Quantification of radiation retinopathy after beam proton irradiation in centrally located choroidal melanoma

PTCOG Ocular Statement: Expert Summary of Current Practices and Future Developments in Ocular Proton Therapy

Although rare cancers, ocular tumors are a threat to vision, quality of life, and potentially life expectancy of a patient. Ocular proton therapy (OPT) is a powerful tool for successfully treating this disease. The Particle Therapy Co-Operative Ocular Group) formulated an Evidence and Expert-Based Executive Summary of Current Practices and Future Developments in OPT: comparative dosimetric and clinical analysis with the different OPT systems is essential to set up planning guidelines, implement best practices, and establish benchmarks for eye preservation, vision, and quality of life measures. Contemporary prospective trials in select subsets of patients (eg, tumors near the optic disc and/or macula) may allow for dosimetric and clinical analysis between different radiation modalities and beamline systems to evaluate differences in radiation delivery and penumbra, and resultant tumor control, normal tissue complication rates, and overall clinical cost-effectiveness. To date, the combination of multimodal imaging (fundus photography, ultrasound, etc), ophthalmologist assessment, and clip surgery with radiation planning have been keys to successful treatment. Increased use of three-dimensional imaging (computed tomography/magnetic resonance imaging) is anticipated although its spatial resolution might be a limiting factor (eg, detection of flat diffuse tumor parts). Commercially produced ocular treatment-planning systems are under development and their future use is expected to expand across OPT centers. Future continuity of OPT will depend on the following: (1) maintaining and upgrading existing older dedicated low-energy facilities, (2) maintaining shared, degraded beamlines at large proton therapy centers, and (3) developing adapted gantry beams of sufficient quality to maintain the clinical benefits of sharp beam conformity. Option (1) potentially offers the sharpest beams, minimizing impact on healthy tissues, whereas (2) and (3) potentially offer the advantage of substantial long-term technical support and development as well as the introduction of new approaches. Significant patient throughputs and close cooperation between medical physics, ophthalmology, and radiation therapy, underpinned by mutual understanding, is crucial for a successful OPT service.

A Systematic Comparison of Dose Distributions Delivered in 125I Plaque Brachytherapy and Proton Radiation Therapy for Ocular Melanoma

PURPOSE

To characterize dose distributions with ¹²⁵I plaque brachytherapy compared with proton radiation therapy for ocular melanoma for relevant clinical scenarios, based on tumor base diameter (d), apical height (h), and location.

METHODS AND MATERIALS

Plaque and proton treatment plans were created for 4 groups of cases: (1) REF: 39 instances of reference midsize circular-base tumor (d = 12 mm, h = 5 mm), in locations varying by retinal clock hours and distance to fovea, optic disc, and corneal limbus; (2) SUP: 25 superiorly located; (3) TEMP: 25 temporal; and (4) NAS: 25 nasally located tumors that were a fixed distance from the fovea but varying in d (6-18 mm) and h (3-11 mm). For both modalities, 111 unique scenarios were characterized in terms of the distance to points of interest, doses delivered to fovea, optic disc, optic nerve at 3 mm posterior to the disc (ON@3mm), lens, and retina. Comparative statistical evaluation was performed with the Mann-Whitney U test.

RESULTS

Superior dose distributions favored plaque for sparing of (1) fovea in large (d + h ≥ 21 mm) NAS tumors; (2) ON@3mm in REF cases located ≤4 disc diameters from disc, and in NAS overall. Protons achieved superior dose sparing of (1) fovea and optic disc in REF, SUP, and TEMP; (2) ON@3mm in REF >4 disc diameters from disc, and in SUP and TEMP; and (3) the lens center overall and lens periphery in REF ≤6 mm from the corneal limbus, and in TEMP with h = 3 mm. Although protons could completely spare sections of the retina, plaque dose was more target conformal in the high-dose range (50% and 90% of prescription dose).

CONCLUSIONS

Although comparison between plaque and proton therapy is not straightforward because of the disparity in dose rate, prescriptions, applicators, and delivery techniques, it is possible to identify distinctions between dose distributions, which could help inform decisions by providers and patients.

Prospective Assessment of Early Proton Therapy-Induced Optic Neuropathy in Patients With Intracranial, Orbital or Sinonasal Tumors: Impact of A Standardized Ophthalmological Follow Up

PURPOSE

Proton therapy (PT) can be a good option to achieve tumor control while reducing the probability of radiation induced toxicities compared to X-ray-based radiotherapy. However, there are still uncertainties about the effects of PT on the organs in direct contact with the irradiated volume. The aim of this prospective series was to report 6-month follow-up of clinical and functional optic neuropathy rates of patients treated by proton therapy using a standardized comprehensive optic examination.

METHODS AND MATERIALS

Standardized ophthalmological examinations were performed to analyze subclinical anomalies in a systematic way before treatment and 6 months after the end of proton therapy with: Automatic visual field, Visual evoked potential (VEP) and optic coherence of tomography (OCT).

RESULTS

From October 2018 to July 2020 we analyzed 81 eyes. No significant differences were found in the analysis of the clinical examination of visual functions by the radiation oncologist. However, considering VEP, the impairment was statistically significant for both fibers explored at 30'angle (p:0.007) and 60'angle (p <0.001). In patients with toxicity, the distance of the target volume from the optical pathways was more important with a p-value for 30'VEP at 0.035 and for 60'VEP at 0.039.

CONCLUSIONS

These results confirm uncertainties concerning relative biological effectiveness of proton therapy, linear energy transfer appears to be more inhomogeneous especially in areas close to the target volumes. The follow-up of patients after proton therapy is not an easy process to set up but it is necessary to improve our knowledges about the biological effects of proton therapy in real life. Our study which will continue during the coming years, suggests that follow-up with in-depth examinations such as VEP as a biomarker could improve the detection of early abnormalities.

Radiation therapy for uveal melanoma: a review of treatment methods available in 2021

PURPOSE OF REVIEW

Radiation therapy has become the standard of care for the treatment of uveal melanoma. We intend to outline the current radiation therapy methods that are employed to treat uveal melanoma. We will outline their relative benefits over one another. We will also provide some background about radiation therapy in general to accustom the ophthalmologists likely reading this review.

RECENT FINDINGS

Four main options exist for radiation therapy of uveal melanoma. Because the eye is a small space, and because melanomas are relatively radioresistant, oncologists treating uveal melanoma must deliver highly focused doses in high amounts to a small space. Therapies incorporating external beams include proton beam therapy and stereotactic radiosurgery. Stereotactic radiosurgery comes in two forms, gamma knife therapy and cyberknife therapy. Radiation may also be placed directly on the eye surgically via plaque brachytherapy. All methods have been used effectively to treat uveal melanoma.

SUMMARY

Each particular radiotherapy technique employed to treat uveal melanoma has its own set of benefits and drawbacks. The ocular oncologist can choose amongst these therapies based upon his or her clinical judgment of the relative risks and benefits. Availability of the therapy and cost to the patient remain significant factors in the ocular oncologist's choice.

Radiation-Induced Optical Coherence Tomography Angiography Retinal Alterations in Patients With Nasopharyngeal Carcinoma

Aim: The aim of the study was to investigate the early neurovascular alterations of the retina in radiation encephalopathy (RE) patients with normal-ranged visual acuity after radiotherapy for nasopharyngeal carcinoma.

Methods: Fifty-five RE patients and 54 healthy age-matched subjects were enrolled in this retrospective cross-sectional case–control study. The best corrected visual acuity (LogMAR) of the included eye should not be more than 0. The vessel density and thickness of different locations in the retina were acquired automatically using optical coherence tomography angiography (OCTA). The data were then compared between the RE patients and the controls. The location included the whole retina, the superficial vascular plexus (SVP)/the ganglion cell complex (GCC), the deep vascular plexus (DVP), and the choroid in the macular area, as well as the inside disc and peripapillary area in the optic nerve head (ONH). The risk factors in OCTA retinal impairments were analyzed using a backward multiple linear regression. The relationships between mean deviation (MD) and pattern standard deviation (PSD) in the visual field (VF) and the OCTA parameters were also analyzed in RE patients.

Results: The vessel density of the GCC was significantly reduced in RE patients compared with controls (p = 0.018), and the reductions were mainly shown in the parafoveal (p = 0.049) and perifoveal fields (p = 0.006). The thickness of the GCC was correspondingly reduced (whole image GCC mean thickness: p = 0.044; parafoveal thickness: p = 0.038; perifoveal thickness: p = 0.038). In addition, the sub-foveal choroidal thickness (p = 0.039) was also reduced in RE patients. The vessel density of the GCC (R² = 0.643) and DVP (R² = 0.777) had a significant positive correlation with high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A1 (ApoA1) and had a significant negative correlation with age (GCC: HDL-C, β = 29.89, p = 0.005; ApoA1, β = 78.92, p = 0.002; age, β = −0.886, p = 0.001; DVP: HDL-C, β = 40.09, p = 0.003; ApoA1, β = 62.65, p = 0.013; age, β = −1.31, p = 0.001). The vessel density of the GCC also had a significant negative correlation with apolipoprotein B (ApoB) (β = −32.18, p = 0.006). In the VF, MD had a significant positive correlation with the vessel density inside disc (R² = 0.241, β = 0.304, p = 0.045), whereas PSD showed a significant negative correlation with the vessel density inside disc and the average GCC thickness, respectively (R² = 0.437; vessel density inside disc, β = −0.358, p = 0.004; average GCC thickness, β = −0.510, p < 0.001).

Conclusion: With the aid of OCTA, we found that neurovascular alterations of the retina may exist in RE patients with normal-ranged visual acuity. Herein, we suggest the implementation of OCTA to assist ophthalmologists in the early detection and consistent monitoring of radiation-related eye diseases to avoid delayed diagnosis.

EXTENDED FIELD IMAGING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FOR THE STUDY OF RETINAL AND CHOROIDAL CHANGES AFTER RADIATION THERAPY FOR CHOROIDAL MELANOMA: Comparison With Wide-Field Angiography

PURPOSE

Radiation retinopathy is a common side effect of ocular radiotherapy with no long-term effective therapy. Optical coherence tomography angiography (OCTA) and wide-field fluorescein angiography (FA) are widely used for the study of radiation maculopathy and peripheral nonperfusion, respectively. We investigated the role of extended field imaging (EFI-OCTA) for the study of retinal and choroidal alterations after radiotherapy for choroidal melanoma.

METHODS

Cross-sectional observational study of 20 eyes of 20 patients diagnosed with radiation retinopathy. All patients underwent a complete imaging evaluation including FA and indocyanine green angiography (ICGA) with 55° and 102° lens (Spectralis Heidelberg Engineering, Heidelberg, Germany). Optical coherence tomography angiography imaging was performed with the Zeiss PlexElite 9000 Swept Source OCTA (Carl Zeiss Meditec, Dublin, CA) using a 12 × 12-mm volume scan pattern centered on the fovea and a +20.00-diopter lens specifically designed to obtain EFI examination. The imaging methods were then compared in terms of visible field of view, extension of nonperfused areas, and vessel density.

RESULTS

The mean extension ratio of EFI-OCTA compared to OCTA without EFI, FA/ICGA 55° and FA/ICGA 102° was, respectively, 1.98 ± 0.02, 1.21 ± 0.01 and 0.36 ± 0.003. The mean extension of retinal and choroidal nonperfused areas evaluated by EFI-OCTA (63.03 ± 48.21 and 38.63 ± 30.83 mm2) were significantly higher than with OCTA without EFI (40.40 ± 34.87 and 24.26 ± 21.82 mm2, P < 0.001) but lower than with FA/ICGA 102° (140.7 ± 69.23 and 108.3 ± 69.51 mm2, P < 0.001). No significant differences were found between mean extension of retinal and choroidal ischemic areas measured with EFI-OCTA and FA/ICGA 55° (69.64 ± 51.92 and 47.23 ± 33.59 mm2). The mean vessel density of EFI-OCTA (retina and choroid segmentation) was significantly different compared to OCTA without EFI (P < 0.05). Retinal vessel density was negatively correlated to retinal extension of nonperfused areas (r = -0.5, P = 0.02), and choroidal vessel density was negatively correlated to choroidal nonperfused areas (r = -0.6, P = 0.003) measured with EFI-OCTA.

CONCLUSION

In our series, EFI-OCTA captured larger areas than OCTA without EFI and FA/ICGA with 55° lens. EFI-OCTA images showed a good definition of retinal and choroidal vascular changes after radiotherapy, suggesting a possible role of this safe and noninvasive imaging technique in the follow-up of patients with radiation retinopathy.