Radiation induced toxicity and tumour control in pts treated for uveal melanoma with ru-106 plaques

Purpose or Objective: In a retrospective study of 100 consecutive patients treated with Ru-106 eye plaques for uveal melanoma from 2005 to 2008 at our clinic, we aimed to investigate the correlation between the dose to the optic nerve and optic nerve damage; the dose to the macula and macular damage; and the minimum dose to the tumour and tumour control. Material and Methods: Pre-treatment fundus images were imported into Plaque Simulator TM and the tumour was retrospectively contoured by an ophthalmologist. The plaque position was determined from the radiation scar on posttreatment images. 3D dosimetric data was calculated. The point doses to the optic nerve and macula and minimum dose to the tumour were estimated. TCP, and damage to the optic nerve and macula, were determined from the patients' notes. The correlations between optic nerve damage, macular damage and TCP with dose, dose rate, gender, and plaque type was investigated using univariate and multivariate analyses. Results: 16 % of the patients developed optic nerve damage. Only optic nerve dose was correlated with damage to the optic nerve (p=0,000063) in univariate analysis. 51% of the patients had macular damage. Only macular dose was correlated with damage (p=0,00049) in univariate analysis. 32 % of the patients did not achieve tumour control. TCP was correlated with minimum tumour dose and gender in univariate analysis. Patients with minimum doses > 80 Gy had 100% TCP. For 80% of the patients with tumour recurrence, the plaque did not geometrically overlap the tumour. Dose response curves were drawn for optic nerve damage, macular damage and TCP. Such curves could not be found in the literature so no comparison was possible. Previously published values for TCP are similar to, or higher than, the one found in the present material. However, the papers citing higher values have selected patients with smaller tumours, which tend to have higher values of TCP. We emphasise that the number of patients is quite small and that a study of a large patient cohort is planned. Conclusion: Tumour control only failed in patients who received less than the prescription dose. The use of image guided planning software (such as Plaque Simulator TM) may aid in optimizing tumour control in the future. The present analysis presents the first reported dose response curves for damage to the optic nerve and macula. This information may be useful in delivering the optimal treatments in future.