruthenium-106 versus palladium-103 in the treatment of choroidal melanoma.

For the treatment of choroidal melanoma, palladium-103 (Pd-103) and ruthenium-106 (Ru-106) plaque brachytherapy shows reduced toxicity compared with the historical standard iodine-125. No report has directly compared the clinical outcomes between Pd-103 and Ru-106, and the reasons for the selection of one over the other remain purely theoretical. Patients with choroidal melanoma with apical tumor height up to 5mm were included. Patients from Emory University were treated with Pd-103 between 1993 and 2012. Patients from Cleveland Clinic were treated with Ru-106 between 2005 and 2010. Medical records were retrospectively reviewed. We compared post-treatment visual acuity (VA), toxicity, and oncologic outcomes. Pd-103 patients (n=124) and Ru-106 patients (n=42) had a median follow-up of 4.2 and 5.0 years, respectively. Radiation retinopathy-free survival was similar for both radioisotopes, but Ru-106 had lower grades of retinopathy (P=0.006). Pd-103 was associated with worse VA preservation (20/40) by year 3 (odds ratio: 3.8; 95% confidence interval: 1.01-14.31, P=0.048). Pd-103 was associated with higher distant metastases-free survival (DMFS) in multivariate analysis (hazard ratio: 0.10; 95% confidence interval: 0.02-0.38; P<0.001). Ru-106 had lower grades of radiation retinopathy and improved long-term VA preservation, but also inferior DMFS, compared with Pd-103. Because of the inherent limitations of a retrospective analysis, the significance of the inferior DMFS for Ru-106 remains unclear, although the suggestion of a slight inferiority in terms of DMFS for Ru-106 is consistent with the other limited literature. On the basis of this study, we believe that both radioisotopes remain appropriate for the treatment of small choroidal melanomas up to 5mm in apical height.