Rapid onset of radiation maculopathy after whole-brain radiation therapy: A case report

Early anti-VEGF treatment for radiation maculopathy and optic neuropathy: lessons learned

Radiation therapy has saved both sight and life for eye cancer patients. The most common methods include ophthalmic plaque brachytherapy and external beam techniques. However, subsequent dose-dependent radiation vasculopathy invariably occurs within and around the targeted zone. In 2006, Finger discovered that periodic intravitreal anti-vascular endothelial growth factor (anti-VEGF) bevacizumab could reverse and suppress intraocular radiation vasculopathy. At first, it was administered at the onset of radiation-related vision loss. Though bevacizumab induced regression of macular oedema, retinal haemorrhages and cotton-wool infarcts, most patients were left with residual retinal damage, manifest as metamorphopsia and loss of vision. These results led to earlier and earlier anti-VEGF interventions: first after signs of progressive radiation retinopathy, and then for signs of radiation maculopathy, and finally for high-risk eyes with no clinical signs of retinopathy. Earlier initiation of intravitreal anti-VEGF therapy typically resulted in greater restoration and preservation of macular anatomy, reductions of retinal haemorrhages, resolution of cotton-wool spots and vision preservation. Recent research on optical coherence tomography angiography (OCT-A) has revealed that radiation vasculopathy occurs prior to clinical ophthalmic signs or symptoms. Therefore, it seemed reasonable to consider treating high-risk patients (considered certain to eventually develop radiation maculopathy) to prevent or delay vision loss. Herein, we describe the evolution of treatment for radiation maculopathy as well as recent research supporting anti-VEGF treatment of high-risk patients immediately following radiation to maximize vision outcomes.

Proteomic dissimilarities of primary microglia and BV2 cells under stimuli

Microglia are the static resident cells possessing the phagocytic properties in the central nervous system (CNS). In many relevant studies, the immortalized murine microglial cell line BV2 has been used as a tool in primary microglia (PM) relevant studies. Microglia participate in neuroinflammation by converting into M1- and M2-like phenotypes. In this study, we established M1- and M2-like phenotype response models by exposing PM and BV2 cells to lipopolysaccharides (LPS) and interlukin-4 (IL-4), respectively, and discovered the proteomic differences between the two types of microglia. It turned out that the BV2 cells responses to LPS and IL-4 were narrower and weaker than that of PM. In addition, irradiation, which has been shown to activate microglia and induces neuroinflammation, was also used as a treatment in this study. The results showed that BV2 cells have stronger capacity of DNA damage repair. Besides, irradiation had a negative effect on the regulation of KEGG pathways such as proteasome, ribosome, oxidative phosphorylation and TCA cycle in both cells. Furthermore, the KEGG pathways including cell cycle and DNA replication (significantly down-regulated), and antigen processing and presentation and FC γ R mediated phagocytosis (significantly up-regulated) were only found in irradiated PM. These data demonstrate that PM is more fragile to irradiation. Results in this study indicate that BV2 cells only partially model PM and thus using BV2 in microglia related studies should be carefully considered.

Damage to the Superior Retinae After 30 Gy Whole-Brain Radiation

Purpose

The most common treatment protocol for whole-brain radiation therapy (WBRT) is 30 Gy in 10 fractions. This regimen entails a low risk of radiation retinopathy, with fewer than a dozen reported cases. We describe a case of radiation retinopathy that was confined to the superior retinae. These regions were the only portions of the eyes that were included in the treatment field.

Methods and Materials

Observational case report consisting of clinical examination, review of radiation treatment planning and implementation, computerized visual field testing, and fundus photography.

Results

A 36-year-old man with metastatic lung adenocarcinoma developed radiation retinopathy 16 months after WBRT to 30 Gy in 10 fractions. The retinopathy was largely confined to the superior halves of the retinae. There was corresponding geographic inferior visual field loss in both eyes. Review of the patient's treatment protocol revealed that the superior retinae received a substantial radiation dose, approaching 30 Gy, whereas the inferior retinae were essentially outside the treatment field.

Conclusions

In this patient, the correlation between the treatment field and the resulting local development of radiation retinopathy demonstrated unequivocally that the relatively low dose used in routine WBRT (ie, 30 Gy in 10 fractions) can induce radiation retinopathy.

Volumetric modulated arc therapy (VMAT) for hippocampal-avoidance whole brain radiation therapy: planning comparison with Dual-arc and Split-arc partial-field techniques

BACKGROUND

Although whole brain radiation therapy (WBRT) provides palliation and prophylaxis, reduces local recurrence probability and improves overall survival, it is evident that WBRT is associated with neurocognitive deficits due to radiation induced damage of the hippocampus. Therefore, minimizing hippocampal dose to the least possible level is of high clinical relevance. In dual-arc conventional volumetric modulated arc therapy (dac-VMAT), the large irradiation field for whole brain planned target volume (PTV) requires a wide jaw opening in which substantial low dose volume to the hippocampus may be produced due to suboptimal multi-leaf collimator (MLC) movements. The present study investigates the potential of a radiation therapy technique with split-arc and reduced field size, namely split-arc partial-field volumetric modulated arc therapy (sapf-VMAT) to spare the hippocampus during WBRT.

METHODS

Computed tomography and magnetic resonance images of 20 patients with brain metastases were retrieved in this retrospective planning study. The hippocampus was manually delineated by single radiation oncologist strictly following the RTOG 0933 atlas definition. Plans delivering 30 Gy in 10 fractions were generated for each patient using dac-VMAT and sapf-VMAT. Dosimetric parameters from both techniques were compared by paired t-test.

RESULTS

The results demonstrated that radiation dose to the hippocampus was significantly reduced using sapf-VMAT relative to dac-VMAT plans. sapf-VMAT (7.86Gy, p = 0.001) had significantly lowered average D_100% compared to dac-VMAT (9.23 Gy). Decrease in hippocampus D_max using sapf-VMAT (13.23 Gy, p = 0.001) was statistically significant when compared to dac-VMAT (16.33 Gy). The resulting mean dose to the hippocampus was 9.16 Gy for the for sapf-VMAT. Mean dose of sapf-VMAT was significantly lower than dac-VMAT (10.85 Gy, p < 0.05). In both eyes, sapf-VMAT demonstrated significantly lower D_mean compared to dac-VMAT (p < 0.05). Whole brain PTV coverage was not compromised in both techniques.

CONCLUSION

sapf-VMAT has demonstrated significant dose reduction to the hippocampus and both eyes compared to dac-VMAT.