Intraocular concentrations of chemotherapeutic agents after systemic or local administration

Update on chemotherapy modalities for retinoblastoma: Progress and challenges

Retinoblastoma stands as a paradigm of success in treating malignancies among pediatric patients. Over recent decades, the approach to managing retinoblastoma has evolved significantly, transitioning from the preservation of patients' lives to the preservation of eyes and vision while minimizing treatment-related complications. Chemotherapy, administered through diverse routes, has solidified its role as the cornerstone of retinoblastoma treatment. In addition to intravenous chemotherapy (IVC), alternative administration routes, including intraarterial (IAC), intravitreal, intracameral, and periocular delivery, have emerged as promising modalities for retinoblastoma management. Numerous studies have demonstrated outstanding outcomes, achieving nearly 100% salvage rates for eyes classified under groups A-C. However, for advanced intraocular retinoblastoma (groups D and E eyes), IAC appears to offer superior local control rates compared to IVC. Intravitreal injection of chemotherapeutic agents, when administered in a controlled and secure manner, holds promise in averting the need for enucleation and radiotherapy in advanced retinoblastoma cases presenting with vitreous seeds. The optimal chemotherapy strategy remains meticulously tailored based on numerous factors. This review provides a comprehensive update on chemotherapy across various routes, encompassing key considerations, dosages, administration methods, treatment outcomes, and potential complications. Furthermore, it explores emerging potential treatments and outlines future directions aimed at enhancing treatment outcomes.

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.

Ten-year experience with intracameral chemotherapy for aqueous seeding in retinoblastoma: long-term efficacy, safety and toxicity

AIMS

To report long-term results of intracameral chemotherapy (ICC) for aqueous seeding (AS) in retinoblastoma.

METHODS

Retrospective study including 20 patients with primary (n=4) or secondary non-iatrogenic (n=16) AS treated with ICC according to a previously described technique between 2011 and 2020 with at least 1-year follow-up.

RESULTS

AS control was initially achieved in all cases with a mean 5 injections of melphalan (n=13) or topotecan (n=7). Three eyes had an isolated AS relapse at a mean interval of 8 months after the first ICC course, which regressed with a second course of intracameral melphalan. Concomitant interciliary process seed implantation was treated with additional brachytherapy if sectorial (n=3) or proton therapy if annular (n=1). Other therapies including systemic, intra-arterial chemotherapy and/or focal treatments were given in 15 eyes to treat concomitant tumour sites. Eye preservation was achieved in 85% of the eyes (n=17/20) at a mean event-free follow-up of 45 months for aqueous disease, and 40 months for any other intraocular tumour activity. Three cases were enucleated due to refractory non-aqueous disease. All patients are alive without metastasis (mean follow-up of 48 months after first ICC). ICC-related intraocular toxicity included iris atrophy (n=5), cataract (n=4), posterior synechiae (n=2) and iris heterochromia (n=1). No patient suffered irreversible vision loss. Useful to normal vision was found in 82% of the cases (n=14/17).

CONCLUSION

ICC appears to be safe and efficient for AS without irreversible vision-threatening adverse effects. More data are needed to determine any superiority in efficiency/toxicity of topotecan versus melphalan.

Efficacy and Safety of Low-Intensity Pulsed Ultrasound-Induced Blood-Retinal Barrier Opening in Mice

Systemic drugs can treat various retinal pathologies such as retinal cancers; however, their ocular diffusion may be limited by the blood-retina barrier (BRB). Sonication corresponds to the use of ultrasound (US) to increase the permeability of cell barriers including in the BRB. The objective was to study the efficacy and safety of sonication using microbubble-assisted low-intensity pulsed US in inducing a transient opening of the BRB. The eyes of C57/BL6J mice were sonicated at different acoustic pressures (0.10 to 0.50 MPa). Efficacy analyses consisted of fluorescein angiography (FA) performed at different timepoints and the size of the leaked molecules was assessed using FITC-marked dextrans. Tolerance was assessed by fundus photographs, optical coherence tomography, immunohistochemistry, RT-qPCR, and electroretinograms. Sonication at 0.15 MPa was the most suitable pressure for transient BRB permeabilization without altering the morphology or function of the retina. It did not increase the expression of inflammation or apoptosis markers in the retina, retinal pigment epithelium, or choroid. The dextran assay suggested that drugs up to 150 kDa in size can cross the BRB. Microbubble-assisted sonication at an optimized acoustic pressure of 0.15 MPa provides a non-invasive method to transiently open the BRB, increasing the retinal diffusion of systemic drugs without inducing any noticeable side-effect.

Aqueous seeding in intraocular retinoblastoma: A review

The management of retinoblastoma is complex. With increasing treatment modalities and increasing experience with each treatment modality, the globe salvage rates have drastically improved with time. Aqueous seeding in an eye with retinoblastoma is classified as group E based on International Classification of Intraocular Retinoblastoma, and most group E eyes were enucleated a decade earlier. Newer modalities of treatment have improved the globe salvage rates in group E eyes including those with aqueous seeding. Various globe salvage treatment modalities attempted for the management of aqueous seeds include external beam radiotherapy, plaque radiotherapy, intra-arterial chemotherapy, periocular chemotherapy, intravitreal chemotherapy and intracameral chemotherapy. Of all treatment modalities, intracameral chemotherapy holds promise for the management of aqueous seeds in selected patients, but it should be done with the utmost care by a trained ocular oncologist. Enucleation is still the preferred modality of treatment for eyes with advanced retinoblastoma and anterior segment invasion. This review focuses on the current evidence on aqueous seeding, highlighting the pathogenesis, classification, clinical presentation, treatment and outcomes.

A single-arm study of systemic and sub-Tenon chemotherapy for Groups C and D intraocular retinoblastoma: A Children's Oncology Group study (ARET 0231)

BACKGROUND

Eyes with Group D intraocular retinoblastoma have low salvage rates. A pilot study showed safety and efficacy of sub-Tenon's fascia carboplatin with systemic chemotherapy supporting further study.

METHODS

Children with newly diagnosed bilateral intraocular retinoblastoma with at least one remaining Group C or D eye were treated with six courses of carboplatin/etoposide/vincristine (CEV) with sub-Tenon's fascia carboplatin for Group C/D eyes during courses 2-4. Local ophthalmic therapy started at course 3. The primary study objective was to determine the 1-year failure rate of Group D eyes.

RESULTS

The study closed prematurely due to poor accrual and 22 of 30 patients were evaluable for failure rate, contributing 25 Group D and four Group C eyes. Among the 25 Group D eyes, there were 13 failures within the first year of study enrollment including eight needing external beam radiotherapy (EBR) and five needing enucleation, resulting in 1-year failure rate of 52%. The failure rate was significantly lower than the historical rate of 70% (P = .039). The 1-year eye preservation rate for Group D eyes was 80% (20/25). One-year failure rate for Group C eyes was 25% (1/4); 1-year preservation rate was 100% without need for EBR. Systemic toxicity included Grade 3 hearing loss in two subjects, infections, neutropenia, and thrombocytopenia. Ocular toxicities included periorbital fat atrophy (13/29 = 45% eyes), optic nerve atrophy (1/29 = 3% eyes), and restrictive fibrosis (1/29 = 3% eyes).

CONCLUSIONS

Sub-Tenon's fascia carboplatin plus CEV was partially effective in Group D intraocular retinoblastoma but had unacceptable ocular toxicities.

Comparison of ocular pharmacokinetics of etoposide and its nanoemulsion after subtenon administration in rabbits

Background Subtenon anticancer drugs are given as an adjunct to systemic chemotherapy for conditions like retinoblatoma. This study evaluated the ocular kinetics of nano-emulsion formulation of etoposide (NanoEt) and compared it with an equal dose of commercially available alcohol-based etoposide formulation in healthy rabbits. Methods A nanoemulsion formulation of NanoEt was developed and then evaluated for its ocular kinetics by subtenon administration in healthy rabbits. After the sterile subtenon administration of the drug, the eyes were enucleated after CO2 euthanasia at time intervals of 2 h, 6 h, 12 h, and 24 h, and ocular tissues, blood, and plasma were separated. The concentration of etoposide in the ocular tissues and blood was quantified using liquid chromatography tandem mass spectrometry (LC MS/MS). Results This study found that subtenon injection of NanoEt showed 24 times higher concentration in rabbit retina compared to an equal dose of conventional marketed formulation. Based on the ocular tissue bioavailability calculations (AUC0-24), the present study revealed that the formulation enhanced 90% ocular bioavailability of etoposide, when it was injected in the form of nano-emulsion in most of the tissues. Conclusions NanoEt has better bioavailability compared to the commercial alcohol-based formulation for subtenon injection. Low systemic exposure showed further advantage for its projected use in retinoblastoma (Rb) as an adjunct therapy. Further studies in Rb animal models are required to evaluate its safety and efficacy, for its clinical utility.

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.

Periocular topotecan for vitreous seeds in retinoblastoma

Purpose:

Refractory or recurrent vitreous seeds account for a large proportion of failure of eye salvage in retinoblastoma. The purpose of this study is to evaluate the efficacy of periocular topotecan (POT) in the management of vitreous seeds in retinoblastoma.

Methods:

Retrospective, interventional study of patients with retinoblastoma with vitreous seeds who received POT concurrent with intravenous chemotherapy (IVC).

Results:

Thirty-eight eyes of 35 patients received POT. Five eyes (13%) belonged to International Classification of Retinoblastoma group C, 23 eyes (61%) belonged to group D, and 10 eyes (26%) belonged to group E. Primary treatment included IVC with a combination of carboplatin, etoposide, and vincristine for a mean of 6 cycles (median 6; range 6–9). Concurrent to IVC from the fourth cycle onward, all patients received POT. Focal vitreous seeds were present in 20 eyes (53%) which received a mean of 3 injections (median 3; range 1–7). Diffuse vitreous seeds were present in 18 eyes (47%) which received a mean of 4 injections (median 5; range 1–7). At a mean follow-up of 8.5 months (median 5 months; range 1–15 months), regression of focal and diffuse vitreous seeds was achieved in 16 eyes (80%) and 8 eyes (44%), respectively. In all, 24 eyes (63%) had complete remission of vitreous seeds with POT given concurrently with IVC. Eye salvage was possible in 19 eyes (95%) with focal vitreous seeds and 12 eyes (68%) with diffuse VS. Enucleation was necessary for persistent vitreous seeds and viable tumor in five eyes (13%), viable tumor alone in one eye (0.02%), and recurrent vitreous seeds in one eye (0.02%). None of the patients developed systemic metastasis.

Conclusion:

POT administered concurrent with IVC is safe and effective in the initial management of vitreous seeds.

Etoposide-Loaded Poly(Lactic-co-Glycolic Acid) Intravitreal Implants: In Vitro and In Vivo Evaluation

Etoposide-loaded poly(lactic-co-glycolic acid) implants were developed for intravitreal application. Implants were prepared by a solvent-casting method and characterized in terms of content uniformity, morphology, drug-polymer interaction, stability, and sterility. In vitro drug release was investigated and the implant degradation was monitored by the percent of mass loss. Implants were inserted into the vitreous cavity of rabbits' eye and the in vivo etoposide release profile was determined. Clinical examination and the Hen Egg Test-Chorioallantoic Membrane (HET-CAM) method were performed to evaluate the implant tolerance. The original chemical structure of the etoposide was preserved after incorporation in the polymeric matrix, which the drug was dispersed uniformly. In vitro, implants promoted sustained release of the drug and approximately 57% of the etoposide was released in 50 days. In vivo, devices released approximately 63% of the loaded drug in 42 days. Ophthalmic examination and HET-CAM assay revealed no evidence of toxic effects of implants. These results tend to show that etoposide-loaded implants could be potentially useful as an intraocular etoposide delivery system in the future.

Safety and efficacy of posterior sub-Tenon's carboplatin injection versus intravitreal melphalan therapy in the management of retinoblastoma with secondary vitreous seeds

AIM

To evaluate the safety and efficacy of posterior sub-Tenon's carboplatin injection compared to intravitreal melphalan injection in the management of retinoblastoma (RB) with secondary vitreous seeds. The outcome measures were vitreous seeds regression, need for other treatment modalities to achieve ocular salvage and treatment side effects.

METHODS

A prospective interventional comparative nonrandomized study included RB eyes developed secondary vitreous seeds during the period of follow up. They subdivided into two groups: study group I where posterior sub-Tenon's carboplatin (20 mg/2 mL) was injected and study group II where intravitreal melphalan (20 µg /0.1 mL) was injected. The injections repeated every 2-4wk.

RESULTS

Thirty-three eyes were included in the study. Seventeen eyes (16 patients) in study group I and 16 eyes (16 patients) in study group II. Ten eyes (30.3%) were completely salvaged following local chemotherapies. Ocular salvage was 23.5% following posterior sub-Tenon's carboplatin injection versus 37.5% following intravitreal melphalan raised to 47.1% and 75% with addition of external beam radiotherapy (EBR) with no statistically significant difference between the study groups (P=0.16). A statistically significant correlation was found between ocular salvage rate and type of vitreous seeds either dust, spheres and clouds (r=0.42, P=0.015) and eyes harbor new solid tumor growth (r=0.35, P=0.045). The mean and median follow up periods following local chemotherapy injections were 2.0y in the study group I and 2.37y in the study group II. Few complications were reported: periorbital edema in all eyes and ocular motility disturbances in 13 eyes (76.5%) following posterior sub-Tenon's carboplatin injection. Vitreous hemorrhage developed in 2 eyes (12.5%) and localized retinopathy in 5 eyes (31.25%) following intravitreal melphalan.

CONCLUSION

Local chemotherapy for treatment of RB with secondary vitreous seeds is safe and can salvage 30.3% of eyes without EBR. There is a superiority of intravitreal melphalan in ocular salvage however, no statistically significant difference between both groups.

Intravitreal Carboplatin Concentration and area under Concentration versus Time Curve after Intravitreal and Periocular Delivery

Purpose.

To determine platinum (Pt) concentrations and area under the concentration versus time curve (AUC) of the vitreous humor after periocular or transcorneal intravitreal administration of carboplatin in rabbits.

Methods.

Eighteen albino rabbits were included in an in vivo experiment. Each animal received a single dose of either 30 mg of carboplatin by periocular injection (POI30 group: n=6) or 15 mg by periocular injection (POI15 group: n=6), or 0.05 mg by transcorneal intravitreal injection (TII group: n=6), respectively, into the right eye. Vitreous humor from the right eyes and plasma samples were collected post dose at 1, 2, 6, 24, 48, 168, and 336 hours or 448 hours, respectively. Flameless atomic absorption spectroscopy was employed to analyze total platinum concentrations in blood and vitreous humor. AUC was calculated using the trapezoidal rule.

Results.

Pt concentration was mostly <1 mg/L (0–3.15 mg/L) in the vitreous humor samples and ≥2 mg/L (2.33–7.3 mg/L) in the blood samples 1 hour after administration in POI groups. Markedly higher Pt concentrations were found 1 hour after intravitreal (TII) administration (10.285–66.759 mg/L) and decreased below 1 mg/L no less than 168 hours after administration. The mean AUC for Pt in vitreous humor was significantly lower (p=0.0001) after both POI30 and P0I15 administration compared to TII route (8.955 ± 2.464 mg/L/min).

Conclusions.

These findings proved that intravitreal carboplatin delivery enables the achievement of relatively stable concentrations and AUC of platinum in the rabbit vitreous humor. This moreover suggests that transcorneal intravitreal delivery of carboplatin aiming to treat retinoblastoma vitreous seeding is a promising mode of chemotherapy.

Pharmaceutically inhibiting polo-like kinase 1 exerts a broad anti-tumour activity in retinoblastoma cell lines

BACKGROUND

Retinoblastoma is the most common malignant cancer of the eye in children. Although metastatic retinoblastoma is rare, cure rates for this advanced disease remain below 50%. High-level polo-like kinase 1 expression in retinoblastomas has previously been shown to be correlated with adverse outcome parameters. Polo-like kinase 1 is a serine/threonine kinase involved in cell cycle regulation at the G2/M transition. Polo-like kinase 1 inhibition has been demonstrated to have anti-tumour effects in preclinical models of several paediatric tumours. Here, we assessed its efficacy against retinoblastoma cell lines.

METHODS

Expression of polo-like kinase 1 was determined in a panel of retinoblastoma cell lines by polymerase chain reaction and western blot analysis. We analysed viability (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT assay), proliferation (5-bromo-2'-deoxyuridine enzyme-linked immunosorbent assay), cell cycle progression (propidium iodid staining) and apoptosis (cell death enzyme-linked immunosorbent assay) in three retinoblastoma cell lines after treatment with two adenosine triphosphate-competitive polo-like kinase 1 inhibitors, BI6727 or GSK461364. Activation of polo-like kinase 1 downstream signalling components including TP53 were assessed.

RESULTS

Treatment of retinoblastoma cells with either BI6727 or GSK461364 reduced cell viability and proliferative capacity and induced both cell cycle arrest and apoptosis. Polo-like kinase 1 inhibition also induced the p53 signalling pathway. Analysis of key players in cell cycle control revealed that low nanomolar concentrations of either polo-like kinase 1 inhibitor upregulated cyclin B1 and increased activated cyclin-dependent kinase 1 (phosphorylated at Y15) in retinoblastoma cell lines.

CONCLUSIONS

These preclinical data indicate that polo-like kinase 1 inhibitors could be useful as components in rationally designed chemotherapy protocols to treat patients with metastasized retinoblastoma in early phase clinical trials.

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.

Chemotherapy in Retinoblastoma: Current Approaches

Retinoblastoma (RB) is the most common childhood malignant intraocular tumor. Although enucleation and external beam radiotherapy have been historically used, today the most commonly used eye-sparing approach is chemotherapy. Chemotherapy can be used in both intraocular and extraocular RB cases. Chemotherapeutic agents may be applied in different ways, including systemic, subconjunctival, intra-arterial and intravitreal routes. The main purposes of application of systemic therapy are to reduce the tumor size for local treatment (chemoreduction), or to reduce the risk of metastasis after enucleation surgery (adjuvant therapy). Intra-arterial chemotherapy with the current name “super-selective intra-arterial infusion therapy” could be applied as primary therapy in tumors confined to the retina or as a secondary method in tumor recurrence. The most important advantage of intra-arterial therapy is the prevention of systemic chemotherapy complications. Intravitreal chemotherapy is administered in the presence of persistent or recurrent vitreous seeding. The term “extraocular RB” includes orbital invasion and metastatic disease. Current treatment for orbital invasion is neoadjuvant chemotherapy followed by surgical enucleation and adjuvant chemotherapy and radiotherapy after surgery. In metastatic disease, regional lymph node involvement, distant metastases, and/or central nervous system (CNS) involvement may occur. Among them, CNS involvement has the worst prognosis, remaining at almost 100% mortality. In metastatic disease, high-dose salvage chemotherapy and autologous hematopoietic stem cell rescue therapy are the possible treatment options; radiotherapy could also be added to the protocol according to the side of involvement.

Risk definition and management strategies in retinoblastoma: current perspectives

This manuscript focuses on high-risk factors of metastatic disease in retinoblastoma and evaluation of the current treatments of retinoblastoma. Presence of histopathologic high-risk factors is associated with a higher risk of local recurrence and systemic metastasis. Currently, globe-sparing therapies, including systemic chemotherapy, intra-arterial chemoreduction, intravitreal chemotherapy, focal consolidation, and combination therapies, are being used and investigated actively. Major advances are being made in the diagnosis and management of retinoblastoma that will lead to improved morbidity and mortality rates in patients with retinoblastoma. By saving the globes, fronting with some high-risk factors for metastasis would be inevitable. International multi-institutional prospective studies could resolve current uncertainties regarding the main tumor treatment regimens for each patient and indications for chemoprophylaxis for high-risk-factor-bearing retinoblastoma cases.

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.

In vivo intraocular distribution and safety of periocular nanoparticle carboplatin for treatment of advanced retinoblastoma in humans

PURPOSE

To study the intraocular distribution and safety of polymethylmethacrylate nanoparticles loaded with carboplatin after posterior subtenon injection in humans.

DESIGN

Prospective, interventional, comparative case series.

METHODS

Six patients (mean age: 26.83 ± 7.5 years), scheduled to undergo planned uniocular enucleation in an institutional setting, were randomly divided into 3 groups. Each group received a 10 mg/mL posterior subtenon injection of nanoparticle carboplatin in the eye to be enucleated. Two eyes were enucleated 6, 24 and 72 hours post injection. Intravenous blood was collected during enucleation. The concentration of carboplatin reaching various intraocular tissues was determined by inductively coupled plasma atomic emission spectroscopy. The drug toxicity in the ocular tissues was assessed by histopathology and high-resolution transmission electron microscopy.

RESULTS

The highest level of carboplatin was detected in retinas (8.33 ± 1.69 mg/g), up to 24 hours post treatment. The intravitreal concentration continued to increase gradually until 72 hours (3.46 ± 0.26 mg/g). The choroids and lenses showed very low levels of carboplatin after 6 hours, with negligible amounts at 72 hours. No signs of tissue damage were observed on histopathology or electron microscopy. Intravenous concentration of carboplatin was undetectable in all patients.

CONCLUSION

Results may indicate an increased facilitated trans-scleral transport of nanoparticle carboplatin, with a sustained-release behavior but without any associated short-term ocular or systemic side effects in humans. The very high concentrations achieved in vitreous and retina after a single posterior subtenon injection may be clinically useful for adjunctive treatment of advanced intraocular retinoblastoma with vitreous seeds. However, further studies are needed to assess long-term toxicity and clinical efficacy.

Carboplatin +/- topotecan ophthalmic artery chemosurgery for intraocular retinoblastoma

Purpose

Carboplatin administered systemically or periocularly can result in dramatic and prompt regression of retinoblastoma. However, both routes are rarely curative alone and have undesirable side effects. We aimed to assess the efficacy and toxicity of carboplatin +/− topotecan delivered by ophthalmic artery chemosurgery whereby chemotherapy is infused into the eye via the ophthalmic artery.

Methods

This retrospective, IRB-approved study investigated retinoblastoma patients whom received carboplatin +/− topotecan ophthalmic artery chemosurgery. Patient survival, ocular survival, hematologic toxicity, ocular toxicity, second cancer development and electroretinogram response were all evaluated.

Results

57 carboplatin +/− topotecan infusions (of 111 total) were performed in 31 eyes of 24 patients. The remaining infusions were melphalan-containing. All patients were alive and no patient developed a second malignancy at a median follow up of 25 months. The Kaplan-Meier estimate of ocular survival at two years was 89.9% (95% confidence interval [CI], 82.1–97.9%) for all eyes. Grade 3 or 4 neutropenia developed in two patients and one patient developed metastatic disease. By univariate analysis, neither increasing maximum carboplatin/topotecan dose nor cumulative carboplatin/topotecan dose was associated with statistically significant reduction in the electroretinogram responses.

Conclusion

Carboplatin +/− topotecan infusions are effective for ophthalmic artery chemosurgery in retinoblastoma: they demonstrate low hematologic and ocular toxicity and no statistically significant influence on electroretinogram responses, and used in conjunction with melphalan-containing OAC, demonstrate excellent patient survival and satisfactory ocular survival.

Retinoblastoma frontiers with intravenous, intra-arterial, periocular, and intravitreal chemotherapy

In this report, we explore retinoblastoma diagnostic accuracy and review chemotherapy alternatives for retinoblastoma using intravenous, intra-arterial, periocular, and intravitreal routes. A review of 2775 patients referred for management of retinoblastoma, disclosed 78% with confirmed retinoblastoma and 22% with simulating lesions, termed pseudoretinoblastomas. Children ≤2 years old showed leading pseudoretinoblastomas of persistent fetal vasculature, Coats disease, and vitreous haemorrhage, whereas those >5 years showed simulators of Coats, toxocariasis, and familial exudative vitreoretinopathy. The diagnosis of retinoblastoma should be established before planning therapeutic strategy. Chemotherapy strategy depends on tumour laterality and stage of disease. If bilateral retinoblastoma, intravenous chemotherapy (IVC) is important as first-line therapy for control of intraocular disease, prevention of metastasis, and reduction in prevalence of pinealoblastoma and long-term second malignant neoplasms. Bilateral groups D and E retinoblastoma receive additional subtenon's carboplatin boost for improved local control. If unilateral disease is present, then intra-arterial chemotherapy (IAC) is often considered. IAC can be salvage therapy following chemoreduction failure. Unilateral retinoblastoma of groups D and E are managed with enucleation or globe-conserving IVC and/or IAC. Intravitreal chemotherapy is cautiously reserved for recurrent vitreous seeds following other therapies. In conclusion, the strategy for retinoblastoma management with chemotherapy depends on tumour laterality and stage of disease. Bilateral retinoblastoma is most often managed with IVC and unilateral retinoblastoma with IAC, but if advanced stage, combination IVC plus IAC or enucleation.

Retinal toxicity after repeated intravitreal carboplatin injection into rabbit eyes

BACKGROUND

The aim of this study was to assess retinal toxicity in a rabbit model after carboplatin delivered as repeated transcorneal intravitreal injection, in order to determine the highest possible safe dose for use in human retinoblastoma "seeding" tumor chemotherapy.

METHODS AND RESULTS

We used six albino rabbits in an in vivo experiment and injected 0.008 mg of carboplatin intravitreally (iv) 4 times at two-week intervals. 0.08 mL saline was injected into the left eye. We recorded electroretinograms (ERGs) before the first carboplatin injection and after the fourth injection. Platinum concentration was measured 1 h after the fifth additional injection. We found reduced dark-adapted b-wave amplitudes and, light-adapted b-wave and a-wave amplitudes. The differences between right and left eyes was significant but we found no histopathologic retinal changes.

CONCLUSIONS

0.008 mg of carboplatin is probably the highest possible safe dose for the treatment of retinoblastoma patients. Questionable is direct extrapolation of retinal toxicity from the rabbit eye model to the human eye.

Ophthalmic artery chemosurgery for the management of retinoblastoma in eyes with extensive (>50%) retinal detachment

BACKGROUND

Superselective delivery of chemotherapy through the ophthalmic artery, i.e. ophthalmic artery chemosurgery, has been used for the treatment of advanced intraocular retinoblastoma. Herein, we evaluate the efficacy of ophthalmic artery chemosurgery for retinoblastoma associated with >50% retinal detachment.

PROCEDURE

Retrospective review of 37 eyes of 34 retinoblastoma patients who had extensive (>50%) bullous non-rhegmatogenous retinal detachments and received ophthalmic artery chemosurgery either as primary treatment or as "salvage" treatment after failed multi-cycle intravenous chemotherapy and/or external beam radiation (mean follow-up, 21 months). Data on patient and ocular survival, complications of ophthalmic artery chemosurgery treatments, time course of retinal reattachment, and serial electroretinograms (ERG) were collected.

RESULTS

A total of 134 ophthalmic artery chemosurgery injections were performed. All children survive. Five eyes (5/37; 14%) were enucleated for progression of disease. The Kaplan-Meier enucleation-free survival rate at 2 years was 87.9% (95% confidence interval, 76.5-99.3%). The retina reattached in 28 eyes (28/37; 76%) and the 30-Hz flicker ERGs improved by >25 µV in seven eyes (7/37; 19%), remained stable (change < 25 µV) in 26 eyes (26/37; 70%), and decreased by >25 µV in four eyes (4/37; 11%). The Kaplan-Meier retinal reattachment rate was 58% after 3 months and three ophthalmic artery chemosurgery infusions (95% confidence interval, 41.9-74.1%).

CONCLUSIONS

Ophthalmic artery chemosurgery is effective in preventing enucleation, promoting retinal reattachment and preserving or improving retinal function in the majority of eyes with advanced retinoblastoma and >50% retinal detachment that would otherwise be considered for enucleation.

Evaluation of toxicity after periocular and intravitreal administration of carboplatin in rabbit eyes

The aim of this study was to characterize the extent of toxicity of focal carboplatin administration and to identify the dose limiting toxicity in rabbit eyes depending on administered concentrations. New Zealand white male rabbits (n = 18) were treated with 1 of 3 regimens: a single periocular injection of 15 mg of carboplatin (group I), a single periocular injection of 30 mg of carboplatin (group II) and a single transcorneal intravitreal injection of 0.05 mg of carboplatin (group III). Ophthalmologic examinations and vitreous samplings were performed under dissociative anaesthesia at regular intervals during next 2 (groups I and III) or 3 (group II) weeks. Carboplatin concentrations in vitreous samples were assessed by atomic absorption spectroscopy. At the end of experiments, all rabbit eyes were obtained for histopathologic examination. Clinical and histological evidence of toxicity was graded into four grades according to anatomical structures of the rabbit eye. The dose limiting toxicity was reached in group II after periocular injection of 30 mg of carboplatin and in group III after intravitreal injection of 0.05 mg of carboplatin. No systemic toxicity was observed in any group. Focal carboplatin administration may decrease systemic exposure to this cytotoxic drug in the retinoblastoma treatment. This moreover suggests that focal carboplatin administration is a promising approach and challenge for advanced retinoblastoma chemotherapy.

Intra-arterial and oral digoxin therapy for retinoblastoma

PURPOSE

Preclinical studies demonstrate that cardiac glycosides such as ouabain and digoxin have antitumor effects on retinoblastoma cells in vitro and in a xenograft murine model of retinoblastoma.

METHODS

Based on these findings, we report a case of intra-arterial followed by systemic oral digoxin therapy in a patient with unilateral retinoblastoma that had failed prior intra-arterial chemotherapy.

RESULTS

Oral administration of digoxin produced no effect, while intra-arterial digoxin therapy produced a modest but measurable response that was likely limited by the inability to achieve sustained drug concentration in the eye.

CONCLUSIONS

This case highlights both the potential promise and limitations of cardiac glycoside therapy in retinoblastoma.

Ophthalmic vasculature alterations following systemic chemotherapy and periocular Carboplatin treatment of advanced retinoblastoma

The purpose of this study was to report significant alterations in orbital vasculature following combined systemic chemoreduction/laser ablation and periocular carboplatin treatment and to discuss treatment implications in two cases of advanced retinoblastoma. Assessment of orbital and ophthalmic vasculature was done following nine cycles of systemic chemotherapy. Intra-arterial chemotherapy was provided 6 months following completion of systemic chemoreduction, when the tumor was clearly active and progressive. Orbital angiography of both eyes, performed prior to the intra-arterial melphalan injection, documented sclerosis of the ophthalmic artery vasculature with delayed transit time, decreased choroidal blush, and anomalous vessels in the eye receiving periocular carboplatin injections. The orbital vasculature in the contralateral eye was not affected. Orbital and ophthalmic vascular alterations may occur with the use of combined systemic chemotherapy and periocular carboplatin. Systemic chemotherapy and focal transpupillary laser tumor ablation, alone, did not appear to impact the orbital and ophthalmic vascular supply. Impaired vascular supply may have significant influence on the impact of the efficacy of standard and future experimental therapeutic options.

Orbital fibrosis and intraocular recurrence of retinoblastoma following periocular carboplatin

A 5-month-old infant with bilateral advanced retinoblastoma underwent six cycles of systemic chemotherapy. In an attempt to salvage the second eye, three serial injections of periocular carboplatin were given for persistent vitreous seeding. Following the third injection, the patient developed periocular ecchymosis and magnetic resonance imaging demonstrated abnormal signal characteristics at the site of injection. An orbital biopsy did not demonstrate extraocular tumor extension, but histopathologic examination revealed severe orbital fibrosis and fat necrosis. Following the biopsy, the patient developed an intraocular tumor recurrence at the same location where the carboplatin injections had been given and enucleation was performed to prevent tumor spread. In this case, a child developed orbital scarring and intraocular tumor recurrence at the site of injection following treatment with periocular carboplatin.

Superselective ophthalmic artery chemotherapy as primary treatment for retinoblastoma (chemosurgery)

PURPOSE

To report on our 3-year experience with the use of superselective ophthalmic artery infusion of chemotherapy as initial, primary treatment for intraocular retinoblastoma.

DESIGN

Prospective, institutional review board-approved clinical trial.

PARTICIPANTS

Twenty-eight eyes of 23 newly diagnosed retinoblastoma patients (Reese-Ellsworth [RE] group V, 25 eyes; RE IV, 1 eye; RE III, 1 eye; RE II, 1 eye), ages 3-88 months (mean, 22; median, 11) followed for 3-37 months (mean, 15; median, 14).

METHODS

Cannulation of 1 or both ophthalmic arteries in young children with retinoblastoma was performed via the femoral artery under general anesthesia on an outpatient basis and chemotherapy (melphalan [n = 12], melphalan plus topotecan [n = 7], melphalan plus topotecan and carboplatin [n = 3], or melphalan plus carboplatin [n = 1]) infused.

MAIN OUTCOME MEASURES

Patient survival, eye survival, systemic toxicity, complete blood counts, ophthalmic examination, retinal photography, and electroretinograms.

RESULTS

We treated 23 newly diagnosed retinoblastoma patients initially with 75 separate intra-arterial chemotherapy infusions (range, 1-6 treatments; mean, 3.2) over a 3-year period. All children survived. Only 1 of the 28 eyes came to enucleation (for progressive disease). No eye was enucleated for ocular complications of the procedure and the only adverse ophthalmic findings were occasional transient lid edema, forehead hyperemia, and loss of nasal lashes. Kaplan-Meier enucleation free was 100% at 12 months and 89% at 2 years (95% confidence interval, 43%-98%). There were no deaths, strokes, or transfusions of any blood products; no effect on red cell count; 9 cycles of grade 3 and 1 cycle of grade 4 neutropenia; and no hospitalizations, episodes of fever/neutropenia, or complications at the site of femoral artery puncture.

CONCLUSIONS

The ophthalmic artery(s) of children can safely be repeatedly canulated in very young children and high concentrations (but low doses) of chemotherapy infused on an outpatient basis. When used as initial therapy superselective chemotherapy delivered through the ophthalmic artery prevented enucleation, primary radiation or the use of systemic chemotherapy in 27 of 28 eyes.

Lack of activity of oral etoposide for relapsed intraocular retinoblastoma

BACKGROUND

Intravenous etoposide is widely used in multiagent chemotherapy regimens for intraocular retinoblastoma despite the lack of phase II data documenting its efficacy. Because oral etoposide has been found to be highly effective in patients with relapsed medulloblastoma and neuroblastoma who had previously received intravenous etoposide, we investigated its use for intraocular retinoblastoma.

PROCEDURE

A pilot trial of oral etoposide (50 mg/m2/ day for 21 days) in five children (6 eyes) with relapsed refractory intraocular retinoblastoma was performed. All had previously received chemotherapy, including intravenous etoposide in four patients, and all had received radiation therapy. Three patients (3 eyes) had vitreous seeds. Response was evaluated after one cycle.

RESULTS

No serious acute toxicity was encountered, and no responses were noted. Four patients (5 eyes) had progressive disease. Stable disease was noted in one eye without vitreous disease. One patient developed secondary acute myeloid leukemia 30 months after exposure to oral etoposide.

CONCLUSIONS

Oral etoposide was not an effective agent in this population. The role of etoposide in the treatment of higher risk intraocular retinoblastoma deserves further study.

Localization of multidrug resistance-associated protein 2 in the nonpigmented ciliary epithelium of the eye

The nonpigmented epithelium (NPE) of the ciliary body represents an important component of the blood-aqueous barrier of the eye. Many therapeutic drugs penetrate poorly across the NPE into the aqueous humor of the eye interior. Several of these therapeutic drugs, such as methotrexate, vincristine, and etoposide, are substrates of the multidrug resistance-associated protein 2 (MRP2). Abundant MRP2 protein was detected by Western blot in homogenates of human ciliary body and freshly dissected porcine NPE. In cultured porcine NPE, the intracellular accumulation of the MRP2 substrates calcein (1.8-fold), 5-(and-6)-carboxy-2',7'-dichlorofluorescein (22.1-fold), and doxorubicin (1.9-fold) was significantly increased in the presence of 50 microM MK571 ((E)-3-[[[3-[2-(7-chloro-2-quinolinyl)-ethenyl]phenyl]-[[3-dimethylamino)-3-oxopropyl]thio]methyl]thio]-propanoic acid), an MRP inhibitor. In addition, the intracellular accumulation of the MRP2 substrate glutathione methylfluorescein was increased by 50 microM MK571 (4.3-fold), 500 microM indomethacin (2.6-fold), and 50 microM cyclosporin A (2.1-fold) but not by 500 microM sulfinpyrazone. These data are consistent with MRP2-mediated transport activity in cultured NPE, and MRP2 mRNA (reverse transcriptase-polymerase chain reaction) and protein (Western blot) were detected in the cultured cells. Immunolocalization studies in native human and porcine eyes showed MRP2 protein at the apical interface of the NPE and pigmented cell layers. Close examination of MRP2 immunoreactivity supported the conclusion that MRP2 is localized in the apical membrane of the NPE. MRP2 at the apical membrane of NPE cells may be involved in protecting intraocular tissues from exposure to potentially harmful toxins.

Fibrin sealant for retinoblastoma: where are we?

Chemoreduction is currently the most popular treatment strategy for intraocular retinoblastoma worldwide. Despite the dramatic clinical responses obtained with multiagent systemic chemotherapy regimens, enthusiasm for this treatment approach has been tempered by the potential toxicities of these drugs in the pediatric population. As a response to these concerns, novel approaches for the local delivery of chemotherapeutic agents to ocular structures have been investigated by both clinicians and scientists. Ocular oncologists have developed the periocular injection of carboplatin as a method for controlling intraocular tumor growth of retinoblastoma while minimizing systemic drug exposure. In parallel, the pharmaceutical industry has introduced drug-delivery systems to the posterior segment of the globe for a variety of ocular diseases. One example of the collaborative work by ophthalmologists and biopharmaceutical scientists is the use of fibrin sealants as a targeted drug-administration device, formulated to deliver sustained concentrations of chemotherapy at the site of application. This review integrates the recent ophthalmology and pharmaceutics literature on the potential role of fibrin sealants for periocular chemotherapy administration in the treatment of retinoblastoma.

Treatment of retinoblastoma: Current status and future perspectives

Treatment of retinoblastoma must be individualized. Most patients with unilateral, non-metastatic retinoblastoma can be cured with enucleation alone. In patients with histologic risk factors, adjuvant chemotherapy is recommended, with the addition of orbital radiation for patients with trans-scleral involvement or tumor present at the level of the cut end of the optic nerve. Patients with metastases require intensive chemotherapy and consolidation with autologous hematopoietic stem cell rescue. Patients with bilateral or multifocal disease represent a major challenge. Cure of the disease is the first priority, but the therapeutic approach also has to consider eye and vision preservation. The approach is conservative, and only eyes with very advanced disease are enucleated upfront. Patients are treated with chemotherapy and intensive focal treatments, with the aim of delaying or avoiding radiation therapy and enucleation. For patients with early intraocular stage (Reese-Ellsworth groups I-III and International Groups A-B), the two-drug combination of vincristine and carboplatin is recommended. Patients with more advanced intraocular disease (Reese-Ellsworth groups IV-V and International Groups C-D) require more intensive chemotherapy. Standard of care for these patients incorporates etoposide into the regimen. Effective agents with good intraocular penetration, such as topotecan, are being investigated. Because most failures are secondary to progression of the vitreous seeds, subconjunctival carboplatin is added in cases with poor response of the vitreous tumors. Patients must be monitored very closely, with examinations under anesthesia every 4 to 6 weeks, and focal treatments are applied during the procedure. These include cryotherapy for small anterior tumors, thermotherapy and laser photocoagulation for small posterior tumors, and brachytherapy for larger tumors. New treatment approaches under development include the refinement of periocular chemotherapy administration using slow-release devices, the use of suicide gene therapy with local delivery of the herpes simplex thyrosine kinase gene (followed by systemic administration of ganciclovir), and the development of small-molecule inhibitors of the MDMX-p53 interaction.

In vitro and in vivo evaluation of carboplatin delivery to the eye using hydrogel-iontophoresis

PURPOSE

To investigate in vitro and in vivo hydrogel-iontophoresis delivery of carboplatin to the eye.

METHODS

Iontophoresis was applied on agar gels resembling the eye using different current intensities and durations. Transscleral iontophoresis was performed on healthy rabbits, applying 0, 1, and 3 mA current for 10 min.

RESULTS

Similar drug concentrations were obtained in all experimental groups, in in vitro and in vivo studies, regardless of the iontophoretic current applied. A 20-mm penetration depth was found for carboplatin at the agar model. High drug levels were found at the sclera and retina, while lower levels were found at ocular fluids.

CONCLUSION

Carboplatin-iontophoretic application at the above conditions does not have an obvious advantage over passive penetration due to high diffusion properties and insufficient molecular charge. Passive carboplatin diffusion from loaded hydrogels inserted in the lower cul-de-sac should be further investigated as a potential clinical treatment for intraocular retinoblastoma.

A phase I/II study of direct intraarterial (ophthalmic artery) chemotherapy with melphalan for intraocular retinoblastoma initial results

OBJECTIVE

To develop a technique that would allow us to cannulate repeatedly the ophthalmic artery of young children with advanced retinoblastoma, to find a dose of melphalan that would be tolerable and tumoricidal for retinoblastoma when given intraarterially, and to study the local ocular and systemic side effects of intraarterial melphalan in these children.

DESIGN

Phase I/II clinical trial.

PARTICIPANTS

Ten children with advanced retinoblastoma (Reese-Ellsworth V) eyes who were indicated for enucleation were entered into an institutional review board-approved protocol of ophthalmic artery infusion of melphalan to avoid enucleation.

METHODS

Cannulation of the ophthalmic artery was performed by a femoral artery approach using microcatheters while the children were under anesthesia and anticoagulated. Chemotherapy (melphalan) was infused into the artery over a 30-minute period.

MAIN OUTCOME MEASURES

Ophthalmic examinations, retinal photography, and electroretinograms were used to document local toxicity, whereas physical examinations and complete blood counts were used to measure systemic toxicity.

RESULTS

The ophthalmic arteries were successfully cannulated in 9 cases (total, 27 times), as many as 6 times in 1 patient. Dramatic regression of tumors, vitreous seeds, and subretinal seeds were seen in each case. No severe systemic side effects (sepsis, anemia, neutropenia, fever, or death) occurred. No transfusions were required (red cells or platelets). Three patients developed conjunctival and lid edema that resolved without treatment. There was no toxicity to the cornea, anterior segment, pupil, or motility. One (previously irradiated) eye developed retinal ischemia; another eye had no toxicity after intraarterial chemotherapy but did develop a radiationlike retinopathy after brachytherapy. Vision stabilized or improved in all but 1 patient after treatment. Electroretinograms were generally poor (advanced eyes were treated), but in 2 cases, the electroretinogram improved after treatment (and resolution of a retinal detachment). Seven eyes avoided enucleation. Two intraarterially treated eyes were enucleated, with no viable tumors identified pathologically.

CONCLUSIONS

We developed a technique of direct ophthalmic artery infusion of melphalan for children with retinoblastoma. The technique had minimal systemic side effects (one patient had grade 3 neutropenia) and minimal local toxicity. Among the first 9 cases treated with this technique, 7 eyes destined to be enucleated were salvaged.

Current management strategies for intraocular retinoblastoma

Survival rates for retinoblastoma patients have increased dramatically over the last century, with documented 5-year survival figures reaching 87-99% in developed countries. During the last decade, there has been a dramatic paradigm shift in the treatment approach for intraocular retinoblastoma, emphasising chemoreduction protocols and minimising the use of external beam radiation. The recognition of the increased risk for second non-ocular cancers with external beam radiation contributed to the growing emergence of chemotherapy. Although chemoreduction protocols vary slightly between institutions, many centres are currently treating intraocular retinoblastoma with carboplatin, vincristine and etoposide as a three-drug regimen given in two to six cycles. Clinical studies have demonstrated that systemic chemotherapy must be combined with other modalities, such as laser treatment and cryotherapy, for adequate tumour control and many eyes with advanced intraocular disease require salvage therapy with radiation or enucleation. Therefore, modern centres treating retinoblastoma continue to manage patients with a variety of modalities, individualising the therapy according to the patient's presentation and clinical course.

Diagnosis and management of retinoblastoma

BACKGROUND

Retinoblastoma is a highly malignant tumor of the eye that manifests most often in the first 3 years of life.

METHODS

Published articles were reviewed to evaluate the clinical features and current methods of diagnosis and to assess the trends in management.

RESULTS

This malignancy leads to metastatic disease and death in 50% of children worldwide but in less than 5% of children in the United States and other developed nations with advanced medical care. Over the past decade, there has been a trend away from enucleation and external beam radiotherapy and toward chemoreduction followed by focal therapies. This is largely due to more effective chemotherapeutic regimens, improved focal treatment modalities, and the desire to avoid loss of the globe and/or exposure to radiotherapy. Chemoreduction and focal therapies are most successful for eyes with minimal to moderate retinoblastoma, with enucleation needed in less than 15% of cases. Eyes with very advanced retinoblastoma require enucleation in approximately 50% of cases.

CONCLUSIONS

Progress in the clinical recognition and management of retinoblastoma has led to high survival rates. Improved methods of treatment using chemoreduction and focal treatments without the need for external beam radiotherapy allow preservation of the eye in some cases, often with visual function.

Ischemic necrosis and atrophy of the optic nerve after periocular carboplatin injection for intraocular retinoblastoma

PURPOSE

To report four cases of optic nerve neuropathy in three children treated with periocular carboplatin injections for unilateral or bilateral intraocular retinoblastoma.

DESIGN

Retrospective, observational case series.

METHODS

SETTING

University-based Ophthalmology Practice.

STUDY POPULATION

Four eyes of three children with retinoblastoma enucleated after nonsuccessful multimodality treatment including periocular carboplatin injections.

OBSERVATION PROCEDURES

The enucleated eyes were routinely processed and evaluated by light microscopy. A retrospective chart review of all four cases was performed.

RESULTS

Three enucleated eyes (Reese-Ellsworth groups III and VB) were obtained from two children with bilateral multifocal retinoblastoma, and one eye (Reese-Ellsworth group IIB) was harvested from a child with unilateral retinoblastoma. All affected eyes underwent three to seven periocular carboplatin injections before enucleation. Additional treatment modalities included systemic chemotherapy, transpupillary thermotherapy, transscleral cryotherapy, and external beam radiotherapy. Histopathologic evaluation of the enucleated eyes revealed focal areas of ischemic necrosis or atrophy of the optic nerve along with dystrophic calcification and mild inflammation in the surrounding fibrovascular adipose tissue.

CONCLUSIONS

Periocular injections of carboplatin may be a useful treatment approach in the management of patients with advanced intraocular retinoblastoma and may minimize systemic side-effects. However, ophthalmologists and pediatric oncologists should be aware of potential marked local complications with periocular carboplatin delivery, including ischemic optic neuropathy. Modifying the injection site/location (for example, subtenon space) or adding other delivery routes adjuncts (for example, fibrin sealant) deserves further study.

Continuing challenges in the management of retinoblastoma with chemotherapy

The management of retinoblastoma has gradually changed over the past 10 years. Over 95% of children with retinoblastoma in the United States are cured with modern techniques. The challenge remains, however, in maintaining the eye and vision. There is a trend away from enucleation and external beam radiotherapy toward focal conservative treatments involving primary chemoreduction in conjunction with thermotherapy and cryotherapy. This is related to earlier detection of the disease, recognition of more effective chemotherapeutic agents, more focused local treatment modalities, and, most importantly, knowledge of the long-term risks of external beam radiotherapy. Enucleation is still preferable for retinoblastoma that fills most of the eye, especially when the disease is unilateral or when there is concern for tumor invasion into the optic nerve, choroid, or orbit. The orbital integrated implant is placed after enucleation and provides acceptable prosthesis motility and appearance. External beam radiotherapy is still vital for treating advanced retinoblastoma, especially when there is diffuse vitreous or subretinal seeding after failure of other methods and preservation of vision is a priority. The most important recent advance in the management of retinoblastoma is the use of intravenous chemotherapy for tumor reduction, a technique of neoadjuvant chemotherapy termed "chemoreduction." This is followed by tumor consolidation with focal measures such as thermotherapy, cryotherapy, and plaque radiotherapy. This strategy provides reduced tumor volume and often permits consolidation with methods other than radiotherapy. It appears that vision can be preserved in some cases with these methods, avoiding some of the local complications like radiation cataract or macular edema that have been found with radiotherapy techniques. External beam radiotherapy and enucleation can now be avoided in most cases of Reese-Ellsworth groups I (minimal disease) through IV (moderate disease) retinoblastoma. The most advanced stage of retinoblastoma, Reese-Ellsworth group V, continues to provide the greatest difficulty for management, and external beam radiotherapy and enucleation are often employed in addition to chemoreduction to save the child's life. A collaborative prospective study in North America is currently under way to further study the benefits and risks of chemoreduction for minimal, moderate, and advanced retinoblastoma.

Retinal function after subconjunctival injection of carboplatin in fibrin sealant

PURPOSE

To evaluate retinal function in a rabbit model after subconjunctival delivery of carboplatin in balanced saline solution (BSS) or fibrin sealant to determine possible retinal toxicity.

METHODS

One group of rabbits (n = 5) received a unilateral subconjunctival injection of 12.2 +/- 1.0 mg/mL of carboplatin (Paraplatin) in BSS. Another group of rabbits (n = 5) received 25.1 +/- 7.7 mg/mL of carboplatin in fibrin sealant (Hemaseel APR). Rabbits injected with fibrin sealant only (n = 2) and BSS only (n = 2) were used as control groups. Electroretinographic recordings consisted of a series of intensities presented under dark- and light-adapted conditions. Electroretinograms were recorded before the injection (baseline) and 2 days, 1, 2, and 3 weeks after the injection. After 3 weeks, all rabbit eyes were obtained for histopathologic examination.

RESULTS

Transient reductions in the dark-adapted b-wave amplitudes were noted 2 days after treatment for eyes injected with carboplatin compared with the vehicle-only treatment groups. Other treatment groups and postinjection time points showed no significant changes from baseline. Retinal structure and thickness were normal 3 weeks after treatment for all treatment groups.

CONCLUSION

Subconjunctival delivery of carboplatin in fibrin sealant or BSS does not have a toxic effect on retinal function or structure in a non-tumor-bearing rabbit model at the doses used in this study at 3 weeks' follow-up.

Transscleral permeability and intraocular concentrations of cisplatin from a collagen matrix

This study determined the in vitro permeability of cisplatin through isolated human sclera as delivered by a collagen matrix vehicle. Short-term and long-term intraocular levels of cisplatin were also measured in the rabbit eye after a subconjunctival injection. Cisplatin in either a collagen matrix vehicle or a control balanced salt solution (BSS) vehicle was applied to human sclera mounted in a specially designed in vitro perfusion chamber. The amount of cisplatin that diffused across the sclera was measured in hourly samples for 24 h using atomic absorption spectrometry. In vivo studies were also performed in Dutch Belted rabbits given subconjunctival injections of cisplatin in collagen matrix or in BSS. Eyes were enucleated at 1.5 h and 2 weeks after injection, frozen, and dissected to determine the intraocular cisplatin concentrations. Cisplatin had a peak in vitro scleral permeability constant of 8.3+/-1.2 x 10(-6) and 20.1+/-1.8 x 10(-6) cm/s, delivered in collagen matrix and in BSS, respectively (mean+/-S.D.). At the end of the in vitro experiments, 35.9+/-4.6% of the cisplatin remained in the collagen matrix, while 0.8+/-0.2% remained in the BSS vehicle. Subconjunctival injection of cisplatin in the collagen matrix vehicle achieved 3.3+/-0.1 microg/ml in the vitreous humor at 1.5 h and 0.1+/-0.1 microg/ml at 2 weeks. This vehicle also achieved a cisplatin concentration of 73.5+/-23.9 microg/mg in the choroid and retina at 1.5 h and 3.2+/-1.3 microg/mg at 2 weeks. Compared to BSS, the collagen matrix vehicle provided a more controlled release of cisplatin, and after subconjunctival injection into rabbits, attained higher drug levels in several ocular tissues.

Treatment of intraocular retinoblastoma with vincristine and carboplatin

PURPOSE

To evaluate the efficacy of chemoreduction using vincristine and carboplatin in preventing or delaying external-beam radiotherapy (EBRT) or enucleation in patients with intraocular retinoblastoma.

PATIENTS AND METHODS

Twenty-five patients (43 eyes) with newly diagnosed intraocular retinoblastoma received primary treatment with eight courses of vincristine and carboplatin. Focal treatments were delayed until documentation of disease progression. Outcome measures for each eye were length of time to disease progression, avoidance or delay of EBRT, and globe survival. Event-free survival was defined as the length of time to EBRT or enucleation.

RESULTS

Disease in all eyes responded to chemotherapy and progressed in only two patients before completion of the eight courses of therapy. Disease in all but four eyes progressed and required focal treatments. Event-free survival estimates at 2 years were 59.2% +/- 12.0% for Reese-Ellsworth group I, II, and III eyes and 26.3% +/- 9.2% for group IV and V eyes. Nineteen eyes (44.2%) required EBRT and 13 eyes (30.2%) were enucleated. The ocular salvage rate was 83.3% for Reese-Ellsworth group I to III eyes and 52.6% for group IV and V eyes. For those patients receiving EBRT, the median time from enrollment to EBRT was 9.5 months (median age at EBRT, 21 months).

CONCLUSION

In combination with appropriate early intensive focal treatments, chemoreduction with vincristine and carboplatin, without etoposide, may be an alternative treatment for patients with early-stage intraocular retinoblastoma, although additional studies are needed. Patients with advanced intraocular disease require more aggressive treatments.