Novel 3D conformal technique for treatment of choroidal melanoma with external beam photon radiotherapy

Abstract

To report a 3D conformal radiotherapy (3D-CRT) technique that utilises a specific eye immobilisation and treatment set-up method as an alternative to stereotactic radiotherapy (SRT), for treatment of juxtapapillary choroidal melanoma (CM) and report early treatment outcomes of this technique. A contact lens and rod system was designed to provide eye immobilisation and a treatment reference point for 3D-CRT. The technique is described in detail in the body of the paper. A retrospective chart review was conducted to report freedom from local progression (FFLP) and radiation toxicity in a cohort of patients treated with a dose of 50 Gy in five fractions. Eleven eligible patients with juxtapapillary CM were treated between 2003 and 2009. The median follow-up was 3.2 years (range 1.2-5.3). The FFLP was 100% (95% confidence interval 71.5-100). The reproducibility of the set-up and eye immobilisation for fractionation was excellent. The mean dose to the planning target volume was 51.4 Gy (interquartilic range 51.0-51.9). Normal tissue dose constraints were achieved; however, the quality of the 3D-CRT plan was variable. The highest acute radiation toxicity score was Common Toxicity Criteria version 3 grade 1. Vision outcomes were poor. In this small series, a novel non-stereotactic technique was found to be an accurate method for the treatment of CM with a high rate of freedom from tumour progression, in keeping with the SRT series. The quality of the conformal plan was variable. Investigation of the optimal dose-fractionation schedule to minimise late radiation toxicity without compromise of tumour control is the focus of ongoing clinical research at our centre.