Ocular and systemic toxicity of intravitreal topotecan in rabbits for potential treatment of retinoblastoma

Ocular side effects of oncological therapies: Review

With the advance of cancer therapy in recent years, the knowledge of the mechanisms involved in this disease has increased, which has meant an increase in the quality of life and survival of patients with tumor pathologies previously considered incurable or refractory to treatment. The number of drugs used has increased exponentially in number, and although the implicit toxicity is lower than that of conventional antineoplastic therapy, they lead to the appearance of new associated adverse effects that the ophthalmologist must recognize and manage.

Therapy for Vitreous Seeding Caused by Retinoblastoma. A Review

Retinoblastoma is the most common primary malignant intraocular tumor in children. Seeding, specifically the dispersion of the tumor into the adjacent compartments, represents a major parameter determining the degree of retinoblastoma according to the International Classification of Retinoblastoma. In this article we focused on vitreous seeding, one of the main limiting factors in the successful "eye preservation treatment" of retinoblastoma. This article presents an overview of the history of vitreous seeding of retinoblastoma, established treatment procedures and new-research modalities. The introduction of systemic chemotherapy in the treatment of retinoblastoma at the end of the 1990s represented a significant breakthrough, which enabled the progressive abandonment of radiotherapy with its attendant side effects. However, the attained concentrations of chemotherapeutics in the vitreous space during systemic chemotherapy are not sufficient for the treatment of vitreous seeding, and the toxic effects of systemic chemotherapy are not negligible. A significant change came with the advent of chemotherapy in situ, with the targeted administration of chemotherapeutic drugs, namely intra-arterial and intravitreal injections, contributing to the definitive eradication of external radiotherapy and a reduction of systemic chemotherapy. Although vitreous seeding remains the most common reason for the failure of intra-arterial chemotherapy, this technique has significantly influenced the original treatment regimen of children with retinoblastoma. However, intravitreal chemotherapy has made the greatest contribution to increasing the probability of preservation of the eyeball and visual functions in patients with advanced findings. Novel local drug delivery modalities, gene therapy, oncolytic viruses and immunotherapy from several ongoing preclinical and clinical trials may represent promising approaches in the treatment of vitreous retinoblastoma seeding, though no clinical trials have yet been completed for routine use.

Selective Induction of Intrinsic Apoptosis in Retinoblastoma Cells by Novel Cationic Antimicrobial Dodecapeptides

Host defense peptides represent an important component of innate immunity. In this work, we report the anticancer properties of a panel of hyper-charged wholly cationic antimicrobial dodecapeptides (CAPs) containing multiple canonical forms of lysine and arginine residues. These CAPs displayed excellent bactericidal activities against a broad range of pathogenic bacteria by dissipating the cytoplasmic membrane potential. Specifically, we identified two CAPs, named HC3 and HC5, that effectively killed a significant number of retinoblastoma (WERI-Rb1) cells (p ≤ 0.01). These two CAPs caused the shrinkage of WERI-Rb1 tumor spheroids (p ≤ 0.01), induced intrinsic apoptosis in WERI-Rb1 cells via activation of caspase 9 and caspase 3, cleaved the PARP protein, and triggered off the phosphorylation of p53 and γH2A.X. Combining HC3 or HC5 with the standard chemotherapeutic drug topotecan showed synergistic anti-cancer activities. Overall, these results suggest that HC3 and HC5 can be exploited as potential therapeutic agents in retinoblastoma as monotherapy or as adjunctive therapy to enhance the effectiveness of currently used treatment modalities.

The Role of Cryotherapy in Vitreous Concentrations of Topotecan Delivered by Episcleral Hydrogel Implant

Transscleral diffusion delivery of chemotherapy is a promising way to reach the vitreal seeds of retinoblastoma, the most common intraocular malignancy in childhood. In this in vivo study, the delivery of topotecan via lens-shaped, bi-layered hydrogel implants was combined with transconjunctival cryotherapy to assess whether cryotherapy leads to higher concentrations of topotecan in the vitreous. The study included 18 New Zealand albino rabbits; nine rabbits received a topotecan-loaded implant episclerally and another nine rabbits received transconjunctival cryotherapy superotemporally 2 weeks before implant administration. Median vitreous total topotecan exposures (area under the curve, AUC) were 455 ng·h/mL for the cryotherapy group and 281 ng·h/mL for the non-cryotherapy group, and were significantly higher in the cryotherapy group, similar to maximum levels. Median plasma AUC were 50 ng·h/mL and 34 ng·h/mL for the cryotherapy and non-cryotherapy groups, respectively, with no statistically significant differences between them. In both groups, AUC values in the vitreous were significantly higher than in plasma, with plasma exposure at only approximately 11–12% of the level of vitreous exposure. The results confirmed the important role of the choroidal vessels in the pharmacokinetics of topotecan during transscleral administration and showed a positive effect of cryotherapy on intravitreal penetration, resulting in a significantly higher total exposure in the vitreous.

Ocular and systemic toxicity of high-dose intravitreal topotecan in rabbits: Implications for retinoblastoma treatment

Although many more eyes of children with retinoblastoma are salvaged now compared to just 10 years ago, the control of vitreous seeding remains a challenge. The introduction of intravitreal injection of melphalan has enabled more eyes to be salvaged safely but with definite retinal toxicity. Intensive treatment with high-dose intravitreal topotecan may be a strategy to control tumor burden because of its cell cycle-dependent cytotoxicity and the proven safety in humans. Therefore, we evaluated the ocular and systemic safety of repeated high-dose intravitreal injections of topotecan in rabbits. Systemic and ocular toxicity was assessed in non-tumor-bearing rabbits after four weekly injections of three doses of topotecan (10μg, 25μg, and 50μg) or vehicle alone. Animals were evaluated weekly for general and ophthalmic clinical status. One week after the last injection, vitreous and plasma samples were collected for drug quantification and the enucleated eyes were subjected to histological assessment. Weight, hair loss, or changes in hematologic values were absent during the study period across all animal groups. Eyes injected with all topotecan doses or vehicle showed no signs of anterior segment inflammation, clinical or histologic evidence of damage to the retina, and ERG parameters remained unaltered throughout the study. Vitreous and plasma topotecan lactone concentrations were undetectable. Four weekly intravitreal injections of topotecan up to 50μg in the animal model or a 100μg human equivalent dose were not toxic for the rabbit eye. High doses of topotecan may show promising translation to the clinic for the management of difficult-to-treat retinoblastoma vitreous seeds.

Hydrogel implants for transscleral diffusion delivery of topotecan: In vivo proof of concept in a rabbit eye model

Treatment of retinoblastoma (Rb) has greatly improved in recent years in terms of survival and eye salvage rates, using mainly intra-arterial or intravitreal chemotherapy. However, the treatment of vitreous tumor seeding still represents a challenge and it is of great interest to develop new strategies to deliver pharmacologically sufficient drug amounts to the vitreous humor. In the present work, we present a lens-shaped bi-layered hydrogel implant for delivery of topotecan (TPT) via transscleral diffusion. The implant consists of an inner TPT-loaded poly(2-hydroxyethyl methacrylate) (pHEMA) layer adjacent to the sclera and an outer covering poly(2-ethoxyethyl methacrylate) (pEOEMA) layer impermeable to TPT. TPT-loaded pHEMA samples exhibit long-lasting in vitro cytotoxicity against the Rb cell line Y79. In an in vivo experiment, pHEMA/pEOEMA implants are successfully surgically administered to the posterior segment of rabbit eyes. The determination of TPT pharmacokinetics demonstrates the attainment of promising levels of TPT (10 ng/ml) in vitreous humor 8 h after implant placement. The results from the pilot experiment constitute the proof of principle for the use of the proposed implants as a drug delivery system for the local treatment of intraocular diseases.

Evaluation of intravitreal topotecan dose levels, toxicity and efficacy for retinoblastoma vitreous seeds: a preclinical and clinical study

Background

Current melphalan-based intravitreal regimens for retinoblastoma (RB) vitreous seeds cause retinal toxicity. We assessed the efficacy and toxicity of topotecan monotherapy compared with melphalan in our rabbit model and patient cohort.

Methods

Rabbit experiments: empiric pharmacokinetics were determined following topotecan injection. For topotecan (15 μg or 30 µg), melphalan (12.5 µg) or saline, toxicity was evaluated by serial electroretinography (ERG) and histopathology, and efficacy against vitreous seed xenografts was measured by tumour cell reduction and apoptosis induction. Patients: retrospective cohort study of 235 patients receiving 990 intravitreal injections of topotecan or melphalan.

Results

Intravitreal topotecan 30 µg (equals 60 µg in humans) achieved the IC₉₀ across the rabbit vitreous. Three weekly topotecan injections (either 15 µg or 30 µg) caused no retinal toxicity in rabbits, whereas melphalan 12.5 µg (equals 25 µg in humans) reduced ERG amplitudes 42%–79%. Intravitreal topotecan 15 µg was equally effective to melphalan to treat WERI-Rb1 cell xenografts in rabbits (96% reduction for topotecan vs saline (p=0.004), 88% reduction for melphalan vs saline (p=0.004), topotecan vs melphalan, p=0.15). In our clinical study, patients received 881 monotherapy injections (48 topotecan, 833 melphalan). Patients receiving 20 µg or 30 µg topotecan demonstrated no significant ERG reductions; melphalan caused ERG reductions of 7.6 μV for every injection of 25 µg (p=0.03) or 30 µg (p<0.001). Most patients treated with intravitreal topotecan also received intravitreal melphalan at some point during their treatment course. Among those eyes treated exclusively with topotecan monotherapy, all eyes were salvaged.

Conclusions

Taken together, these experiments suggest that intravitreal topotecan monotherapy for the treatment of RB vitreous seeds is non-toxic and effective.

Conservative management of retinoblastoma: Challenging orthodoxy without compromising the state of metastatic grace. "Alive, with good vision and no comorbidity"

Retinoblastoma is lethal by metastasis if left untreated, so the primary goal of therapy is to preserve life, with ocular survival, visual preservation and quality of life as secondary aims. Historically, enucleation was the first successful therapeutic approach to decrease mortality, followed over 100 years ago by the first eye salvage attempts with radiotherapy. This led to the empiric delineation of a window for conservative management subject to a "state of metastatic grace" never to be violated. Over the last two decades, conservative management of retinoblastoma witnessed an impressive acceleration of improvements, culminating in two major paradigm shifts in therapeutic strategy. Firstly, the introduction of systemic chemotherapy and focal treatments in the late 1990s enabled radiotherapy to be progressively abandoned. Around 10 years later, the advent of chemotherapy in situ, with the capitalization of new routes of targeted drug delivery, namely intra-arterial, intravitreal and now intracameral injections, allowed significant increase in eye preservation rate, definitive eradication of radiotherapy and reduction of systemic chemotherapy. Here we intend to review the relevant knowledge susceptible to improve the conservative management of retinoblastoma in compliance with the "state of metastatic grace", with particular attention to (i) reviewing how new imaging modalities impact the frontiers of conservative management, (ii) dissecting retinoblastoma genesis, growth patterns, and intraocular routes of tumor propagation, (iii) assessing major therapeutic changes and trends, (iv) proposing a classification of relapsing retinoblastoma, (v) examining treatable/preventable disease-related or treatment-induced complications, and (vi) appraising new therapeutic targets and concepts, as well as liquid biopsy potentiality.

Protective role of melatonin on retinal ganglionar cell: In vitro an in vivo evidences

Oxidative stress triggers ocular neurodegenerative diseases, such as glaucoma or macular degeneration. The increase of reactive oxygen and nitrogen species in retinal ganglion cells (RGCs) causes damage to the structure and function of the axons that make up the optic nerve, leading to cell death arising from apoptosis, necrosis or autophagy in the RCGs. The use of antioxidants to prevent visual neurodegenerative pathologies is a novel and possibly valuable therapeutic strategy. To investigate in vitro and in vivo neuroprotective efficacy of melatonin (MEL) in RGCs, we used a model of oxidative glutamate (GLUT) toxicity in combination with l-butionin-S, R-sulfoximine (BSO), which induces cell death by apoptosis through cytotoxicity and oxidative stress mechanisms. Histological sectioning and immunohistochemical assays using the TUNEL technique were performed to determine the damage generated in affected cells and to observe the death process of RGCs. Whit BSO-GLUT the results revealed a progressive RGCs death without any significant evidence of a decreased retinal function after 9 days of treatment. In this way, we were able to develop a retinal degeneration model in vivo to carry out treatment with MEL and observed an increase in the survival percentage of RGCs, showing that BSO-GLUT could not exert an oxidant effect on cells to counteract the effect of MEL. These findings reveal that MEL has a neuroprotective and antiapoptotic effect as evidenced by the reduction of oxidative stress damage. MEL demonstrated in this model makes it a promising neuroprotective agent for the treatment of ocular neurodegenerative diseases when administered locally.

A three-dimensional organoid model recapitulates tumorigenic aspects and drug responses of advanced human retinoblastoma

Persistent or recurrent retinoblastoma (RB) is associated with the presence of vitreous or/and subretinal seeds in advanced RB and represents a major cause of therapeutic failure. This necessitates the development of novel therapies and thus requires a model of advanced RB for testing candidate therapeutics. To this aim, we established and characterized a three-dimensional, self-organizing organoid model derived from chemotherapy-naïve tumors. The responses of organoids to drugs were determined and compared to relate organoid model to advanced RB, in terms of drug sensitivities. We found that organoids had histological features resembling retinal tumors and seeds and retained DNA copy-number alterations as well as gene and protein expression of the parental tissue. Cone signal circuitry (M/L⁺ cells) and glial tumor microenvironment (GFAP⁺ cells) were primarily present in organoids. Topotecan alone or the combined drug regimen of topotecan and melphalan effectively targeted proliferative tumor cones (RXRγ⁺ Ki67⁺) in organoids after 24-h drug exposure, blocking mitotic entry. In contrast, methotrexate showed the least efficacy against tumor cells. The drug responses of organoids were consistent with those of tumor cells in advanced disease. Patient-derived organoids enable the creation of a faithful model to use in examining novel therapeutics for RB.

Intravitreal topotecan in the management of refractory and recurrent vitreous seeds in retinoblastoma

BACKGROUND/AIM

To evaluate the efficacy of intravitreal topotecan for refractory or recurrent vitreous seeds in retinoblastoma.

METHODS

Intravitreal injection of topotecan hydrochloride (30 µg/0.15 mL) was provided every 3 weeks by the safety enhanced technique.

RESULTS

The study included 17 consecutive patients with retinoblastoma with refractory or recurrent vitreous seeds. Five eyes (29%) belonged to International Classification of Retinoblastoma group C and 12 eyes (71%) belonged to group D. Primary treatment included triple drug intravenous chemotherapy for a mean of 10 cycles (median, 9 cycles; range, 6-18 cycles). Fifteen patients (88%) had undergone 56 periocular carboplatin injections with a mean of 4 injections (median, 3 injections; range, 1-8 injections), concurrent with intravenous chemotherapy. A total of 53 intravitreal topotecan injections were performed in 17 eyes of 17 consecutive patients with refractory or recurrent vitreous seeds with a mean of 3 injections (median, 3 injections; range, 2-6 injections). Complete regression of vitreous seeds was achieved in 17 of 17 eyes (100%). At a mean follow-up of 23.8 months (median, 24 months; range, 15.1-34.1 months), one eye (6%) with a recurrent retinal tumour needed enucleation, and the rest of the 16 eyes (94%) maintained complete regression. Final visual acuity could be reliably assessed in all 16 eyes (100%), of whom 12 eyes (75%) had visual acuity ≥20/200. None of the patients developed ocular or systemic complications.

CONCLUSION

Three-weekly intravitreal topotecan appears effective and safe in controlling focal or diffuse refractory or recurrent vitreous seeds in retinoblastoma.

Systematic review of the current status of programs and general knowledge of diagnosis and management of retinoblastoma

BACKGROUND

This systematic review aims to report the current knowledge of retinoblastoma (Rb) and its implications in Mexico. We analyzed clinical and demographic data of patients with Rb at select hospitals with Rb programs or that treat and refer patients with Rb, and identified the gaps in practice. We propose solutions to improve diagnosis, provide adequate treatment, and improve patient uptake.

METHODS

A general review was conducted on PubMed of peer-reviewed literature on Rb in Mexico. Ophthalmology Department Heads or Directors of Rb programs at seven hospitals in Mexico were contacted for data available on their patients with Rb.

RESULTS

Five hospitals provided clinical data on 777 patients with Rb in a period spanning 2000-2015. Of the 122 patients with treatment, 83.4% underwent enucleation. From 33 to 45.3% of Rb tumors in Mexico reach an advanced intraocular stage of development. Knowledge of the disease is limited, despite the fact that the Mexican Retinoblastoma Group has elaborated Rb treatment guidelines and is developing a national Rb registry. Especially in the Southern states, prevalence and outcomes are comparable to African and Asian countries, and only few patients are referred to national treatment centers. Only three institutions have comprehensive Rb programs.

CONCLUSIONS

There is an immediate need in Mexico to expand primary care providers' knowledge of Rb and to expand and upgrade current Rb programs to meet the needs of the population adequately. Diagnosis and care of Rb patients in Mexico can also be improved by the establishment of a national Rb registry and a national early detection program, and by increased use of the national treatment protocol.

Retinoblastoma: achieving new standards with methods of chemotherapy

The management of retinoblastoma (RB) has dramatically changed over the past two decades from previous radiotherapy methods to current chemotherapy strategies. RB is a remarkably chemotherapy-sensitive tumor. Chemotherapy is currently used as a first-line approach for children with this malignancy and can be delivered by intravenous, intra-arterial, periocular, and intravitreal routes. The choice of route for chemotherapy administration depends upon the tumor laterality and tumor staging. Intravenous chemotherapy (IVC) is used most often in bilateral cases, orbital RB, and as an adjuvant treatment in high-risk RB. Intra-arterial chemotherapy (IAC) is used in cases with group C or D RB and selected cases of group E tumor. Periocular chemotherapy is used as an adjunct treatment in eyes with group D and E RB and those with persistent/recurrent vitreous seeds. Intravitreal chemotherapy is reserved for eyes with persistent/recurrent vitreous seeds. In this review, we describe the various forms of chemotherapy used in the management of RB. A database search was performed on PubMed, using the terms “RB,” and “treatment,” “chemotherapy,” “systemic chemotherapy,” “IVC,” “IAC,” “periocular chemotherapy,” or “intravitreal chemotherapy.” Relevant English language articles were extracted, reviewed, and referenced appropriately.

The role of intravitreal chemotherapy for retinoblastoma

Targeted therapy in retinoblastoma (RB) is widely accepted as the current management tool with an aim of increasing drug availability at the tumor location. Inevitably the effect is several times higher compared to systemic delivery of chemotherapeutic drugs and carries less systemic toxicity. Despite tremendous advancement in saving life, eye salvage in advanced RB especially with active vitreous seeds remains a challenge. The hypoxic environment of the vitreous and reduced vitreous concentration of the drugs delivered makes these tumor seeds resistant to chemotherapy. Direct delivery of chemotherapeutic drugs into the vitreous cavity aids to overcome these challenges and is progressively being accepted worldwide. However, intraocular procedure in RB was abandoned due to high risk of extraocular tumor dissemination. Recently, the forbidden therapeutic technique was re-explored and modified for safe use. Although eye salvage rate has tremendously improved after intravitreal chemotherapy (IVitC), retinal toxicity, and vision salvage are yet to be validated. In our preliminary report of intravitreal melphalan in 11 eyes, we reported 100% eye salvage and 0% recurrence with an extended 15 months mean follow-up. In this review, we analyzed published reports on IVitC in RB via PubMed, Medline, and conference proceedings citation index, electronic database search, without language restriction that included case series and reports of humans and experimental animal eyes with RB receiving IVitC.

Sustained-release hydrogels of topotecan for retinoblastoma

Treatment of retinoblastoma, the most common primary ocular malignancy in children, has greatly improved over the last decade. Still, new devices for chemotherapy are needed to achieve better tumor control. The aim of this project was to develop an ocular drug delivery system for topotecan (TPT) loaded in biocompatible hydrogels of poly(ε-caprolactone)-poly(ethyleneglycol)-poly(ε-caprolactone) block copolymers (PCL-PEG-PCL) for sustained TPT release in the vitreous humor. Hydrogels were prepared from TPT and synthesized PCL-PEG-PCL copolymers. Rheological properties and in vitro and in vivo TPT release were studied. Hydrogel cytotoxicity was evaluated in retinoblastoma cells as a surrogate for efficacy and TPT vitreous pharmacokinetics and systemic as well as ocular toxicity were evaluated in rabbits. The pseudoplastic behavior of the hydrogels makes them suitable for intraocular administration. In vitro release profiles showed a sustained release of TPT from PCL-PEG-PCL up to 7days and drug loading did not affect the release pattern. Blank hydrogels did not affect retinoblastoma cell viability but 0.4% (w/w) TPT-loaded hydrogel was highly cytotoxic for at least 7days. After intravitreal injection, TPT vitreous concentrations were sustained above the pharmacologically active concentration. One month after injection, animals with blank or TPT-loaded hydrogels showed no systemic toxicity or retinal impairment on fundus examination, electroretinographic, and histopathological assessments. These novel TPT-hydrogels can deliver sustained concentrations of active drug into the vitreous with excellent biocompatibility in vivo and pronounced cytotoxic activity in retinoblastoma cells and may become an additional strategy for intraocular retinoblastoma treatment.

Targeting Survivin Enhances Chemosensitivity in Retinoblastoma Cells and Orthotopic Tumors

Treatments for retinoblastoma (Rb) vary depending on the size and location of the intraocular lesions and include chemotherapy and radiation therapy. We examined whether agents used to treat Rb induce a pro-survival phenotype associated with increased expression of survivin, a member of the inhibitor of apoptosis family of proteins. We document that exposure to carboplatin, topotecan or radiation resulted in elevated expression of survivin in two human Rb cell lines but not in normal retinal pigmented epithelial (RPE) cells. Cellular levels of survivin were attenuated in Rb cells exposed to an imidazolium-based survivin suppressant, Sepantronium bromide (YM155). Protein expression patterns of survivin in RPE cells were not altered following treatment protocols involving exposure to YM155. Including YM155 with chemotherapy or radiation increased levels of apoptosis in Rb cells but not in RPE cells. Intraocular luciferase expressing Rb tumors were generated from the Rb cell lines and used to evaluate the effects of carboplatin and YM155 on in-vivo survivin expression and tumor growth. Carboplatin induced expression of survivin while carboplatin combined with YM155 reduced survivin expression in tumor bearing eyes. The combination protocol was also most effective in reducing the rate of tumor regrowth. These results indicate that targeted inhibition of the anti-apoptotic protein survivin provides a therapeutic advantage for Rb cells and tumors treated with chemotherapy.

Intravitreal Topotecan Inhibits Laser-induced Choroidal Neovascularization in a Rat Model

Purpose:

A two-phase preclinical study was designed to determine the safe dose of intravitreal topotecan and its inhibitory effect on experimental choroidal neovascularization (CNV) in a rat model.

Methods:

In phase I, 42 rats were categorized into 6 groups, 5 of which received intravitreal topotecan injections of 0.125 μg, 0.25 μg, 0.5 μg, 0.75 μg, and 1.0 μg/5 μl, respectively; the control group received an injection of normal saline. Ophthalmic examination and electroretinography (ERG) were performed on days 7 and 28, and enucleated globes were processed for histopathology and immunostaining for glial fibrillary acidic protein. In phase II, CNV was induced via laser burns in 20 rats and the animals were divided into 2 groups. One group received topotecan and the other received normal saline intravitreally. Four weeks later, mean scores of fluorescein leakage on fluorescein angiography as well as mean CNV areas on histology sections were compared.

Results:

In phase I, clinical, ERG and histopathologic results were unremarkable in terms of retinal toxicity in all groups. Based on the results of phase I, a dose of 1 μg/5 μl topotecan was chosen for phase II. Leakage scores obtained from late-phase fluorescein angiography were significantly lower in topotecan-treated than control eyes (P < 0.01) four weeks after induction of CNV. Compared to control eyes, topotecan-treated eyes showed a significantly lower incidence of fibrovascular proliferation (8.7% vs. 96.2%) and significantly smaller areas of CNV (P < 0.01).

Conclusion:

Intravitreal injection of topotecan at a dose of 1 μg/5 μl is safe and may be a promising treatment for CNV.

Targeted retinoblastoma management: when to use intravenous, intra-arterial, periocular, and intravitreal chemotherapy

PURPOSE OF REVIEW

The management of retinoblastoma is complex and involves strategically chosen methods of enucleation, radiotherapy, chemotherapy, laser photocoagulation, thermotherapy, and cryotherapy. Chemotherapy has become the most common eye-sparing modality. There are four routes of delivery of chemotherapy for retinoblastoma, including intravenous, intra-arterial, periocular, and intravitreal techniques. The purpose of this review is to discuss the current rationale for each method and the anticipated outcomes.

RECENT FINDINGS

The diagnosis of retinoblastoma should be clinically established prior to embarking on a chemotherapy protocol. There are over 25 conditions that can closely simulate retinoblastoma in a young child. In addition, enucleation is an acceptable method for management, particularly with advanced retinoblastoma. Intravenous chemotherapy is generally used for germline mutation (bilateral, familial) retinoblastoma with excellent tumor control for groups A, B, and C and intermediate control for group D eyes. Intra-arterial chemotherapy is used as primary therapy in selected cases for nongermline mutation (unilateral) retinoblastoma with excellent control, and also used as secondary therapy for recurrent solid retinoblastoma, subretinal seeds, and vitreous seeds. Periocular chemotherapy is employed to boost local chemotherapy dose in advanced bilateral groups D and E eyes or for localized recurrences. Intravitreal chemotherapy is used for recurrent vitreous seeds from retinoblastoma. Patients at high risk for metastases should receive intravenous chemotherapy.

SUMMARY

Chemotherapy is effective for retinoblastoma and the targeted treatment route depends on the clinical features and anticipated outcomes.

Update on Ophthalmic Oncology 2013: Retinoblastoma and Uveal Melanoma

PURPOSE

The aim of this study was to discuss the clinical and translational content of the literature as well as advancement in our knowledge pertaining to retinoblastoma and uveal melanoma that were published from January to December 2013.

DESIGN

This study is a literature review.

METHODS

The search terms retinoblastoma and uveal melanoma were used in a MEDLINE literature search. Abstracts were studied, and the most relevant articles were selected for inclusion and further in-depth review.

RESULTS

In retinoblastoma, fewer eyes are lost because of the expanded use of ophthalmic artery chemosurgery and intravitreal melphalan, and the past year marks a deepening in our understanding of these modalities. Knowledge on the genetic underpinnings of uveal melanoma has broadened to include genes associated with a favorable prognosis. This is accompanied by promising results in the treatment of metastatic uveal melanoma.

CONCLUSIONS

This past year, there were important advancements in our knowledge of retinoblastoma and uveal melanoma.

Local and systemic toxicity of intravitreal melphalan for vitreous seeding in retinoblastoma: a preclinical and clinical study

PURPOSE

Intravitreal melphalan is emerging as an effective treatment for refractory vitreous seeds in retinoblastoma, but there is limited understanding regarding its toxicity. This study evaluates the retinal and systemic toxicity of intravitreal melphalan in retinoblastoma patients, with preclinical validation in a rabbit model.

DESIGN

Clinical and preclinical, prospective, cohort study.

PARTICIPANTS

In the clinical study, 16 patient eyes received 107 intravitreal injections of 30 μg melphalan given weekly, a median of 6.5 times (range, 5-8). In the animal study, 12 New Zealand/Dutch Belt pigmented rabbits were given 3 weekly injections of 15 μg of intravitreal melphalan or vehicle to the right eye.

METHODS

Electroretinogram (ERG) responses were recorded in both humans and rabbits. For the clinical study, ERG responses were recorded at baseline, immediately before each injection, and at each follow-up visit; 82 of these studies were deemed evaluable. Median follow-up time was 5.2 months (range, 1-11). Complete blood counts (CBCs) were obtained on the day of injection at 46 patient visits. In the animal study, ERG responses were obtained along with fluorescein angiography, CBCs, and melphalan plasma concentration. After humane killing, the histopathology of the eyes was evaluated.

MAIN OUTCOME MEASURES

For the clinical study, we measured peak-to-peak ERG amplitudes in response to 30-Hz photopic flicker stimulation with comparisons between ERG studies before and after intravitreal melphalan. For the animal study, we collected ERG parameters before and after intravitreal melphalan injections with histopathologic findings.

RESULTS

By linear regression analysis, over the course of weekly intravitreal injections in retinoblastoma patients, for every additional injection, the ERG amplitude decreased by approximately 5.8 μV. The ERG remained stable once the treatment course was completed. In retinoblastoma patients, there were no grade 3 or 4 hematologic events. One week after the second injection in rabbits, the a- and b-wave amplitude declined significantly in the melphalan treated eyes compared with vehicle-treated eyes (P<0.05). Histopathology revealed severely atrophic retina.

CONCLUSIONS

Weekly injections of 30 μg of melphalan can result in a decreased ERG response, which is indicative of retinal toxicity. These findings are confirmed at an equivalent dose in rabbit eyes by ERG measurements and by histopathologic evidence of severe retinal damage. Systemic toxicity with intravitreal melphalan at these doses in humans or rabbits was not detected.

Electroretinogram monitoring of dose-dependent toxicity after ophthalmic artery chemosurgery in retinoblastoma eyes: six year review

Purpose

To report electroretinogram responses of retinoblastoma children under anesthesia before and after treatment with chemotherapeutic drugs (melphalan, topotecan, carboplatin) delivery by ophthalmic artery chemosurgery (OAC).

Methods

A cohort study of 81 patients with retinoblastoma treated with OAC. All patients treated with OAC at our center through May 2012 for whom the requisite ERG data were available are included in the analysis. This study recorded the ERG 30 Hz flicker amplitude response changes from baseline, at 3 and 12 months following OAC treatment completion. Both univariate and multivariate linear regression models were evaluated, with generalized estimating equations to correct for correlations within patients. Independent numerical variables included maximum doses and cumulative doses of melphalan, topotecan and carboplatin.

Results

By univariate analysis, both melphalan and topotecan appear to be associated with changes in ERG amplitude at both 3 and 12 months; but for the most part, these changes are minimal and likely clinically insignificant. By multivariate analysis, maximum and cumulative melphalan have a modest, temporary effect on the ERG amplitude change, which is apparent at 3 months but no longer evident at 12 months after completing treatment. By multivariate analysis, topotecan and carboplatin do not appear to adversely effect the change in ERG response.

Conclusion

Melphalan has the strongest, and carboplatin the weakest association with reduction in ERG response amplitudes; but for the most part, these changes are minimal and likely clinically insignificant. These conclusions apply only over the dose ranges used here, and should be applied with caution.

Ocular side effects following intravitreal injection therapy for retinoblastoma: a systematic review

PURPOSE

To describe the ocular side effects in patients receiving intravitreal injection therapy (IViT) for retinoblastoma.

METHODS

PubMed (1946-present), Scopus (all years), Science Citation Index (1900-present) and Conference Proceedings Citation Index-Science (1990-present) electronic databases were searched to identify all published reports of therapeutic intravitreal injections for retinoblastoma in humans.

RESULTS

Ten studies with original IViT ocular side effect data were included in this systematic review. In these combined reports, a total of 1287 intravitreal injections were given to 306 eyes of 295 patients, with a mean follow-up of 74.1 months. Two hundred sixty-one (88.5%) patients received comparatively standard melphalan IViT doses (8-30 mcg). Ocular side effects occurred in 38 patients (17 significant, 21 minor). The proportion of patients experiencing potentially significant ocular side effects following standard melphalan IViT regimens was 0.031 (8/261; 95% CI 0.013 to 0.06). The side effects of these eight included iris atrophy in three, two each with chorioretinal atrophy and vitreous haemorrhage and one with retinal detachment. Of the other nine patients with significant complications, five experienced sight-threatening complications following dramatic dose escalations (four with melphalan, one with thiotepa), three experienced complications that are commonly associated with concurrent therapies given to these patients and one had a retinal detachment. Of the 61 patients receiving IViT via safety-enhancing injection techniques, all six significant side effects were either attributed to the therapeutic dose or confounded by concurrent treatments.

CONCLUSIONS

Significant ocular complications following IViT for retinoblastoma are uncommon, and this risk may be reduced further by the use of careful injection technique and standard dosing regimens. Care must be taken in the dosing of intravitreal treatments to avoid potentially irreversible vision loss.