Stereotactic fractionated irradiation of optic nerve sheath meningioma: a new treatment alternative

Abstract

Background: Primary optic nerve sheath meningioma (ONSM) is a rare but almost invariably blinding tumour when its natural history is observed in a "wait and see" strategy. Surgery has hitherto only been advocated in case of progressive disease involving intracranial structures, as it leads to iatrogenic blindness in the overwhelming majority of cases. Therefore, treatment options bearing lesser risk of functional deterioration are highly desirable, both in cases of intracranial involvement as well as during earlier phases of the disease which are currently generally left untreated. The authors report the outcome of the largest series of patients to date treated by stereotactic fractionated irradiation as a new treatment approach in ONSM at all stages. Methods: 15 patients (16 nerves) underwent stereotactic fractionated conformal irradiation with a total dose of 54 Gy, using standard fractionation. Main outcome parameters included visual acuity and visual field, as well as three dimensional remission as documented by imaging. Results: Tumour control was confirmed in all 15 patients undergoing stereotactic fractionated conformal irradiation (mean follow up 37 (range 12-71) months). No patient developed functional deterioration during or after treatment. Moreover, visual acuity improved by more than two lines in one patient and the visual field improved in six cases. Visual outcome in the other patients remained unchanged. There were no significant side effects of radiation therapy. Conclusion: These data provide convincing evidence that stereotactic fractionated conformal irradiation is an effective treatment option for primary ONSM with minimal treatment related morbidity. It should therefore be considered as therapeutic option both in early stage ONSM where surgery cannot be justified as well as in later stages, where surgery is so far considered the first line approach.

Primary tumours of the optic nerve and its sheath

“…32,33 To date, the only long-term data reflect the results after treatment using conventional fractionated radiation therapy; 34 however, there is increasing evidence that stereotactic or conformal fractionated radiation therapy may result in improved visual outcome with fewer complications. 29,[35][36][37] I recommend that patients with optic nerve sheath meningiomas who have good visual function be followed without intervention until or unless they begin to experience progressive loss of vision, at which time I recommend stereotactic or conformal fractionated radiation therapy, whereas patients who present with significant visual loss should be given the option to undergo radiation therapy immediately. In such patients, the progression of visual loss may be extremely slow, occurring over many years.…”

Primary optic nerve sheath meningioma

“…Other side effects were dry eye, orbital pain (in a patient suffering form migraine), and iritis, which responded well to local steroid therapy. In contrast, the other studies dealing with pONSM providing clearly documented treatment parameters [57][58][59] showed excellent treatment outcome (improved or stable vision in 100% of patients in both studies) and no toxicity to optic pathways were observed. The follow-up in these studies ranged from 1-7 years (mean, 3 years; median, 2 years), 58 and 1-6 years (median, 35.5 months).…”

“…The characteristics of these studies and the outcome are given in Table 1, including the most recent multi-institutional study by Baumert et al, 78 and smaller studies of Richards et al, 79 Landert et al, 80 a report of a case by Paridaens et al, 81 and the most recent report by Sitathanee et al, 82 all published later on. Liu et al, 58 Becker et al, 59 as well as Pitz et al 57 and Baumert et al 78 reported on pONSM exclusively/separately. Turbin et al 43 provided the longest follow-up, reporting on 18 pONSM of a total of 64 ONSM patients, without specifying the details on the outcome for pONSM.…”

“…Two German studies dealt with a group of patients suffering from primary as well as from secondary ONSM treated by an identical standardized SFRT protocol. Detailed ophthalmologic data of the pONSM patients of these 2 studies have been given in Pitz et al 57 In none of their patients was any decline in visual function noted. Excluding those eyes already being blind at the initiation of treatment, the rate of improvement of either visual acuity or visual field was 58%.…”

“…4,13,14,28,41,53,54 These data, coupled with those showing the effectiveness of RT slowly, but definitely, challenged surgery as the treatment of choice in primary ONSM. 37,42,[55][56][57][58][59][60] It is likely that this would remain largely confined to continuously progressing, large, uni-or bilateral tumors in nonfunctioning eyes so as to prevent major intracranial spread, preferably by en bloc excision.…”