External beam radiation therapy for choroidal neovascularization

Radiotherapy for age related macular degeneration causes transient lens transparency changes

AIM

Evaluation of potential side effects of photon radiotherapy on the transparency of the lens.

METHODS

The anterior segments of 14 phakic eyes from patients suffering from subfoveal neovascularisation as a result of age related macular degeneration (AMD) were documented by Scheimpflug photography (Topcon SL-45, Kodak Tmax 400) before the start of radiotherapy as well as 6 and 12 months afterwards. All negatives were evaluated by microdensitometry, and peak heights for distinct layers of the lens were used for statistical comparison. External beam radiotherapy (6 MeV photons) consisted of a total dose of 20 Gy, delivered as 10 fractions of 2 Gy.

RESULTS

Six and 12 months following irradiation statistical comparison of the ratios in density change of lenses from irradiated versus non-irradiated fellow eyes revealed statistically significant (p</=0.05) loss of transparency of layers 5 and 7 of the nuclear region. In layer 1 (capsuloepithelial complex) the changes were close to significance. At the 12 month examination, however, all of these significant changes had disappeared.

CONCLUSION

Six months following radiotherapy for AMD, both the anterior capsuloepithelial region and the nuclear layers showed precataractous changes. As most of these significant differences had disappeared after 12 months, it is obvious that these findings reflect acute radiation damage to the lens epithelial cells and an ionising effect on the proteins of the lens nucleus. Long term studies will have to be carried out to demonstrate whether or not this acute radiation damage, which is expressed as a transient increase in light scattering of some layers of the lens, actually does lead to permanent transparency changes, thus reflecting radiation cataractogenesis, and if so, after what time interval and to what extent cataract occurs.

Treatment of age-related macular degeneration

Age-related macular degeneration (AMD), while rapidly becoming more prevalent due to an aging population, is still poorly understood and treatment modalities are limited. Fortunately, advances are being made in the treatment of AMD that may greatly alter the outcome of this debilitating disease. Treatments for both wet and dry AMD are reviewed.

External beam radiotherapy in exudative age-related macular degeneration: a pooled analysis of phase I data

In recent years external beam radiotherapy (EBRT) has been proposed as a treatment for the wet form of age-related macular degeneration (AMD) where choroidal neovascularization (CNV) is the hallmark. While the majority of pilot (Phase I) studies have reported encouraging results, a few have found no benefit, i.e. EBRT was not found to result in either improvement or stabilization of visual acuity of the treated eye. The natural history of visual loss in untreated CNV of AMD is highly variable. Loss of vision is influenced mainly by the presenting acuity, and size and composition of the lesion, and to a lesser extent by a variety of other factors. Thus the variable outcome reported by the small Phase I studies of EBRT published to date may simply reflect the variation in baseline factors. We therefore obtained information on 409 patients treated with EBRT from eight independent centres, which included details of visual acuity at baseline and at subsequent follow-up visits. Analysis of the data showed that 22.5% and 14.9% of EBRT-treated eyes developed moderate and severe loss of vision, respectively, during an average follow-up of 13 months. Initial visual acuity, which explained 20.5% of the variation in visual loss, was the most important baseline factor studied. Statistically significant differences in loss of vision were observed between centres, after considering the effects of case mix factors. Comparisons with historical data suggested that while moderate visual loss was similar to that of the natural history of the disease, the likelihood of suffering severe visual loss was halved. However, the benefit in terms of maintained/improved vision in the treated eye was modest.

Radiation-associated choroidal neovasculopathy

PURPOSE

To characterize a newly discovered choroidal vascular abnormality in patients who have received radiation therapy for subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration.

DESIGN

Two-center cross-sectional study.

PARTICIPANTS

In the United States, there were 95 patients who were treated with 10 or 12 Gy of external beam photons. In Belgium, 98 patients were treated with 20 Gy. These patients were examined retrospectively for the presence of a specific CNV abnormality.

RESULTS

During the follow-up period, an unusual vascular growth pattern was identified in 12 patients (12.6%) of those treated in the United States and in 7 (7.1%) of those treated in Belgium. These patients developed round or oval vascular blebs along the outer border of their neovascular lesions. These blebs profusely leaked fluorescein dye and could be imaged best by indocyanine green angiography. Patients with these blebs appeared to have a marked propensity for loss of visual acuity.

CONCLUSION

An unusual pattern of new vessel growth occurred in 19 of the 193 patients with CNV treated with radiation. This new entity, termed radiation-associated choroidal neovasculopathy, is a recognizable disorder that appears to have a particularly poor prognosis.

A prospective, randomized, double-masked trial on radiation therapy for neovascular age-related macular degeneration (RAD Study). Radiation Therapy for Age-related Macular Degeneration

OBJECTIVE

To determine the efficacy of external beam radiation therapy on choroidal neovascularization (CNV) secondary to age-related macular degeneration (ARMD).

DESIGN

Multicenter, parallel, randomized, double-masked clinical trial performed at nine ophthalmic and radiotherapeutic centers.

PARTICIPANTS

Two hundred five patients were randomly assigned either to treatment with 8 fractions of 2 Gy external beam irradiation (n = 101) or to control with 8 fractions of 0 Gy (sham treatment, n = 104). Both patients and ophthalmologists were masked with regard to applied treatment. Patients with subfoveal classic or occult CNV, visual acuity of 20/320 or greater on the Early Treatment Diabetic Retinopathy Study chart, lesion size of 6 disc areas or less, history of visual symptoms of 6 months or less, and absence of foveal hemorrhage were recruited.

INTERVENTION

In the treatment group, external beam irradiation with 8 fractions of 2 Gy was performed, whereas in the control group, sham treatment with 8 fractions of 0 Gy was applied.

MAIN OUTCOME MEASURES

Primary outcome measure was the difference in visual acuity between baseline and after 1 year of follow-up.

RESULTS

One hundred eighty-three patients (89.3%) completed the 1-year follow-up. The mean reduction in visual acuity was 3.5 +/- 4.7 lines in 88 patients of the 8- x 2-Gy treatment group and 3.7 +/- 3.8 lines in 95 patients of the 8- x 0-Gy control group. This difference was not statistically significant (P = 0.53, Mann-Whitney U test). At 1 year, 51.1% of treated patients and 52.6% of control subjects lost three or more lines (P = 0.88). Visual acuity in the presence of classic CNV dropped by 3.7 +/- 4.4 lines in 33 patients of the treatment group versus 4.3 +/- 3.9 lines in 36 patients of the control group (P = 0.47). Visual acuity in 114 patients with occult CNV dropped by 3.4 +/- 4.9 in the treatment group (55 patients) versus 3.4 +/- 3.8 lines in the control group (59 patients) (P = 0.80).

CONCLUSIONS

In this randomized study, radiation therapy at a dose of 16 Gy applied in 8 fractions of 2 Gy provided no benefit as a treatment for subfoveal CNV secondary to ARMD at 1 year.

External beam radiotherapy for subretinal neovascularization in age-related macular degeneration: is this treatment efficient?

PURPOSE

Control of the natural course of subretinal neovascularization (SRNV) in age-related macular degeneration (AMD) is difficult. Only a subset of patients is suitable for laser coagulation. This prospective study aimed to determine the efficacy and individual benefit of external beam radiotherapy (EBRT).

METHODS AND MATERIALS

The prospective trial included 287 patients with subfoveal neovascularization due to AMD which was verified by fluorescein angiography. Patients have been treated between January 1996 and October 1997. All patients received a total dose of 16 Gy in 2-Gy daily fractions with 5-6 MeV photons based on computerized treatment planning in individual head mask fixation. This first analysis is based on 73 patients (50 women, 23 men, median age 74.3 years), with a median follow-up of 13.3 months and a minimum follow-up of 11 months.

RESULTS

All patients completed therapy and tolerability was good. First clinical control with second angiography was performed 6 weeks after irradiation, then in 3-month intervals. Eighteen patients with SRNV refusing radiotherapy served as a control group and were matched with 18 irradiated patients. After 7 months median visual acuity (VA) was 20/160 for the irradiated and 20/400 for the untreated patients. One year after radiotherapy final median VA was 20/400 in both groups.

CONCLUSION

These results suggest that 16 Gy of conventionally fractionated external beam irradiation slows down the visual loss in exudative AMD for only a few months. Patients' reading vision could not be saved for a long-term run.

Macular translocation for subfoveal choroidal neovascularization in age-related macular degeneration: a prospective study

PURPOSE

To conduct a prospective study of macular translocation in patients with subfoveal choroidal neovascularization secondary to age-related macular degeneration.

METHODS

In 10 eyes of 10 patients with subfoveal choroidal neovascularization and best-corrected visual acuity ranging from 20/50 to 20/800 (median, 20/111), the fovea was relocated by means of scleral imbrication, intentional retinal detachment with small posterior retinotomies, and partial fluid-air exchange. In two eyes, the choroidal neovascular membranes were removed at the time of macular translocation; in seven eyes they were photocoagulated in the postoperative period; and in one eye the membrane was removed during reoperation to unfold a macular fold.

RESULTS

All 10 eyes were followed up for 6 months. The median postoperative foveal displacement was 1286 microm (range, 114 to 1,919 microm). In three eyes (30%), a foveal fold formed postoperatively requiring reoperation, with one of these eyes requiring a second reoperation for a rhegmatogenous retinal detachment. Best-corrected visual acuity improved in four eyes (median, 10.5 letters) and decreased in six eyes (median, 14.5 letters). The median change in visual acuity was a decrease of 5 letters. The final best-corrected visual acuity was 20/80 in two eyes, 20/126 in one eye, 20/160 in four eyes, 20/200 in one eye, 20/250 in one eye, and 20/640 in one eye.

CONCLUSIONS

Our initial experience with limited macular translocation suggests that this surgical technique is unpredictable. However, in patients with subfoveal choroidal neovascularization from age-related macular degeneration, it offers the potential for improving visual function and may be associated with less loss of vision than the disease itself, if allowed to progress. Further refinements in surgical indications and technique are needed to make this procedure safer, more predictable, and more beneficial.

Long term results of radiotherapy for subfoveal choroidal neovascularisation in age related macular degeneration

BACKGROUND/AIMS

Radiotherapy has been proposed as an alternative treatment for patients with subfoveal choroidal neovascularisation (CNV) that is untreatable according to macular photocoagulation study guidelines. This prospective study was designed to evaluate whether radiotherapy may affect the functional and anatomical outcome in a large cohort of patients affected by subfoveal CNV, with a follow up period up to 24 months.

METHODS

212 patients (231 eyes) with newly diagnosed subfoveal CNV not amenable to laser therapy were included in this study. Two radiotherapy methods, the lateral beam technique (6 MV, 20 Gy in five fractions) and lateral arc therapy (25 MV, 16 to 20 Gy, in four or five fractions), were used. Comparisons of best corrected visual acuity (VA), fluorescein (FA) and indocyanine green (ICG) angiography, at inclusion and 6, 12, 18, and 24 months after radiotherapy were performed using univariate analysis.

RESULTS

A VA improvement of two or more lines was observed in 34% at 12 months, 31% at 18 months, and 32% of the eyes at 24 months. Paired comparisons of CNV areas in FA and ICG showed no significant change between baseline and each visit. However, 12 and 18 months after treatment, 47% of the eyes showed a decrease of 10% or more in CNV size both in ICG and FA. Radiation side effects included radiation retinopathy (eight eyes), optic neuropathy (four eyes), choroidal vasculopathy (five eyes), and branch retinal vein occlusion (three eyes).

CONCLUSION

Compared with the natural course of subfoveal CNV, the results of this prospective study suggest that radiotherapy could stabilise visual and anatomical outcome in selected cases.

Randomized trial of radiation for age-related macular degeneration

PURPOSE

To assess external beam radiation efficacy for subfoveal neovascularization associated with age-related macular degeneration.

METHODS

All patients were evaluated in the same institution. In this prospective trial, 27 eyes (27 patients) with subfoveal neovascularization associated with age-related macular degeneration were randomized to either single fraction radiation (750 centigray) or observation. Endpoints were assessed by fluorescein angiography and Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity. Examiners were masked to patient treatment status. Parametric and nonparametric statistical analyses were performed.

RESULTS

Twenty-seven patients were entered into the trial with a mean age of 76 years (range, 64 to 89) and a mean follow-up of 17 months (range, 7 to 32). The visual acuity loss was slightly less in the irradiated group, a finding of borderline significance (P < .046). There was no significant difference in fluorescein angiographic evidence of subretinal neovascular membrane change in the control group vs the irradiated group.

CONCLUSIONS

External beam radiation, at this dose and fractionation, did not appear harmful. There was slightly less visual loss in irradiated eyes. No difference in fluorescein angiographic characteristics of subfoveal neovascularization size or progression in eyes with age-related macular degeneration was noted.

Radiation therapy for age-related macular degeneration

Neovascular age-related macular degeneration is the most common cause of severe irreversible blindness in the Western world in people older than age 50. Laser photocoagulation is the only proven treatment for this disease; however, fewer than 20% of patients are eligible for this treatment because the majority of choroidal neovascularization membranes are not visible by ophthalmoscopy or angiography. In addition, many patients elect not to undergo this treatment because laser treatment of subfoveal neovascular membranes results in immediate and permanent central visual loss. Several treatments are under investigation, including external-beam radiation therapy. There are multiple publications of early trials using radiation therapy, but to date there is only one randomized published study. This article reviews these trials and summarizes the status of radiation therapy as a treatment for macular degeneration.

Radiation therapy in exudative age-related macular degeneration

It has been suggested that ionizing radiation at doses relatively safe to the optic nerve and retina exert an inhibitory and occlusive effect on the endothelial proliferation of choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD). The encouraging results of early studies in preservation or improvement of visual acuity and regression of the CNV gave rise to many clinical trials in different centers. Disparate radiation doses, dose fractions, type and rate of radiation administration have been used to determine the efficacy of radiotherapy in AMD. Conflicting treatment responses have been reported by different centers. Some studies provided evidence of beneficial treatment outcome in AMD, and others could not show any efficacy of ionizing radiation in the visual and morphological evolution of the disease. Data from the literature and our experience indicate that radiotherapy can be effective in regressing the leakage of the CNV in AMD. However, despite treatment visual deterioration continues and new CNV lesions develop. The observation of morphological progression in the disease process might be related to an unfavorable effect of radiation on the pathogenesis of AMD.

Age-related macular degeneration. Can we stem this worldwide public health crisis?

Age-related macular degeneration, the leading cause of legal blindness in people over age 60 worldwide, represents a public health crisis that deserves the attention and understanding of all physicians. The dry form of the disease is more common than the wet, but the wet form causes the most severe vision loss. Other than vision aids (e.g., glasses, magnifiers), no treatments or preventive measures are currently available for patients with dry macular degeneration, and laser photocoagulation with fluorescein angiography is the only clinically proven therapy for neovascular disease. Indocyanine green angiography is a promising new imaging tool that may improve detection of patients likely to benefit from laser therapy. Until better diagnostic and treatment options are available, early screening and patient education offer the best hope for reducing the widespread devastation caused by this disease.