Visual Outcomes after Proton Beam Irradiation for Choroidal Melanomas Involving the Fovea

Abstract

Purpose: To report visual outcomes in patients undergoing proton beam irradiation of tumors located within 1 disc diameter of the fovea.

Design: Retrospective review.

Participants: Patients with choroidal melanoma involving the fovea treated with proton beam therapy between 1975 and 2009.

Methods: Three hundred fifty-one patients with choroidal melanomas located 1 disc diameter (DD) or less from the fovea and more than 1 DD away from the optic nerve were included in this study. In a subgroup of 203 of the patients with small and medium choroidal melanomas, the effect of a reduced dose of radiation, 50 Gy (relative biological effectiveness [RBE]) versus 70 Gy (RBE), on visual outcomes was analyzed. The Kaplan-Meier method and Cox regression analysis were performed to calculate cumulative rates of vision loss and to assess risk factors for vision loss, respectively.

Main outcome measures: Visual acuity and radiation complications, which included radiation maculopathy, papillopathy, retinal detachment, and rubeosis, were assessed.

Results: Three hundred fifty-one patients were included in this study with a mean follow-up time of 68.7 months. More than one-third of patients (35.5%) retained 20/200 or better vision 5 years after proton beam irradiation. For those patients with a baseline visual acuity of 20/40 or better, 16.2% of patients retained this level of vision 5 years after proton beam irradiation. Tumor height less than 5 mm and baseline visual acuity 20/40 or better were associated significantly with a better visual outcome (P < 0.001). More than two-thirds (70.4%) of patients receiving 50 Gy (RBE) and nearly half (45.1%) of patients receiving 70 Gy (RBE) retained 20/200 or better vision 5 years after treatment, but this difference was not significant. Approximately 20% of patients with these smaller macular tumors retained 20/40 vision or better 5 years after irradiation.

Conclusions: The results of this retrospective analysis demonstrate that despite receiving a full dose of radiation to the fovea, many patients with choroidal melanoma with foveal involvement maintain useful vision. A radiation dose reduction from 70 to 50 Gy (RBE) did not seem to increase the proportion of patients who retain usable vision.