TWELVE-MONTH SAFETY AND VISUAL ACUITY RESULTS FROM A FEASIBILITY STUDY OF INTRAOCULAR, EPIRETINAL RADIATION THERAPY FOR THE TREATMENT OF SUBFOVEAL CNV SECONDARY TO AMD

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.

Brachytherapy for Central Serous Chorioretinopathy

Brachytherapy is widely used for the treatment of choroidal melanoma and has recently been explored for the treatment of wet age-related macular degeneration. We propose the use of low dose radiation via episcleral brachytherapy in refractory cases of central serous chorioretinopathy (CSCR). The pathogenesis of CSCR involves dilatation and hyperpermeability of large choroidal vessels. Low dose radiation can induce intimal proliferation in large choroidal vessels and decrease their hyperpermeability. Concerns about the use of brachytherapy in CSCR include damage to the choriocapillaris or the retinal vessels. This can be addressed with the use of a specialized device through which a very precise and appropriate dose can be delivered. The dose of the radiation delivered decreases exponentially at a depth of approximately 0.5–1.5 mm from the devise–sclera interface. Considering an increased choroidal thickness in cases of CSCR, delivery of a safe dose can be assured.

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.

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.

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.

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.

[Adjuvant stereotactic low energy radiation therapy of exudative age-dependent macular degeneration (Oraya system)]

With respect to the increasing number of patients and the risk and burden for patients caused by injections, a reduction in the number and frequency of injections with vascular endothelial growth factor (VEGF) inhibitors in exudative age-related macular degeneration (ARMD) is desirable. Stereotactic low-voltage x-ray irradiation seems to be a promising approach. For this purpose the Oraya system is available and has shown positive results in initial studies. Pending presentation of phase II and III study data this adjuvant irradiation should only be used in clinical trials.

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.

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.

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).

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.

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.

Radiation maculopathy after epimacular brachytherapy for the treatment of subfoveal choroidal neovascularization secondary to age-related macular degeneration

PURPOSE

To describe a case of radiation maculopathy after a 24-Gy single-fraction epimacular brachytherapy delivered concomitantly with ranibizumab for the treatment of age-related macular degeneration.

METHODS

Case report.

RESULTS

An 82-year-old man with neovascular age-related macular degeneration was treated with epiretinal brachytherapy and 2 intraocular injections of ranibizumab with initial good response. Nineteen months after initial treatment, visual acuity decreased and the patient was diagnosed of radiation maculopathy.

CONCLUSION

Radiation-related ocular side effects such as maculopathy may become evident several years after the treatment. Thus, vascular abnormalities that may appear in the follow-up of these patients can easily be misdiagnosed as a complication of the previous choroidal neovascularization.

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.

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.