Proton Beam Irradiation for Neovascular Age-Related Macular Degeneration

One-Year Efficacy and Safety of Proton-Beam Irradiation Combined with Intravitreal Conbercept for Refractory or Recurrent Polypoidal Choroidal Vasculopathy: A Pilot Study

Introduction

To investigate the efficacy and safety of proton-beam irradiation (PBI) combined with intravitreal conbercept (IVC) injection for refractory or recurrent polypoidal choroidal vasculopathy (PCV).

Methods

A prospective interventional clinical trial included 12 patients with refractory PCV (defined as persistent exudation or fluid after six consecutive injections at monthly intervals and/or photodynamic therapy) or recurrent PCV (defined as new exudative signs after six monthly injections and/or photodynamic therapy) treated between January 2019 and September 2020. Every patient underwent single PBI (14 GyE) with concomitant IVC (0.5 mg) within 1 week and further doses of IVC were administered pro re nata.

Results

By the 12-month follow-up, the subretinal fluid was completely absorbed in 9 eyes (81.8%). The angiographic regression and closure rates of the polyps were 60% (12/20) and 90% (18/20), respectively. The mean number of IVC injections was 3.1 ± 1.37. The mean BCVA improved by 20 letters (P = 0.006). The mean central macular thickness (CMT) decreased from 476.50 ± 123.63 μm to 317.70 ± 89.34 μm (P = 0.004). The areas of branching vascular networks and polyps decreased by 37.2% and 72.3%, respectively. Radiation retinopathy was observed in five eyes, but no systemic adverse events were observed.

Conclusion

PBI combined with IVC appears to promote polyp regression and closure, reduce CMT, and improve BCVA, with a favorable safety profile, after 12 months. Therefore, PBI may be a useful adjuvant therapy for patients with refractory or recurrent PCV.

Trial Registration

Proton-Beam Irradiation Combined with Intravitreal Conbercept for Refractory or Recurrent Polypoidal Choroidal Vasculopathy: Prospective Phase II Clinical Study (ChiCTR2000038987).

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.

Phase I/II randomized study of proton beam with anti-VEGF for exudative age-related macular degeneration: long-term results

BACKGROUND/OBJECTIVE

To determine if treatment of exudative age-related macular degeneration (eAMD) using proton beam therapy (PBT) combined with intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy is safe and effective long term.

SUBJECT/METHODS

Thirty eyes with newly diagnosed eAMD were enrolled in a phase I/II prospective, sham-controlled double-masked university study. Eyes were randomized 1:1:1-24 GyE, 16 GyE or sham radiation, and treated with three initial monthly intravitreal ranibizumab or bevacizumab. Subsequent anti-VEGF reinjection was based on monthly optical coherence tomography and examination for 2 years and standard of care thereafter.

RESULTS

A total of 23 eyes completed 2-year study follow-up, of which 16 maintained monthly follow-up. Mean best-correct visual acuity (BCVA) at 2 years was similar among treatment groups (p > 0.05). The 24 GyE group required fewer anti-VEGF injections when compared with the sham group at 2 years (4.67 ± 1.9 vs 9.67 ± 3.5; p = 0.017). Extended follow-up (mean 4 years) available in 22 eyes showed persistent reduced need for anti-VEGF therapy among eyes treated with 24 GyE compared with sham radiation (2.0 ± 1.6 vs 4.84 ± 2.4 per year, p = 0.008). New and increasing geographic atrophy (GA), noted in some eyes in all treatment groups, resulted in decreased mean BCVA from baseline for the 24 GyE group on extended follow-up (p = 0.009). Possible mild radiation retinopathy noted in 15% of eyes was not visually significant.

CONCLUSIONS

Initial treatment combining PBT (24 GyE) with intravitreal anti-VEGF therapy appears to decrease the need for anti-VEGF reinjection in eyes with newly diagnosed eAMD. Radiation retinopathy risk was low and does not appear visually significant. Long-term vision was limited by GA development especially in the 24 GyE group.

[Adjuvant radiotherapy during anti-VEGF in neovascular age-related macular degeneration]

Single adjuvant radiotherapy during anti-VEGF therapy could be in certain indications an alternative to the gold standard of sole intravitreal anti-VEGF drug injection in neovascular age-related macular degeneration. First clinical trials showed efficacy due to reduction of anti-VEGF injection numbers by 100 kV collimated beam radiotherapy. After consideration and performance of adjuvant radiotherapy, results of the course should be centrally registered in order to carry out further analysis.

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.

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.

Current knowledge and trends in age-related macular degeneration: today's and future treatments

PURPOSE

To address the most dynamic and current issues concerning today's treatment options and promising research efforts regarding treatment for age-related macular degeneration. This review is aimed to serve as a practical reference for more in-depth reviews on the subject.

METHODS

An online review of the database PubMed and Ovid were performed, searching for the key words age-related macular degeneration, AMD, VEGF, treatment, PDT, steroids, bevacizumab, ranibizumab, VEGF-trap, radiation, combined therapy, as well as their compound phrases. The search was limited to articles published since 1985. All returned articles were carefully screened, and their references were manually reviewed for additional relevant data. The web page www.clinicaltrials.gov was also accessed in search of relevant research trials.

RESULTS

A total of 363 articles were reviewed, including 64 additional articles extracted from the references. At the end, only 160 references were included in this review.

CONCLUSION

Treatment for age-related macular degeneration is a very dynamic research field. While current treatments are mainly aimed at blocking vascular endothelial growth factor, future treatments seek to prevent vision loss because of scarring. Promising efforts have been made to address the dry form of the disease, which has lacked effective treatment.

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.

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.

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.

Particle therapy for noncancer diseases

Radiation therapy using high-energy charged particles is generally acknowledged as a powerful new technique in cancer treatment. However, particle therapy in oncology is still controversial, specifically because it is unclear whether the putative clinical advantages justify the high additional costs. However, particle therapy can find important applications in the management of noncancer diseases, especially in radiosurgery. Extension to other diseases and targets (both cranial and extracranial) may widen the applications of the technique and decrease the cost/benefit ratio of the accelerator facilities. Future challenges in this field include the use of different particles and energies, motion management in particle body radiotherapy and extension to new targets currently treated by catheter ablation (atrial fibrillation and renal denervation) or stereotactic radiation therapy (trigeminal neuralgia, epilepsy, and macular degeneration). Particle body radiosurgery could be a future key application of accelerator-based particle therapy facilities in 10 years from today.

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.

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.

Kilovoltage stereotactic radiosurgery for age-related macular degeneration: assessment of optic nerve dose and patient effective dose

Age-related macular degeneration (AMD) is a leading cause for vision loss for people over the age of 65 in the United States and a major health problem worldwide. Research for new treatments of the wet form of the disease using kilovoltage stereotactic radiosurgery is currently underway at Oraya Therapeutics, Inc. In the present study, the authors extend their previous computational stylized model of a single treated eye [Med. Phys. 35, 5151-5160 (2008)] to include full NURBS-based reference head phantoms of the adult male and female using anatomical data from ICRP Publication 89. The treatment was subsequently modeled in MCNPX 2.5 using a 1 x 1 x 1 mm3 voxelized version of the NURBS models. These models incorporated several organs of interest including the brain, thyroid, salivary glands, cranium, mandible, and cervical vertebrae. A higher resolution eye section at 0.5 x 0.5 x 0.5 mm3 voxel resolution was extracted from the head phantoms to model smaller eye structures including the macula target, cornea, lens, vitreous humor, sclera/retina layer, and optic nerve. Due to lack of literature data on optic nerve pathways, a CT imaging study was undertaken to quantify the anatomical position of the optic nerve. The average absorbed doses to the organs of interest were below generally accepted thresholds for radiation safety. The estimated effective dose was 0.28 mSv which is comparable to diagnostic procedures such as a head radiograph and a factor of 10 lower than a head CT scan.

The effectiveness and safety of proton radiation therapy for indications of the eye : a systematic review

BACKGROUND AND PURPOSE

: Proton radiation has been used for the treatment of uveal melanoma since 1975, but few studies have been conducted to assess its efficacy and safety. This paper aims to systematically review the effects and side effects of proton therapy for any indication of the eye.

MATERIAL AND METHODS

: A range of databases were searched from inception to 2007. All studies that included at least ten patients and that assessed the efficacy or safety of proton therapy for any indication of the eye were included.

RESULTS

: The search generated 2,385 references, of which 37 met the inclusion criteria. Five controlled trials, two comparative studies and 30 case series were found, most often reporting on uveal melanoma, choroidal melanoma and age-related macular degeneration (AMD). Methodological quality of these studies was poor. Studies were characterized by large differences in radiation techniques applied within the studies, and by variation in patient characteristics within and between studies. Results for uveal melanoma and choroidal melanoma suggest favorable survival, with, however, significant rates of side effects. Results for choroidal hemangioma and AMD did not reveal beneficial effects from proton radiation.

CONCLUSION

: There is limited evidence on the effectiveness and safety of proton radiation due to the lack of well-designed and well-reported studies. There is a need to lift evidence on proton therapy to a higher level by performing dose-finding randomized controlled trials (RCTs), comparative studies of proton radiation versus standard given alternatives and prospective case studies enrolling only patients treated with up-to-date techniques, allowing extrapolation of results to similar patient groups.

Dosimetry characterization of a multibeam radiotherapy treatment for age-related macular degeneration

Age-related macular degeneration (ARMD) is a major health problem worldwide. Advanced ARMD, which ultimately leads to profound vision loss, has dry and wet forms, which account for 20% and 80% of cases involving severe vision loss, respectively. A new device and approach for radiation treatment of ARMD has been recently developed by Oraya Therapeutics, Inc. (Newark, CA). The goal of the present study is to provide a initial dosimetry characterization of the proposed radiotherapy treatment via Monte Carlo radiation transport simulation. A 3D eye model including cornea, anterior chamber, lens, orbit, fat, sclera, choroid, retina, vitreous, macula, and optic nerve was carefully designed. The eye model was imported into the MCNPX2.5 Monte Carlo code and radiation transport simulations were undertaken to obtain absorbed doses and dose volume histograms (DVH) to targeted and nontargeted structures within the eye. Three different studies were undertaken to investigate (1) available beam angles that maximized the dose to the macula target tissue, simultaneously minimizing dose to normal tissues, (2) the energy dependency of the DVH for different x-ray energies (80, 100, and 120 kVp), and (3) the optimal focal spot size among options of 0.0, 0.4, 1.0, and 5.5 mm. All results were scaled to give 8 Gy to the macula volume, which is the current treatment requirement. Eight beam treatment angles are currently under investigation. In all eight beam angles, the source-to-target distance is 13 cm, and the polar angle of entry is 300 from the geometric axis of the eye. The azimuthal angle changes in eight increments of 45 degrees in a clockwise fashion, such that an azimuthal angle of 0 degreee corresponds to the 12 o'clock position when viewing the treated eye. Based on considerations of nontarget tissue avoidance, as well as facial-anatomical restrictions on beam delivery, treatment azimuthal angles between 135 degrees and 225 degrees would be available for this treatment system (i.e., directly upward and entering the eye from below). At beam directions approaching 225 degrees and higher, some dose contribution to the optic nerve would result under the assumption that the optic nerve is tilted cranially above the geometric axis in a given patient, a feature not typically seen in past studies. A total treatment dose of 24 Gy would be delivered in three 8 Gy treatments at these selected azimuthal angles. Dose coefficients, defined as the macula radiation absorbed dose per unit air kerma in units of Gy/Gy, were 16% higher for 120 kVp x-ray beams in comparison to those at 80 kVp, thus requiring only 86% of the integrated tube current (mAs) for equivalent dose delivery. When 0.0, 0.4, and 1.0 mm focal spot sizes were used, the dose profiles in the macula are very similar and relatively uniform, whereas a 5.5 mm focal spot size produced a more nonuniform dose profile. The results of this study dem onstrate the therapeutic promise of this device and provide important information for further design and clinical implementation for radiotherapy treatments for ARMD.