Predicting Visual Acuity Deterioration and Radiation-Induced Toxicities after Brachytherapy for Choroidal Melanomas

Abstract

Ruthenium-106 (Ru-106) brachytherapy is an established modality for eye-preserving treatment of choroidal melanoma. To achieve optimal treatment outcomes, there should be a balance between tumour control and the risk of healthy tissue toxicity. In this retrospective study, we examined normal tissue complication probability (NTCP) for visual acuity deterioration and late complications to aid the understanding of dose-dependence after Ru-106 treatments. We considered consecutive patients diagnosed with choroidal melanoma and primarily treated at a single institution from 2005–2014. Treatment plans were retrospectively recreated using dedicated software and image guidance to contour the tumour and determine the actual plaque position. Dose distributions were extracted from each plan for all relevant anatomical structures. We considered visual acuity deterioration and late complications (maculopathy, optic neuropathy, ocular hypertension, vascular obliteration, cataract and retinal detachment). Lasso statistics were used to select the most important variables for each analysis. Outcomes were related to dose and clinical characteristics using multivariate Cox regressions analysis. In total, 227 patients were considered and 226 of those were eligible for analysis. Median potential follow-up time was 5.0 years (95% CI: 4.5–6.0). Visual acuity deterioration was related to optic disc-tumour distance and dose metrics from the retina and the macula, with retina V10Gy showing the strongest correlation. Macula V10Gy was the only dose metric impacting risk of maculopathy, while optic disc-tumour distance also proved important. Optic disc V50Gy had the largest impact on optic neuropathy along with optic disc-tumour distance. Optic disc V20Gy was the only variable associated with vascular obliteration. Lens D2% had the largest impact on the risk of cataract along with older age and the largest base dimension. We found no variables associated with the risk of ocular hypertension and retinal detachment. Visual acuity deterioration and most late complications demonstrated dependence on dose delivered to healthy structures in the eye after Ru-106 brachytherapy for choroidal melanomas.

Dose-Response and Normal Tissue Complication Probabilities after Proton Therapy for Choroidal Melanoma

“…Importantly, these data cannot be compared directly with the hypofractionated physical doses used for choroidal melanomas. Similarly, the current results will not be applicable to brachytherapy with ruthenium 106 31 because of the different dose-fractionation and dose-rate effects and different underlying radiobiology of the radiation methods.…”

Single-Fraction Adjuvant Electronic Brachytherapy after Resection of Conjunctival Carcinoma

“…A dosimetric advantage of kilovoltage application on this kind of tissue surface is also remarkable, due to its sharp fall-off dose profile compared to photon- or electron-based teletherapy units [ 21 , 22 ]. This feature allows better OAR sparing, as historical data report elevated rates of cataract, higher-grade conjunctivitis, uveitis and ulcer, amongst others [ 42 , 43 , 44 ]. Newly published data suggested that proton therapy might also be an optimal EBRT option.…”

106Ruthenium eye plaque brachytherapy in the management of medium sized uveal melanoma

“…Barker also suggested that the brachytherapy-planning protocols used for 125 I, for example COMS, were not sufficient for 106 Ru plaque brachytherapy due to the dosimetric difference between 125 I und 106 Ru. Three large 106 Ru treatment series with a mean dose of 100 Gy to the apex reported 5-year local control rates at 78, 82, and 84% respectively [19][20][21]. Another prospective study of 106 Ru brachytherapy on 450 patients reported that a 5-year local control rate of 97.9% could be achieved if a minimalscleral radiation dose of 300-400 Gy was used [22].…”