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

External carotid artery to ophthalmic artery flow associated with internal carotid artery stenosis

PURPOSE

One of the most devastating complications of facial filler injection is sudden ischemic blindness. However, its mechanisms and predisposing factors are poorly understood. The purpose of this study was to investigate the prevalence of external carotid artery (ECA) to ophthalmic artery (OA) anterograde flow in patients with internal carotid artery (ICA) stenosis and in a control population without carotid disease.

METHODS

In this cross-sectional cohort study, two groups of patients who underwent catheter cerebral angiography over a 5-year period were identified: patients with symptomatic ICA stenosis and a control group of patients with refractory epistaxis undergoing embolization. Angiograms were reviewed by an interventional neuroradiologist. The primary outcome measure was the presence of ECA to OA flow, defined as choroidal blush before filling of the circle of Willis. Secondary outcome measures included the percentage and location of ICA stenosis and ECA anastomotic branches involved.

RESULTS

The study included 149 patients with ICA stenosis and 69 control patients. ECA to OA flow was more prevalent in patients with ICA stenosis (34.9%) compared to controls (2.9%) (p < .001). Logistic regression demonstrated that for each 10% increase in ICA stenosis over 70%, there was 2.8 times increased risk of ECA to OA flow (p < .001).

CONCLUSIONS

ECA to ICA anterograde flow can be demonstrated in approximately 3% of control patients and in over 1/3 of patients with symptomatic carotid stenosis. This provides a plausible pathway for small filler particles to pass with blood flow from the facial to the ophthalmic circulation.

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.

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.