The treatment of uveal melanoma by ruthenium plaques

Abstract

Abstract Purpose Plaque radiotherapy is the first choice of treatment for choroidal melanomas. The standard practice is to position the plaque centrically in relation to the tumour, with a 2mm physical safety margin in all directions. The author has developed techniques for administering brachytherapy with plaques positioned eccentrically, with their posterior edge aligned with the posterior tumour margin. This allows a higher apex dose to be given while reducing the radiation delivered to optic nerve and fovea. Methods The tumour is localized by transillumination and its anterior margin marked on the sclera with a pen. The 'plaque‐tumour difference' measurement is then marked on the sclera at the point where the anterior plaque margin should be. A transparent plaque template is sutured to the sclera. The position of the plaque is checked with a right‐angled fibre‐optic transilluminator, which is passed through a perforation near the posterior edge of the template. If the template is positioned correctly, then with binocular indirect ophthalmoscopy one should see the 'sunset sign', which occurs when the transilluminator is exactly at the posterior tumour margin. Results Eccentric ruthenium plaque positioning has been practised in Liverpool for over a decade. The results have been published. Local tumour control rates have been good (partly because of case selection). Radiation maculopathy and optic neuropathy have been rare if the tumour has not extended within 1 mm of these structures. The main cause of visual loss has been maculopathy, caused by exudation from the irradiated tumour. Methods for treating such exudation are described. Conclusion Plaque radiotherapy is effective for choroidal melanomas up to 5 mm in thickness. It achieves good local tumour control with preservation of vision in most cases.