[Radiotherapy for choroidal neovascularization in age-related macular degeneration. A pilot study using low- versus high-dose photon bean radiation]

Abstract

Purpose: Several pilot studies have indicated that low-dose radiation therapy might have a beneficial effect on the course of choroidal neovascularization (CNV) in age-related macular degeneration (AMD). This study aimed to ascertain whether such treatment might halt the progression of neovascular AMD and whether a low or a high radiation dose should be applied.

Patients: The patients comprised some randomized to 0 vs 10 vs 36 Gy of radiation and (after a change of the study protocol became necessary) others who participated in a prospective, controlled non-randomized pilot study. Enclosed were eyes with visual acuity of > or = 0.1 and < or = 0.6 revealing a juxta-subfoveal CNV either of the occult type (type 1) or the classic type (isolated or as part of a predominantly occult lesion).

Results: Eyes treated with 10 Gy for occult CNV (n = 12) were subject to severe visual loss in 41.6% of the cases compared to 38.5% in the control group (n = 13) at 12 months of follow-up. For eyes treated with 10 Gy because of classic CNV, the corresponding figures were 33% (n = 18) and 57% (n = 14) respectively. At 18 months of follow-up, the percentages were 63% and 75% respectively. Fluorescein angiographic growth of classic and occult CNV could not be halted by 10 Gy, while a temporary growth retardation was observed in cases irradiated with 36 Gy.

Conclusion: In the study presented, the natural course of occult CNV could not be improved by irradiation with 10 or 36 Gy. In cases of classic CNV, low-dose irradiation with 10 Gy postponed severe visual loss by a maximum of 18 months. A positive treatment effect was also observed in cases irradiated with 36 Gy; however, a 25% incidence of radiation retinopathy seems unacceptable.