Ruthenium-106 versus iodine-125 plaque brachytherapy of 571 choroidal melanomas with a thickness of ≥5.5 mm

Abstract

BackgroundEpiscleral brachytherapy is the most common eye-preserving treatment for medium-sized choroidal melanomas. γ-emitting iodine-125 (125I) and β-emitting ruthenium-106 (106Ru) are widely used. The latter is however generally reserved for thinner tumours (<6 mm). In this study, we compare ocular and patient survival in thicker tumours treated with the respective radioisotope.MethodsAll patients with ≥5.5 mm thick choroidal melanomas who were treated with plaque brachytherapy at a single institution between 1 November 1979 and 31 December 2015 were included (n=571). Size-controlled Cox regression HRs for postbrachytherapy enucleation, repeated brachytherapy and melanoma-related mortality were calculated, as well as Kaplan-Meier disease-specific survival and relative 10-year survival in matched subgroups.Results317 patients were treated with 106Ru and 254 with 125I. The rate of repeated brachytherapy was significantly higher among patients treated with 106Ru (8%) than with 125I (1%, p<0.001). Size-controlled Cox regression HRs for postbrachytherapy enucleation (125I vs 106Ru 0.7, p=0.083) and melanoma-related mortality were not significant (125I vs 106Ru 1.1, p=0.63). Similarly, Kaplan-Meier disease-specific and relative 10-year survival was comparable in matched groups of 5.5–7.4 mm (relative survival 106Ru 59%, 125I 56%) and ≥7.5 mm thick tumours (relative survival 106Ru 46%, 125I 44%).ConclusionsRates of repeated brachytherapy were significantly higher among patients treated with 106Ru versus 125I for thick choroidal melanomas. There were, however, no significant differences in rates of enucleation or patient survival.