Abstract
Purpose: :
Brachytherapy is usually administered with the plaque overlapping the entire tumor margin by at least 1-2mm. With posterior tumors, our practice is to position the plaque with its posterior edge aligned with the posterior tumor margin. We audited ocular outcomes after eccentrically-placed ruthenium plaque radiotherapy of choroidal melanoma.
Methods: :
Patients were included if receiving primary ruthenium brachytherapy for choroidal melanoma during the three years up to the 31st July 2007. A perforated template was used to facilitate plaque positioning. For posterior tumors, the template was positioned so that transillumination produced a glow at the posterior tumour margin (‘sunset sign’). Minimum doses of 300-350 Gy and 80-90 Gy were prescribed to the sclera and apex respectively.
Results: :
The cohort comprised 162 patients (93 female and 69 male). The time to the last known visual acuity had a median of 23 months. The initial visual acuity was 20/40 or better in 94.6%, 20/60 to 20/200 in 13.0% and worse than 20/200 in 1.9% of patients. The tumors had a mean basal diameter of 11.7mm. Ten tumors exceeded 5.4 mm in height. Tumor extension to within 5mm of optic disc, fovea or both occurred in 18 (11.1%), 28 (17.3%) and 27 (16.7%) cases respectively. Risk factors for visual loss were proximity to optic disc or fovea, initial visual acuity worse than 20/40 and tumor height exceeding 5.4 mm. In 66 patients with none of these risk factors, 92% retained 20/40 or better and 5 had vision of 20/60 - 20/200. In 72 with one risk factor, 74.3% retained 20/16 - 20/40 and 95.7% had vision of 20/200 or better. In 12 patients with 2 risk factors, these percentages were 25.0% and 91.7%. Only 3 patients had 3 risk factors and one retained vision of 20/200 or better. Three patients had local tumor recurrence and were treated respectively by proton beam radiotherapy, plaque radiotherapy and enucleation (the only eye lost in this series).
Conclusions: :
Eccentric plaque radiotherapy of choroidal melanoma achieves good rates of local tumor control, ocular retention and preservation of vision.
Keywords: melanoma • choroid • radiation therapy