Tumour control probability after Ruthenium-106 brachytherapy for choroidal melanomas

Abstract

Purpose: Ruthenium-106 (Ru-106) brachytherapy is a common eye-preserving treatment for choroidal melanomas. However, a dose-response model describing the relationship between the actual delivered tumour dose and tumour control has, to the best of our knowledge, not previously been quantified for Ru-106 brachytherapy; we aimed to rectify this. Material and methods: We considered consecutive patients with primary choroidal melanomas, treated with Ru-106 brachytherapy (2005–2014). Dosimetric plans were retrospectively recreated using 3D image-guided planning software. Pre-treatment fundus photographies were used to contour the tumour; post-treatment photographies to determine the accurate plaque position. Patient and tumour characteristics, treatment details, dose volume histograms, and clinical outcomes were extracted. Median follow-up was 5.0 years. The relationship between tumour dose and risk of local recurrence was examined using multivariate Cox regression modelling, with minimum physical tumour dose (D99%) as primary dose metric. Results: We included 227 patients with median tumour height and largest base dimension of 4 mm (range 1–12, IQR 3–6) and 11 mm (range 4–23, IQR 9–13). The estimated 3 year local control was 82% (95% CI 77–88). Median D99% was 105 Gy (range 6–783, IQR 65–138); this was the most significant factor associated with recurrence (p