Radiation Retinopathy After Fractionated Stereotactic Conformal Radiotherapy for Primary Intraorbital Optic Nerve Sheath Meningioma

Abstract

There are just two reported cases of radiation retinopathy after fractionated stereotactic radiotherapy (SFRT) for optic nerve sheath meningioma (ONSM) (1,2). We report a further case of radiation retinopathy secondary to fractionated stereotactic conformal radiotherapy (SCRT) for biopsy-proven ONSM. A 42-year-old woman developed increasing proptosis of the right eye. Visual acuity was 20/16 in both eyes. Color vision was normal and there was no relative afferent pupillary defect. Visual fields were normal. Hertel exophthalmometry disclosed 9 mm of right axial proptosis. Ophthalmoscopy was normal. MRI showed a well-demarcated round intraconal orbital mass that abutted the globe and exhibited contrast enhancement (Fig. 1). A biopsy of the tumor disclosed an epithelial membrane antigen (EMA)-positive meningothelial meningioma (Fig. 2).FIG. 1: Postcontrast TI axial MRI shows an enhancing mass in the intraconal space of the right orbit that abuts the globe.FIG. 2: Tumor biopsy specimen (hematoxylin and eosin) shows a syncytial growth pattern and no mitotic figures, consistent with a meningothelial meningioma, World Health Organization Grade 1.The patient underwent fractionated SCRT to a total dose of 54 Gy in 30 divided fractions of 1.8 Gy. The maximum dose to the posterior retina was 54 Gy. The anterior half of the retina received a dose of <16.2 Gy. Two years after completion of radiotherapy, several cotton wool spots were noted in the right posterior pole (Fig. 3). Visual acuity remained 20/16 in each eye. Blood glucose level and antinuclear antibody were normal.FIG. 3: A. Right fundus photograph taken 2 years after completion of radiotherapy shows multiple cotton wool spots and a retinal hemorrhage inferior to the fovea, findings consistent with radiation retinopathy. B. Right fundus fluorescein angiogram shows late perivenous staining.A retinal fluorescein angiogram showed areas of capillary closure, microaneurysms, and venous staining in the right fundus (Fig. 3). Visual acuity dropped over the next 6 months to 20/40, and new blot hemorrhages were noted, but no edema or proliferative changes were seen. In the first reported case of radiation retinopathy after SFRT for ONSM (1), the patient received the same treatment as did our patient: 30 fractions of 1.8 Gy for a total dose of 54 Gy. The posterior retina received 27-48 Gy. Fluorescein angiography showed findings similar to those of our patient. These changes worsened over the next few months despite laser photocoagulation. The second report consisted of a letter by Levi (2) about a 57-year-old man diagnosed with optic nerve sheath meningioma who underwent SFRT with the same tumor dose (2). Five years after treatment, visual acuity dropped, and fluorescein angiography showed findings similar to those of our patient. Our case differs from the two previously reported cases in that the diagnosis was biopsy-proven and that 3D conformal methods were used to minimize collateral radiation damage. Many patients have now received radiotherapy for ONSM, and this is only the third reported case of radiation retinopathy. Our patient may have been relatively more vulnerable to radiation retinopathy because of the biopsy and the fact that the treatment field included the posterior retina, as in the case reported by Subramanian et al (1). In the case reported by Levi (2), the radiation dose to the posterior retina and the proximity of the tumor to the globe were not mentioned. Whether ONSM would respond to doses lower than 54 Gy in 30 fractions (the standard dose) is not known. It may be prudent to examine the possibility of treatment using a lower radiation dose, particularly for ONSMs that abut the globe. Radhika Krishnan, MA (Cantab), MRCOphth Indu Kumar, MRCOphth Graham Kyle, FRSCEd, FRCOphth Ophthalmology Department Walton Daycase and Outpatient Centre University Hospital Aintree Liverpool, UK [email protected] David John Husband, MRCP (UK), FRCR Clatterbridge Centre for Oncology Bebington, Cheshire, UK