Twelve-month short-term safety and visual-acuity results from a multicentre prospective study of epiretinal strontium-90 brachytherapy with bevacizumab for the treatment of subfoveal choroidal neovascularisation secondary to age-related macular degeneration

Real-world experience of using stereotactic radiotherapy combined with anti-vascular endothelial growth factor to treat neovascular AMD

INTRODUCTION

Adjunctive treatment or longer-acting drugs are required to treat nAMD to help ease burdens for patients and hospital clinics alike. Stereotactic therapy is one such option, providing a reduction in the number of injections over time.

OBJECTIVE

To determine the clinical outcomes in a cohort of patients with nAMD receiving a combination therapy of stereotactic radiotherapy (SRT) with intravitreal anti-VEGF injections (IVI).

METHOD

A retrospective analysis of 74 patients with nAMD, who had received IVI and SRT (16 Gray maximum dose to the macula) at a large tertiary university eye hospital, between March 2018 and September 2019 was performed. The number of IVIs, visual acuity (VA), and central retinal thickness (CRT) were evaluated at 12, 24, and 36 months after patients received SRT and compared to the same time interval prior to SRT.

RESULTS

Follow-up data at 12, 24, and 36 months following and prior to SRT was available for 74, 48, and 22 patients respectively. Overall there was a significant reduction in the number of injections post-SRT. Twelve months following SRT, the median number of IVI was reduced by 1 (p < 0.05). The reduction in the median number of IVI was significantly reduced by 3 and 6 injections at 24- and 36-month follow-up respectively (p < 0.05). The CRT was significantly reduced post-SRT compared to the baseline values at all time periods. There was no statistically significant difference in VA at 12-month follow-up compared to baseline. The VA, however, significantly decreased at 24- and 36-month follow-up (p < 0.05).

CONCLUSION

A therapy combining SRT with IVI has shown an overall reduction in the number of injections required in nAMD patients at 12, 24, and 36 months following SRT compared to IVI treatment alone. These real-world outcomes are comparable to other studies while also confirming the maintenance of the reduced frequency of required IVI for patients with nAMD.

Ocular Therapeutics and Molecular Delivery Strategies for Neovascular Age-Related Macular Degeneration (nAMD)

Age-related macular degeneration (AMD) is the leading cause of vision loss in geriatric population. Intravitreal (IVT) injections are popular clinical option. Biologics and small molecules offer efficacy but relatively shorter half-life after intravitreal injections. To address these challenges, numerous technologies and therapies are under development. Most of these strategies aim to reduce the frequency of injections, thereby increasing patient compliance and reducing patient-associated burden. Unlike IVT frequent injections, molecular therapies such as cell therapy and gene therapy offer restoration ability hence gained a lot of traction. The recent approval of ocular gene therapy for inherited disease offers new hope in this direction. However, until such breakthrough therapies are available to the majority of patients, antibody therapeutics will be on the shelf, continuing to provide therapeutic benefits. The present review aims to highlight the status of pre-clinical and clinical studies of neovascular AMD treatment modalities including Anti-VEGF therapy, upcoming bispecific antibodies, small molecules, port delivery systems, photodynamic therapy, radiation therapy, gene therapy, cell therapy, and combination therapies.

Radiotherapy for neovascular age-related macular degeneration

BACKGROUND

Radiotherapy has been proposed as a treatment for new vessel growth in people with neovascular age-related macular degeneration (AMD).

OBJECTIVES

To examine the effects of radiotherapy on neovascular AMD.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS and three trials registers and checked references of included studies. We last searched the databases on 4 May 2020.  SELECTION CRITERIA: We included all randomised controlled trials in which radiotherapy was compared to another treatment, sham treatment, low dosage irradiation or no treatment in people with choroidal neovascularisation (CNV) secondary to AMD.

DATA COLLECTION AND ANALYSIS

We used standard procedures expected by Cochrane. We graded the certainty of the evidence using GRADE. We considered the following outcomes at 12 months: best-corrected visual acuity (BCVA) (loss of 3 or more lines, change in visual acuity), contrast sensitivity, new vessel growth, quality of life and adverse effects at any time point.  MAIN RESULTS: We included 18 studies (n = 2430 people, 2432 eyes) of radiation therapy with dosages ranging from 7.5 to 24 Gy. These studies mainly took place in Europe and North America but two studies were from Japan and one multicentre study included sites in South America. Three of these studies investigated brachytherapy (plaque and epimacular), the rest were studies of external beam radiotherapy (EBM) including one trial of stereotactic radiotherapy. Four studies compared radiotherapy combined with anti-vascular endothelial growth factor (anti-VEGF) with anti-VEGF alone. Eleven studies gave no radiotherapy treatment to the control group; five studies used sham irradiation; and one study used very low-dose irradiation (1 Gy). One study used a mixture of sham irradiation and no treatment. Fifteen studies were judged to be at high risk of bias in one or more domains. Radiotherapy versus no radiotherapy There may be little or no difference in loss of 3 lines of vision at 12 months in eyes treated with radiotherapy compared with no radiotherapy (risk ratio (RR) 0.82, 95% confidence interval (CI) 0.64 to 1.04, 811 eyes, 8 studies, I² = 66%, low-certainty evidence). Low-certainty evidence suggests a small benefit in change in visual acuity (mean difference (MD) -0.10 logMAR, 95% CI -0.17 to -0.03; eyes = 883; studies = 10) and average contrast sensitivity at 12 months (MD 0.15 log units, 95% CI 0.05 to 0.25; eyes = 267; studies = 2). Growth of new vessels (largely change in CNV size) was variably reported and It was not possible to produce a summary estimate of this outcome. The studies were small with imprecise estimates and there was no consistent pattern to the study results (very low-certainty evidence). Quality of life was only reported in one study of 199 people; there was no clear difference between treatment and control groups (low-certainty evidence). Low-certainty evidence was available on adverse effects from eight of 14 studies. Seven studies reported on radiation retinopathy and/or neuropathy. Five of these studies reported no radiation-associated adverse effects. One study of 88 eyes reported one case of possible radiation retinopathy. One study of 74 eyes graded retinal abnormalities in some detail and found that 72% of participants who had radiation compared with 71% of participants in the control group had retinal abnormalities resembling radiation retinopathy or choroidopathy. Four studies reported cataract surgery or progression: events were generally few with no consistent evidence of any increased occurrence in the radiation group. One study noted transient disturbance of the precorneal tear film but there was no evidence from the other two studies that reported dry eye of any increased risk with radiation therapy. None of the participants received anti-VEGF injections. Radiotherapy combined with anti-VEGF versus anti-VEGF alone People receiving radiotherapy/anti-VEGF were probably more likely to lose 3 or more lines of BCVA at 12 months compared with anti-VEGF alone (RR 2.11, 95% CI 1.40 to 3.17, 1050 eyes, 3 studies, moderate-certainty). Most of the data for this outcome come from two studies of epimacular brachytherapy (114 events) compared with 20 events from the one trial of EBM. Data on change in BCVA were heterogenous (I² = 82%). Individual study results ranged from a small difference of -0.03 logMAR in favour of radiotherapy/anti-VEGF to a difference of 0.13 logMAR in favour of anti-VEGF alone (low-certainty evidence). The effect differed depending on how the radiotherapy was delivered (test for interaction P = 0.0007). Epimacular brachytherapy was associated with worse visual outcomes (MD 0.10 logMAR, 95% CI 0.05 to 0.15, 820 eyes, 2 studies) compared with EBM (MD -0.03 logMAR, 95% CI -0.09 to 0.03, 252 eyes, 2 studies). None of the included studies reported contrast sensitivity or quality of life. Growth of new vessels (largely change in CNV size) was variably reported in three studies (803 eyes). It was not possible to produce a summary estimate and there was no consistent pattern to the study results (very low-certainty evidence). For adverse outcomes, variable results were reported in the four studies. In three studies reports of adverse events were low and no radiation-associated adverse events were reported. In one study of epimacular brachytherapy there was a higher proportion of ocular adverse events (54%) compared to the anti-VEGF alone (18%). The majority of these adverse events were cataract. Overall 5% of the treatment group had radiation device-related adverse events (17 cases); 10 of these cases were radiation retinopathy. There were differences in average number of injections given between the four studies (1072 eyes). In three of the four studies, the anti-VEGF alone group on average received more injections (moderate-certainty evidence).

AUTHORS' CONCLUSIONS

The evidence is uncertain regarding the use of radiotherapy for neovascular AMD. Most studies took place before the routine use of anti-VEGF, and before the development of modern radiotherapy techniques such as stereotactic radiotherapy. Visual outcomes with epimacular brachytherapy are likely to be worse, with an increased risk of adverse events,  probably related to vitrectomy. The role of stereotactic radiotherapy combined with anti-VEGF is currently uncertain. Further research on radiotherapy for neovascular AMD may not be justified until current ongoing studies have reported their results.

Low-Energy Stereotactic Radiotherapy for Treatment of Exudative Age-Related Macular Degeneration in a Treat-and-Extend Regimen

BACKGROUND AND OBJECTIVE

To evaluate the effectiveness and safety of low-energy stereotactic radiotherapy (SRT) combined with anti-vascular endothelial growth factor (VEGF) treatment following a treat-and-extend regimen (TER) in wet age-related macular degeneration (AMD).

PATIENTS AND METHODS

Before/after SRT, the authors compared retrospective consecutive case series of 50 patients requiring frequent anti-VEGF treatment (every 4 or 6 weeks) in wet AMD, treated with a single session of SRT and TER (same manner pre/post-SRT). Outcomes were visual acuity (VA), recurrence-free interval, and central retinal thickness (CRT).

RESULTS

After SRT, CRT was reduced from baseline (407.3 μm ± 153.2 μm) to 12 months (320.2 μm ± 112.1 μm; P < .001), with statistical significance from month 2 onward. VA was stable for 12 months (64.0 letters ± 15.1 letters vs. 63.6 letters ± 16.2 letters). The mean recurrence-free interval increased from 4.24 weeks ± 0.66 weeks to 7.52 weeks ± 3.05 weeks at 12 months (P < .001). No severe side effects were observed.

CONCLUSION

Low-energy SRT, combined with anti-VEGF TER, was associated with reduced injection frequency and preserved VA during 12 months of follow-up. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:86-93.].

Phase I/II Randomized Study of Proton Beam with Anti-Vascular Endothelial Growth Factor for Exudative Age-Related Macular Degeneration: One-Year Results

OBJECTIVE

To assess the safety and efficacy of proton beam therapy (PBT) as an adjunct to intravitreal anti-vascular endothelial growth factor (VEGF) for the treatment of exudative age-related macular degeneration.

DESIGN

Phase I/II, interventional, prospective, randomized, sham-controlled double-blinded study.

PARTICIPANTS

Eyes with newly diagnosed exudative age-related macular degeneration with vision between 20/40 and 20/400 were included. Exclusion criteria included diabetes or other ocular comorbidities affecting vision.

METHODS

Eyes were randomized to receive either 16 GyE, 24 GyE, or sham PBT. All eyes had 3 monthly intravitreal anti-VEGF treatments, followed by monthly visits with treatments as needed.

MAIN OUTCOME MEASURES

Mean change in best-corrected visual acuity (BCVA), mean number of anti-VEGF injections, proportion of eyes with >15 letters BCVA decrease, proportion of eyes developing radiation retinopathy or papillopathy, proportion of eyes with cataract progression, and mean changes central retinal thickness on OCT and lesion size on angiography at 1 year.

RESULTS

Of 30 enrolled eyes, 22 completed follow-up monthly for 12 months for analysis. The BCVA improved by a mean of 8 letters (0.48±0.36 logarithm of the minimum angle of resolution) overall from baseline. Overall, central retinal thickness decreased from 340±155 to 246±48 (P = 0.008) at 12 months. The mean change in BCVA and central retinal thickness was not different among the 3 study groups. The mean number of anti-VEGF injections at 12 months was 6.13 for sham irradiation arm, 5.52 in the 16 GyE arm, and 3.83 for the 24 GyE arm (P = 0.004 between sham and 24 GyE). No eye had severe visual loss, radiation retinopathy, or papillopathy.

CONCLUSIONS

No safety issue was noted associated with combining 16 GyE or 24 GyE PBT with intravitreal anti-VEGF therapy in eyes with exudative age-related macular degeneration. Overall improvements in BCVA and imaging parameters were not affected by the addition of PBT, but the number of anti-VEGF treatments needed was significantly lower with the addition of 24 GyE PBT.

Current advances in the treatment of neovascular age-related macular degeneration

INTRODUCTION

Age-related macular degeneration (AMD) is the most common cause of permanent central visual acuity loss in persons over 65 years of age in industrialized nations. Today, intravitreal vascular endothelial growth factor (VEGF) inhibitors are the mainstay of treatment worldwide. Areas covered: The following review covers the current treatments and challenges of wet AMD management. It also covers emerging therapies including radiation, latest generation anti-VEGF agents, and combination therapies. Expert opinion: Current neovascular AMD therapy is aimed at decreasing the VEGF effect at the choroidal neovascularization (CNV) complex. The most important existing challenges in the treatment of neovascular AMD are improving visual outcomes, decreasing the treatment burden, and minimizing geographic atrophy. Clinicians are using many treatment strategies to minimize intravitreal injections without sacrificing visual outcomes. Combination of anti-VEGF therapy with other previously available treatments that target a different pathophysiological mechanism may be a reasonable clinical strategy to minimize intravitreal injections. Many exciting novel drugs that target newly discovered pathways associated with CNV development and progression hold clinical promise. The results of ongoing randomized clinical trials will answer the important concerns surrounding new drugs and delivery devices: safety and visual outcomes.

Epimacular Brachytherapy for Previously Treated Neovascular Age-Related Macular Degeneration (MERLOT): A Phase 3 Randomized Controlled Trial

PURPOSE

To assess the safety and efficacy of epimacular brachytherapy (EMB) for patients with chronic, active, neovascular age-related macular degeneration (AMD).

DESIGN

Phase 3 randomized controlled trial.

PARTICIPANTS

Patients (n = 363) with neovascular AMD already receiving intravitreal ranibizumab injections.

INTERVENTION

Either pars plana vitrectomy with 24-gray EMB and ongoing pro re nata (PRN) ranibizumab (n = 224) or ongoing PRN ranibizumab monotherapy (n = 119).

MAIN OUTCOME MEASURES

The coprimary outcomes, at 12 months, were the number of PRN ranibizumab injections and Early Treatment of Diabetic Retinopathy Study (ETDRS) best-corrected visual acuity (VA). Secondary outcomes included the proportion of participants losing fewer than 15 ETDRS letters, angiographic total lesion size, choroidal neovascularization (CNV) size, and optical coherence tomography (OCT) foveal thickness. A predefined subgroup analysis tested the influence of baseline ocular characteristics on the response to EMB.

RESULTS

The mean number of PRN ranibizumab injections was 4.8 in the EMB arm and 4.1 in the ranibizumab monotherapy arm (P = 0.068). The mean VA change was -4.8 letters in the EMB arm and -0.9 letters in the ranibizumab arm (95% confidence interval of difference between groups, -6.6 to -1.8 letters). The proportion of participants losing fewer than 15 letters was 84% in the EMB arm and 92% in the ranibizumab arm (P = 0.007). In the EMB arm, the mean total lesion size increased by 1.2 mm(2) versus 0.4 mm(2) in the ranibizumab arm (P = 0.27). The CNV size decreased by 0.5 mm(2) in the EMB arm and by 1.3 mm(2) in the ranibizumab arm (P = 0.27). The OCT foveal thickness decreased by 1.0 μm in the EMB arm and by 15.7 μm in the ranibizumab arm (P = 0.43). Most subgroups favored ranibizumab monotherapy, some significantly so. One participant showed retinal vascular abnormality attributed to radiation, but otherwise safety was acceptable.

CONCLUSIONS

These results do not support the use of EMB for chronic, active, neovascular AMD. Safety is acceptable out to 12 months, but radiation retinopathy can occur later, so further follow-up is planned.

Context for Protons as Adjunctive Therapy in Neovascular Age-Related Macular Degeneration: A Review

In the last few years we have witnessed increasing availability of proton therapy in the United States and worldwide. As a result, proton therapy is considered as either a primary or adjunctive approach for numerous indications where conventional radiation therapy shows promise but is accompanied by toxicities. Age-related macular degeneration (AMD) remains the leading cause of adult blindness in industrialized nations, and third worldwide, following cataract and glaucoma. Current standard therapy is intravitreal injection of anti-vascular endothelial growth factor agents. While this treatment shows improvement and stabilization in visual acuity for 40% of patients, 60% still experience disease progression. These injections are costly, necessitate repeated office visits, and carry the risk of endophthalmitis. The pathophysiology underlying neovascular AMD (nAMD) underscores the need to simultaneously target multiple pathways to retain useful vision. Radiation can be antiangiogenic, anti-inflammatory, and antiproliferative. Early photon therapy clinical trials were heterogeneous, and a Cochrane review of data demonstrated usefulness in treatment of nAMD but recommended further studies. Advantages of proton therapy over photon therapy include the ability to deliver a focal dose to the target while minimizing dose to normal structures, which is enhanced by unique treatment planning software that uses fluorescein angiography to verify target location and allows conformation of dose to the irregular shape and thickness characteristic of choroidal neovascular membranes, the pathognomonic finding in nAMD. Preliminary data suggest a potential role for proton therapy in the treatment of nAMD. In this article we review previous treatments for AMD, including those with both photon and proton radiation, and recommend future directions for clinical investigations to evaluate the role of proton therapy as an adjunct to antiangiogenic therapy, the current standard of care in this challenging setting.

One-year results from clinical practice of epimacular strontium-90 brachytherapy for the treatment of subfoveal choroidal neovascularization secondary to AMD

BACKGROUND AND OBJECTIVE

To evaluate clinical feasibility, safety, and efficacy of epiretinal strontium-90 brachytherapy in subfoveal choroidal neovascularization (CNV) due to age-related macular degeneration (AMD) in eyes unresponsive to repeated anti-VEGF injections.

PATIENTS AND METHODS

A retrospective, single-center study on patients treated with strontium-90 brachytherapy for CNV secondary to neovascular AMD. Patients underwent pars plana vitrectomy with a single 24 Gy dose brachytherapy. They were re-treated with anti-VEGF injections on an as-needed basis if subretinal or intraretinal fluid was detected on optical coherence tomography imaging.

RESULTS

Twenty-two patients were treated, and 20 completed 12 months of follow-up. Ten patients maintained stable vision, eight gained vision, and two lost more than three Snellen lines. The mean best corrected visual acuity change from baseline was -8 ± 5.7 letters. A mean of 5.5 ± 4.4 anti-VEGF injections were administered throughout 12 months.

CONCLUSION

Epimacular brachytherapy is feasible in clinical practice. While some patients benefit from the treatment and need significantly fewer as-needed injections, others appear not to react to irradiation treatment after 1 year of follow-up. Larger numbers of patients are needed to evaluate therapeutic efficacy and to determine which patients can benefit from combined radiation and anti-VEGF therapy.

Macular epiretinal brachytherapy in treated age-related macular degeneration (MERITAGE): month 24 safety and efficacy results

PURPOSE

To evaluate the safety and efficacy of epimacular brachytherapy for the treatment of chronic, active neovascular age-related macular degeneration.

METHODS

A prospective, multicenter, interventional noncontrolled clinical trial recruited 53 participants with previously treated neovascular age-related macular degeneration. Participants underwent pars plana vitrectomy with a single 24 Gray dose of epimacular brachytherapy, delivered using an intraocular cannula containing a Strontium 90/Yttrium 90 source that was positioned over the active lesion. Participants were retreated with ranibizumab, administered monthly as needed, using predefined retreatment criteria. Coprimary outcomes at 24 months were the proportion of participants losing <15 Early Treatment of Diabetic Retinopathy Study letters and mean number of ranibizumab retreatments.

RESULTS

Over 24 months, 68.1% lost <15 letters with a mean of 8.7 ranibizumab retreatments. Mean change in visual acuity was -6.3 (standard deviation, 18.9) letters. There was one case of nonproliferative radiation retinopathy.

CONCLUSION

The apparent reduction in ranibizumab retreatment was less evident in Year 2 than Year 1, with the moderate reduction in visual acuity extending into the second year. Although radiation retinopathy occurred in one case, it was not vision threatening and safety remained acceptable.

Epimacular brachytherapy for wet AMD: current perspectives

Age-related macular degeneration (AMD) is considered the most common cause of blindness in the over-60 age group in developed countries. There are basically two forms of presentation: geographic (dry or atrophic) and wet (neovascular or exudative). Geographic atrophy accounts for approximately 85%–90% of ophthalmic frames and leads to a progressive degeneration of the retinal pigment epithelium and the photoreceptors. Wet AMD causes the highest percentage of central vision loss secondary to disease. This neovascular form involves an angiogenic process in which newly formed choroidal vessels invade the macular area. Today, intravitreal anti-angiogenic drugs attempt to block the angiogenic events and represent a major advance in the treatment of wet AMD. Currently, combination therapy for wet AMD includes different forms of radiation delivery. Epimacular brachytherapy (EMBT) seems to be a useful approach to be associated with current anti-vascular endothelial growth factor agents, presenting an acceptable efficacy and safety profile. However, at the present stage of research, the results of the clinical trials carried out to date are insufficient to justify extending routine use of EMBT for the treatment of wet AMD.

Current treatment limitations in age-related macular degeneration and future approaches based on cell therapy and tissue engineering

Age-related macular degeneration (AMD) is the leading cause of blindness in the Western world. With an ageing population, it is anticipated that the number of AMD cases will increase dramatically, making a solution to this debilitating disease an urgent requirement for the socioeconomic future of the European Union and worldwide. The present paper reviews the limitations of the current therapies as well as the socioeconomic impact of the AMD. There is currently no cure available for AMD, and even palliative treatments are rare. Treatment options show several side effects, are of high cost, and only treat the consequence, not the cause of the pathology. For that reason, many options involving cell therapy mainly based on retinal and iris pigment epithelium cells as well as stem cells are being tested. Moreover, tissue engineering strategies to design and manufacture scaffolds to mimic Bruch's membrane are very diverse and under investigation. Both alternative therapies are aimed to prevent and/or cure AMD and are reviewed herein.

Therapies for neovascular age-related macular degeneration: current approaches and pharmacologic agents in development

As one of the leading causes of blindness, age-related macular degeneration (AMD) has remained at the epicenter of clinical research in ophthalmology. During the past decade, focus of researchers has ranged from understanding the role of vascular endothelial growth factor (VEGF) in the angiogenic cascades to developing new therapies for retinal vascular diseases. Anti-VEGF agents such as ranibizumab and aflibercept are becoming increasingly well-established therapies and have replaced earlier approaches such as laser photocoagulation or photodynamic therapy. Many other new therapeutic agents, which are in the early phase clinical trials, have shown promising results. The purpose of this paper is to briefly review the available treatment modalities for neovascular AMD and then focus on promising new therapies that are currently in various stages of development.

Influence of eye size and beam entry angle on dose to non-targeted tissues of the eye during stereotactic x-ray radiosurgery of AMD

Age-related macular degeneration is a leading cause of vision loss for the elderly population of industrialized nations. The IRay® Radiotherapy System, developed by Oraya® Therapeutics, Inc., is a stereotactic low-voltage irradiation system designed to treat the wet form of the disease. The IRay System uses three robotically positioned 100 kVp collimated photon beams to deliver an absorbed dose of up to 24 Gy to the macula. The present study uses the Monte Carlo radiation transport code MCNPX to assess absorbed dose to six non-targeted tissues within the eye-total lens, radiosensitive tissues of the lens, optic nerve, distal tip of the central retinal artery, non-targeted portion of the retina, and the ciliary body--all as a function of eye size and beam entry angle. The ocular axial length was ranged from 20 to 28 mm in 2 mm increments, with the polar entry angle of the delivery system varied from 18° to 34° in 2° increments. The resulting data showed insignificant variations in dose for all eye sizes. Slight variations in the dose to the optic nerve and the distal tip of the central retinal artery were noted as the polar beam angle changed. An increase in non-targeted retinal dose was noted as the entry angle increased, while the dose to the lens, sensitive volume of the lens, and ciliary body decreased as the treatment polar angle increased. Polar angles of 26° or greater resulted in no portion of the sensitive volume of the lens receiving an absorbed dose of 0.5 Gy or greater. All doses to non-targeted structures reported in this study were less than accepted thresholds for post-procedure complications.

Differential sensitivity of choroidal endothelial, retinal ganglion, and retinal pigment epithelial cells in vitro to proton radiation

PURPOSE

To evaluate the differential sensitivity of choroidal endothelial, retinal pigment epithelial, and retinal ganglion cells to escalating doses of proton beam radiation and to establish a safe dose range for the management of choroidal neovascularization associated with age-related macular degeneration (AMD).

DESIGN

Laboratory investigation.

METHODS

Proliferating simian choroidal endothelial cells (RF/6A), differentiated rat retinal ganglion cells (RGC-5), and serum-starved human retinal pigment epithelial cells (ARPE-19) were exposed to 2, 4, 8, and 12 cobalt gray equivalent of proton beam radiation and cell viability was quantified on day 9. Reactive oxygen species levels were analyzed.

RESULTS

Significant decline of choroidal endothelial cell viability was noted as dose escalated from 4 to 8 cobalt gray equivalent with maximum effect observed at 12 cobalt gray equivalent. RGC-5 and ARPE-19 cell count decreased to 95% and 62.7% at 8 cobalt gray equivalent, respectively. Sub-analysis between 4 and 8 cobalt gray equivalent radiation revealed significant decrease in choroidal endothelial cell viability (43.1% at 7 cobalt gray equivalent and 32.3% at 8 cobalt gray equivalent of radiation). Correspondingly, RGC-5 and ARPE-19 cells did not show decrease in cell count or viability. Reactive oxygen species levels significantly increased in radiation-treated choroidal endothelial cells (8.3%-11.9%).

CONCLUSIONS

At 6-8 cobalt gray equivalent proton beam radiation, retinal ganglion and retinal pigment epithelial cells are preserved while choroidal endothelial cells are completely inhibited. This dosage offers optimum therapeutic safety window for treatment using proton beam radiation for exudative AMD.

16 and 24 Gy low-voltage X-ray irradiation with ranibizumab therapy for neovascular age-related macular degeneration: 12-month outcomes

PURPOSE

To describe the 12-month safety and efficacy outcomes of 16 or 24 Gy radiation using low-voltage x-ray irradiation in conjunction with intravitreal ranibizumab for neovascular age-related macular degeneration (AMD).

DESIGN

Prospective, phase I, open-label, nonrandomized uncontrolled safety study.

METHODS

setting: Institutional. study population: Neovascular AMD patients. intervention: One x-ray irradiation treatment at 16 or 24 Gy was administered externally through 3 locations in the inferior pars plana. After 2 initial monthly loading doses of ranibizumab, subsequent ranibizumab was administered according to predetermined criteria. main outcome measures: Visual acuity, number of ranibizumab injections, safety and efficacy metrics at 12 months.

RESULTS

Forty-seven eyes of 47 patients were enrolled and completed 12 months of follow-up: 16 Gy (n = 28) and 24 Gy (n = 19). There was no evidence of radiation retinopathy, optic neuropathy, or cataract. The mean visual acuity improved in both groups: +8.4 ± 11.9 letters and +7.8 ± 12 letters for 16 and 24 Gy, respectively. In both groups, 100% of subjects lost <15 letters, with 76% and 79% gaining ≥0 letters in the 16 Gy and 24 Gy groups, respectively. Patients received a mean of 1.0 additional injection over 12 months. The mean change in optical coherence tomography central subfield thickness from baseline to month 12 was -107 and -87 μm for the 16 Gy and 24 Gy groups, respectively.

CONCLUSION

One treatment of 16 or 24 Gy low-voltage x-ray therapy with as-needed ranibizumab appears safe in subjects with neovascular AMD at 12 months. An overall improvement in visual acuity was observed. No radiation-related adverse effects were reported.

Preferred therapies for neovascular age-related macular degeneration

PURPOSE OF REVIEW

This report reviews the current treatment strategies and the most recent clinical trials in the treatment of neovascular age-related macular degeneration.

RECENT FINDINGS

The functional and anatomic outcomes achieved in the pivotal ranibizumab trials with monthly injections set the standard for comparison. Since then, various modified dosing regimens with the aim of lessening the treatment burden associated with monthly injections have been investigated. Additionally, level I evidence now exists for the noninferiority of bevacizumab, as compared to ranibizumab, in the treatment of neovascular age-related macular degeneration (AMD) through 1 year of follow-up. Aflibercept has emerged as a new anti- vascular endothelial growth factor (VEGF) therapy showing encouraging treatment results at 1 year. Novel treatments combined with anti-VEGF agents such as localized radiation are currently being investigated.

SUMMARY

Anti-VEGF monotherapy remains the preferred therapy for the management of neovascular AMD at the present time. Aflibercept is a new, FDA-approved, effective, anti-VEGF agent available for clinical use. Ongoing clinical trials will help determine the optimal dosing regimens for all of these agents, as well as the long-term efficacy and safety of combination therapy modalities.

Stereotactic radiotherapy for neovascular age-related macular degeneration: 52-week safety and efficacy results of the INTREPID study

PURPOSE

To determine the safety and efficacy of low-voltage, external-beam, stereotactic radiotherapy (SRT) for patients with neovascular age-related macular degeneration (nvAMD).

DESIGN

Randomized, double-masked, sham-controlled, multicenter, clinical trial.

PARTICIPANTS

Two hundred thirty patients with onset of nvAMD within 3 years who received 3 or more injections of ranibizumab or bevacizumab within the preceding year and who needed continuing ranibizumab or bevacizumab treatment.

INTERVENTIONS

Participants were randomized 2:1:2:1 to 16 Gy plus pro re nata (PRN) ranibizumab, sham 16 Gy plus PRN ranibizumab, 24 Gy plus PRN ranibizumab, or sham 24 Gy plus PRN ranibizumab, respectively.

MAIN OUTCOME MEASURES

The primary efficacy end point was the mean number of ranibizumab injections at 52 weeks. Secondary end points were change in mean best-corrected visual acuity (VA), loss of fewer than 15 Early Treatment Diabetic Retinopathy Study letters, gain of 0 or more and 15 or more letters, and change in angiographic total lesion size and choroidal neovascularization (CNV) lesion size.

RESULTS

Both the 16-Gy and 24-Gy SRT arms received significantly fewer ranibizumab treatments compared with the sham arms: mean number of treatments, 2.64 (median, 2), 2.43 (median, 2), and 3.74 (median, 3.5), respectively (P = 0.013 and P = 0.004, respectively, vs. sham). Change in mean VA was -0.28, +0.40, and -1.57 letters for the 16-Gy, 24-Gy, and sham arms, respectively. The 16-Gy, 24-Gy, and sham arms lost fewer than 15 letters in 93%, 89%, and 91% of eyes, respectively, with 53%, 57%, and 56% gaining 0 or more letters, respectively, and 4% gaining 15 letters or more in all arms. Mean total angiographic lesion area changed by -1.15 mm(2), +0.49 mm(2), and +0.75 mm(2), respectively; mean CNV lesion area decreased by 0.16 mm(2), 0.18 mm(2), and 0.10 mm(2), respectively. Optical coherence tomography central subfield thickness decreased by 85.90 μm, 70.39 μm, and 33.51 μm, respectively. The number of adverse events (AEs) and number of serious AEs (SAEs) were similar across arms. No AEs were attributed to radiation. No SAEs occurred in the study eye.

CONCLUSIONS

A single dose of SRT significantly reduces ranibizumab retreatment for patients with nvAMD, with a favorable safety profile at 1 year. Whereas chronic nvAMD typically results in loss of VA over time, SRT is associated with relatively well-preserved VA over 1 year.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Age-related macular degeneration revisited--piecing the puzzle: the LXIX Edward Jackson memorial lecture

PURPOSE

To present the current understanding of age-related macular degeneration (AMD) pathogenesis, based on clinical evidence, epidemiologic data, histopathologic examination, and genetic data; to provide an update on current and emerging therapies; and to propose an integrated model of the pathogenesis of AMD.

DESIGN

Review of published clinical and experimental studies.

METHODS

Analysis and synthesis of clinical and experimental data.

RESULTS

We are closer to a complete understanding of the pathogenesis of AMD, having progressed from clinical observations to epidemiologic observations and clinical pathologic correlation. More recently, modern genetic and genomic studies have facilitated the exploration of molecular pathways. It seems that AMD is a complex disease that results from the interaction of genetic susceptibility with aging and environmental factors. Disease progression also seems to be driven by a combination of genetic and environmental factors.

CONCLUSIONS

Therapies based on pathophysiologic features have changed the paradigm for treating neovascular AMD. With improved understanding of the underlying genetic susceptibility, we can identify targets to halt early disease and to prevent progression and vision loss.

The past, present, and future of exudative age-related macular degeneration treatment

Treatment of exudative age-related macular degeneration has been revolutionized within the last 6 years with the introduction of vascular endothelial growth factor neutralizing agents. Previously popular “destructive treatments,” such as laser photocoagulation and photodynamic treatment have either been abandoned or used as an adjunct to pharmacotherapy. Despite the increase in vision after antivascular endothelial growth factor (VEGF) agents, they require repetitive and costly intravitreal injections that also carry the inherit risks of infection, retinal tears, and detachment. Several new and more potent VEGF inhibitors are at different stages of development. The goal of evolving pharmacotherapy is to preserve the therapeutic effect while reducing or eliminating the discomfort of intravitreal drug delivery, as well as identify new therapeutic targets. Complement inhibitors, immunomodulators, integrin inhibitors are a few of the new class of drugs that are expected to be in our armamentarium soon. Current medications act to decrease leakage through abnormal subretinal choroidal vasculature and promote involution. However, these medications are only effective in treating the active stage of the choroidal neovascular membrane. Restoration of vision of a large number of patients with involuted choroidal neovascular membranes is warranted. For this purpose, tissue engineering techniques have been employed to reconstruct the subretinal anatomy. Discovery of biomarkers, pharmacogenetics, and very specific targeting holds the promise of increased potency and safety in the future.

Radiation therapy for neovascular age-related macular degeneration

In the enormity of the public health burden imposed by age-related macular degeneration (ARMD), much effort has been directed toward identifying effective and efficient treatments. Currently, anti-vascular endothelial growth factor (VEGF) injections have demonstrated considerably efficacy in treating neovascular ARMD, but patients require frequent treatment to fully benefit. Here, we review the rationale and evidence for radiation therapy of ARMD. The results of early photon external beam radiation therapy are included to provide a framework for the sequential discussion of evidence for the usage of stereotactic radiation therapy, proton therapy, and brachytherapy. The evidence suggests that these 3 modern modalities can provide a dose-dependent benefit in the treatment of ARMD. Most importantly, preliminary data suggest that all 3 can be used in conjunction with anti-VEGF therapeutics, thereby reducing the frequency of anti-VEGF injections required to maintain visual acuity.

Pilot study of the delivery of microcollimated pars plana external beam radiation in porcine eyes: 270-day analysis

Objective. To determine the dose response and toxicity threshold of micro-collimated X-rays delivered to porcine maculae by a stereotactic radiosurgical system after 270 days. Methods. Twelve eyes of six Yucatan mini-swine were randomized to receive up to 90 Gy to the retina, using an office-based trans-pars plana delivery system. To determine the safety profile of this radiation delivery, ophthalmic examination, fundus photography, fluorescein angiography (FA), and spectral domain optical coherence tomography (SD-OCT) were obtained at multiple time points up to 270 days post treatment. Results. No abnormalities were noted on external examination. Cataracts were noted in 4 of 12 eyes. Dose and time-dependent changes were noted on fundus examination, FA, ICG and SD-OCT. No significant abnormalities were seen in the control, 16 Gy or 24 Gy groups using any modality. Histopathology revealed a dose response effect with no discernable lesions in the 16 Gy group. Conclusion. The X-ray delivery system precisely targets the porcine retina in vivo with little effect on surrounding structures. No ophthalmic or intracranial adverse effects were noted at clinically relevant doses at 270 days following radiation delivery.

Combination of bevacizumab and irradiation on uveal melanoma: an in vitro and in vivo preclinical study

BACKGROUND

Radiotherapy (RT) is the standard treatment for uveal melanoma. However it can cause damage to the retina and optic nerve. This study examined the in vitro and in vivo effects of the anti-VEGF monoclonal antibody bevacizumab associated with radiotherapy (RT) on tumor growth and tumor proliferation and vasculature on OCM-1 human uveal melanoma cell line.

METHODS

The anti-proliferative effects of bevacizumab, RT and their combination were tested both in vitro (OCM-1 cells co-cultured with HUVEC cells in Transwell plates) and in vivo (OCM-1 tumor xenografts in nude mice). In addition, treatment effects in vitro on VEGF secretion, as well as treatment effects in vivo on tumor proliferation (Ki67 labelling), tumor vasculature (VEGFR2 labelling) and VEGF tumoral concentration were analyzed.

RESULTS

Bevacizumab given alone had a significant impact on tumor growth in vivo (and moderate effects in vitro). The bevacizumab-RT combination had additive effects in vitro (tumor cell proliferation) and in vivo (tumor growth), which translated into a significant decrease in Ki67 expression, VEGFR2 labelling and VEGF tumoral content.

CONCLUSIONS

The bevacizumab-RT combination could be a promising clinical option to explore for the management of human uveal melanoma, since it may allow RT dose reduction without loss of antitumor efficacy.

Macular epiretinal brachytherapy in treated age-related macular degeneration: MERITAGE study: twelve-month safety and efficacy results

PURPOSE

To evaluate the safety and efficacy of epimacular brachytherapy (EMB) for the treatment of chronic, active, neovascular age-related macular degeneration (AMD).

DESIGN

Prospective, multicenter, interventional, noncontrolled clinical trial.

PARTICIPANTS

Fifty-three eyes of 53 participants with neovascular AMD requiring frequent anti-vascular endothelial growth factor (VEGF) retreatment.

METHODS

Participants underwent pars plana vitrectomy with a single 24-Gy dose of EMB delivered using an intraocular, handheld cannula containing a strontium 90/yttrium 90 source positioned over the active lesion. Participants were retreated with ranibizumab administered monthly as needed, using predefined retreatment criteria. Optical coherence tomography (OCT) was undertaken monthly, with images assessed by an independent reading center.

MAIN OUTCOME MEASURES

Coprimary outcomes at 12 months were proportion of participants with stable vision (losing <15 Early Treatment Diabetic Retinopathy Study [ETDRS] letters) and mean number of anti-VEGF retreatments.

RESULTS

Before enrollment, participants had received an average of 12.5 anti-VEGF injections. After a single treatment with EMB, 81% maintained stable vision, with a mean of 3.49 anti-VEGF retreatments in 12 months. Mean ± standard deviation change in visual acuity was -4.0±15.1 ETDRS letters. Mean ± standard deviation OCT central retinal thickness increased by 50±179 μm. Common adverse events included conjunctival hemorrhage (n = 38), cataract (n = 16), resolving vitreous hemorrhage (n = 6), and eye pain (n = 5).

CONCLUSIONS

Epimacular brachytherapy produces stable visual acuity in most participants with previously treated, active disease. Epimacular brachytherapy may reduce the need for frequent anti-VEGF retreatment.

Three-year safety and visual acuity results of epimacular 90 strontium/90 yttrium brachytherapy with bevacizumab for the treatment of subfoveal choroidal neovascularization secondary to age-related macular degeneration

PURPOSE

To evaluate the long-term safety and visual acuity outcomes associated with epimacular strontium 90 brachytherapy combined with intravitreal bevacizumab for the treatment of subfoveal choroidal neovascularization because of age-related macular degeneration.

METHODS

Thirty-four treatment-naive patients with predominantly classic, minimally classic, and occult subfoveal choroidal neovascularization lesions participated in this prospective, 2-year, nonrandomized multicenter study. Subjects from 1 center (n = 19) were reconsented and followed-up for 3 years. Each subject received a single 24-Gy beta irradiation treatment via an intraocular delivery device and 2 planned injections of bevacizumab at treatment and 1 month later. Additional bevacizumab therapy was permitted based on prespecified retreatment criteria. Adverse events were observed, and best-corrected visual acuity was measured using Early Treatment Diabetic Retinopathy Study vision charts. Subjects were evaluated every 3 months during the first year of follow-up and every 6 months during Years 2 and 3 of follow-up.

RESULTS

All 34 subjects were followed-up for 24 months and 19 were followed-up through 36 months. With up to 24 months of follow-up, 12 of 24 phakic patients (50%) exhibited ≥ 2 grades of progression in Lens Opacification Classification System (LOCS) II lens classification; 5 eyes underwent cataract extraction before the Month 36 visit. There was 1 case of nonproliferative retinopathy identified at 36 months of follow-up that did not have an adverse effect on visual acuity, was stable at 43 months of follow-up, and was isolated to the parafoveal region. Mean best-corrected visual acuity demonstrated an average gain of +15.0 and -4.9 letters at 12 months and 24 months, respectively; the drop in mean gain at Month 24 was largely attributable to cataract formation. At 36 months (n = 19), the mean best-corrected visual acuity was +3.9, 90% (17 of 19) of eyes had lost <15 letters from baseline, 53% (10 of 19) had gained ≥ 1 letter, and 21% (4 of 19) had gained ≥ 15 letters. Through 36 months, 11 eyes required additional bevacizumab retreatment therapy and received a mean of 3.0 injections (range, 2-7 injections).

CONCLUSION

Epimacular brachytherapy shows promise as a therapeutic option for subfoveal neovascular age-related macular degeneration. The procedure was safe and well tolerated, with a reasonable risk-benefit profile that warrants further study in larger subject populations. The most common adverse event was cataract progression/formation. Surgical complications are similar to those expected from standard vitrectomy trials. This novel device is currently being evaluated in two prospective, randomized, controlled trials in treatment-naive subjects (CABERNET) and in subjects already treated with anti-vascular endothelial growth factor therapy (MERLOT).

Cost analysis comparing adjuvant epimacular brachytherapy with anti-VEGF monotherapy for the management of neovascular age-related macular degeneration

AIMS

To consider the cost implication of adopting epimacular brachytherapy (EMB) for the treatment of neovascular (wet) age-related macular degeneration (wAMD), compared with ranibizumab or bevacizumab monotherapy.

METHODS

This analysis compared the cumulative 3-year costs of anti-VEGF (vascular endothelial growth factor) monotherapy to EMB combined with anti-VEGF therapy. Two patient groups were considered: newly diagnosed (treatment-naïve) patients; and patients already receiving chronic anti-VEGF therapy.

RESULTS

In the treatment-naïve patients, the highest cumulative treatment costs were associated with ranibizumab monotherapy (£25,658), followed by bevacizumab monotherapy (£16,177), EMB with ranibizumab (£14,002), then EMB with bevacizumab (£10,289). In previously treated patients, the highest treatment costs were ranibizumab monotherapy (£18,355), followed by EMB with ranibizumab (£17,428), bevacizumab monotherapy (£16,177), then EMB with bevacizumab (£12,129).

CONCLUSION

EMB combined with anti-VEGF treatment has the potential to yield considerable cost savings, compared with anti-VEGF monotherapy. If the ongoing large studies of EMB confirm the published feasibility data, then adjuvant EMB may represent a cost-effective alternative to anti-VEGF monotherapy.

Epimacular brachytherapy for the treatment of retinal angiomatous proliferation

PURPOSE

The purpose of this study was to present a case of a retinal angiomatous proliferation (RAP) treated with epimacular brachytherapy that was refractory to continued ranibizumab therapy.

PATIENTS

An interventional case report of an 89-year-old woman with angiographically confirmed RAP had shown a poor response to 8 anti-vascular endothelial growth factor (anti-vascular endothelial growth factor) retreatment injections over a 10-month period.

METHODS

The patient underwent pars plana vitrectomy combined with beta irradiation of the RAP lesion using a Strontium-90 applicator (NeoVista). The device was positioned over the lesion to deliver 24 gray over 4.5 minutes. Early Treatment Diabetic Retinopathy Study best-corrected visual acuity with full refraction was undertaken monthly by trial-certified examiners, independent of the operating surgeon. The main outcome measures were Early Treatment Diabetic Retinopathy Study best-corrected visual acuity, central retinal thickness measured by optical coherence tomography, and the number of anti-vascular endothelial growth factor retreatments.

RESULTS

Preoperative best-corrected visual acuity was 53 letters (20/80), improving to 69 letters (20/50) at 12 months and 71 letters (20/40) at 21 months. Only one ranibizumab retreatment was required, at Month 2. Optical coherence tomography central retinal thickness reduced from 312 μm to 224 μm with a return of the normal foveal contour. There was full regression of the RAP lesion on clinical examination, with a reduction in lesion activity demonstrated by fundus fluorescein angiography.

CONCLUSION

This is the first reported case of RAP treated with epimacular brachytherapy, with encouraging results. Epimacular brachytherapy may be a new treatment option for refractory RAP lesions requiring frequent intravitreal ranibizumab, but further studies are needed.

Management of neovascular age-related macular degeneration in clinical practice: initiation, maintenance, and discontinuation of therapy

Neovascular age-related macular degeneration (AMD) is a leading cause of irreversible visual loss in elderly populations. In recent years, pharmacological inhibition of vascular endothelial growth factor (VEGF), via intravitreal injection of ranibizumab (Lucentis) or bevacizumab (Avastin), has offered the first opportunity to improve visual outcomes in patients diagnosed with this disorder. In this paper, we provide recommendations on how bevacizumab and ranibizumab may be best applied in current clinical practice, with an emphasis on their underlying pharmacology and efficacy. In addition, we review current guidelines for the initiation, maintenance, and discontinuation of anti-VEGF therapies, as well as emerging treatment strategies and future directions in the field.

Ten-year follow-up of eyes treated with stereotactic fractionated external beam radiation for neovascular age-related macular degeneration

PURPOSE

To determine the long-term effects of stereotactic fractionated external beam radiation on eyes treated for neovascular age-related macular degeneration.

METHODS

A retrospective review of all eyes treated with stereotactic fractionated external beam radiation (20-40 Gy, 2-Gy fractions) between 1997 and 2000 was performed to identify eyes with ≥ 2-year follow-up for analysis. A subset was imaged prospectively using a high-resolution Fourier-domain optical coherence tomography.

RESULTS

Among 94 eyes treated, 33 eyes (32 subjects) had ≥ 2-year follow-up information (mean follow-up, 6.2 years; range, 2-10 years). Final visual acuity ranged from 20/50 to no light perception. Final macular findings included central geographic atrophy (49%), disciform scar (30%), and active choroidal neovascular membrane (9%). Fourier-domain optical coherence tomography images of three eyes with geographic atrophy revealed photoreceptor layer loss within areas of geographic atrophy with intact retinal morphology in areas of radiation exposure outside geographic atrophy. Radiation retinopathy was suspected in 18% and confirmed by fluorescein angiography in 15%, ranging from mild to neovascular glaucoma/phthisis bulbi (2 eyes). Mean time from stereotactic fractionated external beam radiation to development of radiation retinopathy was 5.4 years (range, 1-10 years).

CONCLUSION

A moderate rate of delayed radiation retinopathy was noted in eyes with neovascular age-related macular degeneration treated with stereotactic fractionated external beam radiation. Geographic atrophy was a common finding.

16-Gy low-voltage x-ray irradiation with ranibizumab therapy for AMD: 6-month safety and functional outcomes

BACKGROUND AND OBJECTIVE

To describe the 6-month safety and preliminary efficacy outcomes of the use of 16-Gy radiation with intravitreal ranibizumab for patients with neovascular age-related macular degeneration (AMD).

PATIENTS AND METHODS

A single treatment of a non-invasive, externally delivered low-voltage 16-Gy x-ray irradiation was administered in one session through three locations in the inferior pars plana. Optical coherence tomography (OCT) and Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA) examinations were performed at 1 week, 1 month, and monthly thereafter, with quarterly fluorescein angiography (FA). After the two initial ranibizumab injections, subsequent injections were administered according to the following criteria: VA decline of 10 ETDRS letters compared with baseline, increase of 100-μm central foveal thickness on OCT compared with baseline, the development of new submacular hemorrhage, and the development of a new area of classic choroidal neovascularization on FA.

RESULTS

Twenty-six patients completed a 6-month follow-up. There was no evidence of radiation retinopathy, optic neuropathy, or cataract. The mean baseline ETDRS score was 46.6 letters (range: 5 to 80; standard deviation [SD]: 21.5). At 6 months, the corresponding ETDRS score was 55.6 letters (range: 25 to 80; SD: 18.9) and the mean change in VA was 9.5 ETDRS letters (SD: 10.3). On responder analysis, 96% lost 15 or fewer ETDRS letters, 81% gained 0 or more ETDRS letters, and 50% gained 15 or more ETDRS letters. Patients received a total of 13 ranibizumab injections following two initial injections. At 6 months, patients received an average of 0.5 additional injections following the initial two mandated injections.

CONCLUSION

A single treatment of externally applied, non-invasive 16-Gy low-voltage x-ray therapy in conjunction with ranibizumab demonstrated an overall improvement of VA in patients with neovascular AMD at 6 months with no radiation-related adverse effects.

Neovascular age-related macular degeneration: opportunities for development of first-in-class biopharmaceuticals

Age-related macular degeneration (AMD) is a condition that may cause blindness. The prevalence of the disease in the Western world is estimated at 1-2% of the population. Over the past decade, treatment of neovascular AMD has been shifting from destruction of newly formed blood vessels towards inhibitors that silence the vascular endothelial growth factor (VEGF) pathway. Such agents are often first-in-class biopharmaceuticals that benefit from the fact that they can be locally administered in an immune-privileged environment with slow clearance. These new VEGF pathway inhibitors have improved therapeutic effects over conventional treatment and have promoted the identification of novel targets for inhibition of AMD angiogenesis. This review describes the rationale behind the shift from conventional to current treatment options and discusses investigational, most notably biopharmaceutical, drugs that are in clinical trials. It also provides possible points for improvement of these treatments, specifically regarding their delivery.

Radiation therapy for neovascular age-related macular degeneration

Antivascular endothelial growth factor (anti-VEGF) therapies represent the standard of care for most patients presenting with neovascular (wet) age-related macular degeneration (neovascular AMD). Anti-VEGF drugs require repeated injections and impose a considerable burden of care, and not all patients respond. Radiation targets the proliferating cells that cause neovascular AMD, including fibroblastic, inflammatory, and endothelial cells. Two new neovascular AMD radiation treatments are being investigated: epimacular brachytherapy and stereotactic radiosurgery. Epimacular brachytherapy uses beta radiation, delivered to the lesion via a pars plana vitrectomy. Stereotactic radiosurgery uses low voltage X-rays in overlapping beams, directed onto the lesion. Feasibility data for epimacular brachytherapy show a greatly reduced need for anti-VEGF therapy, with a mean vision gain of 8.9 ETDRS letters at 12 months. Pivotal trials are underway (MERLOT, CABERNET). Preliminary stereotactic radiosurgery data suggest a mean vision gain of 8 to 10 ETDRS letters at 12 months. A large randomized sham controlled stereotactic radiosurgery feasibility study is underway (CLH002), with pivotal trials to follow. While it is too early to conclude on the safety and efficacy of epimacular brachytherapy and stereotactic radiosurgery, preliminary results are positive, and these suggest that radiation offers a more durable therapeutic effect than intraocular injections.

Assessment of targeting accuracy of a low-energy stereotactic radiosurgery treatment for age-related macular degeneration

Age-related macular degeneration (AMD), a leading cause of blindness in the United States, is a neovascular disease that may be controlled with radiation therapy. Early patient outcomes of external beam radiotherapy, however, have been mixed. Recently, a novel multimodality treatment was developed, comprising external beam radiotherapy and concomitant treatment with a vascular endothelial growth factor inhibitor. The radiotherapy arm is performed by stereotactic radiosurgery, delivering a 16 Gy dose in the macula (clinical target volume, CTV) using three external low-energy x-ray fields while adequately sparing normal tissues. The purpose of our study was to test the sensitivity of the delivery of the prescribed dose in the CTV using this technique and of the adequate sparing of normal tissues to all plausible variations in the position and gaze angle of the eye. Using Monte Carlo simulations of a 16 Gy treatment, we varied the gaze angle by ±5° in the polar and azimuthal directions, the linear displacement of the eye ±1 mm in all orthogonal directions, and observed the union of the three fields on the posterior wall of spheres concentric with the eye that had diameters between 20 and 28 mm. In all cases, the dose in the CTV fluctuated <6%, the maximum dose in the sclera was <20 Gy, the dose in the optic disc, optic nerve, lens and cornea were <0.7 Gy and the three-field junction was adequately preserved. The results of this study provide strong evidence that for plausible variations in the position of the eye during treatment, either by the setup error or intrafraction motion, the prescribed dose will be delivered to the CTV and the dose in structures at risk will be kept far below tolerance doses.

Radiotherapy for neovascular age-related macular degeneration

BACKGROUND

Radiotherapy has been proposed as a treatment to prevent new vessel growth in people with neovascular age-related macular degeneration (AMD).

OBJECTIVES

The aim of this review was to examine the effects of radiotherapy on neovascular AMD.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) in The Cochrane Library Issue 3, 2010, MEDLINE (January 1950 to March 2010), EMBASE (January 1980 to March 2010), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to March 2010), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (March 2010) and ClinicalTrials.gov (http://clinicaltrials.gov) (March 2010). There were no language or date restrictions in the search for trials. The electronic databases were last searched on 23 March 2010. We also wrote to investigators of trials included in the review to ask if they were aware of any other studies.

SELECTION CRITERIA

We included all randomised controlled trials in which radiotherapy was compared to another treatment, sham treatment, low dosage irradiation or no treatment in people with choroidal neovascularisation secondary to AMD.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the data. We combined relative risks using a random-effects model. We estimated the percentage of the variability in effect estimates that was due to heterogeneity, rather than sampling error, using I(2).

MAIN RESULTS

Thirteen trials (n=1154) investigated external beam radiotherapy with dosages ranging from 7.5 to 24 Gy; one additional trial (n=88) used plaque brachytherapy (15Gy at 1.75mm for 54 minutes/12.6 Gy at 4mm for 11 minutes). Most studies found effects (not always significant) that favoured treatment. Overall there was a small statistically significant reduction in risk of visual acuity loss in the treatment group. There was considerable inconsistency between trials and the trials were considered to be at risk of bias, in particular because of the lack of masking of treatment group. Subgroup analyses did not reveal any significant interactions, however, there were small numbers of trials in each subgroup (range three to five). There was some indication that trials with no sham irradiation in the control group reported a greater effect of treatment. The incidence of adverse events was low in all trials; there were no reported cases of radiation retinopathy, optic neuropathy or malignancy. Three trials found non-significant higher rates of cataract progression in the treatment group.

AUTHORS' CONCLUSIONS

This review currently does not provide convincing evidence that radiotherapy is an effective treatment for neovascular AMD. If further trials are to be considered to evaluate radiotherapy in AMD then adequate masking of the control group must be considered.