Background and purpose: It has been suggested that the actual dose rate of an irradiating source may be a distinct influencing factor for the biological effect after brachytherapy with ruthenium-106 for uveal melanoma. The purpose of this study was to investigate a hypothesized impact of the dose rate on the clinical and echographic course after brachytherapy.
Patients and methods: In total, 45 patients were included in this retrospective study. According to the actual dose rate, two groups were defined: group 1 with a dose rate <4 Gy/h and group 2 with a dose rate >or=4 Gy/h. Regarding age, tumor height, basal diameter, scleral and apical dose, differences between the groups were not significant. Clinical parameters, including early and late side effects, and echographic courses were compared.
Results: A significantly lower metastatic rate was found in group 2. Using univariate Cox proportional hazards regression, only dose rate predicted metastatic spread significantly (p<0.05), while in a multivariate analysis, using age at the time of treatment, greatest tumor height and greatest basal diameter as covariates, the variable dose rate was of borderline significance (p=0.077). Patients in group 2 had more early side effects and more pronounced visual decline, but these differences were of borderline significance with p-values of 0.072 and 0.064, respectively.
Conclusion: These data suggest that a higher dose rate may confer a lower risk for metastatic spread, but may be associated with more side effects and more pronounced visual decline.