Rabbit Model of Intra-Arterial Chemotherapy Toxicity Demonstrates Retinopathy and Vasculopathy Related to Drug and Dose, Not Procedure or Approach

Assessment of Retinal Microvasculature and Choroidal Vascularity After Intra-arterial Chemotherapy for Retinoblastoma

PURPOSE

To evaluate changes in retinal microvascular density and choroidal vascularity in patients with retinoblastoma (RB) after intra-arterial chemotherapy (IAC).

DESIGN

Retrospective clinical cohort study.

METHODS

This study included 12 unilateral RB eyes treated with IAC (RB tumor), 12 contralateral normal eyes (RB fellow), and 12 healthy controls. The macular retinal thickness and retinal microvascular structure, including the foveal avascular zone (FAZ) area, macular and peripapillary superficial vessel density (SVD), and deep vessel density (DVD), were measured by optical coherence tomography angiography (OCTA). The choroidal thickness (ChT) and choroidal vascularity, including total choroidal area (TCA), luminal area (LA), stromal area (SA), and choroidal vascularity index (CVI), were measured by spectral-domain optical coherence tomography (SD-OCT). A comparison among the 3 groups was conducted, and the correlations among the parameters were analyzed.

RESULTS

Among the 3 cohorts, the foveal retinal thickness, SVD, DVD, ChT, TCA, LA, SA, and CVI were significantly lower in RB tumor compared to RB fellow and the control eyes (all P < .01). There were no significant differences in the parameters between the contralateral and control eyes. The correlation analyses indicated a significant negative correlation between the total melphalan dose and foveal and parafoveal DVD, ChT, and LA.

CONCLUSIONS

The retinal microvascular density and choroidal vascularity were lower in unilateral RB treated with IAC, and seemed to be related to the total melphalan dose. There were no measurable changes in the contralateral eyes.

Delayed Surgical Reversal of Optic Nerve Compression Leads to Exponential Degeneration of Optic Nerve Fibers and Selective Sparing of the Small Fibers

Purpose

To evaluate the effectiveness of surgical reversal of experimental optic nerve compression in treating persistent compressive optic neuropathy and to explore the relationship between surgical outcomes and the timing of the procedure.

Methods

Surgical reversal procedures (decompression surgery) were conducted at five time intervals: 1, 3, and 7 days and 2 and 3 weeks following optic nerve compression in a rabbit model. The groups were labeled as DC-1d, DC-3d, DC-7d, DC-2w, and DC-3w, respectively. The study investigated changes in ganglion cell complex (GCC) thickness using spectral-domain optical coherence tomography and the percentage of surviving retinal ganglion cells (RGCs) through immunofluorescence staining and optic nerve axons stained with p-phenylenediamine at 4 weeks after decompression. Additionally, the area distribution of surviving axons was analyzed.

Results

The decline in GCC thickness was halted following decompression. The remaining thickness of the GCC in group DC-1d was found to be statistically significantly higher at 2, 3, and 4 weeks postonset compared to the no-decompression group. Similarly, GCC thickness in group DC-3d was significantly higher at 3 and 4 weeks postonset. The percentage of surviving RGCs and axons at 4 weeks postonset exhibited an exponential correlation with the onset time of decompression, with R2 values of 0.72 and 0.78, respectively. The surviving axon area declined following delayed decompression.

Conclusions

Persistent substantial compression on the optic nerve leads to exponential degeneration of the optic nerve, initially affecting larger optic nerve fibers. Early intervention aimed at relieving the compression on the optic nerve may offer potential benefits in mitigating the degenerative effects and conserving visual function.

Role of optical coherence tomography angiography in retinal tumors: A narrative review

Intraocular tumors constitute a small subset of cases in ophthalmologic practice. Proper diagnosis of intraocular tumors is crucial because some pose threat to vision and life, while others may indicate underlying systemic disorders. Intraocular tumors comprise benign and malignant lesions affecting the retina, choroid, optic disc, iris, and ciliary body. Retinal tumors can be classified as vascular, neural, glial, and retinal pigment epithelial tumors. Optical coherence tomography angiography (OCTA) is a noninvasive imaging modality employed in diagnosis and management of retinal and choroidal vascular diseases, and has enhanced our knowledge in better understanding of the vascular physiology and pathology. Multiple case reports and small series evaluating the role of OCTA in retinal tumors are published in literature. OCTA helps in better understanding of the vascularity of intraocular tumors. In addition to this, OCTA has its role in clinical practice. It helps in identification of small retinal capillary hemangioblastoma (RCH), assessment of treatment response, and identification of tumor recurrence in RCH. It aids in identification of retinal astrocytic hamartoma missed on clinical examination and differentiating retinal astrocytic hamartoma and presumed solitary circumscribed retinal astrocytic proliferation. It helps in assessment of risk of tumor recurrence in retinoblastoma. It helps in differentiating tumors of retinal pigment epithelium (RPE) origin from pigmented tumors of the choroid. It also helps in detection of choroidal neovascular membrane in combined hamartoma of the retina and RPE.

Electroretinographic changes in the inner and outer retinal layers before and after intravenous chemotherapy for retinoblastoma

PURPOSE

To study the inner and outer retinal functions using a full-field electroretinogram (ERG) before and after intravenous chemotherapy (IVC) in children with retinoblastoma (RB).

METHODS

Of the 11 eyes, seven had RB and four were normal. All children were examined under anesthesia using a handheld ERG machine with a standard protocol - light-adapted single-flash ERG (fERG), photopic single-flash 3.0- and 30-Hz flickers, and photopic negative response (PhNR) amplitudes at 72 ms (P72). The amplitudes and peak times were compared before and after IVC.

RESULTS

Post-chemotherapy tumor regressed in all seven eyes. Of the seven eyes, the fERG peak time (a-wave) was delayed in two eyes (29%), whereas the b-wave was delayed in six eyes (86%). The fERG amplitude height for a- and b-waves decreased in five eyes (71%) and six eyes (86%), respectively. In addition, photopic flicker 30-Hz b-wave peak time delayed in five eyes (71%), whereas the b-wave amplitude height decreased in six eyes (86%). Simultaneously, the P72 amplitude height decreased in six eyes (86%), whereas the P-ratio increased in all seven eyes (100%). In comparison, the ERG responses improved in three of the four contralateral normal eyes. Overall, the cone function improved in two eyes (29%), whereas cone bipolar cell and retinal ganglion cell (RGC) function improved in one eye (14%) each.

CONCLUSION

Comparison of light-adapted ERG changes before and after IVC showed reduced amplitudes and delayed peak times for both a and b waveforms, as well as reduced PhNR amplitude attributable to bipolar and RGC injury.

Aqueous VEGF-A Levels as a Liquid Biopsy Biomarker of Retinoblastoma Vitreous Seed Response to Therapy

Purpose

Regression of retinoblastoma vitreous seeds (VS) during intravitreal chemotherapy can be delayed, resulting in supernumerary injections. Similarly, VS relapse may not be clinically evident at first. A predictive biomarker of tumor regression and relapse could help guide real-time clinical decision making. Retinoblastoma is an oxygen-sensitive tumor; paradoxically, VS survive in the hypoxic vitreous. We hypothesized that VS elaborate pro-angiogenic cytokines. The purpose was to determine if pro-angiogenic cytokine signatures from aqueous humor could serve as a biomarker of VS response to treatment.

Methods

Multiplex ELISA was performed on aqueous from rabbit eyes with human retinoblastoma VS xenografts to identify expressed proangiogenic cytokines and changes in aqueous cytokine levels during intravitreal treatment were determined. Confirmatory RNAscope in situ hybridization for VEGF-A was performed on human retinoblastoma tumor sections and VS xenografts from rabbits. For human eyes undergoing intravitreal chemotherapy, serial aqueous VEGF-A levels measured via VEGF-A-specific ELISA were compared to clinical response.

Results

VEGF-A was highly expressed in human retinoblastoma VS in the xenograft model, and was the only proangiogenic cytokine that correlated with VS disease burden. In rabbits, aqueous VEGF-A levels decreased in response to therapy, consistent with quantitative VS reduction. In patients, aqueous VEGF-A levels associated with clinical changes in disease burden (regression, stability, or relapse), with changes in VEGF-A levels correlating with clinical response.

Conclusions

Aqueous VEGF-A levels correlate with extent of retinoblastoma VS, suggesting that aqueous VEGF-A may serve as a predictive molecular biomarker of treatment response.

Angiographic analysis of ophthalmic artery flow direction in children undergoing chemosurgery for retinoblastoma compared to age-matched controls

PURPOSE

Catheter-based intra-arterial chemotherapy (IAC) has revolutionized the treatment of retinoblastoma (RB). Variability in ophthalmic artery (OA) flow, either retrograde from external carotid artery branches, or anterograde from the internal carotid artery, necessitates multiple IAC techniques. We evaluated the direction of OA flow and identify OA flow reversal events over the course of IAC treatment as well in comparison to OA flow direction in non-RB children.

MATERIALS AND METHODS

We performed a retrospective analysis of OA flow direction in all RB patients treated with IAC, along with an age-matched control group who underwent cerebral angiography at our center from 2014 to 2020.

RESULTS

IAC was administered to a total of 18 eyes (15 patients). Initial anterograde OA flow was demonstrated in 66% (n  =  12) of eyes. Five OA reversal events were identified (3/5 anterograde-to-retrograde). All five events were in patients receiving multiagent chemotherapy. No correlation was found between OA flow reversal events and the initial IAC technique. A control group of 88 angiograms representing 82 eyes (41 patients) was utilized. The anterograde flow was observed in 76 eyes (86.4%). Our control group included 19 patients with sequential angiograms. One OA flow reversal event was identified.

CONCLUSION

OA flow direction is dynamic in IAC patients. Anterograde and retrograde OA directional switches do occur and may necessitate delivery technique variation. In our analysis, all OA flow reversal events were associated with multiagent chemotherapy regimens. Both anterograde and retrograde OA flow patterns were observed in our control cohort, suggesting bidirectional flow can occur in non-RB children.

Retinal microvasculature observations of fellow eyes after intra-arterial chemotherapy for unilateral retinoblastoma using optical coherence tomography angiography

Purpose

To investigate the characteristics of the retinal microvasculature of the fellow eyes in patients with unilateral retinoblastoma (RB) after intra-arterial chemotherapy (IAC) through optical coherence tomography angiography.

Methods

This retrospective study enrolled 11 fellow eyes of patients with unilateral RB receiving IAC (group I), nine fellow eyes of patients with unilateral RB receiving IAC and intravenous chemotherapy (IVC) (group II), and 14 age-matched normal eyes (control group). Optical coherence tomography angiography was performed on all individuals. Vascular density of superficial capillary plexus and deep capillary plexus (DCP), foveal avascular zone related parameters, and retinal thickness were measured and compared among the three groups.

Results

There was no statistical difference in age and logMAR visual acuity among the three groups. Compared with the control group, the vascular density of the DCP was lower in group I and II. Decreased vascular density of FD-300 and thinner thickness of outer plexus layer to Bruch's membrane were detected in group II compared with the control group. The vascular density and retinal thickness showed no differences between group I and II.

Conclusion

The decreased vascular density in the DCP without measurable visual impairment was observed in fellow eyes after IAC or IAC + IVC for unilateral RB. Further studies with a larger sample would be necessary to determine the clinical significance of these findings.

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.

Radial Peripapillary Capillary Plexus Perfusion and Endothelial Dysfunction in Early Post-SARS-CoV-2 Infection

Background: Endothelial cells damage and thromboinflammation are considered key elements in the generation of organ impairment in patients with COVID-19 disease. The endothelial function is evaluated by measuring flow-mediated dilation (FMD). We aimed to analyze the association between FMD impairment and retinal vascular parameters in early post-COVID-19 patients. 00118-00199Tomography (OCT), OCT Angiography (OCTA) and slit lamp examination were performed. FMD ≤ 7% was considered as pathological. Our primary outcome was to assess potential differences in the radial peripapillary capillary plexus flow index (RPCP-FI) and RPCP density (RPCP-D) values between post-COVID-19 patients with and without FMD impairment. The associations of other retinal vascular parameters with FMD impairment were assessed as secondary endpoints. Results: FMD impairment was detected in 31 patients (37.8%). RPCP-FI (p = 0.047), age (p = 0.048) and prevalence of diabetes (p = 0.046) significantly differed in patients with FMD ≤ 7% in regression analysis. RPCP-FI was linearly correlated with FMD values (R = 0.244, p =0.027). SCT was found to be lower in patients with impaired FMD (p = 0.004), although this difference was only a trend in binary logistic regression output (p = 0.07). Conclusions: Early post-COVID-19 patients showed a higher prevalence of FMD impairment compared to the general population. Age, diabetes and RPCP-FI were independently correlated with the presence of endothelial impairment in the early post-infective period.

Retinoblastoma and vision

The assessment of vision has a growing importance in the management of retinoblastoma in the era of globe-conserving therapy, both prior to and after treatment. As survival rates approach 98-99% and globe salvage rates reach ever-higher levels, it is important to provide families with information regarding the visual outcomes of different treatments. We present an overview of the role of vision in determining the treatment given and the impact of complications of treatment. We also discuss screening and treatment strategies that can be used to maximise vision.

Intravitreal HDAC Inhibitor Belinostat Effectively Eradicates Vitreous Seeds Without Retinal Toxicity In Vivo in a Rabbit Retinoblastoma Model

Purpose

Current melphalan-based regimens for intravitreal chemotherapy for retinoblastoma vitreous seeds are effective but toxic to the retina. Thus, alternative agents are needed. Based on the known biology of histone deacetylases (HDACs) in the retinoblastoma pathway, we systematically studied whether the HDAC inhibitor belinostat is a viable, molecularly targeted alternative agent for intravitreal delivery that might provide comparable efficacy, without toxicity.

Methods

In vivo pharmacokinetic experiments in rabbits and in vitro cytotoxicity experiments were performed to determine the 90% inhibitory concentration (IC₉₀). Functional toxicity by electroretinography and structural toxicity by optical coherence tomography (OCT), OCT angiography, and histopathology were evaluated in rabbits following three injections of belinostat 350 µg (2× IC₉₀) or 700 µg (4× IC₉₀), compared with melphalan 12.5 µg (rabbit equivalent of the human dose). The relative efficacy of intravitreal belinostat versus melphalan to treat WERI-Rb1 human cell xenografts in rabbit eyes was directly quantified. RNA sequencing was used to assess belinostat-induced changes in RB cell gene expression.

Results

The maximum nontoxic dose of belinostat was 350 µg, which caused no reductions in electroretinography parameters, retinal microvascular loss on OCT angiography, or retinal degeneration. Melphalan caused severe retinal structural and functional toxicity. Belinostat 350 µg (equivalent to 700 µg in the larger human eye) was equally effective at eradicating vitreous seeds in the rabbit xenograft model compared with melphalan (95.5% reduction for belinostat, P < 0.001; 89.4% reduction for melphalan, P < 0.001; belinostat vs. melphalan, P = 0.10). Even 700 µg belinostat (equivalent to 1400 µg in humans) caused only minimal toxicity. Widespread changes in gene expression resulted.

Conclusions

Molecularly targeted inhibition of HDACs with intravitreal belinostat was equally effective as standard-of-care melphalan but without retinal toxicity. Belinostat may therefore be an attractive agent to pursue clinically for intravitreal treatment of retinoblastoma.

Efficacy, Toxicity, and Pharmacokinetics of Intra-Arterial Chemotherapy Versus Intravenous Chemotherapy for Retinoblastoma in Animal Models and Patients

Purpose

Through controlled comparative rabbit experiments and parallel patient studies, our purpose was to understand mechanisms underlying differences in efficacy and toxicity between intra-arterial chemotherapy (IAC) and intravenous chemotherapy (IVC).

Methods

In rabbits, ocular tissue drug levels were measured following IAC and IVC. Retinal toxicity was assessed using electroretinography, fluorescein angiography, optical coherence tomography (OCT) and OCT angiography. Efficacy to eradicate retinoblastoma orthotopic xenografts was compared. In IAC and IVC patients, we measured blood carboplatin pharmacokinetics and compared efficacy and toxicity.

Results

In rabbits receiving IAC, maximum carboplatin levels were 134 times greater in retina (P = 0.01) and 411 times greater in vitreous (P < 0.001), and total carboplatin (area under the curve) was 123 times greater in retina (P = 0.005) and 131 times greater in vitreous (P = 0.02) compared with IVC. Melphalan levels were 12 times greater (P = 0.003) in retina and 26 times greater in vitreous (P < 0.001) for IAC. Blood levels were not different. IAC melphalan (but not IV melphalan or IV carboplatin, etoposide, and vincristine) caused widespread apoptosis in retinoblastoma xenografts but no functional retinal toxicity or cytopenias. In patients, blood levels following IVC were greater (P < 0.001) but, when adjusted for treatment dose, were not statistically different. Per treatment cycle in patients, IVC caused higher rates of anemia (0.32 ± 0.29 vs. 0.01 ± 0.04; P = 0.0086), thrombocytopenia (0.5 ± 0.42 vs. 0.0 ± 0.0; P = 0.0042), and neutropenia (0.58 ± 0.3 vs. 0.31 ± 0.25; P = 0.032) but lower treatment success rates (P = 0.0017).

Conclusions

The greater efficacy and lower systemic toxicity with IAC appear to be attributable to the greater ocular-to-systemic drug concentration ratio compared with IVC.

Translational Relevance

Provides an overarching hypothesis for a mechanism of efficacy/toxicity to guide future drug development.

Retinal capillary involvement in early post-COVID-19 patients: a healthy controlled study

BACKGROUND

Systemic vascular involvement in COVID-19 has been identified in several patients: not only endothelial derangement and increased permeability are reported to be early hallmarks of organ damage in patients with COVID-19 but are also the most important cause of worsening of clinical conditions in severe cases of SARS-CoV-2 infection. There are several reasons to hypothesize that the eye, and the retina in particular, could be a target of organ damage in SARS-CoV-2 infection.

METHODS

This cohort observational study analyzes OCT angiography and structural OCT of 70 post-COVID-19 patients evaluated at 1-month hospital discharge and 22 healthy control subjects. Primary outcomes were macular vessel density (VD) and vessel perfusion (VP); structural OCT features were evaluated as secondary outcomes. In addition, patients and healthy volunteers were evaluated for best corrected visual acuity, slit lamp photograph, and fundus photo image.

RESULTS

VD and VP in 3 × 3 and 6 × 6 mm scans for SCP and DCP showed no significant differences between the groups. Similarly, CMT and GCL did not reveal significant differences between post-COVID-19 and healthy patients. Nine patients (12.9%) featured retinal cotton wool spots and 10 patients had vitreous fibrillary degeneration. The prevalence of epiretinal membrane and macular hole was similar in the two groups. One case of extra papillary focal retinal hemorrhage was reported in the post-COVID-19 group.

CONCLUSIONS

Macula and perimacular vessel density and perfusion resulted unaltered in mild post-COVID-19 patients at 1-month hospital discharge, suggesting no or minimal retinal vascular involvement by SARS-CoV-2.

Retinal toxicities of systemic anticancer drugs

Newer anticancer drugs have revolutionized cancer treatment in the last decade, but conventional chemotherapy still occupies a central position in many cancers, with combination therapy and newer methods of delivery increasing their efficacy while minimizing toxicities. We discuss the retinal toxicities of anticancer drugs with an emphasis on the mechanism of toxicity. Uveitis is seen with the use of v-raf murine sarcoma viral oncogene homolog B editing anticancer inhibitors as well as immunotherapy. Most of the cases are mild with only anterior uveitis, but severe cases of posterior uveitis, panuveitis, and Vogt-Koyanagi-Harada-like disease may also occur. In the retina, a transient neurosensory detachment is observed in almost all patients on mitogen-activated protein kinase kinase (MEK) inhibitors. Microvasculopathy is often seen with interferon α, but vascular occlusion is a more serious toxicity caused by interferon α and MEK inhibitors. Crystalline retinopathy with or without macular edema may occur with tamoxifen; however, even asymptomatic patients may develop cavitatory spaces seen on optical coherence tomography. A unique macular edema with angiographic silence is characteristic of taxanes. Delayed dark adaptation has been observed with fenretinide. Interestingly, this drug is finding potential application in Stargardt disease and age-related macular degeneration.

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.

Complete preclinical platform for intravitreal chemotherapy drug discovery for retinoblastoma: Assessment of pharmacokinetics, toxicity and efficacy using a rabbit model

Current melphalan-based intravitreal chemotherapy regimens for retinoblastoma vitreous seeds are effective, but cause significant ocular toxicity. We describe protocols for each step of a drug discovery pipeline for preclinical development of novel drugs to maximize efficacy and minimize toxicity. These protocols include: 1) determination of vitreous pharmacokinetics in vivo, 2) in vitro assessment of drug cytotoxicity against retinoblastoma based on empiric pharmacokinetics, 3) back-calculation of minimum injection dose to achieve therapeutic concentrations, 4) in vivo determination of maximum-tolerable intravitreal dose, using a multimodal, structural and functional toxicity-assessment platform, and 5) in vivo determination of drug efficacy using a rabbit orthotopic xenograft model of retinoblastoma vitreous seeds. We likewise describe our methodology for direct quantitation of vitreous seeds, and the statistical methodology for assessment of toxicity and efficacy in evaluating novel drugs, as well as for comparisons between drugs.•Multi-step pipeline for intravitreal chemotherapy drug discovery for retinoblastoma, using novel rabbit models.•Detailed protocols for determination of vitreous pharmacokinetics, calculation of optimal dose to inject to achieve therapeutic vitreous levels, determination of maximum tolerable dose using a novel complete toxicity-assessment platform, and in vivo efficacy against retinoblastoma using methodology to directly quantify vitreous tumor burden.•Associated statistical methodology is also presented.

Intravitreal melphalan hydrochloride vs propylene glycol-free melphalan for retinoblastoma vitreous seeds: Efficacy, toxicity and stability in rabbits models and patients

The use of intravitreal chemotherapy has revolutionized the treatment of advanced intraocular retinoblastoma, as intravitreal melphalan has enabled difficult-to-treat vitreous tumor seeds to be controlled, leading to many more eyes being saved. However, melphalan hydrochloride (MH) degrades rapidly in solution, increasing logistical complexity with respect to time between medication preparation and administration for intravitreal administration under anesthesia for retinoblastoma. A new propylene glycol-free melphalan (PGFM) formulation has greater stability and could therefore improve access and adoption of intravitreal chemotherapy, allowing more children to retain their eye(s). We compared the efficacy and toxicity of both formulations, using our rabbit xenograft model and clinical patient experience. Three weekly 12.5 μg intravitreal injections of MH or PGFM (right eye), and saline (left eye), were administered to immunosuppressed rabbits harboring human WERI-Rb1 vitreous seed xenografts. Residual live cells were quantified directly, and viability determined by TUNEL staining. Vitreous seeds were reduced 91% by PGFM (p = 0.009), and 88% by MH (p = 0.004; PGFM vs. MH: p = 0.68). All residual cells were TUNEL-positive (non-viable). In separate experiments to assess toxicity, three weekly 12.5 μg injections of MH, PGFM, or saline were administered to non-tumor-bearing rabbits. Serial electroretinography, optical coherence tomography (OCT) and OCT-angiography were performed. PGFM and MH both caused equivalent reductions in electroretinography amplitudes, and loss of retinal microvasculature on OCT-angiography. The pattern of retinal degeneration observed on histopathology suggested that segmental retinal toxicity associated with all melphalan formulations was due to a vitreous concentration gradient-effect. Efficacy and toxicity were assessed for PGFM given immediately (within 1 h of reconstitution) vs. 4 h after reconstitution. Immediate- and delayed-administration of PGFM showed equivalent efficacy and toxicity. In addition, we evaluated efficacy and toxicity in patients (205 eyes) with retinoblastoma vitreous seeds, who were treated with a total of 833 intravitreal injections of either MH or PGFM as standard of care. Of these, we analyzed 118 MH and 131 PGFM monotherapy injections in whom serial ERG measurements were available to model retinal toxicity. Both MH and PGFM caused reductions in electroretinography amplitudes, but with no statistical difference between formulations. Comparing those patient eyes treated exclusively with PGFM versus those treated exclusively with MH, efficacy for tumor control and globe salvage was equivalent (PGFM vs. MH: 96.2% vs. 93.8%, p = 0.56), but PGFM-treated eyes received fewer injections than MH-treated eyes (average 3.2 ± 1.9 vs. 6.4 ± 2.1 injections, p < 0.0001). Taken together, these rabbit experiments and our clinical experience in retinoblastoma patients demonstrate that MH and PGFM have equivalent efficacy and toxicity. PGFM was more stable, with no decreased efficacy or increased toxicity even 4 h after reconstitution. We therefore now use PGFM over traditional MH for our patients for intravitreal treatment of retinoblastoma.

EPZ015666, a selective protein arginine methyltransferase 5 (PRMT5) inhibitor with an antitumour effect in retinoblastoma

Retinoblastoma (RB) is the most common intraocular malignant tumour in infants, and chemotherapy has been the primary therapy method in recent years. PRMT5 is an important member of the protein arginine methyltransferase family, which plays an important role in various tumours. Our study showed that PRMT5 was overexpressed in retinoblastoma and played an important role in retinoblastoma cell growth. EPZ015666 is a novel PRMT5 inhibitor, and we found that it inhibited retinoblastoma cell proliferation and led to cell cycle arrest at the G1 phase. At the same time, EPZ015666 regulated cell cycle related protein (P53, P21, P27, CDK2) expression. In brief, our study showed that PRMT5 promoted retinoblastoma growth, the PRMT5 inhibitor EPZ015666 inhibited retinoblastoma in vitro by regulating P53-P21/P27-CDK2 signaling pathways and slowed retinoblastoma growth in a xenograft model.

Risk Factors for Acute Choroidal Ischemia after Intra-arterial Melphalan for Retinoblastoma: The Role of the Catheterization Approach

PURPOSE

To identify risk factors for acute choroidal ischemia (ACI) after intra-arterial chemotherapy (IAC) for retinoblastoma.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Two hundred twenty patients (248 eyes) treated with IAC in Lausanne between November 2008 and September 2019 (665 procedures). All patients were evaluated on a monthly basis with fundus photography and fluorescein angiography before and after each IAC injection.

METHODS

Acute choroidal ischemia, defined as any new choroidal ischemia clinically diagnosed within 35 days after an IAC injection, were noted. Eyes with choroidal complications diagnosed later than 35 days after the last IAC injection (n = 7) or those for which the status of the choroid was not assessable (n = 35) were excluded. Specific procedure parameters and treatment regimens were compared between the group of eyes with and without ACI.

MAIN OUTCOME MEASURES

Procedure-related risk factors for ACI after IAC injection and visual acuity assessment in the group of eyes with ACI.

RESULTS

Acute choroidal ischemia developed in 35 of 206 included eyes after a mean of 2 injections. No differences were found between the two study groups regarding age at first IAC injection, disease grouping at diagnosis, previously administered treatments, number of IAC injections, drug dose, mean injection time, injection method (pulsatile vs. continuous), or concomitant intravitreal melphalan use. Treatment regimen (melphalan vs. combined melphalan plus topotecan; P < 0.05), catheterization route (internal carotid artery vs. external carotid or posterior communicating artery; P < 0.001), and catheterization type (occlusive into the ophthalmic artery [OA] vs. nonocclusive; P < 0.001) were included in multivariate analysis, and occlusive catheterization was identified as an independent risk factor for ACI (P < 0.001). In the subgroup undergoing an occlusive procedure, placement of the catheter tip into the OA distal third versus medial and proximal thirds (P = 0.04) and a mean catheter diameter-to-OA lumen ratio of 0.6 or more (P < 0.001) were correlated significantly with ACI. Complete vision loss was noted in 27% of the eyes with ACI that were old enough for visual assessment (n = 9/33), whereas 33% maintained a useful vision ranging between 0.1 and 0.8 (n = 11/33).

CONCLUSIONS

Catheterization of the OA should be attempted from an ostial position or an external carotid approach to minimize the risk of potentially vision-threatening choroidal complications.

Angiographic investigation of orbital vascular variations in the rabbit and implications for endovascular intra-arterial chemotherapy models

BACKGROUND

The New Zealand White rabbit (NZWR) is the first small-animal experimental model of intra-arterial chemotherapy (IAC) for retinoblastoma treatment. The NZWR has dual ophthalmic arteries (OA): the external OA (EOA) arises from the external carotid artery and the internal OA (IOA) from the internal carotid artery. We describe the technique that we have refined for OA catheterization in rabbits, and describe the angioanatomical variations in the OA supply to the NZWR eye and implications for IAC delivery, which were identified as part of a larger project exploring IAC effects in a rabbit retinoblastoma model.

METHODS

We developed techniques to perform angiography of the external and internal carotid arteries and superselective angiography of the EOA and IOA in NZWR using transfemoral access and a microwire/microcatheter system. EOA and IOA supply to the eye was determined angiographically and recorded before selective OA catheterization and angiography.

RESULTS

114 rabbits underwent carotid angiographic evaluation and OA catheterization (161 total eyes evaluated, 112 right, 49 left). Most eyes had a single dominant arterial supply; either IOA or EOA. EOA was dominant in 73% (118/161), and IOA was dominant in 17% (27/161). Co-dominant supply was seen in 10% (16/161). Of the rabbits with bilateral OA catheterization, 25/47 (53%) had bilateral dominant EOA.

CONCLUSION

Successful catheterization of the OA in the NZWR can be readily accomplished with nuanced technique. The external OA is the dominant arterial supply in the majority of NZWR eyes. These findings allow for successful reproduction of OA catheterization studies of IAC for retinoblastoma in NZWR.

Intra-arterial Chemotherapy as Primary Treatment for Cavitary Retinoblastoma: Excellent Response in Eight Tumors

PURPOSE

The "cavitary" form of retinoblastoma has historically demonstrated minimal treatment response with intravenous chemoreduction, showing less robust regression and less reduction in tumor size. Intra-arterial chemotherapy (IAC) has been reported to more effectively treat retinoblastoma, allowing many previously unsalvageable eyes to now be saved. The purpose was to report treatment response of cavitary retinoblastoma tumors to IAC.

DESIGN

Retrospective case series.

PARTICIPANTS

Patients presenting with cavitary retinoblastoma who were treated with IAC.

METHODS

Retrospective case series of all patients presenting with cavitary retinoblastoma between August 2014 and January 2019 who were treated with primary IAC.

MAIN OUTCOME MEASURES

Tumor regression, recurrence, resolution of vitreous and subretinal seeds, number of treatments required, globe salvage, metastasis, and death.

RESULTS

Eight cavitary retinoblastoma tumors in 6 eyes of 4 patients were treated with IAC. One hundred percent of the cavitary tumors regressed (8/8 tumors, in 6/6 eyes), and 100% of vitreous and subretinal seeds regressed, with 100% globe salvage. None of the tumors recurred, no patients developed metastases, and no patients died. Eyes were treated with a median of 4.5 cycles of IAC (range, 1-7), with fewer IAC treatments used in the later patients (1-3 treatments per eye for the most recent 3 eyes, compared with 6-7 treatments per eye for the earliest 3 eyes). Mean reduction in thickness was 73.4% (range, 59.7%-84.6%). Mean reduction in basal diameter was 45.5% (range, 24.8%-56.0%).

CONCLUSIONS

Treatment with IAC results in regression of cavitary retinoblastoma, often with greater reduction in tumor size than has been reported previously with intravenous chemotherapy (IVC). Using up-front triple therapy (e.g., melphalan 0.4 mg/kg, carboplatin 50 mg, and topotecan 2 mg) and noting certain subtle signs of early regression can help to minimize unnecessary additional cycles of treatment.

Severe Periocular Edema after Intraarterial Carboplatin Chemotherapy for Retinoblastoma in a Rabbit (Oryctolagus cuniculus) Model

Endovascular microcatheter-based intraarterial (ophthalmic artery) chemotherapy is becoming widely used for the clinical treatment of intraocular retinoblastoma due to its apparent increased efficacy compared with traditional intravenous chemotherapy; however local ocular complications are not uncommon. Carboplatin is a chemotherapeutic agent used in both intravenous and intraarterial chemotherapy. We used rabbits to assess pharmacokinetics and ocular and systemic toxicity after intraarterial carboplatin infusion. Subsequent to unilateral intraarterial administration of carboplatin, severe unilateral or bilateral periocular edema occurred in 6 adult male New Zealand white rabbits. Time to onset varied from less than 4 h after administration (n = 3, 50 mg) to approximately 24 h afterward (n = 3, 25 mg). After becoming symptomatic, 5 of the 6 animals were promptly euthanized, and the remaining animal (25 mg treatment) was medically managed for 4 d before being euthanized due to intractable edema-related lagophthalmos. Globes and orbits from all 6 euthanized rabbits were harvested en bloc; whole-mount sections were prepared for histologic evaluation, which revealed drug-induced vasogenic edema in confined spaces as the main underlying pathogenesis. Transient and self-limiting periocular edema is a common side effect of intraarterial chemotherapy but is thought to occur predominantly with melphalan monotherapy or combination therapy using melphalan, carboplatin, and topotecan. The severity of this adverse consequence in rabbits was unexpected, and its use in the study was subsequently discontinued. Although the definitive cause for this vasotoxicity and striking clinical presentation is unknown, we suspect species-specific anatomic features and sensitivity might have contributed to amplified complications after intraarterial carboplatin chemotherapy of the eye. Due to the adverse effects of intraarterial carboplatin chemotherapy that we observed in 2 experimental cohorts of rabbits, we recommend caution regarding its use in this species.

Sclero-conjunctival ischaemia secondary to intra-arterial chemotherapy for retinoblastoma

Purpose

Intra-arterial chemotherapy (IAC), delivered directly to the globe via the internal carotid artery is now an established treatment for retinoblastoma. We report a case of anterior segment ischaemia following treatment with multiple intra-arterial chemotherapy (IAC) infusions.

Observations

A 5 month old female presented with bilateral retinoblastoma and was treated with 12 infusions of IAC. Her right eye was enucleated at diagnosis. After her seventh IAC treatment, she developed ipsilateral sixth and third cranial nerve palsies. After the twelfth IAC, she developed an area of conjunctival and scleral ischaemia between 12 and 3 o'clock meridians in her left eye. However, she maintained visual acuity of LogMAR 0.34.

Conclusions and Importance

The median number of IAC treatments in large studies is three. It is possible that repeated doses of IAC have an accumulative negative effect on the ocular blood supply, risking anterior segment and neurologic sequelae. This case highlights the significant challenge of balancing the salvage of eyes and vision with the potentially significant morbidity associated with IAC.

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.