Efficacy and complications of ruthenium-106 brachytherapy for uveal melanoma: a systematic review and meta-analysis

Introduction
The aim of this study was to evaluate the efficacy and vision-threatening complications of brachytherapy with ruthenium-106 (106Ru) plaque to treat uveal melanoma.

Material and methods
A literature review was performed based on results from searching PubMed, Embase, Web of Science, Scopus, and Cochrane databases, using the following key words: “choroidal melanoma”, “uveal melanoma”, “brachytherapy”, and “ruthenium-106”. We included studies performed on more than 30 patients since 1986, reporting on local control rate, complications rate, mean radiation dose, and mean tumor thickness. The cumulative analysis was performed using Metaprop command of Stata v.16, and meta-regression was conducted based on mean tumor thickness and mean radiation dose to tumor’s apex.

Results
Twenty-one retrospective studies were selected, involving 3,913 patients treated primarily with 106Ru plaque brachytherapy. The range of radiation dose to tumor apex was from 70 Gy to 250 Gy. The local control rate following brachytherapy ranged from 59% to 98%, and the overall weighted mean of local control was 84%. However, the heterogeneity between studies’ reports was remarkable (I2 = 95.40%). Meta-regression based on tumor thickness and mean dose of radiation to the apex showed that the studies’ heterogeneity was minimally related to the difference in mean tumor size (I2 = 92%). The correlation between larger tumor size and lower local control rate was statistically significant (p-value = 0.024). There was no significant correlation between the mean radiation dose and local control rate (p-value = 0.679). The most commonly reported complications were cataract and radiation-related retinopathy.

Conclusions
Although the studies’ heterogeneity was high, in a prescription dose ranging from 70 Gy to 250 Gy to the tumor apex, 106Ru brachytherapy seems to be successful in local control of uveal melanoma. The efficacy of 106Ru in controlling uveal melanomas decreased with the increase in tumor thickness. However, these outcomes should be verified in randomized comparative studies.